Pore pressure prediction using combination drilling efficiency and hydro-mechanical specific energy methods

Abstract

Several methods of pore pressure prediction using drilling parameters were introduced and improved to meet the challenges of accurate prediction at a relatively low cost. Knowledge of pore pressure is essential for safe well planning, cost-effective drilling, and operational decision-making. Conventional methods in pore pressure prediction using drilling parameters have limitations on its application of making the normal compaction trendline that is only applicable in clean shale intervals. In this work, the concept of drilling efficiency (DE) and hydro-mechanical specific energy (HMSE) for predicting formation pore pressure is proposed. This method, termed DE-HMSE, is based on the theory that the energy required to break the rock with the bit is a function of in-situ rock’s conditions during drilling. HMSE is the amount of axial, torsional, and hydraulic energy required to break and remove a unit volume of rock, and DE is defined as the ratio of the rock’s confined compressive strength (CCS) to the HMSE. The pore pressure prediction using DE-HMSE method is performed in two wells in Australia and three wells in Thailand. The results are compared to the actual measured pressure in the field and pore pressure prediction from conventional methods such as d-exponent, MSE, HMSE, and DEMSE methods. The results show that all the methods have inaccurate predictions of pore pressure in the depleted zone. However, the DE-HMSE method has the smallest root mean square (RMS) error and better agreement with the measured formation pore pressure compared to the other conventional methods.