To achieve the goals of carbon peaking and carbon neutrality under the backgrounds of poor resource endowments, weak theoretical basis and other factors, the development of the coalbed methane industry of China faces ...To achieve the goals of carbon peaking and carbon neutrality under the backgrounds of poor resource endowments, weak theoretical basis and other factors, the development of the coalbed methane industry of China faces many bottlenecks and challenges. This paper systematically analyzes the coalbed methane resources, key technologies and progress, exploration effect and production performance in China and abroad. The main problems are summarized as low exploration degree, low technical adaptability, low return on investment and small development scale. This study suggests that the coalbed methane industry in China should follow the “two-step”(short-term and long-term) development strategy. The short-term action before 2030, can be divided into two stages:(1) From the present to 2025, to achieve new breakthroughs in theory and technology, and accomplish the target of annual production of 10 billion cubic meters;(2) From 2025 to 2030, to form the technologies suitable for most geological conditions, further expand the industry scale, and achieve an annual output of 30 billion cubic meters, improving the proportion of coalbed methane in the total natural gas production. The long-term action after 2030 is to gradually realize an annual production of 100 billion cubic meters. The strategic countermeasure to achieve the above goals is to adhere to “technology+management dual wheel drive”, realize the synchronous progress of technology and management, and promote the high-quality development of the coalbed methane industry. Technically, the efforts will focus on fine and effective development of coalbed methane in the medium to shallow layers of mature fields, effective development of coalbed methane in new fields, extensive and beneficial development of deep coalbed methane, three-dimensional comingled development of coalbed methane, applying new technologies such as coalbed methane displacement by carbon dioxide, microwave heating and stimulation technology, ultrasonic stimulation, high-temperature heat injection stimulation, rock breaking by high-energy laser. In terms of management, the efforts will focus on coordinative innovation of resource, technology, talent, policy and investment, with technological innovation as the core, to realize an all-round and integrated management and promote the development of coalbed methane industry at a high level.展开更多
Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore charact...Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.展开更多
The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic m...The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.展开更多
As the main unconventional natural gas reservoirs,shale gas reservoirs and coalbed methane(CBM)reservoirs belong to adsorptive gas reservoirs,i.e.,gas reservoirs containing adsorbed gas.Shale gas and CBM reservoirs us...As the main unconventional natural gas reservoirs,shale gas reservoirs and coalbed methane(CBM)reservoirs belong to adsorptive gas reservoirs,i.e.,gas reservoirs containing adsorbed gas.Shale gas and CBM reservoirs usually have the characteristics of rich adsorbed gas and obvious dynamic changes of porosity and permeability.A generalized material balance equation and the corresponding reserve evaluation method considering all the mechanisms for both shale gas reservoirs and CBM reservoirs are necessary.In this work,a generalized material balance equation(GMBE)considering the effects of critical desorption pressure,stress sensitivity,matrix shrinkage,water production,water influx,and solubility of natural gas in water is established.Then,by converting the GMBE to a linear relationship between two parameter groups related with known formation/fluid properties and dynamic performance data,the straight-line reserve evaluation method is proposed.By using the slope and the y-intercept of this straight line,the original adsorbed gas in place(OAGIP),original free gas in place(OFGIP),original dissolved gas in place(ODGIP),and the original gas in place(OGIP)can be quickly calculated.Third,two validation cases for shale gas reservoir and CBM reservoir are conducted using commercial reservoir simulator and the coalbed methane dynamic performance analysis software,respectively.Finally,two field studies in the Fuling shale gas field and the Baode CBM field are presented.Results show that the GMBE and the corresponding straight-line reserve evaluation method are rational,accurate,and effective for both shale gas reservoirs and CBM reservoirs.More detailed information about reserves of shale gas and CBM reservoirs can be clarified,and only the straight-line fitting approach is used to determine all kinds of reserves without iteration,proving that the proposed method has great advantages compared with other current methods.展开更多
Based on the productivity equation of coalbed methane (CBM) well, considering the impact of coal reservoir reformability on gas well productivity, the main production layer optimization index in the “three-step metho...Based on the productivity equation of coalbed methane (CBM) well, considering the impact of coal reservoir reformability on gas well productivity, the main production layer optimization index in the “three-step method” of optimal combination of production layers is corrected, and then the CBM production layer potential index is introduced to evaluate favorable areas for commingled multi-coal seam production. Through analysis of the key parameters of coal reservoirs affecting the CBM productivity index, a development unit division method for areas with multi-coal seams is established, and a quantitative grading index system is proposed. On this basis, the evaluation process of CBM development favorable area is developed: the mature 3-D modeling technology is used to characterize the reservoir physical properties of multi-coal seams in full-scale;the production layer potential index of each grid is calculated, and the production layer potential index contour under single-layer or commingled multi-layer production are plotted;according to the distribution of the contour of production layer potential index, the quantitative index of CBM development unit is adopted to outline the grade I, II, III coal reservoir distribution areas, and thus to pick out the favorable development areas. The practical application in the Yuwang block of Laochang in Yunnan proved that the favorable area evaluation process proposed can effectively overcome the defects of selecting favorable development areas only relying on evaluation results of a major coal seam pay, and enhance the accuracy of the evaluation results, meeting the requirements of selecting favorable areas for multi-coal seam commingled CBM production.展开更多
