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

Shale gas formations typically contain large fractions of clay‑rich rock. Once exposed to water‑based fluids, these clays hydrate and swell, which can block pore throats. For extended horizontal well completions, completion fluids must deliver robust shale inhibition, reservoir protection and reliable high‑temperature performance. These properties directly govern gas‑well output and site operational safety. Below are four core products covering major formulation requirements for shale‑gas completion fluids.

1. Solid Potassium Formate (industrial grade, ≥97% purity)

Core function This base fluid component is widely used for completion fluids in deep shale‑gas horizontal wells. It restrains clay hydration and swelling, stabilizes long horizontal borehole intervals, preserves native pore structures and limits permeability impairment. It also helps balance formation pressure, making it fit for ultra‑deep completion work in Sichuan shale plays and North American shale gas basins.

Product strengths Potassium ions insert themselves into clay crystal lattices to lock clay particles in place, delivering strong inhibition against hydration and sloughing. Being solids‑free, it avoids pore blockage and keeps formation damage to a minimum. It retains stable properties under high‑temperature high‑pressure conditions up to 200 °C. The material is biodegradable and meets global environmental standards for oil‑field operations.

Application guidance Blend with fresh water and selected functional additives to hit target completion‑fluid density. Typical field dosage ranges from 15% to 65%. Thorough mixing is required before pumping downhole.

Operational notes The material readily takes on moisture, so sealed dry storage is mandatory. At high working concentrations, pay close attention to additive compatibility; avoid direct mixing with cationic treatment chemicals.

2. Liquid Potassium Formate (industrial grade, ≥75% purity)

Core function A ready‑to‑use base raw material for shale‑gas completion‑fluid blends. It eliminates on‑site powder dissolution steps and suits continuous completion runs on long horizontal sections as well as wellbore conditioning ahead of fracturing treatments. It balances reservoir protection and borehole stability.

Product strengths Liquid concentrate simplifies field mixing and shortens overall job timelines. Its solids‑free nature inflicts far less formation damage than many conventional completion fluids. It is mildly corrosive, helping safeguard casing and downhole hardware. It mixes well with fracturing fluids and returns easily during flowback.

Application guidance Dose the liquid concentrate directly according to target density, usual addition 30%‑85%. Coagulants and corrosion inhibitors can be incorporated as needed prior to wellbore injection.

Operational notes Viscosity rises under cold conditions, so storage tanks need thermal insulation in winter. Keep containers sealed for long‑term storage to stop water loss and salt crystallization.

3. Solid Sodium Formate (industrial grade, ≥98% purity)

Core function A cost‑effective base ingredient for medium‑depth, normal‑pressure shale‑gas completion fluids. It suppresses clay hydration and assists formation‑pressure control. It works for low‑budget completion on marginal shale‑gas wells and can be co‑formulated with potassium formate.

Product strengths Offers notable cost advantages and cuts total completion‑fluid expenditure. It dissolves easily in water for convenient field mixing; no residual solids to create pore plugging risks. Low corrosivity protects downhole equipment and shows good compatibility with most completion‑fluid auxiliaries.

Application guidance Prepare aqueous solution first before adding into fluid systems. Common dosage sits between 10%‑45%. Mix with potassium formate to strike a balance between inhibition performance and overall cost.

Operational notes Its clay‑inhibiting performance falls short of potassium formate, so it is not recommended for high‑pressure deep shale‑gas wells. Stabilizers must be added under high‑temperature service to prevent performance degradation.

4. Industrial‑Grade Potassium Acetate (solid / liquid grades)

Core function Acts as a pH buffer and auxiliary corrosion inhibitor within shale‑gas completion fluids. It stabilizes system pH for sustained long‑run performance, further curbs shale hydration and mitigates corrosion on casing and downhole tools. Suitable for deep, high‑temperature shale‑gas wells.

Product strengths Powerful pH‑buffering capacity sustains acid‑base balance at elevated temperatures and prevents aggravated clay hydration. It brings extra corrosion‑suppressing effects and lowers casing corrosion rates substantially. It pairs smoothly with formate‑based fluid systems without weakening reservoir‑protection results.

Application guidance For solid‑grade material, make up a 20% aqueous solution before feeding. Liquid concentrate can be dosed straight into the system. Normal usage ranges 0.5%‑3%, adjust on‑the‑fly according to measured completion‑fluid pH.

Operational notes Solid potassium acetate is highly hygroscopic and requires sealed storage. Over‑dosing may alter overall fluid density, hence precise metering is essential.

Field Application Case Study

One deep shale‑gas horizontal well featured a 2 200 m horizontal interval, bottom‑hole temperature of 165 °C and high clay content in shale formations. Offset wells using conventional completion fluids saw formation damage exceeding 35%, which led to disappointing gas output.

Operators switched to a solids‑free completion‑fluid system built around 75% liquid potassium formate. The well finished its full completion cycle 18% faster. Borehole conditions remained stable with no collapse events, and formation‑damage levels dropped below 8%. After fracturing and commissioning, daily gas production was 62% higher than nearby offset wells, confirming dependable field performance.