Interaction of anionic surfactant-nanoparticles for gas - Wettability alteration of sandstone in tight gas-condensate reservoirs

One of the most common sources of formation damage in tight reservoirs of gas-condensate is condensate banking. The condensate level on the porous media reduces the effective permeability to gas, decreasing the gas production primarily because the pressure reaches values that are lower than dew point pressure or because there is a sharp pressure drop in the near wellbore. The primary objective of this study is to develop a nanofluid, based on the interaction between an anionic surfactant and silica (SiO2) nanoparticles, to alter the reservoir wettability from a liquid-wet state to gas-wettability. The SiO2 nanoparticles were modified by an incipient method using a solution of anionic commercial surfactant Silnyl (R) FSJ (SY) at various concentrations from 3.0 to 7.0 wt%. Posteriorly, the nanofluids were prepared with modified SiO2 nanoparticles that were dispersed in an SY solution in deionized water. Nanofluids were initially evaluated at room conditions by contact angle and imbibition tests on oil-wet and water-wet sandstone samples for the wettability alteration to obtain the best concentration ratio of modified nanoparticles and SY in the nanofluid. Different combinations and individual effects of the nanoparticles and SY surfactant were evaluated. Better performance in changing the wettability of the system was achieved for a nanofluid at a concentration of 500 mg/L of SiO2 nanoparticles, which were functionalized with 5.0 wt% of SY and dispersed in an SY solution at 0.46 wt% in deionized water. In water-wet samples, contact angles changed from 0 degrees to 118 degrees and from 32 degrees to 95 degrees for water/rock/air and oil/rock/air systems, respectively. Similarly, for oil-wet samples, the contact angles were modified from 123 degrees to 115 degrees and from 0 degrees to 93 degrees. Coreflooding tests were performed under tight gas-condensate reservoir temperature and pressure conditions. Through the permeability curves and oil recovery, the synthesized nanofluid was observed to alter the wettability of the system from a strongly liquid-wet to a gas-wet condition. Additionally, according to the results, the use of the synthesized nanofluids can reduce the formation damage caused by the condensate banking, favoring the mobility of liquid and leading to a considerable improvement in oil and gas production. The oil recovery increases from 46.6% in the base system to 78.4% after treatment. Additionally, residual saturation of oil was reduced from 29.2% to 17.8% in the base and treated systems, respectively.