Successful Implementation of an EOR Field-Trial Using Surfactant Induced Wettability: Formulation Design, Implementation & Interpretation and Key Lessons Learned

Abstract

Abstract Wettability Alteration from oil-wet to water-wet condition is a very promising EOR technique for producing significant incremental oil recovery from oil-wet tight pores. A thorough lab program led to development of a wettability altering surfactant formulation and was validated via various laboratory Coreflood tests. Wettability Alteration (WA) as an Enhanced Oil Recovery (EOR) technique was implemented in an offshore carbonate reservoir. The field implementation was done in a systematic step wise manner to mitigate the risk in implementing such a technology field wide. An optimal surfactant formulation is developed on the basis of favorable phase behavior at reservoir conditions, the ability to alter wettability to a more water-wet state and cause minimal chemical losses on reservoir minerals in the form of adsorption. Surfactant formulations designed in this work are unique and provide high temperature stability (above 70 °C and in some cases up to 120 °C) and high salinity tolerance (> 12 % TDS and up to 22% TDS in some low temperature cases). Reservoir modelling, logistical challenges, Environmental Health & Safety (EH&S) considerations, field applicability, and cost implications were considered for determining the optimum solution to help de-risk field scale implementation. A long term surfactant injection pilot was then conducted to evaluate efficacy of developed solution at field scale. This paper presents a phased approach to scale up an EOR project in a highly complex offshore carbonate field. Post surfactant injection, a rigorous Monitoring and Surveillance program was put in place to carefully monitor production data and quantify incremental oil gains. The pilot demonstrates the value of a phased approach to implement and monitor EOR project in an offshore carbonate field. Injection-Production data analysis shows no adverse effects at injector and significant volumes of incremental oil produced making the trial a technical as well as economic success.