博乐盆地石炭系地层“涌水携气”现象与页岩气成藏模式探讨

Discussion on"Water Gushing and Gas Carrying"Phenomenon and Formation Model of Shale Gas in Carboniferous Formation in Bole Basin

为了搞清博乐盆地石炭系地层“涌水携气”现象与页岩气成藏模式,根据录井数据分析和现场岩芯观察,结合盆地构造演化特征、烃源岩地化特征、含气性特征、地层压力特征对该现象成因进行了分析,进而对博乐盆地页岩气气藏聚集模式进行了探讨,研究认为在博乐盆地页岩气具有裂缝型和原地型2种成藏模式,其中裂缝型成藏的页岩气主要来源于有机质含量较高的烃源岩生烃,通过开启性断层和裂隙的沟通运移而来,而自身TOC含量一般较低,气藏中以游离气为主,“涌水携气”现象是裂缝型气藏的具体表现。原地型成藏是在盆地中心附近由于烃源岩本身具有较好的生烃条件,生成的页岩气未发生明显运移在原地自生自储,TOC含量控制气藏分布与规模。综合分析2种模式来看,裂缝型气藏模式具有成本低、勘探难度较小,易于实施等优势,是博乐盆地页岩气下一步勘探寻找的方向。

In order to understand the phenomenon of"water gushing and gas carrying"in Carboniferous strata and shale gas accumulation mode in Bole basin,analyzed the cause of this phenomenon according to the analysis of well log data and field core observation,combined with the characteristics of basin tectonic evolution,source rock geochemistry,gas bearing characteristics and formation pressure characteristics,and then discussed the accumulation mode of shale gas reservoir in Bole basin.It is concluded that shale gas in Bole basin has two reservoir formation modes:fractured and autochthonic.Fractured shale gas is mainly derived from source rocks with high organic matter content and migrated through the communication of open faults and fissures,but its TOC content is generally low,and free gas is the main gas in the reservoir.The phenomenon of"water gushing and gas carrying"is the concrete manifestation of fractured gas reservoirs.Autochthonous reservoir formation occurs near the center of the basin because the source rock itself has good hydrocarbon generation conditions,and the shale gas generated is self-generated and self-stored in situ without obvious migration,and TOC content controls the distribution and scale of the gas reservoir.Based on the comprehensive analysis of the two models,the fractured gas reservoir model has the advantages of low cost,small exploration difficulty and easy implementation,which is the next direction of shale gas exploration in Bole basin.