浅层页岩气勘探重大发现与高效开发对策研究——以太阳浅层页岩气田为例

Major discovery and high-efficiency development strategy of shallow shale gas:a case study of Taiyang shale gas field

为揭示四川盆外复杂构造区浅层页岩气赋存条件与单井高产主控因素,拓展山地页岩气勘探领域,实现中国南方浅层页岩气高效开发,中国石油浙江油田公司通过对昭通示范区浅层页岩气老井进行复查、钻压采试验,取得了由浅层页岩气顶底板封盖+页岩自封闭共同构建的“三维封存箱”新认识;结合地质与地形条件,推行山地页岩气地质工程一体化作业技术,实现了国内首个浅层页岩气田的勘探发现与工业开发。研究结果表明:浅层页岩气甜点展布与富集高产具有“多因素耦合控藏”赋存规律,即受沉积期岩相、改造期变形强度及成藏期封闭性三大因素控制成藏,页岩埋深、地层倾角、剥蚀强度与流体势协同控制页岩气赋存,提出由页岩自封闭保存减缓散漏+顺层理小微短距渗运聚补充构建的“聚散动态平衡”是太阳浅层页岩气田形成有效赋存与富集成藏的关键因素。经矿场试验实践验证,创新形成了浅层页岩气高效开发的三大对策,具体为:细化气田开发评价单元,一体化钻井部署优化与平台个性化设计,经济实用的浅层页岩气钻压采工程技术系列。

In order to find out the gas occurrence conditions and controlling factors for high yield well of shallow shale gas in complex structural zone in the peripheral Sichuan Basin,expand exploration field of shale gas in mountainous area and achieve the high-efficiency development of shallow shale gas in southern China,PetroChina Zhejiang Oilfield Company has conducted reexamination on old wells,fracturing and testing on shallow shale gas wells in Zhaotong demonstration area,and obtained a new understanding that a“3D sealing box”is formed jointly by roof/floor cap rocks of shallow shale gas and self-sealing of shale reservoir.By considering the geological and surface conditions,an operation technology of integrated geology and engineering for shale gas in mountainous area has been implemented,which achieved a major discovery and commercial development of the first shallow shale gas field in China.The study results show that the sweet spots,gas enrichment and high production of shallow shale gas are controlled by“multi-factor coupling”,that is,shale gas accumulation is controlled by lithofacies,deformation intensity in the tectonic reconstruction period and sealing capability in the gas accumulation period.The shale burial depth,formation dip,denudation intensity and fluid potential jointly control the occurrence of shale gas.Specially,it is proposed that the“dynamic balance of shale gas accumulation and dispersion”is the key factor for the effective occurrence and enrichment of shallow shale gas of Taiyang gas field,which is complemented by slow gas dispersion owning to the shale self-sealing preservation and bed parallel super-short distance gas migration and accumulation.After the verification by field practice,three major countermeasures have innovatively been formed for high-efficiency development of shallow shale gas,including refinement of development and evaluation units of gas field,integrated drilling deployment and optimization,and personalized design of drilling platform,as well as the economical and practical technology series for drilling,fracturing and production.