Corrosion inhibition and scale inhibition for water injection treatment of oil production

Water injection is a common stimulation technology in petroleum development. It can increase the bottom hole pressure, change the physical properties of the reservoir and reduce the viscosity of the reservoir by water injection treatment, improve the flow of crude oil and oil recovery efficiency, so as to increase the production of oil exploitation.

At present, there are generally three methods of oilfield water injection technology, one is to use clean water injection method to complete the injection of oilfield groundwater. The second is to use sewage injection method, that is, water injection from the oil reservoir. The third is the water injection method of offshore oilfield, which adopts the water injection method at sea. In addition, there are mixed water injection methods.

What are the effects of water injection treatment?

Crude oil displacement effect: In the process of oil recovery, crude oil often forms a depression area at the bottom of the well, which reduces productivity. By injecting water to increase the bottom hole pressure, the pressure difference is created, so that the crude oil is pushed from the depression area to the wellhead, increasing the speed and production of oil.

Fracturing action: Injected water can change the physical properties of the oil reservoir through the action of pressure, so that it can produce cracks or pores, thereby increasing the channel of crude oil flow and improving oil recovery efficiency.

Reduce the viscosity of the oil reservoir: During the underground storage of crude oil, a certain viscosity will be generated due to the action of pressure and temperature, resulting in difficult flow of crude oil. Injecting water reduces the viscosity of the reservoir, making it easier for crude oil to flow to the wellhead.

Replenishment of bottom hole moisture: During oil production, the bottom hole may have low pressure due to factors that make it difficult for crude oil to flow, such as insufficient water. By injecting water, the water at the bottom of the well can be replenished, increasing the pressure at the bottom of the well and promoting the flow of crude oil.

But the water contains a lot of calcium, magnesium and strontium, barium plasma, resulting in calcium magnesium scale, corrosion and other problems of the pipeline. In serious cases, the phenomenon of blocking oil layer will occur, which will reduce the permeability efficiency of oil layer and cause great loss to oil layer in oil field. However, scaling treatment of part of the wellbore and equipment in the well will limit the flow space of the pipeline, thus increasing the friction force and easily providing an environment for bacteria to breed, increasing the degree of rust of the downhole oil equipment and reducing the service time of the well equipment. In serious cases, the thermal efficiency of the equipment will be reduced, resulting in pipeline explosion and finally large-scale shutdown. The normal operation of oil field equipment is seriously harmed, and the production of oil recovery technology is sharply reduced

The emergence of corrosion and scale inhibitor for water injection treatment has greatly facilitated the oil field water injection treatment. The slow-release scale inhibitor can form a protective film with the surface of metal materials to avoid chemical reactions between the metal surface and oxides and acidic substances in water, slow down or avoid metal corrosion and oxidation, and thus extend the service life of equipment and pipelines. At the same time, by controlling the hardness ions (such as calcium and magnesium ions) in the water, the hardness ions can avoid the formation of scale in the water contact parts of the equipment and pipes, so as to reduce the harm of scale to the equipment and pipes, and improve the efficiency and reliability of the equipment.
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