The relationships between permeability and dynamics in hydrocarbon accumulation determine oilbearing potential(the potential oil charge) of low permeability reservoirs.The evolution of porosity and permeability of low...The relationships between permeability and dynamics in hydrocarbon accumulation determine oilbearing potential(the potential oil charge) of low permeability reservoirs.The evolution of porosity and permeability of low permeability turbidite reservoirs of the middle part of the third member of the Shahejie Formation in the Dongying Sag has been investigated by detailed core descriptions,thin section analyses,fluid inclusion analyses,carbon and oxygen isotope analyses,mercury injection,porosity and permeability testing,and basin modeling.The cutoff values for the permeability of the reservoirs in the accumulation period were calculated after detailing the accumulation dynamics and reservoir pore structures,then the distribution pattern of the oil-bearing potential of reservoirs controlled by the matching relationship between dynamics and permeability during the accumulation period were summarized.On the basis of the observed diagenetic features and with regard to the paragenetic sequences,the reservoirs can be subdivided into four types of diagenetic fades.The reservoirs experienced two periods of hydrocarbon accumulation.In the early accumulation period,the reservoirs except for diagenetic fades A had middle to high permeability ranging from 10 × 10^(-3) μm^2 to4207 × 10^(-3) μm^2.In the later accumulation period,the reservoirs except for diagenetic fades C had low permeability ranging from 0.015 × 10^(-3)~ μm^2 to 62 × 10^(-3) μm^2.In the early accumulation period,the fluid pressure increased by the hydrocarbon generation was 1.4-11.3 MPa with an average value of 5.1 MPa.and a surplus pressure of1.8-12.6 MPa with an average value of 6.3 MPa.In the later accumulation period,the fluid pressure increased by the hydrocarbon generation process was 0.7-12.7 MPa with an average value of 5.36 MPa and a surplus pressure of1.3-16.2 MPa with an average value of 6.5 MPa.Even though different types of reservoirs exist,all can form hydrocarbon accumulations in the early accumulation period.Such types of reservoirs can form hydrocarbon accumulation with high accumulation dynamics:however,reservoirs with diagenetic facies A and diagenetic fades B do not develop accumulation conditions with low accumulation dynamics in the late accumulation period for very low permeability.At more than 3000 m burial depth,a larger proportion of turbidite reservoirs are oil charged due to the proximity to the source rock.Also at these depths,lenticular sand bodies can accumulate hydrocarbons.At shallower depths,only the reservoirs with oil-source fault development can accumulate hydrocarbons.For flat surfaces,hydrocarbons have always been accumulated in the reservoirs around the oil-source faults and areas near the center of subsags with high accumulation dynamics.展开更多
Detailed facies analysis of the Neogene successions of the Pishin Belt(Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of t...Detailed facies analysis of the Neogene successions of the Pishin Belt(Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of the northwestern continental margin of the Indian Plate and the Afghan Block. During the Early Miocene, subaerial sedimentation started after the final closure of the Katawaz Remnant Ocean. Based on detailed field data, twelve facies were recognized in Neogene successions exposed in the Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee and floodplain facies associations. Facies associations and variations provided ample evidence to recognize a number of fluvial architectural components in the succession e.g., low-sinuosity sandy braided river, mixed-load meandering, high-sinuosity meandering channels, single-story sandstone and/or conglomerate channels, lateral accretion surfaces(point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to the oblique collision of the Indian Plate with the Afghan Block of the Eurasian Plate along the Chaman-Nushki Fault. Post Miocene deformation of these formations successively caused them to contribute as an additional source terrain for the younger formations.展开更多
Tight gas sands in Whicher Range Field of Perth Basin show large heterogeneity in reservoir characteristics and production behavior related to depositional and diagenetic features. Diagenetic events (compaction and ce...Tight gas sands in Whicher Range Field of Perth Basin show large heterogeneity in reservoir characteristics and production behavior related to depositional and diagenetic features. Diagenetic events (compaction and cementation) have severely affected the pore system. In order to investigate the petrophysical characteristics, reservoir sandstone facies were correlated with core porosity and permeability and their equivalent well log responses to describe hydraulic flow units and electrofacies, respectively. Thus, very tight, tight, and sub-tight sands were differentiated. To reveal the relationship between pore system properties and depositional and diagenetic characteristics in each sand type, reservoir rock types were extracted. The identified reservoir rock types are in fact a reflection of internal reservoir heterogeneity related to pore system properties. All reservoir rock types are characterized by a compacted fabric and cemented framework. But distribution and dominance of diagenetic products in each of them depend on primary depositional composition and texture. The results show that reservoir rock typing based on three aspects of reservoir sandstones (depositional properties, diagenetic features and petrophysical characteristics) is a suitable technique for depiction of reservoir heterogeneity, recognition of reservoir units and identifying factors controlling reservoir quality of tight sandstones. This methodology can be used for the other tight reservoirs.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U1262203)the National Science and Technology Special Grant(No.2011ZX05006-003)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.14CX06070A)the Chinese Scholarship Council(No.201506450029)
