Identification of Downhole Emulsion in a Light Oil Development and Demulsifier Injection for Increasing Production

Abstract

TGT field is located offshore Vietnam, at a water depth of 45m and approximately 100km Southeast of Vung Tau. The field started production in 2011 and is currently producing about 13k bopd. The produced crude is 38-40 deg. API with viscosity of 0.45 cP at reservoir conditions and classified as light oil. The field consists of three wellhead platforms with nearly 40 production wells, all being gas lifted. Emulsion, which is rarely encountered in downhole environment and not reported in the surrounding oil fields, was diagnosed to be present in production tubing of TGT wells by two indications: measured bottom-hole flowing pressure (BHFP) remarkably higher than calculated value, and emulsion observed on surface well fluid samples. Upon completion of the laboratory testing for chemical selection, in early 2020 a field trial was carried out by injecting demulsifier into the production tubing of selected wells via the chemical injection line or together with lift gas. A successful field trial resulted in a clear reduction of BHFP of the wells along with a production increase by approximately 13% from 8 tested wells. Due to the low-cost of the application and major economic gain compared to other IOR methods, long-term downhole demulsifier injection has been applied in additional wells for increasing the field production. Unlike for heavy oil developments, there is a lack of publications on downhole emulsion and demulsification for light oil fields. This paper describes a case study for application in a light oil field, covering identification of the wells having an emulsion issue in the production tubing, laboratory testing for selecting demulsifier, challenges in chemical deployment and the field trial results.