四川盆地东南缘浅层常压页岩气聚集特征与勘探启示  

Accumulation characteristics and exploration enlightenment of shallow normal-pressure shale gas in southeastern Sichuan Basin,SW China

作　　者：云露[1] YUN Lu(Sinopec East China Oil&Gas Company,Nanjing 210019,China)

机构地区：[1]中国石化华东油气分公司,南京210019

出　　处：《石油勘探与开发》2023年第6期1140-1149,共10页Petroleum Exploration and Development

基　　金：中国石化科研项目“南川—武隆地区常压页岩气富集高产机理与目标评价”(P21087-6)。

摘　　要：基于四川盆地东南缘老厂坪背斜浅层常压页岩气井的钻井、测井、实验分析和试气试采等资料分析,开展浅层奥陶系五峰组—志留系龙马溪组页岩储集层地质特征、页岩气赋存机理与吸附解吸规律等研究,以揭示构造复杂区浅层常压页岩气富集高产规律。研究认为:①浅层常压页岩气优质页岩厚度、地球化学、物性、矿物组成等静态指标与中深层页岩气一致,但具有压力系数和含气量较低、吸附气占比高、地应力小、两向应力差异大等地质特点。②构造复杂区浅层页岩具有“总含气量较低(1.1~4.8 m^(3)/t)、吸附气含量较高(2.5~2.8 m^(3)/t)、敏感解吸压力低(1.7~2.5 MPa)、自封闭性好”的气体赋存特征。③页岩吸附气富集主要受有机质丰度、地层温度和压力等因素控制,有机质丰度和地层压力越高、地层温度越低,吸附能力越强,越有利于吸附气赋存。④浅层常压页岩气敏感解吸压力较低,降低流压至敏感解吸压力以下,可实现吸附气快速解吸产出。⑤PD1井的勘探突破揭示以吸附气为主的浅层构造复杂区仍能形成规模页岩储集层,证实四川盆地周缘浅层常压页岩气具有良好的勘探潜力。Based on the drilling,logging,experimental and testing data of Well PD1,a shallow normal-pressure shale gas well in the Laochangping anticline in southeastern Sichuan Basin,the shallow shale gas reservoirs of the Ordovician Wufeng Formation to Silurian Longmaxi Formation(Wufeng–Longmaxi)were investigated in terms of geological characteristics,occurrence mechanism,and adsorption-desorption characteristics,to reveal the enrichment laws and high-yield mechanism of shallow normal-pressure shale gas in complex structure areas.First,the shallow shale gas reservoirs are similar to the medium–deep shale gas reservoirs in static indicators such as high-quality shale thickness,geochemistry,physical properties and mineral composition,but the former is geologically characterized by low formation pressure coefficient,low gas content,high proportion of adsorbed gas,low in-situ stress,and big difference between principal stresses.Second,shallow shales in the complex structure areas have the gas occurrence characteristics including low total gas content(1.1–4.8 m^(3)/t),high adsorbed gas content(2.5–2.8 m^(3)/t),low sensitive desorption pressure(1.7–2.5 MPa),and good self-sealing.Third,the adsorbed gas enrichment of shales is mainly controlled by organic matter abundance,formation temperature and formation pressure:the higher the organic matter abundance and formation pressure,the lower the formation temperature and the higher the adsorption capacity,which is more beneficial for the adsorbed gas occurrence.Fourth,the shallow normal-pressure shale gas corresponds to low sensitive desorption pressure.The adsorbed gas can be rapidly desorbed and recovered when the flowing pressure is reduced below the sensitive desorption pressure.Fifth,the exploration breakthrough of Well PD1 demonstrates that the shallow complex structure areas with adsorbed gas in dominance can form large-scale shale reservoirs,and confirms the good exploration potential of shallow normal-pressure shale gas in the margin of the Sichuan Basin.

关 键 词：浅层常压页岩气 吸附气 吸附解吸 敏感解吸压力 奥陶系五峰组—志留系龙马溪组 四川盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]