深层页岩气非线性渗流的温度效应

Effect of Temperature on Nonlinear Seepage of Deep Shale Gas

为了研究温度变化对高温高压的深层页岩气藏产能的影响,建立了考虑变温吸附和随温度变化的压缩因子和黏度的页岩气非线性渗流模型,推导了考虑弹性变形和吸附应变的非均匀孔隙度和渗透率演化模型,发展了具有显式迭代格式的高效的半解析算法,将数值模拟结果与现场生产数据进行对比,验证了所建立模型和算法的正确性,分析了温度变化对深层页岩游离气、吸附气和总产量的影响.结果表明,压力越高,游离气产量受温度影响越小.当地层温度上升40°C时,浅层页岩游离气的产量降低14.5%,而深层页岩游离气产量增加1.4%.相反,压力越高,温度变化对吸附气产量的影响越大.当温度上升时,浅层和深层页岩吸附气的产量分别降低19.3%和31%.浅层页岩气因温度变化总产量相差约15%,而深层页岩气总产量受温度影响不大.在其他条件相同的情况下,高温高压的深层页岩气前5 a的累计产气量是浅层的1.76倍.所建立的模型和算法可以为深层页岩气的高效开发和优化设计提供参考.

In order to investigate the effect of temperature on deep shale gas production under high pressure and high temperature,a nonlinear seepage model was established firstly,considering particularly on the compressibility factor changed with temperature swing adsorption and temperature-dependent compressibility factor and viscosity.And then,the evolution models of inhomogeneous porosity and permeability were derived considering elastic strain and adsorption induced strain,and an efficient semi-analytical approach was improved with explicit iteration schemes to solve the pressure field.Finally,comparing the simulation results with actual field data,the proposed model and approach were validated,analyzing the effect of temperature change on the free gas production of deep shale,adsorption gas and overall output fully.The results show that the higher the pressure,the smaller the effect of temperature on free gas production.The free gas production of shallow shale can decrease by 14.5%when the temperature increases by 40℃,but the free gas production of deep shale can increase by 1.4%.In contrast,the effect of temperature on adsorbed gas is increase with pressure,the adsorbed gas production of shallow and deep shale can decrease by 19.3%and 31%respectively as the formation temperature increase.The temperature increasing can cause the total gas production of shallow shale to decrease by 15%,while there is little influence on the total gas production of deep shale.Due to the higher pressure and temperature,the total gas production of deep shale is 76%higher than that of shallow shale.The proposed model and approach can provide a reference for the efficient development and optimization design for deep shale gas.