In-situ stress field inversion is to find a model or parameter, which can fit practical data as much as possible. According to the fundamental equations of elastic mechanics, the optimization constraint model based on the least square method is established. The optimization method of in-situ stress field of low permeability reservoirs is proposed. Depending on sequential unconstrained minimization technique, the problem of multiobjective constraint is transformed into unconstrained optimization problem by adding penalty function, and numerical model related with finite element calculation is derived. Reasonable objective function is selected to solve minimum value by applying optimization method to adjust and search design parameters, thus boundary loads are obtained. By use of the inversion boundary loads, finite element forward solution is carried out, so in-situ stress field is determined. According to in-site stress size and direction in typical well for GaoYou W8 fault block of SuBei Basin as constraint, the area stress field is calculated. The example shows that the method is reliable and has high precise, and overcomes disadvantages of regression method and boundary adjusting method. Therefore, the optimization method put forward in this paper can effectively solve the inversion problem of in-situ stress field for low permeability reservoir.
In the process of low-permeability reservoir development, the stress field distribution is needed to know. According to the fundamental equations of elastic mechanics, the basic theory of stress field inversion is established. Mixed-penalty function is adopted, and the multi-well constrained optimization model and method are established, so the numerical inversion method combined the constrained optimization with the finite element method is proposed. According to a small amount of measured stress data of the research area to optimize the stress field, the calculation results of stress field agree well with measured values.
