Wettability Alteration to Reduce Water Blockage in Low-Permeability Sandstone Reservoirs

Abstract

This study is a continuation of our previous work, which focused on a near-wellbore water blockage alleviation by applying a thermally cured silane-functionalized benzoxazine to modify rock wettability. In this new analysis, we have demonstrated that the resin can be applied in low-permeability sandstones (approximately 15 mD as opposed to 100 to 200 mD in the previous study) to change the rock surface wettability from water-wet to intermediate gas-wet. We have also demonstrated that curing temperatures as low as 125 °C (as opposed to 180 °C in our previous study) can significantly change wettability, indicating surface functionalization through the silane moiety and ring-opening polymerization of the benzoxazine moiety. In drainage core flooding experiments at 2.5 wt.% resin loading, compared to untreated samples, brine recovery increments of 6.3 to 6.9% were obtained for curing temperatures of 125 to 180 °C, respectively. A maximum 20% increment in the end-point relative gas permeability was achieved at a curing temperature of 180 °C. A coupled experimental and numerical study, conducted at core and wellbore scales, demonstrates the potential effectiveness of our chemical treatment in improving gas productivity at the field scale. Reservoir simulations indicate a 2.9 to 10.6% improvement in gas deliverability for a treatment radius of 4 to 16 m, respectively.

Mechanism of Salt Precipitation Blockage in Low-Producing Gas Wells and the Method of Acidification Blockage Removal

“…Water removal efficiency also reaches around 85%, making both viable options for blockage removal. (7) In wells with quartz-containing blockages, HCl shows lower dissolution rates, whereas mud acid is more effective, exceeding 80% dissolution. Mud acid demonstrates a significantly higher removal efficiency.…”

“…Preliminary analysis suggests that the surge in blocked wells can be attributed to two primary scenarios. First, low-producing gas wells often exhibit limited liquid carrying capacity, leading to substantial water accumulation in the wellbore, resulting in pronounced effusion and water blockage issues. , Second, low-flow-rate natural gas, containing corrosive gases such as H 2 S and CO 2 , continuously carries saturated water vapor, which increases mineralization levels at the well’s bottom, contributing to scaling and sand deposition within the wellbore. , However, a comprehensive understanding of the blockage types, mechanisms, and appropriate treatment methods remains elusive.…”