Rock Mechanic Characteristics And Prediction For Formation Fracture Pressure And The Fracture Developing Area Of CO₂ Storage Body In Jingbian Oilfield

Jingbian oilfield is located in the middle east of Shanbei slope of Ordos Basin, Chang 62 as the reservoir and Chang 4+51 as the regional caprock constitute reservoir-caprock combinations in the studied intervals. As the CO2 storage experimental area, Jingbian oilfield has an important scientific basis and economic significance. A comprehensive understanding of rock mechanical characteristics and forecasting formation fracture pressure and fracture developing area distribution of CO2 geological storage is a premise of estimating CO2 leakage, and also an important guarantee for enhancing level of CO2 storage and economic efficiency.This article starts with experiment and has an analysis by mathematical methods and numerical simulation basing on fracturing and related geological data. By way of rock mechanics experiment, a series of rock static mechanics parameters are acquired. Combining with geological characteristics, compare the errors of different fracture pressure prediction models by mathematical model method. Choose the appropriate model to forecast formation fracture pressure in Jingbian oilfield. Under tectonic stress field in Ordos basin and sedimentary microfacies distribution in Jingbian oilfield, with finite elements numerical simulation, simulate minimum principal stress distribution constrainted by crustal stress by means of hydraulic fracturing method. Synthesize formation fracture pressure and minimum stress to forecast fracture developing area, providing theoretical guidance for following CO2 injection. Some results and cognition are acquired as following:(1) There are different stress-strain characteristics for different lithology specimens. For argillaceous siltstone, silty mudstone and siltstone, the rock anti-press peak intensity and axial strain when rock breaking both increase with the increasing of confining pressure, while sandstone is opposite. No matter what lithology specimens is, with the increasing of confining pressure, the range of elastic strain decreases and elastic-plastic strain increases.(2) Young’s modulus of sandstone and mudstone increases with the increasing of depth in Jingbian oilfield, and Young’s modulus of mudstone is higher than sandstone. The Poisson’s ratio increases with the increasing of depth, no matter on uniaxial whether formation conditions, Poisson’s ratio of sandstone is higher than mudstone.(3) By means of contrasting four type models, the model of Eaton applies to predict formation fracture pressure distribution in Jingbian oilfield, and the error keeps in less 5%. And vertical stress has a positive correlation with the fracture pressure.(4) Near the CO2 injection area, the minimum principal stress is a tendency of high in east and low in west of Chang 62 and high in the middle and low in both two sides of Chang 4+51, considering formation fracture pressure and minimum principal stress that Region Ⅰ is fracture developing area and Region Ⅱ is possible fracture developing area.