Oilfield services

Oilfield chemistry and services are used by oil production companies for recovery and transportation of produced fluid and further oil processing prior to delivery to customers via a transport company.

Main tasks to be solved by oil companies according to the process are:

Production:

• Reduction of oilfield equipment maintenance costs (scaling, corrosion);
• Improvement of rheological properties and efficiency of transportation of produced fluid (asphaltene wax and paraffin deposits, high viscosity emulsions);
• Bacterial contamination control (SRB).

Transportation:

• Extension of service life of transportation network and oilfield equipment;
• Improvement of flow hydrodynamics;
• Pipeline capacity increase.

Oil treatment:

• Improvement of emulsion separation;
• Corrosion protection of process equipment.

According to specific tasks MIRRICO company offers complex solutions based on own services and individually selected chemical products.

Production

1. Reduction of oilfield equipment maintenance costs (scaling, corrosion)

Premature wear and failure of equipment cause increase of material costs for replacement and re-equipment of the existing oilfield systems.

Premature wear (corrosion) and failure of equipment may be attributed to high corrosive power of the produced fluid towards the material of downhole equipment and oilfield pipelines.

Application of Scimol™ corrosion inhibitors supplied by MIRRICO company considerably increases time between overhauls of the equipment. Inhibition treatment of oilfield equipment can be carried out by continuous injection of corrosion inhibitor into pump suction or by intermittent injection into casing annulus.

Premature failure and requirement to replace equipment is as a rule caused by deposition of CaCO3 and any other salts resulting into serious troubles during oil production such as scaling of the tubing string – reduction of inner diameter of the tubing string and as a result decrease of well production; failure of borehole pumps in case of artificial lift; intensive corrosion of inner surface of tubing string and oil gathering systems pipelines at the spots of localized deposit separation from the wall. Therefore to provide normal operation it is important to take anti-scaling measures by use of scale control chemical agents Descum™ supplied by MIRRICO company which have been successfully used on many sites in different geographical regions and have been acknowledged as high efficiency scale inhibitors and solvents.

Descum™ scale inhibitors and solvents should be used taking into account not only scaling tendency of the produced fluid but composition of already formed scale deposits as well. Treatment of wells with these inhibitors can be carried out through intermittent injection into annulus or via armored capillary injection systems which allow injecting of chemicals into any point of the tubing string. Injection of scale inhibitors through the capillary system into perforated interval provides better spread of the chemical agent in the produced fluid which reduces or prevents formation of inorganic deposits on working parts of pumping equipment.

2. Improvement of rheological properties and efficiency of transportation of produced fluid (asphaltene wax and paraffin deposits, high viscosity emulsions)

As a rule wax and paraffin deposits mostly contain saturated hydrocarbons (paraffins) or aromatic hydrocarbons (asphaltenes and resins). In case of prevailing concentration of paraffins hot oiling will temporarily increase inner diameter of the tubing string and use of a scraper has a short-term effect and often requires well shutdown and in the longer term this method becomes uneconomic. In case of prevailing content of asphaltenes and resins in paraffin deposits the above-mentioned methods are inefficient.

Chemical solution of this problem has many advantages over other methods (scraper, hot oiling), including higher efficiency.

In case of problems related to deposition of organic sediments it is advised to remove the deposits first by injection of a paraffin solvent into well annulus, then apply paraffin inhibitor or dispersant. A method of application is selected according to the temperature conditions of chemical treatment: intermittent injection into the annulus of the producing well, or continuous injection of the chemical agents. Inhibition is only reasonable when temperature of the produced fluid in the point of the chemical injection is higher than paraffin chilling point, otherwise it is recommended to use dispersants.

A pressure increase in the tubing can be prevented through adjustment of rheological properties of the produced fluid. Pour point and viscosity of the produced fluid can be depressed with a depressant which modifies paraffin particles.

MIRRICO company offers a range of Dewaxol™ chemicals which includes inhibitors, solvents, dispersants of paraffin deposits and depressant additives.

Selection of Dewaxol™ chemicals is carried out on the basis of particular physicochemical properties of formation fluid as well as on the basis of factors causing formation of paraffin deposits or increase in pressure in pipelines. According to results of laboratory tests optimal injection rate of the chemical and the recommended application technology are determined.

It is important to take into account that after paraffin control operations failures in oil treatment process may occur caused by dissolved paraffin products delivered to oil treatment facilities with the liquid-gas mixture.

3. Bacterial contamination control (SRB)

Contamination of oil saturated layers with sulfate reducing bacteria (SRB) is one of the reasons for inner corrosion of oil pipelines. SRB are a physiological, not a systematic group, as they include microbes belonging to different taxonomic groups utilizing anaerobic respiration with sulfates. General microbial contamination of produced water occurs during oilfield development with maintenance of reservoir pressure by injection of water without prior bacterial treatment. The most active SRB growth is observed in the bottomhole zone of producing wells as it has all favorable conditions for bacterial activity: optimal water mineralization, residual oil, and optimal temperature. Later on SRB are delivered to surface equipment, adhere on metal surfaces, form a biofilm and act as corrosive agents mostly due to production of corrosive metabolites and formation of corrosive media. The corrosive metabolites are organic and inorganic acids, ferments, hydrogen sulfide.

A hydrogen sulfide corrosion product is iron sulfide (FeS) which if accumulated on the inner pipe surface and other oilfield communications causes formation of a strong galvanic coupling iron/iron sulfide. As the FeS electrode potential is more positive than that of iron, iron sulfide serves as a cathode and the metal surface becomes an anode. Besides formation of mucopolysaccharide slime by the bacteria makes FeS sediments sticky and improves its contact with the anode surface and at the same time protects SRB against unfavorable conditions. All these factors result into sharp increase of corrosion rate (2-4 times) especially that of pit corrosion.

