鸡西盆地南北坳陷带煤储层特征对比研究

Comparative study on coal reservoir characteristics of north-south depression in Jixi Basin

储层物性是影响煤层气储集能力和可采性的关键因素。本次研究主要以鸡西盆地下白垩统城子河组煤层为研究对象。综合运用多种实验分析手段,从煤岩煤质、物性演化、含气特征等方面对盆地南北坳陷带煤储层特征进行对比和评价。结果表明:城子河组14号煤层煤岩镜质体反射率o为0.56%~1.45%,北部坳陷带因叠加了区域岩浆热变质作用,变质程度高于南部坳陷带;煤储层孔隙类型以微小孔为主,且孔隙形态以一端封闭的平行板状孔或尖劈型孔和墨水瓶型孔为代表。以14号主力煤层为例,南部坳陷带煤层渗透率略高于北部坳陷带,渗透性相对较差;北部坳陷带煤层埋深较深,使得孔隙度低于南部坳陷带;北部坳陷带14号主力煤层煤厚与含气量在滴道—东海矿区达到最大,南部坳陷带14号主力煤层煤厚与含气量在平岗—合作矿区达到最大;南部坳陷带煤层气保存条件较好,煤储层含气饱和度高于北部坳陷带,14和16号煤储层含气性饱和度>100%,可作为勘探开发的有利层位。

Reservoir physical properties are the key factors affecting coalbed methane storage capacity and recoverability.This study mainly focused on the coal seam of the lower cretaceous Chengzihe Formation in the Jixi Basin.Comprehensively use a variety of experimental analysis methods to compare and evaluate the characteristics of coal reservoirs in the north-south depression of the basin from the aspects of coal rock quality,physical property evolution,and gas-bearing characteristics.The results show that the coal vitrinite reflectance of No.14 coal seam of Chengzihe Formation is between 0.56%and 1.45%.Due to the superposition of regional magmatic thermal metamorphism,the degree of metamorphism in the northern depression zone is higher than that in the southern depression zone.The pore types of coal reservoirs are mainly micropores,and the pore shape is represented by parallel plate-shaped pores or split-type pores and ink bottle-shaped pores closed at one end.Taking No.14 main coal seam as an example,the coal permeability in the southern depression zone is slightly higher than that in the northern depression zone,and the permeability of coal seam in the Jixi Basin is relatively poor.The main coal seam of the northern depression belt is deeper,making the porosity lower than that of the southern depression belt.The coal thickness and gas content of the No.14 main coal seam in the northern depression belt reached the maximum in the Didao-Donghai mining area,and the coal thickness and gas content of the No.14main coal seam in the southern depression belt reached the maximum in the Pinggang-Hezuo mining area.The preservation conditions of coalbed methane in the southern depression belt are better,and the gas saturation of the coal reservoirs is higher than that in the northern depression belt.In particular,No.14 and No.16 coal reservoirs have gas saturation>100%,which can be used as a favorable horizon for exploration and development.