The Effect of Hole Curvature on the Wellbore Pressure Loss Prediction for Highly Tortuous Ultradeep Wells

Abstract

AbstractDrilling operations in deep and ultra-deep water are increasing around the world. The development of these substantial prospects is very challenging and requires the integration of knowledge with prudent designs at different stages of the well development. However, the cost premium imposed by deep and ultra deepwater wells are higher and many of the discoveries are marginal in terms of the commercial viability. With the increase of developing and operating costs, there is a growing need to reduce the cost of drilling and other allied operations. The hydraulic program for the deep wells constitutes a significant portion of the well planning. Challenges associated with extreme depth, pressures and temperatures translate to additional problems to the well design. As the wells are drilled deeper and deeper, accurate prediction of the wellbore pressures are increasingly important. Also, more wells are drilled in rotary steerable mode. Alternating between the sliding and rotary modes results in hole spiraling and wellbore oscillation becomes more pronounced due to frequent slide drilling. The estimation of pressures during drilling are indispensable for making appropriate well completion decisions. The prediction of wellbore pressures and downhole equivalent circulating density are of critical importance in wells where the pressure must be maintained within narrow limits of pore and fracture pressures.This paper presents a study on how to adapt to the new wellbore hole spiraling effects encountered in ultra deep wells. This paper examines some of these effects, while asserting that it is necessary to integrate this new approach, so that more accurate solutions can be predicted as a result. This new hydraulic design encapsulating hole spiraling effects provides a simple, practical way to view the severity of the wellbore oscillation.