Wireline Logging Operation Uses Water-Based Drilling Fluid in HP/HT Gulf of Mexico Well

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210021, “Wireline Logging in High-Overbalance, High-Pressure/High-Temperature Deepwater Gulf of Mexico Well With Water-Based Reservoir Drilling Fluid,” by Martin Tjioe, Jeremy McCaslin, and Jonathan J. Brege, SPE, Shell, et al. The paper has not been peer reviewed. _ Openhole wireline logging, because of its lower overpull capacity relative to logging while drilling, is subject to increased stuck-tool risk. The risk increases in higher-overbalance environments typical for depleted reservoirs, but other aspects of sticking risk can be managed. The complete paper describes the measures taken in an openhole wireline-logging operation in a deepwater Gulf of Mexico (GOM) well under nearly 7,000-psi overbalance in a high-pressure/high-temperature (HP/HT) slimhole environment using water-based reservoir drilling fluid (RDF) to achieve an efficient logging operation without incurring lost time attributed to conveyance-related issues. Introduction The wireline data-acquisition program was planned for an injector well in the deepwater GOM development field. The goal of the well was to maintain reservoir pressure through waterflooding, maximize recovery, and appraise the downdip portion of the fault block. The target was an aeolian sandstone reservoir at a depth of approximately 25,500 ft total vertical depth subsea featuring 19% porosity and permeability in the tens-of-millidarcy range. The reservoir had depletion of 6,850 psi; the well penetrated 174 ft of the reservoir with a hole size of 7 in. and a deviation of 25°. The injector used an openhole stand-alone-screen completion concept. Water-based RDF was used so that filter-cake material could be removed using a breaker fluid to enable matrix injection. Using a 13.5-lbm/gal mud weight, the wireline operation was performed under a downhole pressure of 17,900 psi (overbalance of 6,950 psi). The maximum temperature recorded during wireline was 320°F. Wireline Data-Acquisition Program The wireline program’s objectives were to acquire safely a profile of pressures and mobilities to identify depletion boundaries and to inform completion operations and acquire temperature data to infer the static formation temperature. During the planning phase, the well was classified as highly challenging, with a high risk of differential sticking based on the analog wireline jobs in the field. The well of interest penetrated the reservoir with the highest depletion encountered in the field at the time; because of its downdip location, it also had one of the higher downhole temperatures in the field. Several learnings from analog wells that are further detailed in the complete paper included the following: - Necessity of good hole cleaning - Reduction of toolstring length - Necessity of a water-based RDF with good fluid properties