Coring Shale Gas Formations with Wireline Coring Technology in a Complex Geological Structure in the Medium Magdalena Valley: A Case History from Colombia

Vivas, Cesar¹; Gray, Mike²; Sierra, Humberto¹; Rodriguez, Sandra³; Tovar, Edward³
¹Halliburton, Bogota, Colombia.
²Halliburton, Aberdeen, United Kingdom.
³Ecopetrol, Bogota, Colombia.

Coring in the Medium Magdalena Valley basin in Colombia has proven to be a major operational challenge because of the highly complex geological structure. The interbedded rock (shale, limestone, and marl) increases the risk of jamming while coring; the rock strength of the La Luna formation increases the difficulty. Historically, the main problems associated with coring operations in the Medium Magdalena Valley basin include premature jamming of the core barrel and poor core recovery. That this is a shale gas well added operational complexities, such as a constant gas inflow that resulted in a challenging tight downhole pressure window.

These issues directly affect the length of the core recovered and the time required for coring operations. Consequently, these challenges reduce the chance of recovering the most valuable core samples, which is the primary goal of the coring operation.

Because the main objective was to core 2,200 ft of a stratigraphic well, the service company was challenged to implement an innovative wireline coring solution. The requirement was to provide a 3-in. core diameter, 50% wider than the conventional 2-in. core diameter, and a fit-for-purpose wireline coring solution was implemented to deliver the core size required.

This paper describes an integrated workflow to successfully implement this wireline coring technology. The workflow includes the orchestration of a multidisciplinary technical team that performed the interdependent processes, including the selection of the core barrel type, core head, mud properties, best practices, and establishing the influence of the design of the bottomhole assembly over the core quality recovered. The successful wireline coring technology implementation proved to be such a success that the operator decided to core 30% (800 ft) more of the initial coring plan. The result was 2,662 ft of core recovered for 91% recovery.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012