Determining the process of densification and tectonic evolution of tight sandstone can help to understand the distribution of reservoirs and find relatively high-permeability areas.Based on integrated approaches of th...Determining the process of densification and tectonic evolution of tight sandstone can help to understand the distribution of reservoirs and find relatively high-permeability areas.Based on integrated approaches of thin section,scanning electron microscopy(SEM),cathode luminescence(CL),nuclear magnetic resonance(NMR),X-ray diffraction(XRD),N2 porosity and permeability,micro-resistivity imaging log(MIL)and three-dimensional seismic data analysis,this work discussed the reservoir characteristics of the member 8 of the Permian Xiashihezi Formation(He 8 sandstones)in the Linxing area of eastern Ordos Basin,determined the factors affecting reservoir quality,and revealed the formation mechanism of relatively high-permeability areas.The results show that the He 8 sandstones in the Linxing area are mainly composed of feldspathic litharenites,and are typical tight sandstones(with porosity<10%and permeability<1 mD accounting for 80.3%of the total samples).Rapid burial is the main reason for reservoir densification,which resulted in 61%loss of the primary porosity.In this process,quartz protected the original porosity by resisting compaction.The cementation(including carbonate,clay mineral and siliceous cementation)further densified the sandstone reservoirs,reducing the primary porosity with an average value of 28%.The calcite formed in the eodiagenesis occupied intergranular pores and affected the formation of the secondary pores by preventing the later fluid intrusion,and the Fe-calcite formed in the mesodiagenetic stage densified the sandstones further by filling the residual intergranular pores.The clay minerals show negative effects on reservoir quality,however,the chlorite coatings protected the original porosity by preventing the overgrowth of quartz.The dissolution of feldspars provides extensive intergranular pores which constitute the main pore type,and improves the reservoir quality.The tectonic movements play an important role in improving the reservoir quality.The current tectonic traces of the study area are mainly controlled by the Himalayan movement,and the high-permeability reservoirs are mainly distributed in the anticline areas.Additionally,the improvement degree(by tectonic movements)of reservoir quality is partly controlled by the original composition of the sandstones.Thus,the selection of potential tight gas well locations in the study area should be focused on the anticline areas with relatively good original reservoir quality.And the phenomena can be referenced for other fluvial tight sandstone basins worldwide.展开更多
Tight sandstone gas in the Linxing Block, eastern Ordos Basin, has been successfully exploited. The high performance is mainly a result of the special geological conditions. The key geological controls for high produc...Tight sandstone gas in the Linxing Block, eastern Ordos Basin, has been successfully exploited. The high performance is mainly a result of the special geological conditions. The key geological controls for high production have been discussed on the basis of seismic data, field observation, sample features, mercury porosimetry, mechanical properties, and basin modeling. Firstly, the coal measures have good gas generation potential, not only because of the existence of coalbeds and organic-rich shales, but also because coal laminae and microbial mats in the shales significantly increase their total organic carbon(TOC) contents. Secondly, except for the uplifted zone of the Zijinshan complex and the eastern fault zone, rare large faults develop in the Carboniferous–Permian sequence, ensuing the sealing capacity of cap rock. Small fractures generally concentrated in the sandstones rather than the mudstones. Thirdly, gas accumulation in the Linxing Block was controlled by the tectonic, burial and thermal histories. Gas accumulation in the Linxing Block started in the Late Triassic, followed by three short pauses of thermal maturation caused by relatively small uplifts;the maximum hydrocarbon generation period is the Early Cetaceous as a combined result of regional and magmatic thermal metamorphisms. Field profiles show abundant fractures in sandstone beds but rare fractures in mudstone beds. Mechanical properties, determined by lithostratigraphy, confine the fractures in the sandstones, increasing the permeability of sandstone reservoirs and retaining the sealing capacity of the mudstone cap rocks. The modern ground stress conditions favor the opening of predominant natural fractures in the NNW-SSE and N-S directions. These conclusions are useful for exploring the potential tight sandstone gas field.展开更多
The transmission medium of natural gas gathering and transportation pipelines usually contains cor-rosive gases,which will cause serious corrosion on the inner wall of the pipelines when they coexist with water.Theref...The transmission medium of natural gas gathering and transportation pipelines usually contains cor-rosive gases,which will cause serious corrosion on the inner wall of the pipelines when they coexist with water.Therefore,it is necessary to add corrosion inhibitor to form a protective film to protect the pipeline.The distribution of corrosion inhibitors in a gathering and transportation pipeline in Moxi gas field was studied by combining experiment and simulation.The Pearson function was used to calculate the experimental and simulation results,and the correlation was more than 80%,indicating a high degree of agreement.The simulation results show that:①The larger the pipe angle,filling speed and gas flow rate,the smaller the particle size,the better the distribution of corrosion inhibitor particles in the pipe.The filling amount will affect the concentration,but the distribution trend is unchanged;②A method to determine the filling mode based on the loss was proposed,and for this pipeline,the loss of corrosion inhibitor was determined to be 5.31×10^(-3) kg/s,and the flling amount was recommended to be adjusted to 2o L/h,which has certain guiding significance for the actual flling strategy of pipeline corrosion inhibitor.展开更多
Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was ...Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was verified using pore-scale flow simulation.The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed.In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs,the effect of effective surface porosity on the permeability in all directions is consistent.With the decrease of effective surface porosity,the sensitivity of permeability to strain increases.The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity,while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity.For layered reservoirs with the same initial tortuosity in all directions,the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop.When the tortuosity is less than 1.6,the decrease rate of horizontal permeability is higher than that of vertical permeability,while the opposite is true when the tortuosity is greater than 1.6.This phenomenon cannot be represented by traditional dynamic permeability model.After the verification by experimental data of pore-scale simulation,the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.展开更多
