Well Test Model and Analytical Method of Finite Conductivity Vertical Fracture Bilinear Flow of Low-Speed Non-darcy Flow

For low-permeability reservoirs, non-Darcy flow is not considered in the current bilinear flow model of vertical fractures, and then, the effect of trigger pressure gradient on bottom pressure is also not considered, which makes difference between the test analysis result and the actual value. Therefore, a new bilinear flow model for finite conductivity vertical fractures with trigger pressure gradient is set up and the typical curve is drawn by studying the non-Darcy seepage law. Finally, the new solution of bottom pressure is obtained. And the influences of flow conductivity, the effect of wellbore storage, the skin effect, trigger pressure gradient, and the effect of boundary distance on typical curves have been analyzed. The researched results show that trigger pressure gradient has greater effect on the typical curve in the later stage. The higher the trigger pressure gradient is, the faster the boundary responses is and the more upward the curve of the later stage is, which even leads the radial fluid flow to disappear. The case study shows that the presented new model not only uses pressure data of a low-permeability reservoir efficiently and increases the accuracy of well test results, but also provides a reliable reference for the dynamic analysis of field fracture wells.