Design of Single and Multi-Well Surfactant-Polymer EOR Tests in a Viscous Oil Reservoir





Surfactant-polymer (SP) flooding is a well-established enhanced oil recovery (EOR) technique that has been extensively evaluated in the laboratory and field pilot scales. The efficacy of the SP process is manifested in its ability to combine the mechanisms of surfactant and polymer methods: mobilization of the discontinuous oil ganglia using surfactant and sweep enhancement of the polymer injection. Modeling of these advanced processes, with adequate upscaling from laboratory to pilot scale, is vital for field implementation design and success. The objective of this work is to conduct a thorough design of field SP pilot tests in a highly viscous sandstone reservoir. The design starts from history matching coreflood experiments, followed by an upscaling to a single well test, an interwell tracer test and finally a multi-well SP pilot test.

Using the numerical simulator CMG-STARS, the workflow begins with constructing and matching key physico-chemical parameters from 8 core floods. Then these parameters are used with the reservoir description to simulate single-well chemical tracer test (SWCT), inter-well tracer test (IWTT) and multi-well SP pilot test. A sector model including 5-spot pattern was used in the pilot simulation studies. The design process of the tests entailed conducting several sensitivities pertaining to polymer type, concentration, SP slug size, well rates and injection production ratio (IPR), tracer concentrations and amounts, and pore volumes injected. A successful history match was achieved with coreflood experiments.

The developed surfactant and polymer models were then used in the SWCT, IWTT and SP pilot models. SP slug size and tracer push volume were the key parameters for the interpretation of SWCT. Injected tracer amount was the most fundamental variable in the design of the IWTT. Based on sensitivity results, design parameters were recommended for each test. To provide recovery-maximizing testing strategy for the SP pilot design, optimization of various parameters including IPR, SP slug size, and polymer concentration was used. As a result, an incremental recovery of 22% was achieved. If new information is acquired from field implemented IWTT, it can provide valuable information about the reservoir characteristics that could further augment the SP pilot design.