Classification and properties of clay stabilizers: Technical selection for different scenarios

Based on differences in chemical composition, mechanism of action, and application scenarios, clay stabilizers for oilfields can be divided into four main categories. Each category has its own focus in terms of performance, cost, and applicable conditions, providing diversified choices for the development of different types of oil and gas reservoirs.
(I) Inorganic Salt and Inorganic Alkali Clay Stabilizers:
These are the earliest clay stabilizers applied in oilfields, mainly including potassium chloride (KCl), sodium chloride (NaCl), ammonium chloride (NH₄Cl), calcium chloride (CaCl₂), and sodium hydroxide (NaOH).
Core characteristics
and advantages: Widely available raw materials, low price (usually 1000-3000 yuan per ton), simple construction process, can be directly dissolved in water and injected into the reservoir; significant short-term anti-swelling effect on expansive clays such as montmorillonite, with an anti-swelling rate of 80%-90% when the addition concentration is 2%-5% ; good compatibility with other chemical agents, and less prone to adverse reactions.
   Limitations: Poor stability, easily diluted and washed away by formation water; short effective period (usually 1-3 months), requiring periodic replenishment; only inhibits expansion through charge neutralization, with poor effect on inhibiting clay particle migration; high concentrations can increase formation water salinity, potentially causing salt deposits and secondary damage.
Applicable Scenarios
  Suitable for shallow, high-porosity, high-permeability conventional oil and gas reservoirs with low clay content (<5%), especially suitable for the pretreatment of drilling and completion fluids, and for temporary anti-swelling needs in short-term production enhancement operations (such as acidizing and fracturing). For example, in a shallow sandstone oilfield, adding 3% potassium chloride to the drilling fluid during drilling effectively inhibited clay swelling, and the reservoir permeability damage rate during drilling decreased from 65% before the addition to 20% .
(II) Inorganic polymer clay stabilizers
These stabilizers are represented by polyaluminum chloride (PAC), polyferric chloride (PFC), and polyaluminum sulfate (PAS), which exert their effects by generating polynuclear hydroxyl complexes through hydrolysis.

Key Features and
Advantages: Moderate price ( 3000-8000 RMB per ton), long-lasting anti-swelling effect with an effective period of 6-12 months; combines charge neutralization and adsorption fixation, effectively inhibiting clay swelling and preventing clay particle migration; good temperature resistance, usable in medium-to-high temperature formations below
120℃ . Limitations: Narrow applicable pH range, stable only under acidic or weakly acidic conditions (pH 3-6); prone to hydrolysis and precipitation in neutral or alkaline formations, leading to secondary reservoir damage; unsuitable for carbonate reservoirs, as the acidic substances produced by hydrolysis will react with carbonate rocks, generating CO₂ and salt precipitates; some products are corrosive and require combination with corrosion inhibitors.
Applicable Scenarios
  It is suitable for sandstone reservoirs, acidic or weakly acidic formations, and medium-low permeability oil and gas reservoirs with moderate clay content (5%-15%), especially suitable for the long-term swelling prevention needs of water-injected oilfields. For example, in a medium-permeability sandstone oilfield, adding 0.5% polyaluminum chloride clay stabilizer to the water injection system significantly reduced clay migration at the bottom of the well, increased the reservoir permeability retention rate from 70% to 85% , and stabilized the daily oil production of the well at 8-10t . (III) Cationic surfactant clay stabilizers
  These stabilizers contain cationic groups (such as quaternary ammonium salts and pyridyl groups) and long-chain alkyl groups in their molecular structure. Representative products include hexadecyltrimethylammonium bromide (CTAB), dodecyl dimethyl benzyl ammonium chloride (1227), and octadecyl ammonium chloride.
Key advantages include
: strong adsorption capacity, adhering firmly to the surface of clay particles through electrostatic adsorption and hydrophobic interactions, resisting water erosion, and an effective period of 12-24 months; combining anti-swelling and anti-migration effects, with an anti-swelling rate exceeding 90%; and good salt resistance, maintaining stability even in formations with a salinity ≤20×10⁴ mg/L.
