Abstract
One of the major challenges envisaged in the application of WAG in multilayered reservoir with large thickness is poor conformance of injectants. Critical premises in the success of any enhanced oil recovery flooding operation is that mobile oil volume should be increased and this increased volume is contacted by driving fluids to enable it to be produced from the producers. This oil volume should not be by-passed by the EOR injectant fluid. Another important aspect is that driving fluids and fluid front of mobilized oil needs to flow more or less equally throughout the reservoir. This happens when reservoir conformance is well addressed. Therefore, controlling the flood front in WAG injection is a major challenge in the success of immiscible WAG injection.
This paper presents laboratory research, lab and pilot design modeling study for developing the suitability of foam for a challenging reservoir. Foam was generated by simultaneous injection of CO2 rich injection gas with selected surfactant formulation initially saturated with surfactant. Effect of series of injection rates were investigated as main parameters for foam propagation and stability under field condition. It was observed that mobility reduction factor (MRF) increases with increasing flow rates and stabilized when the flow rates were decreased.
The effects of multiple injections at fixed flow rates and from low to high rates through Surfactant Alternating Gas (SAG) were compared. SAG at low rates not adequate in generating strong foam thus produced very low MRF. SAG at multiple small slugs from low to high rates generated high MRF caused by frequent contact and mixing between surfactant and gas. Co injection and multiple injection through SAG indicated moderate MRF are obtained at high flow rates as in the near wellbore area and high MRF ensuring good mobility control and sweep efficiency when foam propagates within the reservoir.