Beside bacterial corrosion microorganisms are the cause of congestion of bottom-hole zone of injection wells due to accumulation of bacteria biomass and insoluble metabolic products which leads to reduction of permeability by 30-40% and worse oilfield development conditions. SRB change physicochemical characteristics of the reservoir water as sulfate reduction causes loss of sulfate ion and enrichment with hydrogen sulfide and carbon dioxide and as a result water turns from sodium-sulfate type into sodium-bicarbonate type of water. Furthermore bacterial flora activity causes biodestruction of chemical oil displacement agents and changes quality and composition of oil which results in the first place into increase in its specific weight, viscosity, content of asphaltene-resinous compounds.

The most common method of inhibition of microbial activity in oil reservoirs is application of biocides based on quaternary ammonium salts. Biocides’ efficiency is attributed to their ability to dissolve in phospholipid layers of cell membranes which increases membrane permeability and leads to demise of bacteria. Sulfate reducing bacteria can be efficiently neutralized by Atren™-Bio biocides provided by MIRRICO company.

Injection rate of the biocide is 500 g/t. Injection method – continuous or intermittent injection into the well annulus.

Transportation

1. Pipeline capacity increase

One of the problems during pipeline operation is control of organic and inorganic deposits. Even small amount of scale and paraffin deposits lead to considerable increase of operating pressure and reduction of oil pumping capacity.

Effective chemical solutions are represented by Descum™ and Dewaxol™ chemicals supplied by MIRRICO company which are designed for elimination and prevention of paraffin deposition.

Method of application – continuous injection into the oil pipeline or into the pipeline of the reservoir pressure maintenance system.

According to composition of produced or reservoir water inhibitors of carbonated or sulfate deposits are applied. If results of six component water analysis are available it is possible to conduct laboratory tests with synthetic model without on-site presence. Application of these products is carried out constantly by injection into the treated pipeline.

Pipeline capacity can also be increased by adjustment of thermobaric conditions. Hydranox™ hydrate inhibitors supplied by MIRRICO prevent pipeline blockage with gas hydrate plugs. If compared with thermal insulation/heating operations and mechanical gas discharge, chemical solution is the most appropriate even considering relatively high cost of the chemical agent.

2. Improvement of flow hydrodynamics

Pipeline pressure can be changed to a normal level through adjustment of rheological properties of oil.

Dewaxol™ depressant additives supplied by MIRRICO which depress pour point and viscosity of oil are injected directly into the pipeline.

3. Extension of service life

Oil gathering system and reservoir pressure maintenance system can be protected against carbon dioxide corrosion by application of Scimol™ corrosion inhibitors offered by MIRRICO.

Water dispersible products are supplied for low pressure pipelines. Water dispersible and oil soluble corrosion inhibitors are also available.

High concentration of hydrogen sulfide and/or mercaptans can be neutralized by Asulpher™ hydrogen sulfide scavengers provided by MIRRICO company.

Concentration of hydrogen sulfide scavengers is 5-10 g. per 1 g. of dissolved hydrogen sulfide/mercaptans.

Deoxol™ oxygen scavengers provided by MIRRICO can be also applied. The concentration is 5-10 g per 1 g of dissolved oxygen.

Oil treatment

1. Improvement of emulsion separation

The reason for high stability of oil emulsions is formation of water droplets on the surface of oil phase, protecting layers of natural stabilizers present in oil such as naphthenic acids, resins, asphaltenes, paraffins, ceresines, porphyrins, metal-porphyrine complexes.

Natural surfactants are adsorbed on the surface of the water droplets on the side of oil phase and form protective layers. In this case increase of strength of hydrate films on the globules of emulsified water is observed which in its turn inhibits flocculation and coalescence. Strengthening of hydrate films is also contributed by considerable solids content (rock particles, salt crystals).

Application of Decleave™ demulsifiers provided by MIRRICO helps to reach first class oil treatment quality.

Apart from low residual water content (<0.5%) and low chloride salts content (<100 mg/l) in salable oil these chemicals provide fast separation of oil emulsion with high quality of phase interface. Oil content in the produced water under application of Decleave™ demulsifiers conform with the required level of the oil company (<40 mg/l).

Demulsifiers can be used both for preliminary separation of produced water at the pump station (preliminary water removal unit), and for deep dehydration of oil at oil processing facilities. Decleave™ can be also successfully applied in the oil treatment systems with provided intratubal demulsification.

2. Corrosion protection of process equipment

High concentration of hydrogen sulfide and and/or mercaptans can be neutralized by Asulpher™ hydrogen sulfide scavengers provided by MIRRICO company.

Concentration of hydrogen sulfide scavengers is 5-10 g. per 1 g. of dissolved hydrogen sulfide/mercaptans.

Deoxol™ oxygen scavengers provided by MIRRICO company. Concentration is 8-12 g of the scavenger per each complete and incomplete gram of dissolved oxygen in the water.

Besides, service life of the equipment is extended due to reduction of corrosive components of saleable oil during water removal (Decleave™ demulsifiers).

You can get more detailed information about oilfield chemicals (demulsifiers, corrosion inhibitors, scale inhibitors, paraffin inhibitors, hydrogen sulfide scavengers, oxygen scavengers) provided by MIRRICO company in the “Products” section.

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