Successful PMCD Application Significantly Improved Drilling Efficiency on Carbonate Drilling

Abstract

Two offset wells were drilled in a field in East Malaysia, the original well and a sidetrack from the original well. Both wells experienced total lost circulation and Pressurized Mud Cap Drilling (PMCD) was attempted, but was not successful. A total of 55 days were spent drilling both offset wells, without achieving the primary well objectives. After a 4-year gap, a re-drill well was planned and a specialist PMCD service provider was approached to drill the well. The PMCD team worked closely with the Operator's drilling team through the early stages of planning including well design, completions, fluids, logistics, BHA design, mud pit arrangements and drilling procedures. The lessons learnt from the previous wells were analyzed and precautionary steps were taken to avoid similar mistakes in the planned re-drill well. Field proven PMCD operational procedures were provided and experienced field personnel were assigned for on-site execution. The re-drill well hit total losses and was converted to PMCD after evaluating the characteristics of the well. The section was drilled to the planned Total Depth (TD) in one run, a section length of 430m. A Composite Bridge Plug (CBP) was stripped in hole and set in the previous casing to isolate the carbonate section. The 7″ liner was made up with a drill shoe and run in hole, and the CBP was drilled out. The well went back on losses after drilling the CBP and PMCD mode was re-established and the 7″ liner was stripped in to TD. The liner was then set and cemented at the shoe. The well primary objectives were achieved successfully. This paper elaborates on the planning, drilling and completion phases of a successful PMCD operation, with relevant lessons learned and recommendations for future solutions.

Automated Pattern Recognition in Real-Time Drilling Data for Early Karst Detection

“…Mitigation of these problems by adding Lost Circlation Material (LCM) may give only a short-term effect and cannot help when big karsts need to be plugged [12]. The use of Pressurized Mud Cap Drilling (PMCD), when a sacrificial fluid is pumped through the bit nozzles to fill karsts, is today the most common solution to dealing with total losses in carbonates [13][14][15]. However, rigs are not always equipped with a Rotational Control De-vice (RCD) [16] required for PMCD and a significant volume of sacrificial drilling fluid may not be readily available.…”

Prediction and Early Detection of Karsts—An Overview of Methods and Technologies for Safer Drilling in Carbonates

“…In this case, the well is converted for pressurized mud cap drilling (PMCD) and drilling can be continued with the controllable pumping of sacrificial fluid and drilling cuttings into caves, fractures and other highly permeable zones. The efficiency of this approach was demonstrated by a number of wells drilled in carbonates [15][16][17][18]. However, MPDbased solutions for drilling risk minimization have limitations.…”