An Experimental Approach of a Robust Polymer Gels for Water Shutoff Applications in Carbonate Formations

Controlling unwanted water production is the key for the oil and gas industry. Consequently, water shutoff (WSO) fluids were introduced to favorably plug high permeability water zones or fractures and thereby reducing the water cut. Polymer gels have been utilized extensively to minimize undesired water production, especially from oil producers. Herein we present the study of gelation kinetics of an organically crosslinked polymer (OCP) gel with an adsorption system from intermediate to high reservoir temperatures. In this study, we utilized a cost-effective and environmentally acceptable fluid system. The fluid consists of polymer gel and adsorption constituents for carbonate formations. The system can be pumped downhole to the targeted zones as a single-phase solution with low initial viscosity. A systematic evaluation of the polymer gel for WSO applications is conducted at varied reservoir conditions. This includes a thorough examination of fluid properties at surface conditions before gelation starts, at which the system is referred to as gellant. Furthermore, we studied the properties during and after gelation kicks off at a wide range of temperatures. The emphasis of the experimental investigation was on the kinetics of OCP gelation through performing several rheology experiments at various crosslinker concentrations. The analysis revealed that the viscosity of the gellant at standard conditions was less than 20 cP; thereby, this contributes positively to having smooth surface mixing and pumping requirements for field testing. Based on reservoir temperature and cooling effect, the gelation time can be optimized by altering crosslinker concentrations. At fixed temperatures and varied crosslinker ratios, the gelation time exhibited a linear relationship with crosslinker concentrations. Additionally, the gelation time against temperature experienced an exponential behavior with reversible proportionality. By plotting the acquired data from massive rheological tests, we managed to attain precise correlations of gelation time for each OCP formulation. The gel prevailed in a high thermal stability fluid system to be gelled at a temperature of more than 250°F. Based on the presented lab observations, we concluded that this polymer gel system is expected to be trial tested in the field as WSO fluid for carbonate rocks. The OCP gel is a promising technology to mitigate excess water production from oil producers. Since the system has a low initial viscosity, it can be injected naturally in porous media. The presented work offers an insightful polymer gel system as a WSO fluid designed for treating carbonate rocks.