The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In t...The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In this work,the impact of horizontal anisotropic permeability on CO_(2)-ECBM was numerically investigated.The variation in the staged CH_(4) output inhibition was analyzed.The ideal displacement profile of the CO_(2)-ECBM process was established for the first time.Moreover,the variation in CH_(4) output of different wellbores was discussed.The results showed that 1)low-permeable or weak-anisotropic reservoirs were not conducive to enhanced CH_(4) recovery owing to long inhibition time(>1091 days)and high inhibition level(>36.9%).As permeability and anisotropy increased,due to the accelerated seepage of free water,the hysteresis time and inhibition time could decrease to as short as 5 days and 87 days,respectively,and the inhibition level could weaken to as low as 5.00%.Additionally,the CH_(4) output and CO_(2) injection could increase significantly.2)Nevertheless,high permeability and strong anisotropy easily induced CO_(2) breakthrough,resulting in lower CH_(4) production,CO_(2) injection and CO_(2) storage than expected.While maintaining high efficiency of CO_(2) storage(>99%),upregulating CO_(2) breakthrough concentration from 10%to 20%might ease the unfavorable trend.3)Along the direction of fluid flow,the ideal displacement profile consisted of CO_(2) enriched bank,CO_(2) and CH_(4) mixed bank,CH_(4) enriched bank,and water enriched bank,whereas a remarkable gap in the displacement profiles of the dominant and non-dominant seepage directions was observed.4)The potential of CH_(4) output might vary greatly among different wellbores.The producers along the dominant seepage direction held more potential for CH_(4) recovery in the short-term,while those along the non-dominant seepage direction avoided becoming invalid only if a long-time injection measure was taken for the injectors.These findings pave the way to understand fluid seepage in real complex reservoirs during CO_(2)-ECBM and conduct further field projects.展开更多
In this work,CH4 isothermal adsorption measurements were carried out on 64 coal samples collected from western Guizhou Province of China,and the coalbed methane(CBM)desorption processes were quantitatively analyzed.Th...In this work,CH4 isothermal adsorption measurements were carried out on 64 coal samples collected from western Guizhou Province of China,and the coalbed methane(CBM)desorption processes were quantitatively analyzed.The results show that the Langmuir volume and the Langmuir pressure are controlled by coalification,and tend to increase as the vitrinite reflectance changes from 0.98% to 4.3%.Based on a division method of CBM desorption stages,the CBM desorption process were divided into four stages(inefficient,slow,fast and sensitive desorption stages)by three key pressure nodes(the initial,turning and sensitive pressures).The fast and sensitive desorption stages with high desorption efficiency are the key for achieving high gas production.A theoretical chart of the critical desorption pressure(P_(cd))and its relationship with different pressure nodes was established.The higher-rank coals have the higher initial,turning and sensitive pressures,with larger difference between pressure nodes.Most CBM wells only undergo partial desorption stages due to the differences in P_(cd) caused by the present-gas content.Under the same gas content conditions,the higher the coal rank,the less desorption stages that CBM needs to go through.During coalbed methane co-production from multiple coal seams within vertically superposed pressure systems,the reservoir pressure,the P_(cd),the initial working liquid level(WLL)height,and coal depth are key factors for evaluating whether coal seams can produce CBM simultaneously.It must be ensured that each production layer enters at least the fast desorption stage prior to that the WLL was lower than the depth of each layer.Only on this basis can all layers achieve the maximum gas production.展开更多
Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the me...Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the mechanical and energy properties are analysed using experimental data.The results show that the stress-strain curve could be divided into four stages in a single cycle.The elastic strain and elastic energy density increase linearly with deviatoric stress and are proportional to the confining pressure and loading rate;irreversible strain and dissipated energy density increase exponentially with deviatoric stress,inversely proportional to the confining pressure and loading rate.The internal structure of tectonic coal is divided into three types,all of which are damaged under different deviatoric stress levels,thereby explaining the segmentation phenomenon of stress-strain curve of tectonic coal in the cyclic loading process.Tectonic coal exhibits nonlinear energy storage characteristics,which verifies why the tectonic coal is prone to coal and gas outburst from the principle of energy dissipation.In addition,the damage mechanism of tectonic coal is described from the point of energy distribution by introducing the concepts of crushing energy and friction energy.展开更多
The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation ...The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation of reasonable development plans.This work established a new reservoir pressure prediction model based on the material balance equation(MBE)of coal reservoir,which considers the self-regulating effects of coal reservoirs and the dynamic change of equivalent drainage area(EDA).According to the proposed model,the reservoir pressure can be predicted based on reservoir condition data and the actual production data of a single well.Compared with traditional reservoir pressure prediction models which regard EDA as a fixed value,the proposed model can better predict the average pressure of reservoirs.Moreover,orthogonal experiments were designed to evaluate the sensitivity of reservoir parameters on the reservoir pressure prediction results of this proposed model.The results show that the saturation of irreducible water is the most sensitive parameter,followed by Langmuir volume and reservoir porosity,and Langmuir pressure is the least sensitive parameter.In addition,the pressure drop of reservoirs is negatively correlated with the saturation of irreducible water and the Langmuir volume,while it is positively correlated with porosity.This work analyzed the reservoir pressure drop characteristics of the CBM wells in the Shizhuangnan Block of the Qinshui Basin,and the results show that the CBM reservoir depressurization can be divided into three types,i.e.,rapidly drop type,medium-term stability type,and slowly drop type.The drainage features of wells were reasonably interpreted based on the comprehensive analysis of the reservoir depressurization type;the latter was coupled to the corresponding permeability dynamic change characteristics,eventually proving the applicability of the proposed model.展开更多
