摘要
深部煤层气是中国非常规天然气勘探的一个新领域。从深部地应力状态转换、深部煤层吸附能力地温场负效应、深部温压下煤岩物理性质特殊性3个方面,分析了深部煤层气成藏的地质条件及其基本原理,论证了深部煤层气成藏效应的特殊性。结果显示:深部地应力状态发生转换的临界深度与水平最大主应力有关,对转换临界深度以深的煤储层渗透率造成不利影响;深部地温场对煤层吸附能力影响的负效应大于地层压力的正效应,造成深部煤层含气量同样存在一个临界深度,不能简单采用浅部梯度予以推测;围压是影响深部煤岩力学性质的主要因素,温度和流体压力对煤岩力学性质的影响更为复杂,它们不同程度地影响到煤储层的孔隙性、渗透性和吸附性。由于煤层围岩渗流能力的差异,深部煤层流体压力系统明显受含煤地层沉积格架的控制,可能导致同一套含煤地层中煤层与非煤储层分属于不同的含气系统。在此基础上,进一步提出了"四步递阶"的深部煤层气成藏效应耦合分析思路,为建立深部煤层气有利区带优选方法提供了基础。
Deep coalbed methane（CBM） is a new area in unconventional natural gas exploration of China.Thus,the paper analyzed geological conditions and basic principles of deep CBM reservoirs and discussed the specificity of deep CBM-accumulation effects in three respects including the state transition of deep geo-stress,the negative effect of geothermal field on deep coal adsorptivity,and specific physical properties of coals under temperature and pressure conditions of deep strata.The results show that the critical depth for deep geo-stress state transition is related to the maximum horizontal principal stress,which affects the permeability of deep coal reservoirs in various degrees.The negative effect of deep geothermal field on coal adsorptivity is greater than the positive effect of formation pressure,resulting also in a critical depth for deep CBM content,and the deep CBM content can not be simply predicted using the shallow CBM content gradient.Confining pressure is a major factor that affects mechanical properties of deep coal reservoirs,and the effect of temperature and fluid pressure on mechanical properties is rather complex,it profoundly affects the porosity,permeability and absorptivity of coal reservoirs.As a result of differences in the seepage capability of various surrounding rocks,the fluid pressure system of deep coal seams is significantly controlled by the sedimentary framework of coal-bearing strata,which may lead to different gas-bearing systems for coal and non-coal reservoirs even in the same set of coal-bearing strata.On this basis,an idea named as the four-step hierarchical coupling analysis on deep CBM-accumulation effects was proposed and it provided a basis for the establishment of an optimum method to seek deep favorable CBM zones.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2012年第1期48-54,共7页
Acta Petrolei Sinica
基金
国家自然科学基金重点项目(No.40730422)
国家重大科技专项(2011ZX05033
2011ZX05034)资助
关键词
深部
煤层气
临界深度
温度效应
应力效应
成藏效应
deep stratum
coalbed methane
critical depth
temperature effect
geo-stress effect
hydrocarbon accumulation effect
