Reduction of Salt Deposits on the Surface of Oilfield Equipment by Management of Electrochemical Parameters of the Medium

Abstract

Corrosion activity of the environment is caused by the presence in it of salt ions that are directly involved in the corrosion process causing deposition of inorganic salts on the surface of the equipment. Removal of such active salt ions from the working environment or modifying them from the active to the inactive state signifi cantly reduces the rate of corrosion of the equipment and the amount of salt deposits.The most common cause of damage to oilfi eld equipment is the impact of corrosive environment. Inorganic salt deposits on the surface of the equipment (salt scaling) often cause contamination of the pumped or processed media and reduction of the operational cross-section of the pipeline. Removal of the ions (salts) from the working medium, or their modification from the active state to the inactive signifi cantly reduces the rate of corrosion of equipment and the amount of scaling. Search for low-cost and highly effi cient methods of protection against salt deposits is an important task for the oil and gas industry. Moreover, the search for methods to reduce the corrosiveness of water coming into contact with oilfi eld equipment surfaces is highly relevant.In the development of oil and gas fi elds, a large amount of water is consumed for reservoir pressure maintenance thus prolonging the spouting period and signifi cantly increasing the oil and gas recovery factors of the reservoir. The system of reservoir pressure maintenance (RPM) is a technological equipment complex used for the preparation, transport, and injection of the working reagent and corrosion inhibitors into the petroleum reservoir. For reservoir pressure maintenance, both natural (freshwater and brackish) and sewage (drainage) waters are used, in the composition of which there are reservoir (85%), fresh (10%), and rain (up to 5%) waters. One of the characteristics of wastewater is high content of corrosion-active agents (hydrogen sulfi de, carbon dioxide, oxygen, etc.) that cause destruction of oilfi eld equipment. These gases dissolved in the water lead to the destruction of passive fi lms on the metal and cause depolarization of the cathodic reaction of metal ionization, which leads to the intensifi cation of the corrosion process.High concentration of mineral salts in reservoir environments is another reason for the formation of corrosive agents. For example, upon interaction between calcium sulfate CaSO 4 and methane present in the reservoir, hydrogen sulfi de can be produced. Unlike natural waters, wastewater may contain hydrocarbons and microorganisms, particularly, sulfate reducing bacteria, which reduce hydrogen sulfi de during metabolism.Mineralization of wastewater is mainly determined by the composition of reservoir waters usually categorized into four main types: sodium sulfate, sodium bicarbonate, calcium chloride, and magnesium chloride waters; their mineralization may range from 15 to 250 mg/liter. Calcium chloride reservoir water is found in the oil fi elds most often. The most active ions causing deposition of insoluble sa...

Method of investigation of local corrosion processes on samples from clad steel

“…Thus, the destruction of the cladding layer of the column contributes to a significant increase in the potential difference between the surface of the layer and the body, made of carbon steel. The study of the mechanism of electrochemical processes on the surface of clad steel is necessary conditions for determining the conditions of polarization of a metal surface in order to reduce its corrosion rate [8][9][10]. Timely monitoring of the corrosion state of the cladding layer, under the conditions of the action of the pitting-forming ions, will prevent the destruction of the metal of the column.…”

Cathodic protection of main oil pipeline

“…In addition, the efficiency of electrochemical protection systems (ECPS) is reduced due to the fact that the cathodic protection stations are controlled in most cases by maintaining the specified operating parameters without adapting them to changing load conditions [20][21][22][23]. Under such conditions, it is difficult to establish optimal output modes of cathodic protection plants (CPU), which would provide reliable metal protection throughout the main oil pipeline, taking into account external factors that vary over time (soil resistivity, operation modes of adjacent cathodic protection stations, the presence of wandering currents, DC and AC density, temperature) [24][25][26][27][28].…”

The use of the method of controlling the electrochemical parameters of aqueous solutions to combat complications in the operation of oil field pipelines

“…The use of fresh and waste water pumped into productive formations using reservoir pressure maintenance systems leads to their contamination with various microorganisms. It has been established that microorganisms can participate both directly in the anodic corrosion process, destroying the metal with the formation of corrosion pits, and in the cathodic depolarization process, when the products of their metabolism (for example, hydrogen sulfide) or the microorganisms themselves act as a depolarizer [4][5].…”