A Comparative Study of Real-Time Pore Pressure Gradient Determination by Various Methods (A Case Study)

Determining formation or pore pressure gradient is crucial during drilling, particularly in locations where abnormally high pore pressure can cause major issues including well kicks, fluid inflow, and blowouts. Currently two main methods are utilized to obtain a direct measurement of formation pressure in hydrocarbon zones: drill stem test and repeated formation test; however, these measurements are difficult to get due to the high expenses associated with employing such equipment; therefore, other alternative approaches available in the literature are taking place. A new approach is proposed to estimate the pore pressure from drilling parameters that uses the concept of the mechanical specific energy (MSP). A case study was investigated on a deep exploration well (West Qurna-15) in south of Iraq, where the pore pressure gradient was estimated by various traditional techniques including dc-exponent, resistivity log, and transit time log. The results were compared with the pore pressure gradient being determined from the new developed method based on (MSP) as well as with the actual in situ formation pressure using two statistical approaches (mean absolute error (E) and coefficient of determination (R²). The obtained (E) results were (7.998%), (7.129%), and (3.354%) for dc-exponent, transit time, and (MSP) respectively as shown in Table 2, while (R²) values were (0.71), (0.8259), and (0.9608) for dc-exponent, sonic time, and (MSP), respectively, where a preference of the new method over the rest is shown. The new proposed method could be useful to get a quick indication and speculation of pore pressure gradient, especially when planning to drill a new well adjacent to the well-being investigated by the suggested technique.