Development and Gelation Mechanism of Ultra-High-Temperature-Resistant Polymer Gel

Abstract

To expand the applicability of gel fracturing fluids in ultra-high-temperature reservoirs, a temperature-resistant polymer was synthesized using the solution polymerization method. Subsequently, an ultra-high-temperature-resistant polymer gel was formulated by incorporating an organic zirconium crosslinking agent. A comprehensive investigation was carried out to systematically study and evaluate the steady shear property, dynamic viscoelasticity, and temperature and shear resistance performance, as well as the core damage characteristics of the polymer gel. The obtained results demonstrate that the viscosity remained at 147 mPa·s at a temperature of 200 °C with a shear rate of 170 s−1. Compared with the significant 30.9% average core damage rate observed in the guanidine gum fracturing fluid, the core damage attributed to the polymer gel was substantially mitigated, measuring only 16.6%. Finally, the gelation mechanism of the polymer gel was scrutinized in conjunction with microscopic morphology analysis. We expect that this study will not only contribute to the effective development of deep and ultradeep oil and gas reservoirs but also furnish a theoretical foundation for practical field applications.

A Review of Weak Gel Fracturing Fluids for Deep Shale Gas Reservoirs

“…Ma et al synthesized a heat-resistant polymer as a thickener by solution polymerization, and crosslinked it with an organic zirconium crosslinking agent to prepare an ultra-high-temperature-resistant polymer gel fracturing fluid. After continuous shearing at 200 • C for 1 h, the viscosity could still be maintained at about 0.147 Pa•s, and compared with the guanidine gum fracturing fluid, the core damage rate was significantly reduced [36].…”

A Supramolecular Reinforced Gel Fracturing Fluid with Low Permeability Damage Applied in Deep Reservoir Hydraulic Fracturing

“…During this period, the viscosity did not change with the increase in temperature. When the temperature exceeded 100 • C, the viscosity began to decrease, and the viscosity dropped to 197.8 mPa•s as the temperature reached 200 • C. The viscosity eventually stabilized at 72.35 mPa•s as the shear time continued to 2 h. The criterion of gel fracturing fluid is that the viscosity is greater than 50 mPa•s [25,27]. The final viscosity was sufficient to meet the proppant suspension performance of the gel fracturing fluid, so SRG fracturing fluid fully meets the need for temperature resistance of the gel fracturing fluid applied in deep reservoir hydraulic fracturing.…”

“…Polyacrylamide-based gels are usually formed by crosslinking a polyacrylamidebased polymer with a transition metal crosslinker (Zr-crosslinker or Ti-crosslinker) [25,26]. Generally, the monomer containing the sulfonic acid group is added to the polyacrylamide to improve the temperature and salt resistance of the polymer, and the cyclic monomer is added to improve the thermal stability of the polymer at high temperatures [27].…”