The Maximum Measured Depth of Extended-Reach Well Based on Mud Weight Window for Different Drilling Operating Conditions in Horizontal Drilling

摘要

During the process of horizontal extended-reach drilling (ERD), there are many different drilling operating conditions, including drilling with mud circulation, tripping in and tripping out, etc. In any operating condition, the too large or too small borehole pressure will pose a huge threat to the wellbore stability. Predicting the well’s maximum measured depth (MMD) for only one drilling operation condition is not necessarily a guarantee for the safety of all drilling operations. It is necessary to predict the MMD for all drilling operations. In this study, considering ten different drilling operating conditions, a prediction model of horizontal ERW’s MMD is established based on the dynamic pressure balance of bottom hole, and the predicted MMD mainly depends on annular pressure losses and the mud weight window (MWW). Furthermore, the effects of the model’s parameters on these MMDs are also analyzed. The study shows some MMDs are related to the fracture pressure, namely the upper limit of MWW; while other MMDs are dependent on the collapse pressure, namely the lower limit of MWW. The minimum of these MMDs can be taken as the final MMD of the horizontal ERW. This work provides a practical tool for predicting the MMD of horizontal ERW and also provides theoretical guidance for ensuring the safety of all drilling operations.