Advanced Surfactant-Polymer EOR Pilot in Algyő Field, Hungary; Experiences and Lessons Learned

Extensive R&D activity provided reliable basis for testing a reservoir-specific surfactant-polymer mixture as EOR flooding pilot performed in the largest multi-layered (stacked) hydrocarbon occurrence at the Algyö field. The target formation was a sandstone reservoir with 70 mD permeability on average bearing low viscosity oil (0.64 cP at 98 °C and 190 bar).

The injected SP solution contained a specific surfactant blend developed by MOL and his Hungarian university partners, and a mobility controlling agent was a commercial copolymer of acrylamide and ATBS. For the preparation of the SP solution, after additional filtration, formation water was used at the site. During the pilot period, altogether 1/3 pore volume of SP solution was injected into the reservoir.

The surfactant/polymer solution was injected into two injection wells starting from April 2016 and was intended to finish in 2019, after 45 months of continuous injection period. The injection was started with 100 m3/day/well flow rate of chemical mixture, containing 15,000 ppm surfactant and 1,000 ppm polymer driven into the reservoir using injection well head pressure of 0 bar. Most important parameters and effects of the pilot were continuously recorded and evaluating the reservoir response as a function of the injected volume including both injection and production wells (seven oil wells were operating around the two injection wells). It should be noted that due to the high heterogeneity of the reservoir, a fine tuning of the injection plan supported the technology through the whole frame of the pilot. The successful upscaling of the surfactant manufacturing and the easily available raw materials provided a problem-free supply of surfactant with standard quality. Various laboratory measurements were performed to control the polymer and surfactant concentration as well as the rheological and interfacial properties of injected SP solution. In addition one of the main advantage of the EOR method was that the produced emulsion could be easily broken into bulk fluids.

This paper summarizes the workflow and results of the pilot performed in the past four years. The results of this pilot provided reliable information and adequate basis to start a new project of similar field-scale chemical EOR technology for other blocks, hoping that it will further increase the recovery factor in the Algyö-2 reservoir and yielding substantial incremental oil production in matured, depleted fields in the coming years.