Multifunctional auxiliary chemicals for oil industry

Microbes cause 80 % of the corrosion damage in oil-producing industry.

Many serious problems arise in oil recovery, storage, and transport ranging from increased cost of the basic technological processes to degrading the quality of the oil itself.

Oil recovery

Drilling mineral oil wells is the first and probably the most complex problem in the whole technological cycle. As a rule, oil is produced in remote uninhabited territories with a bleak climate. Due to these difficulties the personnel has to live in temporary camps near the oil wells. The quality of service materials: tubes, backfill cement, and drill liquid plays an important role in the oil recovery process beside that of the drilling machine.

Backfill cement is used for sealing the drilled wells after installation of the tubes for pumping oil to the surface. The basic requirements to such cement are high spreadability of the cement slurry (for penetrating the narrow space between the tubes and the rock) and high mechanical strength (because of high pressure used in the cells).

Cement-polymer mix developed by the Moscow Research and Production Company “Radon” in co-operation with the Institute for Ecotechnologies answers these requirements. The mix contains cationic polyelectrolyte based on polyalkylene guanidines (PAGs).

Drill liquid is another expendable material used in oil well drilling. It is used for cooling the auger and carrying the drill cuttings to the surface. Clay drilling sludge is most commonly applied.

This type of drill sludge is a colloid solution of bentonite in water. To make the colloid solution more stable (which is the more important under the conditions of salt (NaCl + CaCl2) aggression) hydrophilic polyelectrolytes are used. Polyalkylene guanidine and also polyethyleneimine with its guanidine derivatives have a number of advantages for this application.

Extraction of oil from the petroliferous strata is a complex technological problem. The oil, which usually fills porous rock, can be washed away with special flood solutions (surfactant solution, inversion solution based on light hydrocarbon fractions, or polymeric solution). Polymeric flooding solutions have been most often used recently due to the convenience and safety considerations.

The main idea of this technique consists in using water solutions of high molecular mass polymers that have high viscosity. The viscous polymeric solution non-miscible with the less viscous oil can efficiently expel it from the porous rock, acting as a piston.

Cheap and readily available acrylamide polymers partially hydrolysed with caustic soda are usually used for flooding of oil horizons. High viscosity of the diluted solutions of such polymers is due to their extremely high molecular mass (ca. 107).

The important drawback of polyacrylamide (which has molecular structure very similar to that of protein molecules) is its extreme susceptibility to attacks of fungi and other microorganisms. Such attacks, which are usually directed at the very centre of the giant macromolecule, result in a drastic reduction of its molecular weight. This leads to an essential decrease of the viscosity, which is the main working parameter of the polymer solution in the process of oil expelling from the oil horizon.

Biocides are used to protect the polyacrylamide solutions from the attacks of microorganisms living in oil strata.

Polymeric biocides developed by the Institute of Ecotechnologies proved to be the best suited for this purpose. They suppress the oil strata microflora, but they also “heal” the rents in the polyacrylamide macromolecules due to the chemical interaction between the two polymers. Biopag additives have been tested in real oil strata water from the oil fields in Udmurtia. After keeping the floodwater with Biopag additives for several weeks its viscosity did not decrease, but, on the opposite, somewhat increased.

Purification

Oil pumped from the oil well has the form of water-oil emulsion containing a large portion of mineral salts. Such crude oil should be dehydrated before it could be subjected to rectification or other technological processes. Separation of crude oil from water solution of salts is usually achieved via a special technological process using auxiliary polymeric reagents. Cationic polyelectrolytes such as polyguanidines and polyethyleneimines proved to be well suited for this purpose.

Their additional advantage for this technology consists in their anticorrosion properties. This is important because of the usually high corrosion aggressiveness of crude oil, which is due to the presence of hydrogen sulphide, other sulphur-containing compounds, and sulphate-reducing microorganisms.

All these can be effectively neutralised with polyalkylene guanidines as it was shown in purification of textile and tanning industry wastewaters that also contain hydrogen sulphide, other sulphides, and thionic microflora.

Storage

Purification of crude oil and even its rectification into gasoline, diesel oil, and lubricating oils does not solve all the problems connected to the safe keeping of the “black gold”. Similar to polyacrylamide and other organic substances, oil products are susceptible to biodestruction by the biocenoses naturally developing in them. The biocenoses include bacteria, fungi, algae, and other microorganisms.

The biocenoses damaging oil products usually develop at the oil-water interface. (Water layer is always formed at the bottom of an oil tank due to the temperature variations.) Biological damage of oil products can be especially strong at the seaside oil storage facilities in warm climate. Intensive development of such biocenoses can even result in gelation of the oil products.

The Institute of Ecotechnologies has developed special biocidal additives for protection of oil products during storage and transport. The additives contain polyalkylene guanidines soluble in oil products and special homogenising substances.

Even very small concentration of such additive can ensure a long-term (up to twelve months) protection of oil products and bottom-layer water from development of biocenoses. The additives do not change physico-chemical properties of the fuel and form no ash after burning.

Thus, polymeric biocides developed by the Institute of Ecotechnologies find their application in all the stages of oil production, processing, and storage. They help to solve a wide range of problems. Such versatility makes polyguanidines useful reagents for the oil industry.

Alexandr DITYUK, Ph.D. (physics)

Deputy Director of the

Institute of Ecotecnologies

Petr GEMBITSKY, Dr.Sci (chemistry)

Leading Researcher of the

Institute Of Ecotechnologies