Schlumberger

Performance Report: Overcoming a Challenging Narrow Operating Window and Successful Implementation of Automated Managed Pressure Drilling (MPD) & Managed Pressure Cementing (MPC) Offshore Malaysia

Date: 9/18/2013

Revisit of an abandoned well

The original well was one of several over-pressured wells in the project. Although this well was drilled during the field development stage, it also carried the exploratory mission. It was also the first well to penetrate the over-pressured zones across the fault in the field. In the first attempt to reach well TD, the drilling team encountered a steep pressure ramp after drilling through the fault. The 7” liner was set to isolate the fault. While drilling the subsequent 6” hole section, a major coal layer was encountered after only 23 m of drilling. This coal layer lowered the fracture gradient from 19.0 ppg to 18.3 ppg and also caused a severe ballooning/supercharging effect. In addition,the formation pressure in the previous sand indicated a pressure of 16.72 ppg equivalent. Given the narrow pressure window of 1.58 ppg and indications of a pressure ramp, the decision was made to stop drilling and suspend the well until a suitable solution could be found.

Automated Managed Pressure Drilling Strategy

Detailed data analysis and program planning were conducted based on the expected well behavior as learned from the original well. The plan was to re-drill the 6” hole using static underbalanced mud weight with the application of MPD during drilling as well as during the liner running and cementing operations. Application of MPD allowed for better control of the bottom hole pressures given the very narrow pressure window by accurately controlling the amount of surface back pressure applied during dynamic as well as static conditions.

Biggest static underbalanced Cementing job - MPC

In order to maintain the BHP within the operating window during the cementing job, it was necessary to displace the well to a mud weight that was 1.5 ppg below the pore pressure (600 psi) and application of scheduled surface back pressure during the entire operation. The use of the MPD system also made liner rotation be feasible. The Operator was quite satisfied since this was the first time during the campaign that the plugs bumped and cement at the top of the liner was observed.

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