Selective and Reversible Water Shut-Off Technology Based on Emulsion System with Nanoparticles for Low to High Permeabilities Carbonate Reservoirs at HTHS Condition

Abstract This paper presents the evaluation results of Emulsion System with Nanoparticles (ESN) as a water shut-off (WSO) agent. The ESN has unique advantages to overcome crucial hurdles in the existing polymer and gel materials; thermal stability in higher temperature, low sensitivity to mineralization, pseudoplastic characteristic, selectivity of blocking effects for water zone only, and reversibility of blocking effect. The surface modified silica (SiO2) nanoparticles work to reinforce the emulsion stability. The ESN make-up is convenient and quicker by utilizing the on-site oilfield materials such as crude oil and injection water. From the aspect of compatibility to reservoir, the majority of on-site material, mixed with small amount of nanoparticles-based surfactant, never causes any problem. To evaluate the ESN performance for UAE's carbonate reservoirs in high temperature and high salinity (HTHS: 130 °C and 240,000 ppm TDS) condition, physicochemical analysis and core flood tests were performed. The ESN, which was confirmed stable at the HTHS condition, achieved 1-2 orders permeability reductions for intermediate and high Swi cases of the core flood tests using intermediate-high permeability carbonate cores (50-570 mD) while no impact on the low Swi case. The relative permeability analysis confirmed the ESN reversibility by unblocking. Through comparative analysis by incorporating the previous laboratory works using tight cores (10 mD), all the test results proved the technological potentials of ESN successful application in the UAE's oil fields.