Pore-Pressure and Wellbore-Stability Prediction To Increase Drilling Efficiency

Abstract

Technology Today Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Abstract Pore pressure and wellbore stability pose significant challenges to exploration drilling, particularly in regions featuring weaker rocks or subsalt formations. A lack of accurate pore-pressure prediction and wellbore-stability analysis brings many problems, such as blowouts, kicks, hole washouts, wellbore breakout, and stuck pipe. Wellbore instability also adds to drilling time and increased costs, and sometimes leads to abandoning the well before it reaches its objective. Estimates put the cost of these issues at approximately 10% of total drilling time on average. Ending wellbore-instability problems begins with the ability to predict conditions accurately and to reduce the chance of running into trouble. In this paper, commonly used methods for analyses of pore pressure, in-situ stress, and borehole shear failure are evaluated for their strengths and weaknesses. Examples are provided that demonstrate that the integration of predrill pore-pressure and geomechanics analyses with real-time monitoring consistently provides an effective way to mitigate predrill uncertainties and improve well-construction efficiency.