Changes of Operating Procedures and Chemical Application of A Mature Deepwater Tie-back – Aspen Field Case Study

摘要

The Aspen field is located in about 3050 ft water in the Gulf of Mexico on GC243 block and tied back to Bullwinklernproduction facilities on GC65 block via dual 16-mile wet-insulated pipelines. Its first production began in December 2002.rnThe project was a fast-track, marginal field with an assumption of quick reservoir pressure decline. Hydrate is managedrnprimarily by MeOH injection during startup and shutdowns. The reservoir fluids are complex. Downhole sample testsrnshowed asphaltene onset pressure was 6500 psig (~500 psi above bubble point). An asphaltene inhibitor was continuouslyrninjected downhole as well as scale inhibitor since the field was suspected with scale and asphaltene issues in the earlierrnproduction life. The produced water has a total dissolved salt of 230,000 mg/l. The oil production has declined significantlyrnfrom initial production while the water cut reaches up to 80%.rnThe characteristics of field production have been changed significantly since the initial production date. A review wasrnconducted by flow assurance team working with its chemical supplier. During the study period a large amount of fluid testsrnwere conducted and chemical application program were reviewed by chemical supplier’s experts along with the operator’srnengineering team. Planning to field execution took more than one year, resulting in termination of downhole injection ofrnasphaltene inhibitor and scale inhibitor. Additionally there was a reduction in methanol usage and other topside chemicals,rnand the operating guidelines were revised. The financial benefits include cost reduction, as well as quicker startup andrnshutdown.rnThis paper will present the methodologies, organization, tests, recommendations, field execution plan and results afterrnimplementation of the recommendations. The case study also demonstrates how the operation team and engineering supportrnteam of an operator can work with suppliers, utilizing the industry experience, to achieve best results.