川东南下志留统龙马溪组深层页岩等温吸附特征及地质意义

Characteristics of methane isothermal adsorption of deep shale from Lower Silurian Longmaxi Formation in southeastern Sichuan Basin and its geological significance

王强 穆亚蓬 陈显 宋振响 马中良 邱岐

WANG Qiang MU Yapeng CHEN Xian SONG Zhenxiang MA Zhongliang QIU Qi

中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126 河南省有色金属地质矿产局 第二地质大队, 郑州 450016

Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China No.2 Geological Party, Henan Bureau of Geological Survey for Nonferrous Metals, Zhengzhou, Henan 450016, China

目前在四川盆地已实现深层页岩气的勘探突破，然而对深层页岩吸附性能及页岩气赋存状态仍存在一定的争议。为此，开展了川东南涪陵、丁山地区下志留统龙马溪组深层典型页岩样品近地质条件下的高温高压等温吸附实验。实验结果表明，页岩绝对吸附量与过剩吸附量之间存在较大的差别，必须将过剩吸附量校正为绝对吸附量后来评价深层页岩的真实吸附能力。校正后的页岩绝对吸附量随压力的增大呈现“快速上升”、“缓慢上升”和“平稳上升”3个阶段，涪陵及丁山地区深层页岩在110℃、70 MPa条件下绝对吸附量仍可达2.0 m3/t以上，结合深层页岩吸附、游离气比例，深层页岩总含气量可达4.0 m3/t以上，表明深层页岩在高温高压下仍可能具有较好的含气性。深层页岩吸附能力评价可为页岩含气量研究、资源潜力评价和储量评估提供科学依据；针对深层与中浅层页岩游离、吸附气比例的差异，采取针对性的勘探、开采方式可以有效提高页岩气的产能及产气周期。

Breakthrough of the exploration of deep shale gas in the Sichuan Basin, Southwest China, has been achieved for decades, there are still some controversies about the adsorption performance and occurrence state of shale gas in deep strata. Isothermal adsorption experiments were carried out under high temperature and high pressure with typical shale samples from deep stratum of the Lower Silurian Longmaxi Formation in Fuling and Dingshan areas in the southeastern Sichuan Basin. Results show that there is a big difference between absolute adsorption and excess adsorption, thus, it is proposed that the excess adsorption capacity should be corrected to the absolute adsorption capacity when evaluating the adsorption performance of deep shale gas. After correction, the variation of absolute shale adsorption with pressure appeared to have three stages including "rapid rise", "slow rise" and "steady rise". The absolute adsorption capacity of deep shale samples from Fuling and Dingshan areas is higher than 2.0 m3/t at 110℃ and 70 MPa, and combined with the adsorption and free gas ratios of deep shale, the total gas content is more than 4.0 m3/t, indicating that deep shale may still have good adsorption performance under high temperature and high pressure. The evaluation of deep shale adsorption capacity can provide reliable parameters for the study of shale gas content and the evaluation of resource potential and reserve for shale gas. Considering the difference of ratio of free gas to adsorbed gas between deep shale and shallow-medium shale, different exploration and production methods can be adopted to effectively improve the production capacity and production cycle of shale gas.

国家自然科学基金 42072156;国家科技重大专项 2017ZX05036

https://doi.org/10.11781/sysydz202201180