PMCD Technique Enables Coring & Wireline Logging Operations in Total Lost Circulation

Abstract

After reaching target depth (TD) with Pressurized Mud Cap Drilling (PMCD) technique, risks associated with total lost circulation (including potential gas migration and unsustainable fluid logistics) have led to the perception that wireline logging and coring operations in PMCD are not feasible. However, with proper planning and procedures in place these operations are possible. Recent carbonate drilling operations in offshore Sarawak, Malaysia, have proven coring and wireline logging operations can be completed in PMCD conditions. In the first well, Well S, the operator retrieved core samples from three different zones in a gas bearing carbonate reservoir. The coring operation with PMCD, which was the first of its kind in the Asia Pacific Region, created new frontier for carbonate formation evaluation by allowing the acquisition of rock property data from wells once considered to be impossible to drill to TD. In another well, Well X, PMCD wireline logging operations were conducted safely and successfully. Open hole of 509 m was drilled with PMCD, and upon reaching TD the wireline logging pressure control equipment was rigged up to commence the PMCD wireline logging operation. In addition to the comprehensive planning and execution procedures, the increased riser pressure limitation was a main enabler for the PMCD wireline logging operations. Eight wireline runs were performed, collecting critical data for the field development plan (FDP). The gas water contact for the field was determined accurately despite the total lost circulation. Running wireline logging and coring operations with PMCD allowed the operator to not only drill once perceived impossible-to-drill wells, but also to retrieve crucial and valuable data from the well at TD. These operations reduce field volumetric uncertainty. This paper records the planning, execution, and post well analysis of carbonate sections, including the general methodology for the logging and coring operations in PMCD mode, risk and hazard assessment of the operations, results and observations of successful operations in Malaysia with elaboration of issues encountered, and recommended solutions.

Real-Time Detection of Karstification Hazards While Drilling in Carbonates

“…In PMCD, a sacrificial fluid is pumped through the bit nozzles to fill any fractures and caves, while a heavier fluid is pumped into the annulus to maintain the mud cap and prevent gas migration up to the surface. Today this is the most common practice for drilling in carbonates used by drilling companies [10][11][12][13][14].…”

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.…”