Study on pH-Responsive Delayed, Cross-Linking and Weighted Fracturing Fluid.

Area of Science:

• Petroleum Engineering
• Materials Science

Background:

• Deep, high-temperature reservoirs present challenges for hydraulic fracturing due to high pressures and temperatures.
• Conventional polymer fracturing fluids (QCL) exhibit high viscosity and increase wellbore friction, hindering efficient operations.

Purpose of the Study:

• To develop and evaluate a novel pH-responsive polymer fracturing fluid with low friction characteristics.
• To optimize fluid formulation for enhanced sand transport and improved hydrocarbon recovery in challenging reservoir conditions.

Main Methods:

• Investigated the effect of pH on polymer cross-linking and fluid friction using alkali (sodium carbonate) and acid conditions.
• Utilized scanning electron microscopy (SEM) and infrared spectroscopy (IR) to analyze fluid structure and polymer chain behavior at varying pH.
• Proposed and tested a two-stage optimized fluid formulation ('salt + pH + polymer + cross-linking agent') for fracture generation and sand transport.

Main Results:

• Alkali conditions effectively slowed cross-linking and reduced fluid friction, with sodium carbonate proving effective.
• Optimized pH control enhanced polymer hydration and sand-carrying capacity in the low-viscosity stage.
• SEM and IR analyses confirmed that alkali promotes a stable fluid network structure and increases polymer chain negative charges, improving sand transport.

Conclusions:

• The developed pH-responsive fracturing fluid offers a low-friction solution for deep, high-temperature reservoir development.
• Field tests demonstrated reduced operating pressures, stable sand transport, and significant increases in oil and gas production.
• This formulation enhances efficient reservoir development by addressing key challenges associated with conventional fracturing fluids.