摘要:川东南丁山地区是近年来四川盆地页岩气勘探开发的热点区域，裂缝的发育对页岩含气性及保存条件有重要的影响。综合运用野外露头、岩心、测井资料，结合岩石脆性矿物含量、岩石力学参数等数据，深入分析龙马溪组页岩裂缝发育特征和控制因素，并探讨了裂缝发育对含气性的影响。结果表明，丁山地区龙马溪组页岩裂缝主要以构造成因的剪切缝为主，裂缝优势方位共6组，主要包括4组平面剪切缝和2组剖面剪切缝，其发育主要受2个方向、3个阶段的构造应力场影响而成；裂缝延伸稳定，平均密度小，宽度小，充填程度高，主要被方解石和黄铁矿等充填。裂缝受控因素主要包括古构造应力场、构造部位、脆性矿物组分、岩石力学性质等；断层对裂缝发育具有明显的控制作用，其中断层两盘均存在裂缝发育程度急剧下降的临界范围，临界范围内裂缝发育程度高，超过此临界范围，裂缝发育程度变差且变化趋于平缓；不同期次的裂缝中，形成时间晚、规模过大、充填程度不高、与现今地应力方向一致或呈低角度相交的裂缝易造成页岩气的散失，对提高页岩含气性不利；龙马溪组岩石脆性矿物含量高，脆性指数属中等偏上程度，有利于构造缝发育且可压性较好。随着距齐岳山断裂距离的适当增加，龙马溪组页岩埋藏深度适中，地层压力增大，抗压强度增强高，脆性指数适中，构造保存条件变好，有利于不同方位的裂缝发育和页岩含气量的增加，位于该区域的DY2井与DY4井均位于该有利区域，含气性良好。研究结果对下一步深化页岩气勘探开发具有重要指导作用。
关键词: 裂缝特征/
含气性/
页岩/
龙马溪组/
丁山地区
Abstract:Longmaxi Formation in Dingshan area is a hot field in the exploration and development of shale gas in southeastern Sichuan in recent years. And the development of fractures has an important effect on the gas content of shale. Base on the outcrops, cores, logging and seismic data, mineral content of rock and rock mechanics experimental data, the development and controling factors of shale fractures and the influence on the gas bearing properties of shale are analyzed in depth. The results show that the shale of Longmaxi Formation in Dingshan area is dominated by shear faults and mainly consists of 4 sets of plane shear slits and 2 sets of section shear slits. The development of fracture is mainly affected by tectonic stress field in two directions and three stages. The fractures have the features of extend steadily, small average density, small width, high degree of filling, and the fractures are mainly filled with calcite, pyrite and other mineral. Fracture controlled factors mainly include the palaeotectonic stress field, tectonic position, brittleness mineral component and rock mechanical properties. The fault has a significant control over the fracture development, There is a sharp decline critical range of in the degree of fracture development critical rang in the meantime, Beyond this critical range, the degree of fracture development is poor and varies slowly, in the different stages of cracks, the formation time is late, the scale is too large, the degree of filling is not high, fractures at low angles or have the same direction with in-situ stress can easily lead to the loss of shale gas, which is unfavorable to improve the gas bearing capacity of shale. The content of brittle rock in Longmaxi Formation is high, and the brittleness index is medium upper, which is favorable for tectonic development and the fracturing is good. With the appropriate distance from Qiyueshan faults, the shale of Longmaxi Formation have moderate buried depth, brittleness index is moderate and the preservation condition of construct is well, which is beneficial to the development of fractures with different direction and the increase of rock gas content, both DY2 and DY4 wells are located in the favorable area, and the gas content is good. The results of this study will play an important guiding role in further shale gas exploration and development.
Key words:Fracture characteristics/
Gas content/
Shale/
Longmaxi Formation/
Dingshan area
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