重庆涪陵国家级页岩气示范区开发调整井压裂工艺关键技术

Key technologies for development adjustment well fracturing in Chongqing Fuling National Shale Gas Demonstration Area

为提高页岩气田储量动用程度,重庆涪陵国家级页岩气示范区自2018年率先在国内部署页岩气开发调整井并实施压裂。由于一次井网开采后地层非均质性变强、地应力—压力场动态变化导致的压裂造缝预测和有效控制难度增加等问题,给气田采收率整体提升带来极大挑战。为此,以重庆涪陵国家级页岩气示范区焦石坝区块为例,基于井组整体有效动用,提出了以四维动态地质力学模拟分析为核心,以井间精准布缝优化设计、纵向分层促缝—控缝精细化设计和井间干扰识别与实时调控为关键措施的页岩气开发调整井立体缝网精准压裂工艺关键技术。研究结果表明:①老井裂缝低压亏空区产生诱导效应和水平两向应力差增加导致的人工裂缝复杂度降低,是调整井压裂效果受限的主要因素;②密切割增大储层接触面积、多场动态演化规律、多层储层特征差异化等是实现开发调整井压裂精细化设计和现场施工效果的核心方法;③基于地质工程一体化的压裂设计及可迭代式优化压裂施工解决了新老井协同受限、新井改造效率低等难题,下部气层加密井单井测试产量提高10.8%,上部气层单井测试产量提高1倍,新井压裂试气综合费用同比降低20%~30%,单井提产降本效果显著。结论认为,页岩气开发调整井压裂关键技术不仅对同类型页岩气藏开发调整井增产改造具有重要借鉴意义,而且还为示范区开发调整阶段持续稳产、上产提供了有力技术支撑,并有助于推进四川盆地千亿立方米天然气生产基地建设。

To improve the reserve producing degree of shale gas fields,Chongqing Fuling National Shale Gas Demonstration Area has taken the lead in deploying shale gas development adjustment wells and implementing fracturing in China since 2018.The formation heterogeneity becomes stronger after the production in the primary well pattern,and the dynamic change of ground stress and pressure field makes the prediction and effective control of hydraulic fracturing more difficult,which brings great challenges to the overall improvement of the recovery factor of gas field.Taking Jiaoshiba Block of Chongqing Fuling National Shale Gas Demonstration Area as the example,this paper puts forward key technologies for accurate fracturing of stereoscopic fracture networks in shale gas development adjustment wells with four-dimensional dynamic geomechanical simulation and analysis as the core and design optimization of accurate fracture distribution between wells,fine design of vertical layered fracture promotion and control and identification and real-time control of well interference as the key measures,so as to realize the overall effective production of well group.And the following research results are obtained.First,the main factors restricting the fracturing effect of adjustment wells are that inductive effect is generated in the fractured low-pressure depleted zone of old well and the complexity of hydraulic fractures is decreased due to the increase of horizontal bidirectional stress difference.Second,the core methods to achieve fine design and field construction effect of development adjustment well fracturing are the close cut for increasing the reservoir contact area,the multi-field dynamic evolution law and the multi-layer reservoir characteristics differentiation.Third,the fracturing design based on geology-engineering integration and the iterative optimized fracturing construction solve some difficulties,such as limited synergetic effect of old and new wells and low stimulation efficiency of new wells.The test production of single infill well in the lower gas zone increased by 10.8%,and the test production of single well in the upper gas zone was doubled,and the comprehensive cost of fracturing and gas testing of new wells is decreases by 20%-30%year-on-year,indicating a remarkable effect of single-well production increase and cost reduction is achieved.In conclusion,the key technologies for shale gas development well fracturing are of important reference significance to the stimulation of development adjustment wells in similar shale gas reservoirs,provide powerful technical support for the sustainable stable production and production increase in the development adjustment stage of the demonstration area,and are helpful in promoting the construction of the natural gas production base with reserves of one hundred billion cubic meters in the Sichuan Basin.