Mud Cap Application Solves Chronic Drilling Problem in a Highly Fractured, Low Pressure Reservoir

摘要

The Cantarell field is located offshore in the Bay of Campeche, in approximately 50 m of water depth (Fig. 1). The two main productive intervals are the Upper Cretaceous and Jurassic Kimmeridgian. The Cretaceous is highly fractured with well developed, vugular secondary porosity. The Jurassic is also fractured with oomoldic porosity. Both contain sour hydrocarbons. Production from Cantarell began in the early 1980s and today the pore pressure gradient is down to a +/- 0.37 gr/cc equivalent. The productive interval is typically drilled using a 0.90 gr/cc emulsion mud and shortly after penetrating the fractured reservoir, total and uncontrollable loss circulation is experienced. As a result, the cost of drilling in the field has increased considerably due to the high cost of the oil-in-water mud losses and time spent either transporting, generating or waiting on weather to offload more mud to continue drilling. Petroleos Mexicanos (PEMEX) in cooperation with Quantum Reservoir Impact (QRI) reevaluated the current drilling philosophy and recommended the application of a series of steps aimed at solving the current problems. The results obtained have been positive resulting in PEMEX now implementing such steps as part of its drilling philosophy where applicable on a regular basis. This paper will describe the current drilling environment and the techniques implemented in the first successful mud cap application in the Cantarell field. It will also discuss some of the lessons learned as well as the new improved designs being implemented and will conclude with a summary of the benefits obtained and the plans for the future.