龙马溪组页岩微裂缝发育与含气量的关系研究

The Study of the Relationship between Development Shale Micro-feature and Its Gas Production in Longmaxi Formation

为明确四川南部志留统龙马溪组JY1井和YC4井产气量存在差异的原因,探究两口井页岩产气量与微裂缝发育的关系。通过X射线衍射仪测出矿物成分含量,得到JY1井和YC4井脆性矿物的平均含量分别为71.5%和57.4%。结合扫描电子显微镜(SEM)和原子力显微镜(AFM)图像,观测JY1井和YC4井页岩微裂缝形态、分布与尺寸。发现JY1井岩石表面起伏落差较大,高峰和低谷高度差值较YC4井大,这极大地提高JY1井的储集空间和流通性能,使得JY1井比YC4井更有利于页岩气的富集成藏。同时,通过MATLAB软件对AFM图像进行积分处理,计算出微裂缝的有效空间体积与实际页岩体积与微裂缝空间和的平均比值(简称微裂缝占空比)。发现现场解析气量与微裂缝的占空比具有良好的正相关关系。

To clear the reason the of difference in gas production of JY1 and YC4 located in Longmaxi Formation of Silurian in the southern Sichuan Basin,to explore the relationships between the two wells in shale gas production and development of micro-cracks,the mineral content was measured by X-ray and analyzed the relationships between development of micro-cracks and brittle mineral. The average content of brittle minerals in JY1 well and YC4 well are 71. 5% and 57. 4%. Then combined with SEM and AFM,observed shale micro-fractures morphology and distribution,measured the dimensions of micro-fractures. The shale surface of JY1 well is rise and fall,and drop is great. The difference between peak and valley is greater than YC4. This greatly improves the storage space and calculation performance of JY1 well,and has an advantage in the enrichment and accumulation of shale gas over YC4. Many AFM images were processed by the MATLAB software with the integral method. The ratio was calculated of effective volume of micro-fractures and the sum of actual shale volume and fractures volume( percentage of micro-fractures for short). There is a good relationship between desorbed gas and percentage of micro-fractures.