An Organic Gel System for Water Production Issues Post Hydraulic Fracturing

Abstract

Abstract Water production post hydraulic fracturing is an issue that has been facing E&P operators worldwide for a long time. The water quantities produced can be significant with great amount of impurities. This not only reduces the oil production in those wells, but can also cause problems such as sand production, scale, corrosion and erosion. Moreover, it costs the E&P operators a lot of money every year to treat and dispose these produced waters. Crosslinked gels have been used successfully in the oil and gas industry to shut-off water producing zones. This study presents an experimental investigation of a polyacrylamide-based polymer and polyethyleneimine (PEI) system for water shut-off treatments. The polyacrylamide-based polymer has a molecular weight of 40,000 Daltons. PEI crosslinker was obtained in a 50:50 aqueous solution with a molecular weight of 60,000 Daltons. The HP/HT rheometer was used to conduct the viscosity measurements. All experiments were done at a pressure of 400 psi. The shear rate was fixed at 100 s−1 and the temperature was ranged from room temperature to 350℉. The gelation time and the system's viscosity were both studied as a function of polymer concentration and salt concentration in the mixing water. Additionally, the effect of increasing temperature on the gelation time was examined. Moreover, an HP/HT aging cell was used to generate the gel that was used later for compatibility testing with a treated formation water from the Wolfcamp. Increasing the polymer concentration was found to decrease the gelation time and increase the system's viscosity up to a specific limit. Moreover, we observed an increase in the gelation time as the concentration of NaCl was raised in the mixing water, however the system's viscosity decreased. Also, we noticed a decrease in the gelation time as the temperature increased. Finally, no incompatibility issues were observed between the polyacrylamide-based polymer/PEI system and the treated formation water. Polymer-crosslinker systems should be stable and highly viscous to ensure an effective water shut-off operation. This work experimentally investigates the performance of a cheap polyacrylamide-based polymer and PEI organic gel system. The paper shows that the tested system is capable of sealing water production zones and can provide a promising alternative to current water shut-off systems used in the field.