文摘The relationships between permeability and dynamics in hydrocarbon accumulation determine oilbearing potential(the potential oil charge) of low permeability reservoirs.The evolution of porosity and permeability of low permeability turbidite reservoirs of the middle part of the third member of the Shahejie Formation in the Dongying Sag has been investigated by detailed core descriptions,thin section analyses,fluid inclusion analyses,carbon and oxygen isotope analyses,mercury injection,porosity and permeability testing,and basin modeling.The cutoff values for the permeability of the reservoirs in the accumulation period were calculated after detailing the accumulation dynamics and reservoir pore structures,then the distribution pattern of the oil-bearing potential of reservoirs controlled by the matching relationship between dynamics and permeability during the accumulation period were summarized.On the basis of the observed diagenetic features and with regard to the paragenetic sequences,the reservoirs can be subdivided into four types of diagenetic fades.The reservoirs experienced two periods of hydrocarbon accumulation.In the early accumulation period,the reservoirs except for diagenetic fades A had middle to high permeability ranging from 10 × 10^(-3) μm^2 to4207 × 10^(-3) μm^2.In the later accumulation period,the reservoirs except for diagenetic fades C had low permeability ranging from 0.015 × 10^(-3)~ μm^2 to 62 × 10^(-3) μm^2.In the early accumulation period,the fluid pressure increased by the hydrocarbon generation was 1.4-11.3 MPa with an average value of 5.1 MPa.and a surplus pressure of1.8-12.6 MPa with an average value of 6.3 MPa.In the later accumulation period,the fluid pressure increased by the hydrocarbon generation process was 0.7-12.7 MPa with an average value of 5.36 MPa and a surplus pressure of1.3-16.2 MPa with an average value of 6.5 MPa.Even though different types of reservoirs exist,all can form hydrocarbon accumulations in the early accumulation period.Such types of reservoirs can form hydrocarbon accumulation with high accumulation dynamics:however,reservoirs with diagenetic facies A and diagenetic fades B do not develop accumulation conditions with low accumulation dynamics in the late accumulation period for very low permeability.At more than 3000 m burial depth,a larger proportion of turbidite reservoirs are oil charged due to the proximity to the source rock.Also at these depths,lenticular sand bodies can accumulate hydrocarbons.At shallower depths,only the reservoirs with oil-source fault development can accumulate hydrocarbons.For flat surfaces,hydrocarbons have always been accumulated in the reservoirs around the oil-source faults and areas near the center of subsags with high accumulation dynamics.
文摘Detailed facies analysis of the Neogene successions of the Pishin Belt(Katawaz Basin) has enabled documentation of successive depositional systems and paleogeographic settings of the basin formed by the collision of the northwestern continental margin of the Indian Plate and the Afghan Block. During the Early Miocene, subaerial sedimentation started after the final closure of the Katawaz Remnant Ocean. Based on detailed field data, twelve facies were recognized in Neogene successions exposed in the Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee and floodplain facies associations. Facies associations and variations provided ample evidence to recognize a number of fluvial architectural components in the succession e.g., low-sinuosity sandy braided river, mixed-load meandering, high-sinuosity meandering channels, single-story sandstone and/or conglomerate channels, lateral accretion surfaces(point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to the oblique collision of the Indian Plate with the Afghan Block of the Eurasian Plate along the Chaman-Nushki Fault. Post Miocene deformation of these formations successively caused them to contribute as an additional source terrain for the younger formations.
文摘Tight gas sands in Whicher Range Field of Perth Basin show large heterogeneity in reservoir characteristics and production behavior related to depositional and diagenetic features. Diagenetic events (compaction and cementation) have severely affected the pore system. In order to investigate the petrophysical characteristics, reservoir sandstone facies were correlated with core porosity and permeability and their equivalent well log responses to describe hydraulic flow units and electrofacies, respectively. Thus, very tight, tight, and sub-tight sands were differentiated. To reveal the relationship between pore system properties and depositional and diagenetic characteristics in each sand type, reservoir rock types were extracted. The identified reservoir rock types are in fact a reflection of internal reservoir heterogeneity related to pore system properties. All reservoir rock types are characterized by a compacted fabric and cemented framework. But distribution and dominance of diagenetic products in each of them depend on primary depositional composition and texture. The results show that reservoir rock typing based on three aspects of reservoir sandstones (depositional properties, diagenetic features and petrophysical characteristics) is a suitable technique for depiction of reservoir heterogeneity, recognition of reservoir units and identifying factors controlling reservoir quality of tight sandstones. This methodology can be used for the other tight reservoirs.
