涪陵地区五峰-龙马溪组页岩气储层裂缝特征及其控制因素

Reservoir Fracture Characteristics and Controlling Factors of Shale Gas of Wufeng-Longmaxi Formation in Fuling Area

黑色含炭富泥硅质页岩作为页岩气储层的优质岩相在中国南方广泛分布,尤其是奥陶系五峰组和志留系龙马溪组黑色页岩在部分地区已经实现了工业化开采。页岩低孔隙度、低渗透率的特征决定了天然裂缝和压裂改造产生的诱导裂缝对于实现增产至关重要。通过对涪陵地区五峰龙马溪组典型钻井的测井资料进行分析、对岩芯裂缝特征观察,结合薄片的镜下观察,探讨了天然裂缝的发育机制、控制因素以及对诱导裂缝的影响,总结了涪陵地区页岩储层裂缝发育模式与北美地区以及周缘地区的差异,以及该模式在区域尺度、宏观与微观尺度对于页岩气渗流储集的影响。结果表明,该地区的页岩气聚集成藏模式为北美典型模式与受构造作用影响的气藏模式所结合的复合模式。在储层裂缝发育的前提下,封闭成藏、构造高点的特征不可忽视。该模式对于在构造变形强烈的中国南方地区进行页岩气勘探具有指导意义。

As a high quality facies shale gas reservoirs,black carbonaceous siliceous shale rich clay is widely distributed in southern China,especially that the shale of the Ordovician Wufeng formation and the Siluric Longmaxi formation has achieved industrialization production in some areas.Shale characteristics of low porosity and low permeability commitment natural and fracturing induced cracks are very important for the production.Based on the analysis of typical drilling logging data,and the observations of the core crack characteristics and thin section under a microscope,the development mechanism and control factors of natural fracture and their influence to the induced cracks are discussed.Meanwhile,the development model of shale fractures in filing area,and the differences for the development model in this area and in North America as well as the peripheral area are summarized.What’s more,The model how to affect the shale gas seepage gathered at the regional scale,macro and micro scale has been studied.The analysis results show that the region gathered shale gas accumulation model is a composite patterns which combine with north American typical model and conventional gas reservoir model controlled by tectonics.On the premise of reservoir fracture development,closed accumulation and culmination can not be ignored.The model has a guiding significance for shale gas exploration in southern China,where the regional tectonic deformation is very significant.