页岩气井全生命周期物理模拟实验及数值反演

Physical simulation experiment and numerical inversion of the full life cycle of shale gas well

页岩储层极低的孔隙度、渗透率和复杂的赋存、输运状态导致其特有的L型生产特征曲线,而且页岩气流动机理复杂。对页岩气井衰竭开发全生命周期生产过程进行了全直径岩心物理模拟实验,获取了模拟页岩气井生产过程完整的压力、日产气量等重要的生产数据,解决了页岩气井生产时间短以及作业引起的间断性等问题导致难以获取完整生产数据的问题。开发模拟实验研究结果表明,模拟实验生产特征与气井相一致;利用模拟实验数据可以准确判断岩心的临界解吸压力(12 MPa)、游离气量(3 820.8mL)与吸附气量(2 152.2 mL)以及不同时间、地层压力时对应的日产气量中游离气与吸附气比例,废弃压力对应的生产时间和最终采出程度。运用岩心与气井无因次时间的相似性以及试井与相似理论,开展了数值反演计算页岩气井的生产动态曲线,预测气井的开发效果,提出了渗透率与压裂效果(缝网密度)是页岩气藏有效开发的关键,其中渗透率是根本,压裂技术是手段。

Because of ultra-low porosity and permeability as well as complex occurrence and transport state,shale reservoirs have the special production characteristic shown as a L-shaped curve and complicated flow mechanism of shale gas.A full-diameter core physical simulation experiment is conducted on the full lifecycle production process of the depletion-mode development of shale gas well,thus obtaining many important simulated production data including complete pressure and daily gas output in the production process of shale gas well,which has solved the difficulty to collect complete production data resulting from short production time and operation discontinuity.The well development simulation experiment shows the production characteristic consistent with shale gas well.Based on the simulation experiment data,the core critical desorption pressure(12 MPa),free gas volume(3 820.8 mL),adsorbed gas volume(2 152.2 mL),the proportion between free gas and absorption gas of the daily gas output under different time and stratum pressure can be determined accurately as well as the production time and final recovery degree corresponding to abandoned pressure.Using the dimensionless time similarity between core and shale gas well as well as the well testing and the similarity theory,numerical inversion is carried out to calculate the dynamic production curve of shale gas well,predict the development effect of gas well.Meanwhile,permeability and fracturing effect(fracture network density)is proposed as the key for effective development of shale gas reservoirs,and permeability is the fundamental factor and fracturing technology is the method.