构造变形对海相页岩储层渗透率演化的影响  

Effect of structural deformation on permeability evolution of marine shale reservoirs

作　　者：梁明亮[1,2,3] 王宗秀 李春麟[1,2,3] 李会军 张林炎[1,2,3] 冯兴强 张凯逊[1,2,3] LIANG Mingliang;WANG Zongxiu;LI Chunlin;LI Huijun;ZHANG Linyan;FENG Xingqiang;ZHANG Kaixun(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Ministry of Natural Resources,Beijing 100081,China;Key Laboratory of Petroleum Geomechanics,China Geological Survey,Beijing 100081,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部古地磁与古构造重建重点实验室,北京100081 [3]中国地质调查局油气地质力学重点实验室,北京100081

出　　处：《地质力学学报》2020年第6期840-851,共12页Journal of Geomechanics

基　　金：国家自然科学基金项目(41802158);中国地质调查局地质调查项目(DD20160183,DD20190085);国家重点研发计划(2016YFC0600202);中国地质科学院基本科研业务费项目(JYYWF20181201)。

摘　　要：与北美不同,中国南方海相页岩层经历了多期构造改造,页岩储层物性受构造变形作用的影响较大。为了研究构造变形对南方海相页岩储层渗透率的影响特征和机理,以雪峰山西侧地区五峰—龙马溪组页岩为研究对象,利用气体脉冲衰减法、压汞法和扫描电子显微镜等手段对不同变形页岩样品的渗透率、孔隙结构及孔隙形貌特征进行了测试分析,探讨构造变形页岩的渗透率演化特征及其对孔隙结构演化的响应机理。测试结果显示,强烈构造变形页岩的渗透性较原生页岩和弱变形页岩的渗透性显著提高,强变形页岩样品的渗透率在0.2 mD和2.69 mD之间,比未变形和弱变形页岩样品的渗透率(在1.5×10-4 mD和1.7×10-3 mD之间)高三个数量级,表明强构造变形作用对页岩渗透率具有显著促进作用;同时,不同有效压力条件下页岩渗透率的演化特征显示,强变形页岩气体渗透率的压力敏感性比原生页岩和弱变形页岩显著降低。构造变形条件下页岩孔隙结构与渗透率相关性的进一步分析认为,强变形页岩的孔隙结构变化特别是大孔和裂隙的发育,是促进其渗透率增加的主要原因。这些研究结果表明,伴随强烈的构造变形,南方海相页岩易形成大孔和微裂隙发育的孔隙结构特征,有助于强变形页岩层渗透性的显著提高。构造变形页岩渗透率的提高有利于地质条件下气体的运移,一方面,将有利于页岩气往构造高点的迁移和富集从而形成游离气型或外源型页岩气甜点;另一方面,也可能导致页岩气在盖层条件不佳和断裂发育区的散失。Compared to North America,the geological conditions of marine shale reservoirs in South China are highly diversified and complicated due to the multi-tectonic movement,which transformed the structure of shale seams and resulted in structural deformed shale with unique reservoir properties.To investigate the effect of structural deformation on shale permeability,we experimentally examined the impacts of mineralogy,structural and fabric properties,and effective pressure on permeability evolution using two sets of undeformed shales(U)and deformed shales(D)collected from the Wufeng-Longmaxi Formations in the Upper Yangtze Block.Experimental analysis showed that the permeability between 0.2 and 2.69 millidarcies(mD)of strongly deformed shale samples were three orders of magnitude higher than the permeability(between 1.5×10-4 and 1.7×10-3 mD)of undeformed and slightly deformed shale samples.Meanwhile,strong deformation also reduces the pressure sensitivity of shale permeability when effective pressure increases from 700 PSI to 1200 PSI.These results indicated that accompanied by strong tectonic deformation,the shale permeability improved significantly,ant it would contribute to the development of macropore and micro-crack in the strong deformed shale samples.Moreover,the implications of permeability evolution with structural deformation is presented as that it would conducive to the transport and accumulation of shale gas,and may also lead to the leakage of shale gas in areas with poor seal conditions under the geological conditions of tectonic complex areas in South China.

关 键 词：构造变形 海相页岩 渗透率 孔隙结构 富集与散失 

分 类 号：P618.[天文地球—矿床学]