Abstract

Efficient removal of the drilling fluid from tubulars, screens, and near-wellbore mineral surfaces is essential to the successful completion of wells. Cleaning and removal of the non-aqueous drilling fluid (NADF) from all of the well surfaces is not an easy task. Microemulsion fluids provide a highly-successful solution to this problem.

Carefully designed and customized microemulsion fluids have been used to remediate and increase well productivity and injectivity in wells located in the Gulf of Guinea. Due to their uniform wellbore cleanup, optimum results were achieved in open-hole horizontal and highly-deviated wells. The robust microemulsion fluid systems are capable of accommodating changes in temperature, density, and salinity. They restore the water-wettability of the rock and increase injectivity or productivity of the wells.

Some water injectors and oil producers from the Gulf of Guinea exhibited low injection or production rate. The purpose of pumping the treatment downhole was to improve injectivity by removing skin damage and screen blockage by using in-situ generated microemulsions, thus allowing efficient oil production from the formation or water injection at sustainable high-injection rates into the formation.

Field data shows that injectivity and productivity increased after treatment. In some cases, the downhole pressure decreased for the injectors. Cleanup and removal of the NADF from the Gulf of Guinea wells was beyond the capabilities of conventional treatments. Laboratory tests confirmed that the in-situ microemulsion treatment removes the damage and helps to achieve the desired and predicted injection and production rates. This paper presents field data, before and after the successful microemulsion fluid treatment, and describes various laboratory tests performed prior to the Gulf of Guinea field applications.

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