贵州龙马溪组页岩气储层特征及其分布规律

为了评价贵州省志留系下统龙马溪组页岩气资源开发潜力,开展了野外地质调查及页岩气井勘探工作,研究了龙马溪组页岩气储层特征及其分布规律。研究表明:贵州龙马溪组地层主要分布于遵义-余庆一线以北,页岩干酪根类型以I型和II₁型为主,有机碳质量分数普遍小于2%,R_o值为1.5%~3.39%,且下部有机质成熟度明显高于上部;页岩矿物组成以碎屑矿物及黏土矿物为主,表现出较强脆性;页岩孔隙相对发育,以孔隙型、孔隙-裂缝型储集空间为主,主缝、微缝、粘土矿物层间孔缝形成理想的解吸-渗流通道;页岩抗压、抗张强度差异较大,但水介质对页岩强度的影响不大;页岩含气量范围0.63~2.81 m3/t,表现出随深度增加而增大的趋势;扬子地台所历经的多期次构造活动对区域页岩气保存产生了重要影响,正安-务川-沿河以北是贵州龙马溪组页岩气保存的有利区。 

Characteristics and distribution pattern of shale gas reservoir in Longmaxi Formation in Guizhou Province

The work of geology survey and investigation on shale gas has been done to reasonably evaluate the gas resource potential of Lower Silurian Longmaxi Formation. It has been shown by the research that Longmaxi Formation in Guizhou Province mainly distributes in areas north of Zunyi-Yuqing where Ⅰ-type kerogen and Ⅱ₁-type kerogen in the shale predominate and the content of organic carbon in the shale is usually under 2%, with the R_o between 1.5% to 3.39% and the lower part of the formation has higher organic matter maturity. As it formed majorly by detrital minerals and clay minerals, shale shows strong brittleness. Porosity in shale develops comparatively well and the major fracture, micro fracture together with pore and fracture between clay mineral layers form good desorption-seepage channels. Compressive strength is significantly different from tensile strength, while water medium has no obvious effect on the intensity of shale. Shale gas contents are in the range of 0.63~2.81 m3/t, which show increasing trend with the increase of depth. Yangtze platform suffered multi-stage tectonic transform, which caused strong effect on the reserve of shale gas in Longmaxi Formation and the excellent shale gas reservoirs in Guizhou Province mainly distribute in areas north of Zhengan-Wuchuan-Yanhe.