Automated Managed-Pressure Drilling Helps Find Reserves Near Failed Exploration Well
Authors: Wilson Adam 
Published: February 2015

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 151518, ’Automated Managed-Pressure Drilling Allows Identification of New Reserves in an HP/HT Exploration Well in SB Field, Offshore Malaysia,’ by Zulkarnain Ismail, Intan Azian Bt. A. Aziz, Lawrence Umar, SPE, Noor Azree B. Nordin, SPE, and Thanavathy Patma Nesan, Petronas, and Freddy Rojas Rodriguez, Fernando Gallo Zapata, Greg Garcia, Ahmed Waguih, SPE, Bramanta Subroto, and Blaine Dow, SPE, Schlumberger, prepared for the 2012 SPE/IADC Drilling Conference and Exhibition, San Diego, California, 6-8 March. The paper has not been peer reviewed.

The SB field in Block PM on the west side of the Malay basin, Malaysia, is notorious for its steeply rising pressure ramp, narrow drilling operation window, and interbedded sand, coal, and shale formations. Well SBD-2 was the second attempt to reach and cross the F and H sands of this basin. Despite using managed-pressure drilling (MPD), the first attempt failed when an influx exceeded the fracture gradient, resulting in total fluid losses. Because of the shallow pressure ramp and narrow window between pore pressure and fracture gradient, a repeat attempt was initially deemed undrillable. However, the design team felt the target could be reached using automated MPD.

Introduction

The SB field is considered a very challenging area because the pressure and temperature in the depositional environment are abnormally higher than in neighboring fields. Some of the key challenges with this high-pressure/high-temperature (HP/HT) environment are reduced kick tolerance, narrow drilling window between pore pressure and fracture gradient, higher drilling-fluid densities, temperature limitation on formation-evaluation bottomhole-assembly components that limits data acquisition, wellbore ballooning and breathing, and number of personnel with HP/HT drilling experience.

The original well, SBD-1, was only 50 meters away from Well SBD-2. Despite using MPD, the first attempt failed when an influx exceeded kick tolerance and compromised the fracture gradient, resulting in total fluid losses. The failed well cost more than USD 30 million and reached only the F sand, 200 m shy of the geologic target. The offset data gathered from that well helped with the planning of SBD-2 down to X240 m.

The full capabilities of an automated MPD system were applied to mitigate drilling risk. The MPD system was used for early kick detection (EKD), dynamic formation-integrity tests (FITs), dynamic flow checks, and constant-bottomhole-pressure (CBHP) control. With a mud-weight window of less than 0.9 ppg, the system was required to detect and control kicks, identify and control ballooning effects, and maintain the bottomhole pressure (BHP) within the tight high-pressure window.

In total, three sections were drilled with the automated MPD system. The 8½×14¾-in. section required minimum overbalance to manage wellbore breathing and to control potential losses to weaker horizons. In the 10½×12¼-in. section, the system was used to identify and react quickly to kicks in high-pressure sands and also to eliminate wellbore breathing and ballooning. In the final section (8½×9½ in.), the objective was to maintain overbalance in the narrow pressure window between pore pressure and fracture gradient.