Laboratory Evaluation of Reversibility Feature of Physico-Chemical Water Shut-Off Agent for Enhanced Gas Recovery

Abstract

Abstract A paper presents laboratory research conducted to evaluate technological properties of the nanoparticle-induced water shut-off agent and to assess its potential for gas recovery enhancement in geo-physically complicated reservoir conditions. The studied water shut-off agent is an inverse emulsion generated through the synergy of physico-chemical reactions between natural and artificial surfactants with silicon dioxide nanoparticles (NPs). Ultra-hydrophobicity and stability of the nanoparticle-based emulsion (nano-emulsion) conveys game-changing technological properties, resulting in a high performance of the water shut-off agent. Introduced in this paper research program was specifically developed to meet an inquiry of gas-condensate fields operator for an efficient physico-chemical or chemical water shut-off technology with zero secondary damage to reservoir. Therefore, the research program aimed to evaluate technological properties of the emulsion system with nanoparticles (ESN) in the tight sandstone formation conditions 8990 psi and 230°F. Firstly, rheometric study and tests in an autoclave were conducted to measure rheology, stability, compatibility and floating property of the ESN water shut-off agent under heavier polymer-clay fluid. Secondly, core flooding tests were conducted on four sets of natural low-permeable sandstone core columns to assess reversibility feature of the ESN water shut-off agent and a threshold pressure of the gas-condensate breakthrough. Rheology of the investigated water shut-off agent characterized by the share thinning behavior, i.e., viscosity drops under rise of the share rate and the other way around. The pseudoplastic behavior of the ESN perfectly suits applications in gas wells because it improves processes of preparing and pumping the water shut-off fluid downhole, does not float under heavier process fluids and self-controllable in-situ. It was learned that the ESN is compatible with reservoir and process fluids, and stable at reservoir conditions 230°F and 8990 psi. The ESN's blockage reversibility feature was confirmed in core floods. Overall, the research results confirmed innovative properties of the ESN water shut-off technology with its wide-range compatibility and high stability properties.