Summary Advances in improved oil recovery methods over the years have allowed many fields to exist beyond their originally planned lifetime, determined at the plan for development and operation stage. However, the majority of the wells in these mature fields are designed to last only for the planned life of the field. In addition, because drilling new wells requires high capital expenditure, the option of extending the life of existing wells to prolong production at minimal drilling expenditure has garnered interest. Well life extension (LE) can allow for repurposing wells not only from producers to injectors but for other emerging technologies, such as carbon dioxide (CO2) injection in carbon capture and storage (CCS) and for geothermal energy production. For safe operations, well integrity should be the major consideration in well LE and repurposing decisions. Casing is a vital well barrier component in ensuring well integrity during the LE period. In this work, we first present a multidimensional Wiener process methodology to predict the remaining useful life (RUL) of the entire casing string, taking into consideration changes in operating conditions (OCs), such as well integrity incidents and maintenance actions, as these ultimately determine the casing degradation rate. The methodology is especially useful for assessing and predicting well integrity of legacy wells, from which data and records are usually limited, and we cannot apply data-driven models with confidence. In the second part, we show how RUL analysis can be used for well LE decisions considering casing load analysis for different future OCs and purposes. In a case study, we apply these methodologies on a legacy injection well using a casing corrosion log. The well had experienced a tubing leak that led to corrosion inside the production casing. The results show that the well has LE potential but only under timely repair and specific temperature-dependent OCs for CO2 injection with casing collapse as the high-risk failure mode.
Semwogerere et al. (Sun,) studied this question.