Modifying the Wettability of Sandstones Using Nonfluorinated Silylation: To Minimize the Water Blockage Effect

Abstract

Multiphase fluid flow characteristics of a reservoir rock, such as capillary pressure, displacement efficiency, relative permeability, and saturation distribution are substantially influenced by the wettability state of the rock. Being able to change the affinity of the rock toward different fluid phases present in the formation has implications in various petroleum applications (e.g., CO 2 geo-sequestration, EOR, gas production). In this study, silylation of sandstone core samples using nonfluorinated compounds is accomplished using supercritical CO 2 as a solvent and carrier. This approach is cost-effective and less environmentally sensitive compared to other approaches which use fluorinated silylation reagents. By using small molecules to only change the wettability characteristics of core samples without altering other parameters (e.g., rock pore structure) noticeably, the effects of wettability alteration alone on multiphase flow (i.e., relative permeability) can be identified. Spontaneous imbibition tests were conducted on Gray Berea sandstone before and after silylation treatment, which showed a diminished rate of water uptake in the post-treatment sample. The wettability alteration caused by this functionalization and its impact on multiphase flow characteristics were analyzed using core flooding tests. The experimental results show that supercritical CO 2 -based (scCO 2 -based) silylation changes the wettability of the formation from strongly water-wet to intermediate gas-wet. Core flooding tests showed that the effective permeability for the water phase was significantly increased, resulting in higher water removal from the rock matrix. Furthermore, the relative permeability for the gas phase (in this study, CO 2 ) at residual water saturation is higher after treatment. Such an outcome confirms that the change in wettability could be beneficial in geological CO 2 storage as well as gas production.

Tuning the Wetting Properties of SiO2-Based Nanofluids to Create Durable Surfaces with Special Wettability for Self-Cleaning, Anti-Fouling, and Oil–Water Separation

“…Wettability is an essential parameter that can strongly affect the pore-scale flow behavior of a rock-fluid system and the resulting macroscale multiphase properties such as capillary pressure, relative permeability, displacement efficiency, and multiphase fluid saturation. , Accordingly, by altering the wettability of reservoir rocks in a specified way, the multiphase flow characteristics of a formation can be supervised. As a case, the accumulation of water around the wellbore region in gas reservoirs is recognized to negatively influence well deliverability by considerably decreasing the gas-phase relative permeability. , Water blockage can be ascribed to water invasion during drilling, completing a well, or hydraulic fracturing into the hydrophilic reservoir rocks . Similarly, many gas wells in gas-condensate reservoirs suffer a significant loss in productivity as a result of liquids (condensate and water) banking in the proximity of the wellbore area .…”

“…19,20 Water blockage can be ascribed to water invasion during drilling, completing a well, or hydraulic fracturing into the hydrophilic reservoir rocks. 21 Similarly, many gas wells in gascondensate reservoirs suffer a significant loss in productivity as a result of liquids (condensate and water) banking in the proximity of the wellbore area. 22 This phenomenon, known as condensate blocking, emerges when the pressure of the reservoir decreases below the dew point due to the depletion of the reservoir as gas production progresses.…”

Wettability Alteration Using Silane to Improve Water-Alternating-Gas Injectivity

“…Spontaneous imbibition tests in Berea sandstone samples showed a decrease in brine imbibition after treatment, and the relative permeability of water measured in ∼200mD cores was 60% higher than that in the nontreated case. The gas relative permeability also exhibited an increase by 19% . A more comprehensive study was carried out with different silanes and different sandstone samples using either supercritical CO 2 or toluene as the silane solvent carriers.…”

“…The gas relative permeability also exhibited an increase by 19%. 31 A more comprehensive study was carried out with different silanes and different sandstone samples using either supercritical CO 2 or toluene as the silane solvent carriers. All combinations of surfaces, silanes, and carrier fluids resulted in a water contact angle of more than 140°, indicating that the surfaces were rendered hydrophobic, with a slight improvement when using scCO 2 .…”