The method and application of numerical simulation of high-precision stress field and quantitative prediction of multiperiod fracture in carbonate reservoir

Abstract

Structural fractures in carbonate reservoirs contribute prominently to hydrocarbon migration and accumulation. In this paper, the accuracy of structural fracture prediction is improved by two aspects of numerical simulation of traditional tectonic stress field and fracture distribution prediction methods in carbonate reservoirs. (1) The grid generation of finite element models for geological models is prioritized. Next, uniaxial and triaxial compression tests, well logging data, and 3D seismic data volume inversion are used to create a 3D volume of heterogeneous rock mechanics data that accurately reflects the geological body. Then, using the data, attribute assignments are made in the finite element model to create the three-dimensional heterogeneous rock mechanics model. This enhancement significantly diminishes the error induced by attributing rock mechanics parameters to individuals. (2) The size and orientation of in-situ stress are measured using acoustic emission, paleomagnetic, and wave velocity anisotropy tests in combination with imaging logging data. By introducing an adaptive boundary condition method to precisely calculate the in-situ stress magnitude at the applied boundary, we simulate the paleo- and current tectonic stress fields within the study area. The fracture rates for tension and shearing are calculated using the Griffith and Coulomb-Mohr fracture criteria. Based on the statistical results of characteristic fracture parameters at the core and imaging logging scales in the study area, the proportion of tensile and shear fractures is determined, and then the comprehensive fracture coefficient of carbonate reservoirs is calculated. A model for quantitatively predicting the multiperiod linear density of fractures suitable for carbonate reservoirs is developed following a thorough analysis of the various effects of multiperiod tectonic stress on the formation and alteration of reservoir fractures. The utilization of this technique in quantitatively forecasting the linear density of multiperiod fractures in carbonate reservoirs in the Tahe Oilfield, Tarim Basin, exhibits favorable feasibility.