  Limitations: It can cause the reservoir rock surface to change from water-wet to oil-wet, reducing the permeability of the oil and gas phases, leading to increased crude oil flow resistance, and potentially causing a temporary drop in production in some wells; the cost is relatively high (8,000-15,000 yuan per ton); it has poor biodegradability, limiting its application in environmentally sensitive areas; and it has poor compatibility with some anionic chemical agents (such as anionic demulsifiers and dispersants), easily causing flocculation reactions.
Applicable Scenarios
  Suitable for medium-deep oil and gas reservoirs with high clay content ( 10%-20% ) that require long-term stability, especially suitable for reservoirs with sufficient energy and where the permeability of the oil and gas phases has little impact on production. For example, in a deep sandstone oilfield, a clay stabilizer composed of cetyltrimethylammonium bromide and potassium chloride was added at a concentration of 1%. After treatment, the reservoir swelling prevention rate reached 92%, clay migration was effectively inhibited, and the stable production cycle of oil wells was extended by 2-3 years.
(IV) Organic cationic polymer clay stabilizers
  This is currently the most widely used and best-performing type of clay stabilizer. Its molecular chain contains a large number of cationic groups (such as quaternary ammonium salt groups and amine groups). Representative products include polyquaternary ammonium salt-6, polyquaternary ammonium salt-7, cationic polyacrylamide (CPAM), polyamine polymers, etc.
   Key features and
advantages: Wide applicability, suitable for various reservoirs such as sandstone and shale, as well as formations with different pH values such as acidic, neutral, and weakly alkaline; excellent anti-swelling and anti-migration effects, with an anti-swelling rate of over 95% , and can firmly fix clay particles through molecular chain entanglement; strong resistance to water, oil, and acid and alkali erosion, with an effective period of 24-36 months; minimal impact on reservoir wettability, and will not significantly reduce oil and gas phase permeability; good compatibility with other chemical agents, and can be used in combination with acidizing fluids, fracturing fluids, corrosion inhibitors, etc.
   Limitations: Relatively high cost (RMB 10,000-20,000 per ton); molecular chains of some products are prone to breakage under high temperature (>150℃), leading to performance degradation; complex preparation process, and the quality stability of some products needs to be improved.
   Applicable scenarios:
Suitable for various oil and gas reservoirs, especially deep, high-temperature, high-pressure, low-permeability, and ultra-low-permeability oil and gas reservoirs, as well as unconventional oil and gas reservoirs with high clay content (15%-30%) and high risk of damage (such as shale gas and coalbed methane). For example, in a shale gas field in the Sichuan Basin of China, adding 1.5% polyquaternary ammonium salt clay stabilizer to fracturing operations effectively inhibited the expansion and migration of montmorillonite in the shale, increasing the fracturing fluid flowback rate from 60% to 85% , and the daily gas production of shale gas wells reached 150,000 m³, extending the stable production cycle by 3-5 years.
(V) New Special Clay Stabilizers
  As oil and gas development expands into more complex geological formations, new types of specialty clay stabilizers have emerged, mainly including bio-based clay stabilizers, nanomaterial-based clay stabilizers, and smart-responsive clay stabilizers, providing new solutions to the problem of clay damage under extreme conditions.
Bio-based clay stabilizers: Made from natural plant extracts (such as chitosan and starch derivatives) or microbial fermentation products, they feature high biodegradability ( ≥90% ), low toxicity, and environmental friendliness, making them suitable for oil and gas field development in ecologically sensitive areas. For example, chitosan quaternary ammonium salt clay stabilizers achieve a swelling prevention rate of 90% and a biodegradability rate of over 95% , and have been successfully applied in oil fields within the Yellow River Basin ecological protection zone.
Nanomaterial-based clay stabilizers: Utilizing the small size effect and high specific surface area of nanoparticles (such as nano-silica and nano-alumina), they adsorb onto the surface of clay particles and fill interlayer voids, inhibiting swelling and migration. They exhibit excellent temperature and salt resistance and can be used under extreme conditions above 200℃ and mineralization above 30×10⁴ mg/L .
Intelligent responsive clay stabilizers: can automatically adjust their action mode according to changes in the formation environment (such as temperature, pH value, fluid salinity). For example, temperature-responsive stabilizers maintain fluidity at room temperature, but solidify after entering high-temperature formations to form a durable and stable protective layer, which is suitable for high-temperature deep oil and gas reservoirs.