大巴山北缘鲁家坪组变质作用及其对页岩气储层的影响  

The metamorphism of the Lujiaping Formation at the northern Daba Mountains and its influence on shale gas reservoirs

作　　者：余川 汪生秀 汪威 曾春林 王巧丽 张华莲 YU Chuan;WANG Shengxiu;WANG Wei;ZENG Chunlin;WANG Qiaoli;ZHANG Hualian(National Joint Engineering Research Center for Shale Gas Exploration and Development,Chongqing Institute of Geology and Mineral Resources,Chongqing,400042;Key Laboratory of Shale Gas Exploration,Ministry of Natural Resources,Chongqing Institute of Geology and Mineral Resources,Chongqing,400042)

机构地区：[1]页岩气勘探开发国家地方联合工程研究中心,重庆地质矿产研究院,重庆401120 [2]自然资源部页岩气资源勘查重点实验室,重庆地质矿产研究院,重庆401120

出　　处：《地质学报》2020年第11期3461-3470,共10页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划“973”项目(编号2012CB214705-05);重庆市规划和自然资源局科技计划项目(编号KJ2018-028)资助成果。

摘　　要：大巴山北缘下寒武统鲁家坪组具有较好的页岩气发育物质基础,钻探显示了一定的页岩气资源潜力,但页岩含气性非均质性较强。针对鲁家坪组页岩气差异富集问题,以地质调查、钻探、实验测试等资料为基础,深入分析了鲁家坪组变质作用特征及其对页岩储集空间结构的影响。研究揭示,大巴山北缘在强烈的构造活动作用下,普遍发生了区域动力变质作用和区域动力热流变质作用。区域上差异构造作用决定了鲁家坪组页岩变质程度的差异性,部分地区只发生了极低级的动力变质作用;在受到岩浆侵入作用影响的范围(距侵入带约0.3~1.5km),主要表现为区域动力热流变质作用,并伴有不同程度的混合岩化,变质程度相对较高。大巴山北缘鲁家坪组储集物性表现为低孔低渗的特征,区域动力热流变质作用导致鲁家坪组物性明显变差,孔隙结构更加细小致密;动力变质并没有对鲁家坪组储集性能造成明显影响,但在动力变质程度较高的区域,往往构造挤压变形强烈、断裂发育、地层破碎,页岩气保存条件破坏严重。因此,针对大巴山北缘鲁家坪组页岩气勘探,需寻找局部动力变质程度较低的构造稳定区。There exists a strong basis for shale gas development in the Lower Cambrian Series Lujiaping Formation of the northern Daba Mountains where drilling has shown potential shale gas resources with strong heterogeneity.In view of the differential enrichment of shale gas in the Lujiaping Formation,the metamorphic characteristics in the Lujiaping Formation and their influence on shale reservoir space structure are analyzed in-depth based on geological survey,drilling,experimental testing and other data.They reveal that regional dynamic heat flow metamorphism has occurred in the northern margin of the Daba Mountains under the influence of strong tectonic activity.Regional differential tectonics has determined the difference in the degree of shale metamorphism in the Lujiaping Formation and only very low-level metamorphism has occurred in some areas.In the range(about 0.3~1.5 km away from the intrusive zone)affected by magmatic intrusion where the metamorphism degree is relatively high,regional dynamic heat flow metamorphism has resulted in mixed petrolization of different degrees.The physical properties of the Lujiaping Formation in the northern margin of the Daba Mountains are characterized by low porosity and low permeability.Regional dynamic thermal flow metamorphism has led to the obvious deterioration of physical properties and pore structure of the Lujiaping Formation.Dynamic metamorphism has not significantly affected the reservoir performance of the Lujiaping Formation,but the areas with high degree of dynamic metamorphism are often characterized by strong structural compression deformation,developed faults,fractured strata,and the shale gas preservation conditions in these areas have been severely damaged.Therefore,it is necessary to search for structurally stable areas with low degree of local dynamic metamorphism for the shale gas exploration in the Lujiaping Formation at the northern margin of Daba Mountains.

关 键 词：储集物性 孔隙结构 变质作用 页岩气 鲁家坪组 大巴山北缘 

分 类 号：P618.13[天文地球—矿床学]