Abstract:

Tectonic stress analysis is particular important in the course of petroleum exploration and development. The geological structure complexity, its boundary problem, the loading paths, etc. are difficult problems in the numerical simulation of tectonic stress field; and the field stress data is very limited. Because of the unknown tectonic movement and complicated geological structure, tectonic stress field cannot be calculated immediately. The boundary load inversion is a particular important means for tectonic stress field analysis. Starting from the fundamental equations of elastic mechanics, the inverse problem of tectonic stress field of oil-gas reservoirs is proposed. Based on the least square method, a method is presented to identify and calculate inversely the boundary load on the geological model by the stresses in the geological model. The finite element method and the finite difference method are combined to apply the method that chooses the boundary loads as fitting parameters in the objective function. The calculated results are in good agreement with the in-situ measured data. This method has excellent practical value and can provide references to the back analysis of tectonic stress field. This method and model can get over the shortage of common back analysis method such as adjusting boundary loads and regression method; so it can calculate exactly the tectonic stress field by back analysis. The results show that the method is simple, credible and has high precision and rapid calculation velocity. Therefore, it may find its uses in the boundary load inversion of tectonic stress field. This method can provide references to petroleum exploration and production.

Key words: tectonic stress field, finite elements, least square method, finite element inverse analysis