Abandoned Exploration and Appraisal Wells Turned into Long-Term Monitoring Wells for Enhanced Far-Field Reservoir Characterization: Lessons Learned from a Frontier Deepwater Installation

Abstract

Abstract This paper discusses benefits, caveats, and lessons learned of wireless pressure monitoring systems in abandoned exploration and appraisal wells to gain insight into reservoir properties that extend beyond the scope of standard well testing. Appraising large offshore deepwater discoveries requires drilling and evaluating several wells across a field to increase subsurface understanding and reduce development uncertainties. The recent technological advancement of wireless pressure monitoring systems, which utilize electromagnetic telemetry, has enabled operators to capitalize on previously untapped value from exploration and appraisal wells by turning them into long-term observation wells, without compromising abandonment compliance. Even if not tested, these penetrations can provide valuable dynamic data for enhanced reservoir characterization early in the appraisal life cycle and at little incremental cost. Such a system was installed in a deepwater well in Cyprus to further understand potential compartmentalization risks. A nearby well test, executed 3 years after system installation, was successfully monitored by the abandoned penetration. The interference test helped shed light on far-field connectivity, inter-well reservoir properties, and connected volume. This information will improve the fidelity of the geological and reservoir simulation models utilized to inform depletion planning and support field development and commercial decisions. This paper presents novel findings to help ensure data quality and representativeness from such systems, focusing on the overprint of the wellbore environment on the reservoir signal. Specifically, the deployment in a cased wellbore left with drilling fluid revealed lengthier and more complex swap-out dynamics with reservoir fluid than anticipated. As with most new technologies, subsequent installations benefited from these valuable lessons learned, resulting in more robust and reliable implementation practices.