Though traditional methods could recognize some facies, e.g. lagoon facies, backshoal facies and foreshoal facies, they couldn't recognize reef facies and shoal facies well. To solve this problem, back propagation...Though traditional methods could recognize some facies, e.g. lagoon facies, backshoal facies and foreshoal facies, they couldn't recognize reef facies and shoal facies well. To solve this problem, back propagation neural network(BP-ANN) and an improved BP-ANN with better stability and suitability, optimized by a particle swarm optimizer(PSO) algorithm(PSO-BP-ANN) were proposed to solve the microfacies' auto discrimination of M formation from the R oil field in Iraq. Fourteen wells with complete core, borehole and log data were chosen as the standard wells and 120 microfacies samples were inferred from these 14 wells. Besides, the average value of gamma, neutron and density logs as well as the sum of squares of deviations of gamma were extracted as key parameters to build log facies(facies from log measurements)-microfacies transforming model. The total 120 log facies samples were divided into 12 kinds of log facies and 6 kinds of microfacies, e.g. lagoon bioclasts micrite limestone microfacies, shoal bioclasts grainstone microfacies, backshoal bioclasts packstone microfacies, foreshoal bioclasts micrite limestone microfacies, shallow continental micrite limestone microfacies and reef limestone microfacies. Furthermore, 68 samples of these 120 log facies samples were chosen as training samples and another 52 samples were gotten as testing samples to test the predicting ability of the discrimination template. Compared with conventional methods, like Bayes stepwise discrimination, both the BP-ANN and PSO-BP-ANN can integrate more log details with a correct rate higher than 85%. Furthermore, PSO-BP-ANN has more simple structure, smaller amount of weight and threshold and less iteration time.展开更多
Low-frequency components of seismic data tend to characterize thicker litho-stratigraphic units, while high-frequency components tend to characterize thinner isochronous-stratigraphic units. Thus, frequency dependent ...Low-frequency components of seismic data tend to characterize thicker litho-stratigraphic units, while high-frequency components tend to characterize thinner isochronous-stratigraphic units. Thus, frequency dependent interpretation can help to achieve fine sedimentary sequence analysis. However, in current seismic sedimentology method, a certain frequency profile generated by frequency filtering, loses some stratum reflection information, which is out of the limited frequency band. To achieve real frequency dependent stratum reflection profiles with whole stratum information, a time-varying sparse-spiking deconvolution based method is proposed in this paper. A synthetic example and a real delta progradation example show the accuracy and effectiveness of proposed method.展开更多
China’s coalbed methane(CBM) industry is in an extremely important “climbing period” and “strategic opportunity period”,which can be generally characterized by “three low and one small”:low degree of exploratio...China’s coalbed methane(CBM) industry is in an extremely important “climbing period” and “strategic opportunity period”,which can be generally characterized by “three low and one small”:low degree of exploration and development,low adaptability of main technology,low return on investment and small development scale.Under the “carbon peak and neutrality” background,the development status of CBM industry is systematically combed.The resources,technology,management problems and reasons are analyzed.Strategies and countermeasures to accelerate the industrial development are put forward according to the factors such as efficient development of resources,major technical breakthrough,talent team training,policy formulation and implementation,return on investment and so on.The existing problems are as follows:(a) The overall occurrence conditions in China are complicated and the development is difficult compared with the other countries.(b) The research precision accuracy of CBM resource conditions is not enough.(c) The adaptability of technology is poor.(d) The management mode is not suitable.In view of these problems,this paper puts forward the “two steps” development strategy and the technical and management countermeasures of “five in one”.The corresponding “five in one” technology and management countermeasures are the formulation and implementation of relevant safeguard measures in accordance with the principle of collaborative innovation in five aspects:resources,technology,talents,policies and investment.Through the above measures,the dream and grand blueprint of CBM industry shall be realized.展开更多
In order to overcome the deficiencies of current methods for the prediction of the productivity of shale gas hor-izontal wells after fracturing,a new sophisticated approach is proposed in this study.This new model stem...In order to overcome the deficiencies of current methods for the prediction of the productivity of shale gas hor-izontal wells after fracturing,a new sophisticated approach is proposed in this study.This new model stems from the combination several techniques,namely,artificial neural network(ANN),particle swarm optimization(PSO),Imperialist Competitive Algorithms(ICA),and Ant Clony Optimization(ACO).These are properly implemented by using the geological and engineering parameters collected from 317 wells.The results show that the optimum PSO-ANN model has a high accuracy,obtaining a R2 of 0.847 on the testing.The partial dependence plots(PDP)indicate that liquid consumption intensity and the proportion of quartz sand are the two most sensitive factors affecting the model’s performance.展开更多
基金Supported by the China National Science and Technology Major Project (2016ZX05042)。
文摘To achieve the goals of carbon peaking and carbon neutrality under the backgrounds of poor resource endowments, weak theoretical basis and other factors, the development of the coalbed methane industry of China faces many bottlenecks and challenges. This paper systematically analyzes the coalbed methane resources, key technologies and progress, exploration effect and production performance in China and abroad. The main problems are summarized as low exploration degree, low technical adaptability, low return on investment and small development scale. This study suggests that the coalbed methane industry in China should follow the “two-step”(short-term and long-term) development strategy. The short-term action before 2030, can be divided into two stages:(1) From the present to 2025, to achieve new breakthroughs in theory and technology, and accomplish the target of annual production of 10 billion cubic meters;(2) From 2025 to 2030, to form the technologies suitable for most geological conditions, further expand the industry scale, and achieve an annual output of 30 billion cubic meters, improving the proportion of coalbed methane in the total natural gas production. The long-term action after 2030 is to gradually realize an annual production of 100 billion cubic meters. The strategic countermeasure to achieve the above goals is to adhere to “technology+management dual wheel drive”, realize the synchronous progress of technology and management, and promote the high-quality development of the coalbed methane industry. Technically, the efforts will focus on fine and effective development of coalbed methane in the medium to shallow layers of mature fields, effective development of coalbed methane in new fields, extensive and beneficial development of deep coalbed methane, three-dimensional comingled development of coalbed methane, applying new technologies such as coalbed methane displacement by carbon dioxide, microwave heating and stimulation technology, ultrasonic stimulation, high-temperature heat injection stimulation, rock breaking by high-energy laser. In terms of management, the efforts will focus on coordinative innovation of resource, technology, talent, policy and investment, with technological innovation as the core, to realize an all-round and integrated management and promote the development of coalbed methane industry at a high level.
