Surfactant flooding in waxy oil reservoir in Tanjung field, Indonesia: a case study of successful small-scaled field implementation

A small-scale surfactant flooding pilot test was conducted at the Tanjung Field, Indonesia, targeting Zone A reservoir due to its significant remaining oil potential. An Alkyl Ethoxy Carboxylate surfactant was formulated and optimized for Tanjung Field oil and brine characteristics, achieving an ultralow interfacial tension of 0.042 mN/m, compared to an initial oil-brine IFT of 18.3 mN/m. The formulation demonstrated that the interfacial tension remained stable for a thermal stability test at 63 °C for three months. Coreflooding experiments using native core samples confirmed an incremental oil recovery of 25% following a 0.2 PV surfactant slug injection at 2.0 wt% concentration. For the field test, an injector-producer pair with good connectivity and close proximity was selected to ensure rapid response and cost efficiency. The surfactant was injected continuously for four days beginning January 19, 2016, followed by water injection, with production monitored until March 2017. Targeting an effective reservoir pore volume of 10,625 bbl, the test achieved a threefold increase in oil production rate and a total cumulative oil gain of 7,025 bbl at a total cost of only USD 61,812, including chemical and operational expenses.