The Innovative Integration of Wellbore Strengthening and Managed-Pressure Drilling Redraw the Line Between Undrillable and Drillable - Case Study from Offshore Mediterranean Deepwater

Abstract

Managed pressure drilling (MPD) has a reputation for enhancing drilling performance. However, in this study, we use it as a technology for making undrillable wells drillable. In the deepwater of the Mediterranean of Egypt, a gas field has been producing for few years. Water broke through in one well, thus, we must drill a new well to compensate for the reduction in production. Years of production led to pressure depletion, which makes it difficult to drill this well conventionally. In this study, we will discuss the combination of MPD and wellbore strengthening (WS). In addition, we will discuss the challenges we met while drilling and how we tackled them, and the best practices and recommendations for similar applications. The 12¼" × 13½" hole section passed depleted sands, followed by a pressure ramp. First, we drilled the depleted sands and confirmed the pressure ramp top. To strengthen the sand, we spotted a stress-cage pill of 645 bbls with a total concentration of 29 ppb. In addition, we conducted a formation integrity test (FIT), but its value was lower than the required value to drill to the section target depth (TD). Then, we switched to MPD and increased the mud weight. MPD in annular pressure control mode (AP) enabled us to walk the edge as near as possible to the impossible. Drilling this section was challenging due to the narrow mud weight window (MWW). We faced kick-loss cycles, where we had high-gas levels (from 20% to 55%) while drilling with a loss rate from 60 to 255 bph, at the same time. The 8½″ × 9½″ hole section will cover a depleted reservoir. Therefore, we decided to use the MPD to drill this section. To widen the MWW, we decided to stress-caging the hole, as we drill. We loaded the active-mud system with stress-cage materials totaling 39 ppb. We drilled the hole section while keeping the bottom hole pressure (BHP) at 14.6 ppg. We drilled using MPD by maintaining 525-psi surface back pressure (SBP). We used the SBP mode (semi-auto mode) to add connections, resulting in minor background gases and minor losses. This study discusses the application of a novel combination of MPD and WS. It emphasizes how MPD can integrate with other technologies to offer a practical solution to future drilling challenges in deepwater-drilling environments.