保存条件对四川盆地及周缘海相页岩气富集高产的影响机制

Effects of preservation conditions on enrichment and high yield of shale gas in Sichuan Basin and its periphery

魏祥峰 李宇平 魏志红 刘若冰 余光春 王庆波

Wei Xiangfeng Li Yuping Wei Zhihong Liu Ruobing Yu Guangchun Wang Qingbo

中国石化 勘探分公司, 成都 610041

SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

以四川盆地及周缘牛蹄塘组和五峰组-龙马溪组2套页岩层为研究对象，通过对不同地区、不同含气性和产量的典型页岩气井进行解剖，探讨了影响页岩气保存条件的主控因素及评价体系。研究认为：顶底板条件、页岩自身封盖作用是该区页岩气早期滞留于页岩内的关键因素，后期构造改造强度与所持续的时间对页岩气藏的含气丰度具有明显的调整作用；保存条件对页岩气层的含气量、孔隙度、含水饱和度、电阻率以及页岩气气体组分等有明显的影响，保存条件差，页岩气层含气量、孔隙度、电阻率通常较低，含水饱和度、N2含量则较高，这些被影响的参数可以作为评价页岩气保存条件优劣的间接指标。建立了四川盆地及周缘复杂构造区下古生界海相页岩气5大类、28项参数的保存条件综合评价指标体系，即主要是封盖条件、页岩气层自身封堵性、构造作用（构造改造时间、断裂作用、地层变形强度等）等条件在时间和空间上的组合关系，另外页岩气层含气性表征参数和压力系数同样可在一定程度上指示保存条件的优劣。

The main controlling factors of shale gas preservation conditions and evaluation of the Niutitang and Wufeng-Longmaxi formations in the Sichuan Basin and its periphery, were considered in view of typical shale gas wells in different regions with different gas contents and production. The preservation conditions of shale gas were controlled by several factors such as the roof and bottom rocks, the sealing properties of shale itself, the structural reformation degree, and the timing of when the shale reservoirs were reformed, etc. Adjacent rock conditions and its sealing effect was the basic factor determining whether the early formed hydrocarbons were preserved. Late tectonic activity controlled the effusion, degree and abundance of shale gas, and it was a key factor in shale gas preservation. Meanwhile, we found that preservation conditions had an obvious effect on gas content, porosity, electrical resistivity, water saturation and gas composition. With poor preservation conditions, the gas content, porosity and resistivity were low, but water saturation and N2 content were high. All these parameters could be used as indirect indexes of shale gas preservation evaluation. A preservation evaluation system with 5 types and 28 parameters for the Lower Paleozoic marine shale gas was set up, illustrating the time and space combination of sealing conditions, the sealing properties of shale itself, and tectonic effects (structural reformation time and degree, fault). The parameters of gas-bearing capacity of shale layer and the pressure coefficients also guide the evaluation of preservation conditions.

中国石化科技部基础研究项目（P15074）和中国地质调查局地质调查项目（12120115003901）资助。

https://doi.org/10.11781/sysydz201702147