永川深层山地页岩气区块位于华蓥山褶皱带向南呈帚状撒开的低背斜群,构造褶皱强烈,断层发育,龙马溪组目的层具有埋深差异大、地压地温高、水平应力差异大等特征,过路层研磨性强,井壁易失稳,可钻性差。早期地质认识不足导致钻井时效低、施工周期长、复杂情况频发,多口井压裂改造效果不理想。针对永川工区面临的主要问题,分别进行了可钻性实验、硬度实验、研磨性实验、可钻性剖面建立、地层三压力预测、三维地应力有限元及不同水平应力差模式下的裂缝扩展仿真模拟、水平井地质-工程双甜点预测等针对性的地质力学参数研究。研究表明：永川地区地层可钻性级值较高,安全钻井液密度窗口较窄,地应力方向差异较大,高应力差影响水力压裂缝网形成。利用地质力学研究成果,有针对性地进行了工程工艺调整,钻井提速和压裂增产效果明显,对川南深层页岩气开发具有借鉴意义。

Yongchuan deep mountain shale gas block is located in Huayingshan fold belt, which is a low anticline group with broom like spreading to the south. The structural folds are strong and the faults are developed. The target layer of Longmaxi Formation has the characteristics of great difference in burial depth, high ground pressure and ground temperature and large difference in horizontal stress, while the crossing layer has strong abrasiveness, easy instability of well wall and poor drillability. The lack of early geological knowledge leads to low drilling time, long construction period and frequent complex situations, and the fracturing effect of multiple wells is not ideal. In order to solve the main problems faced by Yongchuan work area, researches on the geomechanical parameters, such as drillability, hardness, abrasiveness laboratory experiments, drillability profile establishment, formation three pressure prediction, 3D in-situ stress finite element, simulation and fracture propagation simulation under different horizontal stress difference modes, and horizontal well geological engineering double sweet spot prediction, have been conducted respectively. The results show that the formation drillability level is high, the safe drilling fluid density window is narrow, the difference of in-situ stress direction is large, and the formation of hydraulic fracturing network is affected by high stress difference. Based on the research results of geomechanics, the engineering technology has been adjusted. The drilling speed and fracturing production increase effect are obvious, which has reference significance for the development of deep shale gas in South Sichuan.