储层注气引起地表变形的全场建模与分析

Full-Field Modeling and Analysis of Surface Deformations Induced by Gas Injections into Reservoirs

对储层注气引起地表变形的模拟分析,可用于储层工程灾害预测、指导设计监测岩层变形的倾斜仪安置阵列、校准现有地质模型等,是有效监测地表变形、实施施工过程历史拟合、反演与预测深部储层行为的基础。为对其提供有效的模拟分析,自主研发了用户可控的大规模网格化离散方法,将Eclipse储层模型自动转换并延伸成FLAC3D全场地质模型,将Eclipse储层流动分析结果转换使其为FLA^(3D)岩石力学分析所用,从而实现复杂地质结构储层流动与近远场岩石力学效应的单向耦合。基于此模拟了某大型咸水层二氧化碳封存项目注气一定时间后的地表变形。由于储层注气渗流过程引起的岩体变形在远场十分微小,必须进行高精度的数值计算,而常规模拟流程遇到逼近能力局限性等特殊问题,揭示了其原因并给出了解决方案;探讨了地质模型中储层下伏岩层的厚度对模拟精度的影响。

The simulation analysis of ground surface deformation caused by gas injection into reservoir can predict working hazards in the reservoir,provide design guidance of tiltmeter arrays for monitoring rock strata deformations,and calibrate current geological models.It is thus the basis for monitoring ground surface deformations in an effective manner,implementing history matching for practical processes,and inversions and predictions of deep-lying reservoirs.To provide an effective simulation analysis,we have developed a user-controllable large-scale gridding discretization method that automatically converts Eclipse reservoir models and extends them into FLAC3D full-field geological models,and transforms Eclipse reservoir flow analyses into usable data for FLAC3D rock mechanics analyses.Thus realizes one-way coupled reservoir simulation-geomechanical modelling.On this basis,we have simulated surface deformation in a large-scale saline aquifer CO2storage project that occur after gas injection.Highly accurate numerical computations are required for these studies as the rock mass deformations induced by permeation processes during reservoir injection are very minute.Here,we have demonstrated the causes and have provided solutions for special problems that are encountered during conventional simulation processes,such as limitations in their capacity for approximation.In addition,we have investigated the effect of the underlying stratum thickness of reservoirs in geological models on simulation accuracies.