基于有限元方法的储层地应力修正研究

RESEARCH ON THE GROUND STRESS CORRECTION OF RESERVOIRS BASED ON THE FINITE ELEMENT METHOD

地应力是油气储层评价的基础参数,传统常用的单井地应力求解往往只依托于测井数据及岩石力学实验,未考虑整体力学模型中地层岩石非均质性对地应力的影响。研究以准噶尔盆地中部4区块董11井为例,采用整体力学模型分析的方法对目的储层地应力进行修正。根据地层岩石的物理性质及岩石力学参数对井场周围地区进行划分及整体三维建模,并用ANSYS有限元软件对其整体模型进行力学分析,从而对地应力计算结果进行修正,得出研究区目的层地应力分布情况。研究结果表明,修正后的地应力值与修正前的地应力值在地层薄弱(坚硬)层段水平最小主应力值相差16%~17%左右,水平最大主应力值相差22%~23%左右。修正后的地应力可以很好地体现地层在沉积过程中造成的岩石物理性质非均质性对地应力非均质性的影响,反映了储层地应力的真实变化特征。

Ground stress is the basic parameter for oil and gas reservoir evaluation.The traditional solution of ground stress of single well usually relies on logging data and rock mechanics experiments, without considering the effect of formation rock heterogeneity on ground stress in the whole mechanical model.Therefore, Well Dong 11 in Block 4 in the middle of the Junggar Basin is taken as an example to correct the ground stress of the target reservoir with the analysis method of global mechanics model in this study, then the division of the area around the well site and 3D modeling of the whole well were based on the physical properties of formation rocks and rock mechanics parameters, and the ground stress distribution situation of the target in the study area was obtained with the correction in calculation results of ground stress through mechanical analysis of the integrated model by using the finite element software ANSYS.The results show that the difference value of the level interval minimum principal stress between before correction and after correction in the weak (firm) stratum is about 16%~17%, and that of the maximum principal stress value is about 22%~23%.The corrected ground stress can well reflect the influence of the heterogeneity of rock physical properties on the heterogeneity of ground stress, and reflect the real variation characteristics of reservoir ground stress.