基金Supported by the PetroChina Science and Technology Innovation Fund Project(2021DQ02-1003)Basic Research Project for Central Universities(2022JCCXDC02).
文摘Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.
基金supported by the Fundamental and Commonwealth Geological Survey of Oil and Gas of China(Grant No.DD 20221662)the National Natural Science Foundation of China(NSFC)Program(Grant No.42302124).
文摘The Late Permian was marked by a series of important geological events and widespread organic-rich black shale depositions,acting as important unconventional hydrocarbon source rocks.However,the mechanism of organic matter(OM)enrichment throughout this period is still controversial.Based on geochemical data,the marine redox conditions,paleogeographic and hydrographic environment,primary productivity,volcanism,and terrigenous input during the Late Permian in the Lower Yangtze region have been studied from the Putaoling section,Chaohu,to provide new insights into OM accumulation.Five Phases are distinguished based on the TOC and environmental variations.In Phase I,anoxic conditions driven by water restriction enhanced OM preservation.In Phase II,euxinic and cycling hydrological environments were the two most substantial controlling factors for the massive OM deposition.During Phase III,intensified terrestrial input potentially diluted the OM in sediment and the presence of oxygen in bottom water weakened the preservation condition.Phase IV was characterized by a relatively higher abundance of mercury(Hg)and TOC(peak at 16.98 wt%),indicating that enhanced volcanism potentially stimulated higher productivity and a euxinic environment.In Phase V,extremely lean OM was preserved as a result of terrestrial dilutions and decreasing primary productivity.Phases I,II and IV are characterized as the most prominent OM-rich zones due to the effective interactions of the controlling factors,namely paleogeographic,hydrographic environment,volcanism,and redox conditions.
基金supported by Science and Technology Major Project of Shanxi Province,China(No.20201101002)Science and Technology Major Project of China,China(No.2016ZX05043002)+1 种基金National Natural Science Foundation Project of China,China(No.51874319)Science Foundation of China University of Petroleum(Beijing),China(No.2462020QNXZ003)to support part of this work
文摘As the main unconventional natural gas reservoirs,shale gas reservoirs and coalbed methane(CBM)reservoirs belong to adsorptive gas reservoirs,i.e.,gas reservoirs containing adsorbed gas.Shale gas and CBM reservoirs usually have the characteristics of rich adsorbed gas and obvious dynamic changes of porosity and permeability.A generalized material balance equation and the corresponding reserve evaluation method considering all the mechanisms for both shale gas reservoirs and CBM reservoirs are necessary.In this work,a generalized material balance equation(GMBE)considering the effects of critical desorption pressure,stress sensitivity,matrix shrinkage,water production,water influx,and solubility of natural gas in water is established.Then,by converting the GMBE to a linear relationship between two parameter groups related with known formation/fluid properties and dynamic performance data,the straight-line reserve evaluation method is proposed.By using the slope and the y-intercept of this straight line,the original adsorbed gas in place(OAGIP),original free gas in place(OFGIP),original dissolved gas in place(ODGIP),and the original gas in place(OGIP)can be quickly calculated.Third,two validation cases for shale gas reservoir and CBM reservoir are conducted using commercial reservoir simulator and the coalbed methane dynamic performance analysis software,respectively.Finally,two field studies in the Fuling shale gas field and the Baode CBM field are presented.Results show that the GMBE and the corresponding straight-line reserve evaluation method are rational,accurate,and effective for both shale gas reservoirs and CBM reservoirs.More detailed information about reserves of shale gas and CBM reservoirs can be clarified,and only the straight-line fitting approach is used to determine all kinds of reserves without iteration,proving that the proposed method has great advantages compared with other current methods.
基金Supported by the National Natural Science Foundation of China(No.41772155)the National Science and Technology Major Project of China(No.2016ZX05044-002)the Fundamental Research Funds for the Central Universities of China(No.2015XKZD07)
文摘Based on the productivity equation of coalbed methane (CBM) well, considering the impact of coal reservoir reformability on gas well productivity, the main production layer optimization index in the “three-step method” of optimal combination of production layers is corrected, and then the CBM production layer potential index is introduced to evaluate favorable areas for commingled multi-coal seam production. Through analysis of the key parameters of coal reservoirs affecting the CBM productivity index, a development unit division method for areas with multi-coal seams is established, and a quantitative grading index system is proposed. On this basis, the evaluation process of CBM development favorable area is developed: the mature 3-D modeling technology is used to characterize the reservoir physical properties of multi-coal seams in full-scale;the production layer potential index of each grid is calculated, and the production layer potential index contour under single-layer or commingled multi-layer production are plotted;according to the distribution of the contour of production layer potential index, the quantitative index of CBM development unit is adopted to outline the grade I, II, III coal reservoir distribution areas, and thus to pick out the favorable development areas. The practical application in the Yuwang block of Laochang in Yunnan proved that the favorable area evaluation process proposed can effectively overcome the defects of selecting favorable development areas only relying on evaluation results of a major coal seam pay, and enhance the accuracy of the evaluation results, meeting the requirements of selecting favorable areas for multi-coal seam commingled CBM production.
