摘要
渝东南地区紧邻涪陵页岩气田,区内的下寒武统牛蹄塘组和上奥陶统五峰组下志留统龙马溪组是目前页岩气勘探开发的2套重点层位,相比于涪陵焦石坝地区,改造强度更强,演化程度更高,勘探效果也差别较大,已有研究证明构造运动是盆内与盆外页岩气差异富集的关键控制作用。而对于同样经历了强改造和高演化的渝东南地区下古生界的2套页岩层位来说,2者均具有优质的物质基础,但含气性却差异十分显著。从现场含气量解吸和室内等温吸附实验出发,通过动静态指标对比和相关性研究,分析含气性的关键控制因素。结果表明:下寒武统牛蹄塘组页岩吸附能力较强,但现场解吸气却表现为“高氮、低烃、微含气”的特征;上奥陶统五峰组下志留统龙马溪组页岩吸附能力略逊于下寒武统牛蹄塘组,但含气性却明显好于牛蹄塘组,多口井的解吸气量达到工业下限,气体成分以烃类气体为主。有机质的孔隙结构和富有机质页岩层系底板的封闭性是导致这2套层位含气性差异显著的关键因素。下寒武统牛蹄塘组页岩有机质孔欠发育,致使储集物性较差,而其底板发育不整合面并伴随流体活动,导致气藏遭到破坏,是其含气性差的关键。上奥陶统五峰组下志留统龙马溪组页岩中呈蜂窝状密集发育的有机质孔大大增加了页岩气赋存的空间,加之顶底板的封闭性较好,为页岩气富集提供了良好的条件。通过单井解剖总结建立了渝东南地区下古生界两种典型的页岩气保存散失模型:敛聚保存型聚集模式和底板冲刷破坏散失模式。针对2套目的层的含气性关键控制因素的差异,建议对于下寒武统牛蹄塘组应进一步加强选区指标的研究;上奥陶统五峰组下志留统龙马溪组应进一步加强选带方法的研究。
Southeast Chongqing is close to Fuling shale gasfield.Niutitang Formation and Wufeng-Longmaxi Formation are its two major explorative formations.Compared with Jiaoshiba area,the two formations experienced stronger reformation and had higher thermal maturity,and their explorative results differed obviously,which was caused by tectonic movement.The two formations in Southeast Chongqing have same material resource,but the gas-bearing properties has significant difference.Based on field desorption and isothermal adsorption experiment,according to the comparative study of static and dynamic indexes,the key control factors were discovered.Adsorption capacity of Niutitang Formation was stronger,but its gas-bearing properties was poor that shown the characteristics of low hydrocarbon content and high nitrogen content.Adsorption capacity of Wufeng-Silurian Longmaxi Formation was weaker,but its gas-bearing properties was better than Niutitang Formation.There were several wells whose desorbed gas content reached industrial limit,and its gas composition was mainly hydrocarbon.It was proved that the organic pore structure and floor sealing ability of organic-rich shale were the main control factors for the gas-bearing properties difference of the two shale formations from the Lower Paleozoic in Southeast Chongqing.Organic pores of Niutitang Formation are underdeveloped,resulting in poor reservoir properties,and the unconformity of the bottom is accompanied by fluid activities,resulting in the destruction of gas reservoirs,which is the key to poor gas-bearing properties.Organic pores like honeycomb of Wufeng-Silurian Longmaxi Formation have greatly increased the space of shale gas accumulation,and the sealing of the above and under formation is better,which provides better accumulation conditions for shale gas.Then two typical models of shale gas accumulation for the Lower Paleozoic in the southeastern Chongqing were established including accumulation-preservation model and washing-destruction model.In view of the differences in the key gas-controlling factors of the two formations,it is suggested that the optimal indicators of favorable area should be further researched for Niutitang Formation,and the selection belt method for Wufeng-Silurian Longmaxi Formation should be further researched.
作者
焦伟伟
方光建
汪生秀
张志平
余川
JIAO Weiwei;FANG Guangjian;WANG Shengxiu;ZHANG Zhiping;YU Chuan(National and Local Joint Engineering Research Center of Shale Gas Exploration and Development,Chongqing Institute of Geology and Mineral Resources, Chongqing 401120,China;Key Laboratory of Shale Gas Exploration,Ministry of Land and Resources,Chongqing Institute of Geology and Mineral Resources, Chongqing 401120,China;Chongqing Shale Gas Research Center of State Key Laboratory of Petroleum Resource and Prospecting,Chongqing 401120,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2019年第6期1786-1794,共9页
Journal of China Coal Society
基金
重庆市重点产业共性关键技术创新专项基金资助项目(cstc2016zdcy-zd90001)
重庆市科研院所绩效激励引导专项基金资助项目(cstc2017jxjl90009)
国家科技重大专项资助项目(2016ZX05034003-001)
关键词
渝东南
富有机质页岩
含气性
有机质孔
封闭性
氮气
southeast Chongqing
organic-rich shale
gas-bearing properties
pore structure
sealing ability
作者简介
焦伟伟(1981-),女,河北承德人,正高级工程师,博士。Tel:023-81925886,E-mail:jiaoweiw-210@163.com.
