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川南宜宾地区煤层气资源潜力及有利区优选

Coalbed methane resource potential and favorable area optimization in Yibin Area, Southern Sichuan

  • 摘要: 川南宜宾地区上二叠统煤层气勘探近年来在局部取得突破,优选出该区煤层气有利区从而推进煤层气大规模商业开发任务紧迫,基于煤田钻孔煤层厚度和瓦斯含量等数据,结合页岩气、煤层气勘查的岩心、测井、试井、现场解吸和分析测试等资料,对该区煤层气地质条件、煤层气资源潜力进行了综合评价,并选用煤层埋深、顶底板岩性、厚度、含气量、煤层集中度、煤体结构等地质参数,利用加权求和法进行煤层气有利区优选,结果表明:该区煤层总厚度3.61~10.02 m,平均6.05 m,受沉积环境影响,西部宣威组煤层垂向分布较为集中,东部龙潭组煤层垂向分布较为分散,宣威组C7,C8煤层较集中,为该区煤层气开发主力煤层;煤储层宏观煤岩类型以光亮-半亮型为主,储集空间类型多样,主要发育有胞腔孔、气孔、粒间孔等,煤层镜煤条带中割理发育,孔隙-裂隙系统结构配置合理;煤层现场解吸含气量1.03~18.11 m3/t,平均10.53 m3/t;区内上二叠统煤层气资源量3 465.22×108 m3,资源丰度1.87×108 m3/km2,该区煤层气地质条件与沐爱地区相近,且异常高压储层发育,构造简单,煤层气成藏条件更为优越,区内白胶-底洞、腾达-仙峰地区煤层埋深适中、厚度较厚、含气量高、煤层集中度好、构造简单,以原生-碎裂结构为主,为下一步煤层气勘探重点区域。

     

    Abstract: In recent years, great local breakthroughs have been made in the exploration of coalbed methane in Upper Permian coal measures in Yibin area of southern Sichuan. It is urgent to optimize the favorable area of coalbed methane so as to promote the large-scale commercial development of coalbed methane. Based on the data of coal seam thickness and gas content in the coal field drilling, combined with the data of core, logging, well test, field desorption and analysis test of shale gas and coalbed methane exploration , the geological conditions of coalbed methane and the potential of coalbed methane resources in the area are analyzed.A comprehensive evaluation was carried out, and geological parameters such as coal seam burial depth, roof and floor lithology, thickness, gas content, coal seam concentration, and coal body structure were selected, and the weighted sum method was used to optimize the coalbed methane favorable area. The results show that the total thickness of coal seams in this area is 3.61-10.02 m, with an average of 6.05 m. Affected by the depositional environment, the vertical distribution of Xuanwei Formation coal seam in the west is relatively concentrated, while the vertical distribution of Longtan Formation coal seams in the East is relatively scattered. The C7 and C8 coal seams of the Xuanwei Formation are distributed vertically. It is relatively concentrated and is the main coal seam for CBM development in this area; the macroscopic coal rock types of coal reservoirs are mainly bright and semi-bright, and there are various types of storage spaces, main6ly developed with intracellular pores, air pores, intergranular pores, etc. The cleats are developed in the coal seam strip, and the pore fracture system structure is reasonable. The gas content of desorption coal seam is 1.03-18.11 m3/t, with an average of 10.53 m3/t; The upper Permian CBM resource in this area is 3 465.22×108 m3, and the resource abundance is 1.87×108 m3/km2. The geological conditions of coalbed methane are similar to those in Mu′ai area, and the abnormally high pressure reservoirs are developed with simple structure. The conditions for coalbed methane accumulation are better. The coal seam in the Xianfeng area has moderate burial depth, thick thickness, high gas content, good coal seam concentration, simple structure, and is dominated by primary-fractured structures. It is a key area for the next coalbed methane exploration.

     

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