Petroleum Drilling Techniques, Issue 4, 2018

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The Influence of Dynamic Deformation of Formation Fractures on the Plugging

Abstract

The pressure fluctuation of wellbore during drilling can easily lead to dynamic deformation of formation fractures and affect the plugging effect. In order to solve the problem, the characteristics of fracture closure deformation has been simulated and analyzed. It evaluated the influence of fracture dynamic deformation on leakage plugging by indoor simulation test. The simulation found that fracture closure could be divided into the three stages, i. e. the initial stage, the local deformation stage and the final stage. With the increase of the contact stress on the closed surface of the fracture, the relationship between the contact area and the displacement is a power function. In the case of fracture dynamic deformation, leakage plugging with a non-elastic plugging agent will result in repeated leakage, but the elastic plugging agent can work in a stable manner, and leakage will no longer occur. The research results showed that fracture deformation would damage the sealing layer, and the larger the degree of fracture deformation, the the more intense the damage on the sealing layer. Thus, the elastic plugging agent could better adapt to fracture deformation. Therefore, it is recommended to add elastic plugging agent at certain proportion into the slurry for plugging the fractured formation. In the follow-up plugging operations, the pressure fluctuation of wellbore should be reduced as far as possible, so as to minimize the adverse impacts caused by the dynamic deformation of fractures.