A Retrospective Review of 10 years of Scale Management in a Deepwater Field: From Capex to Plateau Production

Abstract

Abstract The field in question consists of four reservoirs with varying barium levels (15 ppm to 320 ppm). For pressure support seawater injection has been applied from the start of field life. Prior to field start up, studies were conducted to review the order of expected injection water breakthrough for each well, the location of breakthrough along the length of the production sections, the feasibility of bullhead deployed squeezes and the implications of barium ion stripping. These issues were all assessed to generate a scale management strategy for the field. Despite uncertainties in the original reservoir model, the order of injection water breakthrough across the field was observed to be correct and the information on placement proved very useful in building scale squeeze treatments. The challenge of rapid injection water breakthrough in the field during its early life was addressed with development of pre-production squeeze treatments applied during new well completions. This eliminated the need to shut in wells whilst awaiting mobilisation of DSVs for treatment deployment. As the field matures, tailored scale squeeze treatments were developed for each of the 25 production wells. Over the life of the wells the squeeze designs were updated to take into account changing water rates, changing water composition and thus MIC for the squeeze chemical. The positive contribution of the downhole continual injection chemical was also shown to extend the squeeze lifetimes by allowing a lower MIC value to be used for treatment design in the production section of the wells. Optimisation of the scale management programme has seen wells considered to be outside the scale window eliminated from the squeeze treatment campaigns, reduction in chemical volumes being applied and extended squeeze lifetime for treatments based on monthly review of well performance/water chemistry/inhibitor residuals.