Experimental study of small-sized polymeric microgel (SPM) in low- or median-permeability reservoirs

Polymeric Microgel has been applied to reservoirs with varied permeability ranging from 10 to 1000 mD for mobility-control and/or conformance control. For a successful microgel treatment, the microgel particle size must be compatible with the reservoir pore-throat size to ensure effective in-depth transportation. Given such a situation, Small-sized Polymer Microgel (SPM) was developed for microgel treatment in low- and medium-permeability reservoirs. This paper presents an experimental study regarding the applicability of SPM in the low- (<100 mD) or median-permeability (100-300 mD) conditions. The experimental study involved pore-throat size determination, initial particle size distribution, swelling ratio measurements, resistance factor and residual resistance factor measurements, oil displacement experiments, and a pilot test conducted in ZT-21 producing zone located in Pubei Block 7. The result shows SPM has a good compatibility with the reservoir pore-throat size. SPM swells in water, ending up a ultimate swelling ratio of 4.8. During resistance factor and residual resistance factor measurements, SPM solution is effective at reservoir permeability of above 130 mD. That was saying, SPM is recommended to be applied in low- but not median-permeability reservoirs. In the oil displacement test, SPM improved the oil recovery through both SPM injection and post water injection at the core permeability of 95 mD, revealing SPM is available for conformance control purposes. In the pilot test, oil production improved in SPM injection and post water injection stages are 2.1 and 5.2%, respectively. The development of SPM can be contributive to oil and gas industry as it provide a guaranteed material for low-permeability reservoir microgel treatment.