sloilfield chemicals

The clay minerals are widely existed in the reservoir, and 97% of the oilfields have different degrees of clay minerals. Clay minerals include montmorillonite, kaolinite, illite, chlorite etc. The clay will expand in the process of water injection, acidification, fracturing when it encountered water or water base material, and then further dispersed or directly dispersed into small particles within diameter less than 10lm. In normal circumstances, from upper to lower, oil storage layer of montmorillonite content reduced with the increasing for the content of illite and the kaolinite will disappear at a certain depth and chlorite are mainly distributed in the deep. These clay minerals are mainly composed of silica octahedron and alumina tetrahedron, interlayer surfaces are oxygen layer, and the coupling force is weak, when it contact with water, crystal plane surface layer of exchangeable cations in water diffusion and dissociation, to form the electric double layer as a result, on the surface of the sheet structure distributes the negatively charges, crystal layers mutually exclusive, resulting in expansion. Generally, the strata are classified into non expansive clay minerals, but in the erosion of the formation fluid, non expansive clay can be dispersed into a small profit and migration, into the underlying space, blocking the throat, finally reducing the underlying permeability.

In order to reduce the damage of clay minerals, various kinds of clay stabilizers are studied and developed, which can be divided into the following categories:

Inorganic salts clay stabilizer: at the initial stage of oilfield development, using various acids and salts, such as hydrochloric acid, acetic acid, hydrofluoric acid, due to the acid hydrogen ion exchanged with the clay surface of sodium ion and the hydrogen presents a harder tendency to   dissociate than sodium, so that the clay expansions is effectively inhibited. The salts including sodium chloride, potassium chloride, ammonium chloride, calcium chloride and magnesium chloride and its anti-swelling mechanism is reducing the diffusion of the clay surface electric double layer and zeta potential, the metal ion relatively easy to enter clay space and not easy being released, which can effectively neutralize the clay surface electronegativity. Later, the use of hydroxyl, hydroxyl, zirconium and other inorganic cations such as polymer also gained much more eyeballs. The mechanism is that trivalent and trivalent metal ions (A l³⁺ , Cr³⁺, Zr³⁺, Zr⁴⁺, Ti⁴⁺, etc.), these non polar cationic polymer in water can be dissociated to the multi-core hydroxyl bridging ion, reducing its negative electricity, so as to effectively inhibit the expansion of clay. Furthermore, polynuclear hydroxy bridged complex ion will surface with negatively charged clay particles and with negative bottom surface bridging to fix the particle and prevent particle migration. The advantages of anti-swelling is the long valid period compared with salt and cationic surfactant, the disadvantage is that the acid resistance is too low, not suitable for high carbonate content of the bottom, but can use in weak acid condition, the formula is expressed as:

Organic clay stabilizer: organic cation can be more firmly adsorbed on clay particles, and not easy to be replaced by other ions, long-term good, resistant to erosion. But the molecular weight is too large, and the improper usage will plug the low permeability reservoir pore throat, lower reservoir permeability.

Cationic active agent mainly comprises quaternary ammonium salt type based, pyridine salt type based and imidazoline type based etc. Cationic surfactant can dissociate to active cationic on the surface, it can be adsorbed on the surface of the clay particles and clay surface negative charge, making it can be attached on the negatively charged surface of clay and neutralize the electronegativity so as to prevent clay swelling in water. In addition, it can also be through hydrogen bond and electrostatic suction to the surface of the particles and the formation of the inhibition of migration. The utility model has the advantages of strong adsorption capacity, can resist water washing; but the biggest drawback is the reservoir water wettability change for oily wettability, making the water relative permeability decreased at last.

Organic cationic polymer is a polymer that containing nitrogen, sulfur and phosphorus. The high price of cationic polymer can be dissociated in water, and establish the multiple point adsorption with a plurality of clay particles, after adsorption, a protective film layer of adsorption on the surface of clay particles formed, in order to prevent the expansion of clay particles and migration. It has the advantages of low dosage, high efficiency, strong adsorption capacity, low pH, high adaptability and so on.

Organic silane or organic silane ester monomers are firstly being hydrolyzed in water, forming a intermediate product-"Silicon alcohol" with the ability to react. The "Silicon alcohol" is a polymer which is formed by the condensation polymerization, and then the polymer is hydrolyzed by the reaction of hydroxyl groups on the surface of clay. As a result, the clay surface is changed to the surface of the parent oil, and the expansion of the clay in water is inhibited.

Compound clay stabilizer: After mixing inorganic stabilizer and organic compound stabilizer, better effect than the single use of polyhydroxy cationic polymer has been appeared, owing to the  coordination effect of the incorporation of polyhydroxy cationic polymer and inorganic cationic polymer, the inorganic cationic polymer molecular weight general in 400 ~ 1000, similar to its structure and clay of silicon oxygen tetrahedron, so it can touched with negatively charged clay surface closely. And polyhydroxy cationic polymer, although can touch radicals clay surface through hydrogen bonding and hydroxylated closely, due to the molecular weight of the large (about 10⁵ ~ 10⁶), molecular mainly take the coiled conformation. Therefore, it with the clay surface binding as inorganic cationic polymer tightly. So, the effect is better when the compound is used. Because of the high price of inorganic cationic polymer, the use of KCl, NH₄Cl and other organic cationic clay stabilizer is generally used.

The LEAD OILFIELD SERVICE COMPANY has offered the clay stabilizer, including small molecular amine, oligomeric double quaternary ammonium salts, etc for many years, good performance such as high-solubility, strong anti-swelling effect have been reflected and gained lots of high praises from home and abroad customers. At the same time, we can provide customers with a pair of services, for different strata, to provide different types of stabilizer. The LEAD OILFIELD SERVICE COMPANY is willing to grow together with you, to join hands with you to create a better future and make a contribution to the worldwide oilfield business.