Application of Formate Series Products for Shale Gas Production and Completion Fluid Preparation

Shale gas reservoirs contain high clay content, which tends to hydrate and swell, potentially clogging pores. Long horizontal well completions require well completion fluids with stringent shale inhibition, reservoir protection, and high-temperature stability capabilities, directly determining gas well productivity and operational safety. The following four core products precisely address all scenarios for shale gas well completion fluid preparation, as detailed below:

1. Solid potassium formate (industrial grade ≥97%)

Core function: The primary material for deep shale gas horizontal well completion fluids, it effectively inhibits shale hydration expansion, stabilizes long horizontal wellbore sections, preserves shale pore structure, prevents reservoir permeability decline, and balances formation pressure, making it suitable for ultra-deep well completion operations in Sichuan and North American shale gas fields.

Product Advantages: Potassium ions can intercalate into shale crystal layers to immobilize clay, exhibiting excellent inhibition of dispersion collapse; Solid-phase-free formulation prevents shale pore clogging, resulting in minimal reservoir damage; Stable performance under high-temperature and high-pressure conditions (200°C); Biodegradable and compliant with global environmental regulations for oil and gas extraction.

Usage: Add the mixture of completion fluid design density, clean water and proppant agent, the conventional dosage is 15%-65%, mix well and inject into wellbore.

Common issues: Highly hygroscopic, requires sealed and dry storage; high-concentration systems require strict compatibility control to avoid conflicts with cationic treatment agents.

2. Liquid Potassium Formate (Industrial Grade ≥75%)

Core function: Serves as the primary raw material for shale gas completion fluid formulation, enabling rapid preparation without on-site dissolution. It is compatible with long horizontal continuous completion and pre-fracturing well maintenance operations, while balancing reservoir protection and wellbore stability.

Product Advantages: On-site liquid product blending for enhanced convenience, significantly reducing operational cycles; Solid-free formulation with substantially lower damage to shale reservoirs compared to conventional completion fluids; Low-corrosion protective casing and downhole tools; Excellent compatibility with fracturing fluids and high return efficiency.

Usage: The concentrate solution is added directly according to density requirements, with a standard dosage of 30%-85%. It can be optimized with coagulants and corrosion inhibitors, and is directly injected into the wellbore.

Common issues: Viscosity increases at low temperatures; thermal insulation of storage tanks is required during winter; long-term storage necessitates sealing to prevent moisture evaporation and crystallization.

3. Solid sodium formate (industrial grade ≥98%)

Core function: A cost-effective core component for medium-shallow atmospheric shale gas completion fluids, which assists in suppressing shale hydration and balancing formation pressure. It is suitable for low-cost completion operations in marginal shale gas wells and can be used in combination with potassium formate.

Product Advantages: Excellent cost-performance ratio, significantly reducing the overall cost of completion fluids; Good water solubility and easy mixing, no solid phase to prevent reservoir plugging; Low-corrosion protection for downhole tools; Excellent compatibility with various completion fluid additives.

Usage: After preparing the aqueous solution, add it to the completion fluid system at a conventional dosage of 10%-45%. It can be combined with potassium formate to balance inhibition and cost.

Common issues: Its inhibitory effect is weaker than potassium formate, making it unsuitable for high-pressure deep shale gas wells. At high temperatures, it must be used with stabilizers to prevent performance degradation.

4. Industrial-grade Potassium Acetate (Solid/Liquid)

Core function: Serves as a pH buffer and corrosion inhibitor for shale gas completion fluids, regulating pH levels to ensure long-term system stability. It effectively inhibits shale hydration and reduces corrosion of casing and downhole tools, making it suitable for deep, high-temperature shale gas wells.

Product Advantages: Superior pH buffering capability maintains system acid-base stability at high temperatures, preventing intensified shale hydration; provides auxiliary corrosion inhibition to significantly reduce casing corrosion rate; exhibits excellent compatibility with formate systems without compromising reservoir protection efficacy.

Usage: The solid formulation is prepared as a 20% aqueous solution for addition, while the liquid concentrate is added directly. The standard dosage ranges from 0.5% to 3%, with dynamic adjustments based on the pH value of the completion fluid.

Common issues: Solid materials exhibit strong hygroscopicity and require sealed storage; excessive addition may affect system density, necessitating precise dosage control.

5.Industry Use Cases

A deep horizontal well in a shale gas field features a 2,200-meter horizontal section with a wellbore temperature of 165°C and high shale clay content. The conventional completion fluid in adjacent wells caused over 35% reservoir damage, resulting in suboptimal production. After implementing a solid-free completion fluid system primarily composed of 75% liquid potassium formate, the well completed its operation cycle in 18% less time, maintained stable wellbore integrity without collapse, and reduced reservoir damage to below 8%. Following fracturing and commissioning, the well achieved a 62% increase in daily gas production compared to neighboring wells, demonstrating excellent operational stability.