基金financially supported by the National Science and Technology Major Project of China (grant No. 2016ZX05066001–002)the National Science Foundation for Young Scientists of China (grant No. 41702171)the Program for Excellent Talents in Beijing (grant No. 2017000020124G107)
文摘Determining the process of densification and tectonic evolution of tight sandstone can help to understand the distribution of reservoirs and find relatively high-permeability areas.Based on integrated approaches of thin section,scanning electron microscopy(SEM),cathode luminescence(CL),nuclear magnetic resonance(NMR),X-ray diffraction(XRD),N2 porosity and permeability,micro-resistivity imaging log(MIL)and three-dimensional seismic data analysis,this work discussed the reservoir characteristics of the member 8 of the Permian Xiashihezi Formation(He 8 sandstones)in the Linxing area of eastern Ordos Basin,determined the factors affecting reservoir quality,and revealed the formation mechanism of relatively high-permeability areas.The results show that the He 8 sandstones in the Linxing area are mainly composed of feldspathic litharenites,and are typical tight sandstones(with porosity<10%and permeability<1 mD accounting for 80.3%of the total samples).Rapid burial is the main reason for reservoir densification,which resulted in 61%loss of the primary porosity.In this process,quartz protected the original porosity by resisting compaction.The cementation(including carbonate,clay mineral and siliceous cementation)further densified the sandstone reservoirs,reducing the primary porosity with an average value of 28%.The calcite formed in the eodiagenesis occupied intergranular pores and affected the formation of the secondary pores by preventing the later fluid intrusion,and the Fe-calcite formed in the mesodiagenetic stage densified the sandstones further by filling the residual intergranular pores.The clay minerals show negative effects on reservoir quality,however,the chlorite coatings protected the original porosity by preventing the overgrowth of quartz.The dissolution of feldspars provides extensive intergranular pores which constitute the main pore type,and improves the reservoir quality.The tectonic movements play an important role in improving the reservoir quality.The current tectonic traces of the study area are mainly controlled by the Himalayan movement,and the high-permeability reservoirs are mainly distributed in the anticline areas.Additionally,the improvement degree(by tectonic movements)of reservoir quality is partly controlled by the original composition of the sandstones.Thus,the selection of potential tight gas well locations in the study area should be focused on the anticline areas with relatively good original reservoir quality.And the phenomena can be referenced for other fluvial tight sandstone basins worldwide.
基金the National Natural Science Foundation of China(Grant No.41530315,41872160,41372213,41804080)the National Science and Technology Major Project of China(Grant No.2016ZX05066003,2016ZX05066006)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05030I00)Sichuan Science and Technology Support Project(grant No.20I0JZ0037)and China Scholarship Council and British Council(Grant No.201703780094).
文摘Tight sandstone gas in the Linxing Block, eastern Ordos Basin, has been successfully exploited. The high performance is mainly a result of the special geological conditions. The key geological controls for high production have been discussed on the basis of seismic data, field observation, sample features, mercury porosimetry, mechanical properties, and basin modeling. Firstly, the coal measures have good gas generation potential, not only because of the existence of coalbeds and organic-rich shales, but also because coal laminae and microbial mats in the shales significantly increase their total organic carbon(TOC) contents. Secondly, except for the uplifted zone of the Zijinshan complex and the eastern fault zone, rare large faults develop in the Carboniferous–Permian sequence, ensuing the sealing capacity of cap rock. Small fractures generally concentrated in the sandstones rather than the mudstones. Thirdly, gas accumulation in the Linxing Block was controlled by the tectonic, burial and thermal histories. Gas accumulation in the Linxing Block started in the Late Triassic, followed by three short pauses of thermal maturation caused by relatively small uplifts;the maximum hydrocarbon generation period is the Early Cetaceous as a combined result of regional and magmatic thermal metamorphisms. Field profiles show abundant fractures in sandstone beds but rare fractures in mudstone beds. Mechanical properties, determined by lithostratigraphy, confine the fractures in the sandstones, increasing the permeability of sandstone reservoirs and retaining the sealing capacity of the mudstone cap rocks. The modern ground stress conditions favor the opening of predominant natural fractures in the NNW-SSE and N-S directions. These conclusions are useful for exploring the potential tight sandstone gas field.
基金supported by the Sichuan Natural Science Foundation(2023NSFSC0422)the Petrochina's"14th Five-Year plan"Project(2021Dj2804).
文摘The transmission medium of natural gas gathering and transportation pipelines usually contains cor-rosive gases,which will cause serious corrosion on the inner wall of the pipelines when they coexist with water.Therefore,it is necessary to add corrosion inhibitor to form a protective film to protect the pipeline.The distribution of corrosion inhibitors in a gathering and transportation pipeline in Moxi gas field was studied by combining experiment and simulation.The Pearson function was used to calculate the experimental and simulation results,and the correlation was more than 80%,indicating a high degree of agreement.The simulation results show that:①The larger the pipe angle,filling speed and gas flow rate,the smaller the particle size,the better the distribution of corrosion inhibitor particles in the pipe.The filling amount will affect the concentration,but the distribution trend is unchanged;②A method to determine the filling mode based on the loss was proposed,and for this pipeline,the loss of corrosion inhibitor was determined to be 5.31×10^(-3) kg/s,and the flling amount was recommended to be adjusted to 2o L/h,which has certain guiding significance for the actual flling strategy of pipeline corrosion inhibitor.
基金Supported by the National Natural Science Foundation of China(52274048)Beijing Natural Science Foundation Project of China(3222037)Shaanxi Provincial Technical Innovation Project of China(2023-YD-CGZH-02).
文摘Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was verified using pore-scale flow simulation.The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed.In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs,the effect of effective surface porosity on the permeability in all directions is consistent.With the decrease of effective surface porosity,the sensitivity of permeability to strain increases.The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity,while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity.For layered reservoirs with the same initial tortuosity in all directions,the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop.When the tortuosity is less than 1.6,the decrease rate of horizontal permeability is higher than that of vertical permeability,while the opposite is true when the tortuosity is greater than 1.6.This phenomenon cannot be represented by traditional dynamic permeability model.After the verification by experimental data of pore-scale simulation,the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.
