First Successful Execution of Miscible Gas Injection EOR Pilot in Kuwait: Challenges & Opportunities

Abstract

Abstract A hydrocarbon gas injection pilot was successfully conducted in a heterogeneous multilayered Oolitic carbonate reservoir in Kuwait. The pilot strived towards de-risking technical and commercial feasibility for field-scale deployment of miscible CO2 WAG EOR development. The aim was to generate reliable unambiguous pilot performance results on remaining oil saturation, inflow profile and sweep efficiency to better quantify risks and uncertainties. This paper describes design, execution, and results of this pilot and its challenges and opportunities. The pilot was an inverted four-spot, consisted of a pre-flush water injection phase (2016-19), drilling and coring two fiberglass cased observation wells, followed by a gas injection phase (2021-2022). The phases were carried-out sequentially in three target layers, injecting a range of pore volumes in each layer. The pre-flush surveillance program included Inter-well water tracer test (IWTT), time-lapse saturation logging, coring, PLT/ILT, VIT, PGOR and ESP monitoring of the pilot wells. The gas injection phase surveillance in addition constituted gas tracers, pressure transient data and time-lapse saturation logging in the two observation wells to monitor the gas flood front movement. The immediate impact of this miscible gas injection pilot was the bolstering oil production increase and water-cut reduction in several pilot wells in relatively short pilot duration, persuading the management to high-grade CO2 full-field development as in-plan firm project. An integrated analysis of all the gathered data was conducted, providing an insight on reservoir de-saturation, inflow and sweep for the pre-flush and gas injection phases along with the achieved oil gain, assisting better understanding of the implications for future CO2 Water Alternating Gas (WAG) Enhanced Oil Recovery (EOR) full field pattern development. Detailed integrated static and dynamic modeling of the pilot area were conducted using compositional simulation models, incorporating pre-flush and gas injection phase data, history matched to production, injection, GOR, water-cut, pressure, tracer production concentration and arrival time, ILT/PLT and time-lapse saturation logs. This detailed assessment revealed the impact of heterogeneity including horizontal baffles and barriers on the displacement process. The water and gas tracer analysis provided a unique opportunity to conduct Residence Time Distribution (RTD) analysis to assess, quantify, and compare heterogenous flow patterns and swept volumes for both water and gas transport between well pairs in different reservoir layers. Novel integrated workflow consisting of robust surveillance techniques, reservoir modelling workflows along with tracer analysis techniques were used in this complex heterogeneous multi-layered carbonate reservoir study in understanding pore scale and reservoir scale sweep efficiency and its impact on oil recovery. The immediate increase in oil production in pilot and surrounding wells has provided KOC the much-needed opportunity in designing a road map for commercial deployment of CO2 WAG in this world class field.