Abstract
All stages of oil and gas exploration and development involve the study of in-situ stress. Since the traditional two-dimensional and three-dimensional homogeneous models can no longer fulfil the requirements of research and production, numerical simulation of the stress field has become an effective study method. In this study, we took the Jia 2 member in Puguang area as a case to establish a geological model and a mechanical model based on the tectonic framework and the distribution characteristics of the rock mechanical parameters, respectively, and loaded the model with the present-day in-situ stress state calculated from the logging data as the boundary conditions. The simulation results show that 1) the orientation of the maximum horizontal principal stress in the study area is near E-W, and the in-situ stress orientation is locally deflected due to the influence of faults; and 2) the magnitude of in-situ stress is predominantly affected by the burial depth and lithology, and the minimum horizontal principal stress, maximum horizontal principal stress, and differential stress are mainly concentrated in the ranges of 30–60, 50–80, and 10–40 MPa, respectively. We also analysed the opening sequence of the multiple fracture systems during development, using the present-day stress field model. The analysis revealed that the E-W fractures will open first, and the continuously increasing operating pressure will lead to formation breakdown, producing a fracture network.
Highlights
In-situ stress is a natural force that objectively occurs in a rock mass (Jing et al, 2011)
The results show that the present-day maximum horizontal principal stress orientation is near E-W in the Jia 2 member
The simulation results reveal that the present-day in-situ stress state in the Jia 2 member of the Puguang area is dominated by E-W compressive stress (Figure 3)
Summary
In-situ stress is a natural force that objectively occurs in a rock mass (Jing et al, 2011). It is narrowly defined as the internal stress confined in the Earth’s crust (Xie et al, 2008), and broadly defined as the state of stress in the Earth in different geological periods. Paleo-stresses controlled the type of basin, as well as the generation, development, and combination, of geological structures. They affected the migration and accumulation of oil and gas. Present-day in-situ stress influences the injectionproduction well arrangement, hydraulic fracturing plan, hydraulic fracture propagation, casing deformation, and wellbore stability in oil and gas development
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