The purpose of this work is to increase the efficiency of well killing operations for carbonate fractured porous reservoirs with high gas factor, the presence of hydrogen sulphide, and abnormally low formation pressure. Well killing in such conditions is complicated by large losses of technological well killing fluid, which provokes gas kick. In this regard, the calculation of a sufficient well killing fluid volume for operations with a high gas factor in conditions of abnormally low formation pressure is an urgent task, which, along with technological and economic efficiency, should increase the safety of repair work on wells. To solve this problem, a model of filtration of non-Newtonian fluid in the borehole zone was proposed. In the course of this work, the Herschel–Bulkley fluid flow was simulated in a porous medium and in a fracture, and a statistical analysis of field data was performed for comparison with the results obtained by the model. The physical and mathematical model used in this work was built based on continuity equation of the flow and the law of conservation of momentum. As a result, the dependence of the injected well killing fluid volume on the repression applied to the reservoir during the well killing operation was derived. Based on the constructed model, key parameters were obtained which allow us to estimate a fluid volume for successful well killing operation. Then the field data was selected, and statistical analysis was carried out using the parameters identified in the initial model. The retrospective analysis showed good convergence of filed data with the results obtained on the basis of the proposed methodology, which confirmed its validity. As a result, a method for well killing fluid volume estimation was proposed for the conditions of fractured porous reservoirs. It is fair to consider the ratio of the volume of the technological fluid that went into the formation during a successful well killing operation to the repression created during the operation as a criterion for the effectiveness of the use of well killing fluid. This parameter depends on the rheology of the fluid and on the rock filtration-volumetric characteristics. Thus, the proposed analytical model with a simple method for well killing fluid volume estimation allows to predict the parameters for each well killing operation. This methodology can be scaled to other porous and fractured-porous reservoirs.
References
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