Schlumberger

Technical Paper: ECD Management and Pore Pressure Determination with MPD Improves Efficiency in GOM Well

Society: IADC
Paper Number: 140289
Presentation Date: 2011
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Abstract

In early 2010 Stone Energy Corporation restarted development of the Amberjack field in the Gulf of Mexico in which the last two sidetrack wells were drilled eight to ten years ago under difficult circumstances that included depletion, reduced fracture gradient, wellbore instability, and high, unmanageable ECD. With no way to reduce the ECD and maintain a constant BHP in the small margin between fracture gradient and pore pressure it was next to impossible to prevent annular loading and pack-off, stuck pipe, gas influx, and heavy losses. 

Determined to avoid that trouble in their Amberjack redevelopment campaign, Stone employed automated MPD technology in their first slot recovery well, the A-12 ST1 Ibix well.  In the 1800 feet of 8 1/2-in hole that was drilled with MPD, Stone was able to manage the BHP in windows ranging from ± 0.16 ppg while drilling, ± 0.12 ppg while tripping, and ± 0.05 ppg while rolling over the mud from 14.8 to 15.0 ppg.

Given the uncertainty surrounding the pore pressure in their target sand, it was particularly useful for Stone to be able to use the MPD system to confirm the pore pressure at a critical point in the well. After drilling the designated "P-sand", Stone used the MPD system to stage down the BHP in a controlled manner and watch for early signs of influx. Starting at 15.0 ppg the BHP EMW was staged down to 14.65 ppg at which point the system detected a small amount influx indicating the BHP was at or below the "P-sand" pore pressure. Total influx volume was limited to 2.5 bbl and shut-in-casing-pressure was limited to 150psi.

Using MPD Stone was able to avoid the trouble encountered in the four offset wells which cost the previous operator of the field one lost sidetrack and a month of total non-productive time. Over the course of the first two recovery wells, Stone managed constant BHP during 26 connections, mud roll-over operations, and trips in and out of the wells.

Controlling the BHP and ECD with automated MPD allowed Stone Energy to reach their planned targets in significantly less time than previously possible and avoid the wellbore instability and well control events that occurred frequently in previously drilled offset wells.

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