基金the National Natural Science Foundation of China(Grant No.42141012)the National Key R&D Program of China(No.2018YFB0605600)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘The permeability and its horizontal anisotropy induce a critical influence on staged CH_(4) output inhibition process.However,a quantitative evaluation of this influence has been rarely reported in the literature.In this work,the impact of horizontal anisotropic permeability on CO_(2)-ECBM was numerically investigated.The variation in the staged CH_(4) output inhibition was analyzed.The ideal displacement profile of the CO_(2)-ECBM process was established for the first time.Moreover,the variation in CH_(4) output of different wellbores was discussed.The results showed that 1)low-permeable or weak-anisotropic reservoirs were not conducive to enhanced CH_(4) recovery owing to long inhibition time(>1091 days)and high inhibition level(>36.9%).As permeability and anisotropy increased,due to the accelerated seepage of free water,the hysteresis time and inhibition time could decrease to as short as 5 days and 87 days,respectively,and the inhibition level could weaken to as low as 5.00%.Additionally,the CH_(4) output and CO_(2) injection could increase significantly.2)Nevertheless,high permeability and strong anisotropy easily induced CO_(2) breakthrough,resulting in lower CH_(4) production,CO_(2) injection and CO_(2) storage than expected.While maintaining high efficiency of CO_(2) storage(>99%),upregulating CO_(2) breakthrough concentration from 10%to 20%might ease the unfavorable trend.3)Along the direction of fluid flow,the ideal displacement profile consisted of CO_(2) enriched bank,CO_(2) and CH_(4) mixed bank,CH_(4) enriched bank,and water enriched bank,whereas a remarkable gap in the displacement profiles of the dominant and non-dominant seepage directions was observed.4)The potential of CH_(4) output might vary greatly among different wellbores.The producers along the dominant seepage direction held more potential for CH_(4) recovery in the short-term,while those along the non-dominant seepage direction avoided becoming invalid only if a long-time injection measure was taken for the injectors.These findings pave the way to understand fluid seepage in real complex reservoirs during CO_(2)-ECBM and conduct further field projects.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 42130802, 41772132), the Major Projects of Ningxia Key Research and Development Plan (No. 2020BFG2003)the Fundamental Research Funds for the Central Universities (No. 2652019095)the Key Technologies R&D Programme of PetroChina Company Limited (No. 2021DJ2306).
文摘In this work,CH4 isothermal adsorption measurements were carried out on 64 coal samples collected from western Guizhou Province of China,and the coalbed methane(CBM)desorption processes were quantitatively analyzed.The results show that the Langmuir volume and the Langmuir pressure are controlled by coalification,and tend to increase as the vitrinite reflectance changes from 0.98% to 4.3%.Based on a division method of CBM desorption stages,the CBM desorption process were divided into four stages(inefficient,slow,fast and sensitive desorption stages)by three key pressure nodes(the initial,turning and sensitive pressures).The fast and sensitive desorption stages with high desorption efficiency are the key for achieving high gas production.A theoretical chart of the critical desorption pressure(P_(cd))and its relationship with different pressure nodes was established.The higher-rank coals have the higher initial,turning and sensitive pressures,with larger difference between pressure nodes.Most CBM wells only undergo partial desorption stages due to the differences in P_(cd) caused by the present-gas content.Under the same gas content conditions,the higher the coal rank,the less desorption stages that CBM needs to go through.During coalbed methane co-production from multiple coal seams within vertically superposed pressure systems,the reservoir pressure,the P_(cd),the initial working liquid level(WLL)height,and coal depth are key factors for evaluating whether coal seams can produce CBM simultaneously.It must be ensured that each production layer enters at least the fast desorption stage prior to that the WLL was lower than the depth of each layer.Only on this basis can all layers achieve the maximum gas production.
基金We would like to express our gratitude to the reviewers for offering constructive suggestions and comments which improved this manuscript in many aspects. This work was supported by the National Science and Technology Major Project （No. 2016ZX05066）, the National Natural Science Foundation of China （Grant Nos. 41702130, 41672149, and 41672146）, the Fundamental Research Funds for the Central Universities （2015XKZD07）, and Priority Academic Program Development of Jiangsu Higher Education Institutions （PAPD）.
基金funded by the National Major Scientific Research Instrument Development Project(No.41727801)the National Natural Science Foundation of China(Nos.42030810 and 41972168)+1 种基金the Dominant discipline support project of Jiangsu Province(No.2020CXNL11)the Foundation of Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization(No.2019A001).
文摘Compared to intact coal,tectonic coal exhibits unique characteristics.The deformation behaviours under cyclic loading with different confining pressures and loading rates are monitored by MTS815 test system,and the mechanical and energy properties are analysed using experimental data.The results show that the stress-strain curve could be divided into four stages in a single cycle.The elastic strain and elastic energy density increase linearly with deviatoric stress and are proportional to the confining pressure and loading rate;irreversible strain and dissipated energy density increase exponentially with deviatoric stress,inversely proportional to the confining pressure and loading rate.The internal structure of tectonic coal is divided into three types,all of which are damaged under different deviatoric stress levels,thereby explaining the segmentation phenomenon of stress-strain curve of tectonic coal in the cyclic loading process.Tectonic coal exhibits nonlinear energy storage characteristics,which verifies why the tectonic coal is prone to coal and gas outburst from the principle of energy dissipation.In addition,the damage mechanism of tectonic coal is described from the point of energy distribution by introducing the concepts of crushing energy and friction energy.
