Lost circulation is one of the most costly drilling issues and a major contributor of non-productive time. Wellbore strengthening has been successfully applied to reduce the associated cost and increased the wellbore stability in the industry over the past two decades. It is of critical importance to accurately predict the extra drilling mud weight after wellbore strengthening. However, previous research assumed fixed boundary conditions and only considered the stress intensity factor in the calculation of fracture reopening pressure (FROP). The change of pressure boundary on the fracture surfaces was ignored, which may overestimate the FROP. This paper employed a dislocation-based fracture model to determine the FROP in wellbore strengthening. The proposed model is compared with finite element simulation. An excellent match is obtained for the fracture profile and a clear inflection point can be observed between the plugged zone and unplugged zone. We present how wellbore pressure can change the pressure boundary in the model. Thus, the FROP calculation should be modified with the consideration of fracture plug width. Results show that the fracture plugged zone pressure can affect the fracture profile. Specifically, lower fracture plugged zone pressure results in higher FROP. Thus, better wellbore strengthening can be achieved in the depleted sections during drilling. On the other hand, the fracture plug width plays an important role in determining FROP. With a fixed fracture plug location, larger fracture plug width can lead to higher FROP. However, there exists a critical fracture plug width for the maximum FROP, which is the value predicted by the previous research. The study reveals the importance of fracture plugged zone pressure and fracture plug width for FROP in wellbore strengthening. The model is useful for the design of wellbore strengthening materials (WSM), which are critical to achieve the best wellbore strengthening effects.
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