四川盆地东部下志留统龙马溪组页岩储层特征及影响因素

Shale reservoir characteristics and influencing factors of the Lower Silurian Longmaxi Formation in the eastern Sichuan Basin

四川盆地东部下志留统龙马溪组页岩气勘探已取得重大突破,其储层研究尤其是优质储层发育的影响因素对四川盆地海相页岩的下一步勘探具有重要意义。在岩心观察和岩石薄片鉴定的基础上,通过扫描电镜和X射线衍射等分析,对四川盆地东部下志留统龙马溪组储层特征进行了研究,确定了有利储层形成的主控因素。研究区地层矿物成分以石英和黏土矿物为主,方解石、白云石及黄铁矿等的含量较低;干酪根类型以腐泥型（Ⅰ）为主、腐殖腐泥型（Ⅱ_1）次之;TOC质量分数为0.10%~8.67%,平均为1.49%,R_o为1.63%~2.81%,平均为2.18%;地球化学特征为富有机质和高—过成熟;储集空间类型可分为孔隙和裂缝两大类,其中粒间孔、有机质孔及构造缝为主要储集空间。四川盆地东部下志留统龙马溪组页岩储层的发育受沉积环境、页岩脆性及有机质丰度与成熟度等因素的影响。

The shale gas exploration of the Lower Silurian Longmaxi Formation in the eastern Sichuan Basin has achieved a major breakthrough, so the research of reservoir quality, especially the influencing factors of favorable reservoir development, is significant for the next exploration of marine shale in Sichuan Basin. Based on core observation and rock slice identification, combined with scanning electronic microscope X-ray diffraction, this paper studied the reservoir characteristics of the Lower Silurian Longmaxi Formation in the eastern Sichuan Basin, and determined the main controlling factors for the formation of favorable reservoir. The minerals in the study area are mainly composed of quartz and clay minerals, with little calcite, dolomite and pyrite. Kerogen type is mainly sapropel（Ⅰ）, and humic-sapropel（Ⅱ_1）comes second. The mass fraction of TOC is 0.10%-8.67%, and the average value is 1.49%. The R_o is 1.63%-2.81%, and the average value is 2.18%. Geochemical characteristics show a rich organic matter and high maturity. Reservoir space can be divided into two categories： pores and cracks, in which intergranular pores, organic pores and structural fractures are dominant. The shale reservoir development in the study area is affected by the sedimentary environment, shale brittleness, organic matter abundance and maturity.