基金financially supported by the National Natural Science Foundation of China (grants No. 41772159/D0208, No. 41872178)the National Science and Technology Major Project of China (grant No. 2017ZX05064003)
文摘The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation of reasonable development plans.This work established a new reservoir pressure prediction model based on the material balance equation(MBE)of coal reservoir,which considers the self-regulating effects of coal reservoirs and the dynamic change of equivalent drainage area(EDA).According to the proposed model,the reservoir pressure can be predicted based on reservoir condition data and the actual production data of a single well.Compared with traditional reservoir pressure prediction models which regard EDA as a fixed value,the proposed model can better predict the average pressure of reservoirs.Moreover,orthogonal experiments were designed to evaluate the sensitivity of reservoir parameters on the reservoir pressure prediction results of this proposed model.The results show that the saturation of irreducible water is the most sensitive parameter,followed by Langmuir volume and reservoir porosity,and Langmuir pressure is the least sensitive parameter.In addition,the pressure drop of reservoirs is negatively correlated with the saturation of irreducible water and the Langmuir volume,while it is positively correlated with porosity.This work analyzed the reservoir pressure drop characteristics of the CBM wells in the Shizhuangnan Block of the Qinshui Basin,and the results show that the CBM reservoir depressurization can be divided into three types,i.e.,rapidly drop type,medium-term stability type,and slowly drop type.The drainage features of wells were reasonably interpreted based on the comprehensive analysis of the reservoir depressurization type;the latter was coupled to the corresponding permeability dynamic change characteristics,eventually proving the applicability of the proposed model.
基金Project(41272137) supported by the National Natural Science Foundation of China
文摘Though traditional methods could recognize some facies, e.g. lagoon facies, backshoal facies and foreshoal facies, they couldn't recognize reef facies and shoal facies well. To solve this problem, back propagation neural network(BP-ANN) and an improved BP-ANN with better stability and suitability, optimized by a particle swarm optimizer(PSO) algorithm(PSO-BP-ANN) were proposed to solve the microfacies' auto discrimination of M formation from the R oil field in Iraq. Fourteen wells with complete core, borehole and log data were chosen as the standard wells and 120 microfacies samples were inferred from these 14 wells. Besides, the average value of gamma, neutron and density logs as well as the sum of squares of deviations of gamma were extracted as key parameters to build log facies(facies from log measurements)-microfacies transforming model. The total 120 log facies samples were divided into 12 kinds of log facies and 6 kinds of microfacies, e.g. lagoon bioclasts micrite limestone microfacies, shoal bioclasts grainstone microfacies, backshoal bioclasts packstone microfacies, foreshoal bioclasts micrite limestone microfacies, shallow continental micrite limestone microfacies and reef limestone microfacies. Furthermore, 68 samples of these 120 log facies samples were chosen as training samples and another 52 samples were gotten as testing samples to test the predicting ability of the discrimination template. Compared with conventional methods, like Bayes stepwise discrimination, both the BP-ANN and PSO-BP-ANN can integrate more log details with a correct rate higher than 85%. Furthermore, PSO-BP-ANN has more simple structure, smaller amount of weight and threshold and less iteration time.
文摘Low-frequency components of seismic data tend to characterize thicker litho-stratigraphic units, while high-frequency components tend to characterize thinner isochronous-stratigraphic units. Thus, frequency dependent interpretation can help to achieve fine sedimentary sequence analysis. However, in current seismic sedimentology method, a certain frequency profile generated by frequency filtering, loses some stratum reflection information, which is out of the limited frequency band. To achieve real frequency dependent stratum reflection profiles with whole stratum information, a time-varying sparse-spiking deconvolution based method is proposed in this paper. A synthetic example and a real delta progradation example show the accuracy and effectiveness of proposed method.
基金the support from the National Science and Technology Major Project “Research on Key Technologies of Efficient Production and Drainage of Coalbed Methane”(No.2016ZX05042)the support from the Key and Applied Science and Technology Projects of Petro China Co.,Ltd.“Research on Formation Theory of Deep Coalbed Methane and Beneficial Development Technology”(Nos.2023ZZ18,2023ZZ1803,2023ZZ1804)。
文摘China’s coalbed methane(CBM) industry is in an extremely important “climbing period” and “strategic opportunity period”,which can be generally characterized by “three low and one small”:low degree of exploration and development,low adaptability of main technology,low return on investment and small development scale.Under the “carbon peak and neutrality” background,the development status of CBM industry is systematically combed.The resources,technology,management problems and reasons are analyzed.Strategies and countermeasures to accelerate the industrial development are put forward according to the factors such as efficient development of resources,major technical breakthrough,talent team training,policy formulation and implementation,return on investment and so on.The existing problems are as follows:(a) The overall occurrence conditions in China are complicated and the development is difficult compared with the other countries.(b) The research precision accuracy of CBM resource conditions is not enough.(c) The adaptability of technology is poor.(d) The management mode is not suitable.In view of these problems,this paper puts forward the “two steps” development strategy and the technical and management countermeasures of “five in one”.The corresponding “five in one” technology and management countermeasures are the formulation and implementation of relevant safeguard measures in accordance with the principle of collaborative innovation in five aspects:resources,technology,talents,policies and investment.Through the above measures,the dream and grand blueprint of CBM industry shall be realized.
基金This study was financially supported by China United Coalbed Methane Corporation,Ltd.(ZZGSSALFGR2021-581),Bin Li received the grant.
文摘In order to overcome the deficiencies of current methods for the prediction of the productivity of shale gas hor-izontal wells after fracturing,a new sophisticated approach is proposed in this study.This new model stems from the combination several techniques,namely,artificial neural network(ANN),particle swarm optimization(PSO),Imperialist Competitive Algorithms(ICA),and Ant Clony Optimization(ACO).These are properly implemented by using the geological and engineering parameters collected from 317 wells.The results show that the optimum PSO-ANN model has a high accuracy,obtaining a R2 of 0.847 on the testing.The partial dependence plots(PDP)indicate that liquid consumption intensity and the proportion of quartz sand are the two most sensitive factors affecting the model’s performance.
