Well Abandonment and Wellsite Restoration: Case Studies of Well Sites Restored After Oil Production in Onshore Nigeria

Abstract

Abstract Oil and gas production process starts from exploration, to appraisal, to development, and finally to abandonment. Exploration is done on the prospective field to determine presence of hydrocarbon (HC) and if present, an appraisal of the extent and volume of the HC is done. If the quantity of HC is found to be enough, it is developed and produced and after production of the HC reserve, abandonment is done. For the exploratory, appraisal and development processes, wells are drilled, and this drilling involves making holes thousands of feet into the sub soil and the installation of tubulars and other completion accessories to ensure that the hydrocarbon comes to surface with ease and in a safe manner. Wells are abandoned either because it has produced its potential and cannot be used for production anymore, or due to some integrity issues that could only be prevented by abandonment. To abandon a well, the produced/open HC reservoirs are properly isolated to prevent flow into other HC reservoirs or water bearing sands. The installed tubulars and accessories are then retrieved to surface. After abandonment, to further reduce the environmental impact of the oil development, the sites are recommended to be fully restored to the pre-development state as much as possible. This paper details the technical abandonment activities carried out for five wells that have produced for several years in onshore Nigeria. The paper also explains the site restoration activities and shows the various well site restoration stages including the re-vegetation of some of the well sites.