涪陵页岩气藏开采动态地应力演化规律研究

涪陵页岩气田储层孔隙压力和地应力随着页岩气开采不断演化，使得新井的钻井及压裂地层应力环境与在产老井存在明显差异，准确评价老井压后生产过程中的动态地应力演化规律对后期新井部署和压裂改造设计具有重要意义。针对该问题，文章综合考虑页岩气储层地质力学参数、天然裂缝等的非均质性和各向异性，并基于页岩气藏老井压后开采储层四维地应力演化方法，以四川盆地涪陵页岩气L-Z立体井组为例，建立了渗流—应力交叉耦合的动态地质力学模型，模拟了该井组老井压裂复杂裂缝扩展及压后长期开采四维地应力动态演化，研究发现：在67个月的开采时间段内，孔压和地应力不断降低；孔压和地应力的变化集中分布在各生产井轨迹周围，同时受到压裂改造范围的影响；在老井当前改造范围下，压后开采横向波及范围约为压后生产段改造范围的1.6倍，纵向波及范围基本与压后生产段纵向改造范围相等。研究成果为涪陵页岩气立体化新井压裂开发提供了有效的理论与技术支撑。

Study on Dynamic Geostress Evolution Law During Fuling Shale Gas Extraction

The pore pressure and geostress of the Fuling shale gas field reservoir are evolving with the development of shale gas, which makes the stress environment of the drilling and fracturing formation of new wells significantly different from that of the old wells in production. Accurate evaluation of the dynamic geostress evolution law in the production process after the old well is of great significance to the later new well deployment and fracturing reconstruction design. In view of this problem, this paper comprehensively considers the heterogeneity and anisotropy of the geomechanical parameters of shale gas reservoir, natural fractures, etc. , and based on the four-dimensional geostress evolution method of the shale gas reservoir after the old well fracturing, taking the L-Z three-dimensional well group of Fuling shale gas in Sichuan Basin as an example, a dynamic geomechanical model of seepage and stress cross-coupling has been established. The dynamic evolution of the four-dimensional geostress in the old well group after fracturing and fracturing is simulated. It is found that the pore pressure and geostress continue to decrease during the 67 months of extraction;The changes of pore pressure and geostress are concentrated around the trajectory of each production well, and are affected by the scope of fracturing;Under the current reconstruction scope of the old well, the range of transverse wave of post-fracturing mining is about 1. 6 times of that of the post-fracturing production section, and the range of longitudinal wave is basically equal to that of the post-fracturing production section. The research results provide effective theoretical and technical support for the fracturing and development of new wells with three-dimensional shale gas in Fuling.