Establishing Proper Abandonment and Site Restoration Strategy to Reduce Uncertainty in Developing Mature Offshore Field: A Case Study of ONWJ Field in Indonesia

Abstract

Abstract Abandonment and site restoration (ASR) is one of the responsibilities of Oil and Gas Company for the country where it operates. The ASR covers plug and abandon (P&A) of wells and dismantling of surface equipment in order to restore the environment as close as possible to its original state. Current practices in Indonesia's oil and gas business does not put P&A as one of the top priorities, compared to other engineering aspects in petroleum engineering. Therefore, P&A is sometimes regarded as a formality. A case study where long term oil and gas exploration and production with unique rock mechanics in Offshore North West Java (ONWJ) Area has caused subsidence and inherently leading to both production operation and well integrity issues. Several issues namely casing deformation and detachment from main casing strings have been observed and is likely to put harm to oil and gas production in ONWJ Area. Casing issues such as buckling and crumpling, as well as the presence of micro cracks will present complications in safely plugging and abandoning the affected wells. Recommendations based on current practices around the world as well as mitigation solutions done in ONWJ Area such as mechanical stress and/or strain release combined with well condition evaluation and monitoring is maximized as an input to properly design safe and cost efficient P&A strategy for complex, marginal, and offshore wells with integrity issues. This research is aimed to become a benchmark for future uses of P&A not only in ONWJ area but also in Indonesia.