四川盆地涪陵页岩气田江东区块下古生界深层页岩气勘探开发实践与启示

目前埋深大于3 500 m的深层页岩气已逐渐成为中国页岩气勘探开发的重要接替领域，开发过程主要面临地层压力增大、储集物性变差、压裂改造形成复杂缝网困难等问题，开发选区及井位优化部署难度大。江东区块是四川盆地涪陵页岩气田二期产能建设的主要区块，埋深大于3 500 m的深层页岩气面积为57.8 km²，约占区块面积的1/2，目的层为上奥陶统五峰组-下志留统龙马溪组①—⑤小层优质页岩，是一套富碳、富硅、富页理和富黄铁矿的黑色页岩。采用深层页岩气开发评价选区指标体系及水平井井位优化评价技术研究结果表明，影响深层页岩气井开发效果的主要地质因素包括地层埋深、地应力、裂缝发育特征及页岩地层倾角。深层页岩气水平井与最小主应力夹角不超过40°，A与B靶点高差尽量小于300 m。通过江东区块深层页岩气勘探开发实践，单井获得较高的测试产量和可采储量，勘探开发效果较好，研究成果对四川盆地深层页岩气开发具有重要借鉴意义。

Shale gas exploration and development in the Lower Paleozoic Jiangdong block of Fuling gas field,Sichuan Basin

Shale gas exploration and development in China has turned to shales buried in more than 3500 m deep,posing development challenges with their high-pressure,poor physical properties and reluctance to form complex fracture networks after stimulations.The Jiangdong block,one of the major blocks in the phase-Ⅱ productivity construction of the Fuling shale gas field in the Sichuan Basin,contains shale gas at or deeper than such depth in an area of 57.8 km^2,accounting for about half of the total block area.The main targets are the high-quality thin black shale layers(① to ⑤)in the Upper Ordovician Wufeng-Lower Silurian Longmaxi Formations that are rich in carbon,silicon,lamellation and pyrite.By applying an appraisal index system for deep shale gas blocks and an optimized horizontal well location selection method to the shales,we come to the conclusion that the major geological factors influencing the performance of deep shale gas wells are the burial depth,in-situ stress,fracture growth characteristics and dip angle of shale layers.It is therefore recommended that,during horizontal well drilling design,the angle between the wellbore and the minimum principal stress be less than 40°with a level difference between two designed target points(A and B)being kept as less than 300 m as possible.The exploration and development practices in the deep shale in the Jiangdong block have achieved relatively higher test production and recoverable reserves from single wells,which is of realistic guidance and reference for other similar deep shale gas exploration and development in the basin.