RU2496915C1 - Corrosion protection method for pipelines of water-cut oil collecting system - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves preliminary discharge of the main volume of produced water in units for its discharge, oil transport via pipeline with residual water content to a centralised oil preparation station, creation in the pipeline of moved liquid plug of protective coating; with that, liquid plug of solution of oil-soluble corrosion inhibitor in pumped dewatered oil is formed in the pipeline; from time to time, oil phase is accumulated in the water discharge unit by reducing the quantity of its removal to the pipeline and by decreasing the position of "oil-water" boundary level in the unit, and when the specified minimum level is reached, initial amount of removed oil to the pipeline is recovered, and when the accumulated oil phase is being removed from the unit, an oil-soluble corrosion inhibitor in the form of quaternary ammonia compounds of alkyl imido amines is introduced to the above phase in terms of at least 5% of the oil volume.

EFFECT: improving corrosion protection efficiency.

1 dwg

Description

The present invention relates to the oil industry and can be used to combat corrosion of oil pipelines in areas from track water discharge installations to centralized oil treatment facilities.

It is known that in-field transport of waterlogged oil during the development of an oil field is associated with significant corrosion caused by the contact of aggressive produced water with pipe walls.

There is a method of track discharge of the main volume of water in the head of a field oil pipeline, the purpose of which, among other things, is to reduce pipe corrosion due to a significant reduction in the contact of water with metal. Discharge devices for implementing the method are inclined pipes, from the lower part of which stratified water is discharged, and from the upper part, the oil and gas phases / 1, 2 /. Water is then diverted to the reservoir pressure maintenance system (RPM), and oil with a residual (up to 10% by volume) amount of water enters the pipeline. The gas phase is diverted to the consumer, or introduced into the oil pipeline. In order to prevent oil from entering the discharged water and further into the injection wells, the level of the oil-water section in the discharge apparatus is maintained at the level of oil extraction. Thus, the incomplete discharge of water causes its partial flow through the oil line into the pipeline and then to the central point of oil treatment.

The way water discharge method has the disadvantage that the residual amount of water in the field pipeline forms the so-called “underlying layer”, which tends to thicken in the lower sections and causes metal corrosion on the lower surface of the pipes. In the practice of operating interfield oil pipelines, this phenomenon has received the name - “brook” or “groove” corrosion.

A known method of protecting pipelines from corrosion, pumping water-in-oil emulsion, in which the tube is periodically pumped with a plug of produced mineralization water 1.16-1.18 g / cm ³ containing 2.0-2.5 kg / m ³ water-soluble corrosion inhibitor - bactericide / 3 /. The disadvantage of this method is that in this case, water-soluble inhibitors are used, the effectiveness of which is low due to the fact that they can easily pass from the metal surface to the aqueous phase of the stream that does not contain a corrosion inhibitor.

Closest to the proposed invention is a method of applying a protective coating on the inner surface of the pipeline using a protective composition, pushed through the pipeline in the form of a liquid plug between two elastic separators / 4 /. As elastic dividers, rubber balls are used. To move the separators with the protective composition between them, compressed air is used. The method requires a significant consumption of expensive composite compositions, time for emptying the pipeline from the pumped aggressive environment, air injection, etc. Abrasion of elastic dividers leads to leaks, unproductive consumption of protective compounds and incomplete coating of pipes.

The objective of the invention is to increase the efficiency of the method by forming a solution of an oil-insoluble corrosion inhibitor in a dehydrated pumped oil in a liquid tube conduit.

This goal is achieved by the fact that in the known method, including the preliminary discharge of the main volume of produced water in the devices of its line discharge, oil transportation through a pipeline with a residual water content to a centralized oil treatment point, the creation of a movable liquid plug of a protective coating in the pipeline, is periodically produced accumulation of the oil phase in the water discharge apparatus by reducing the amount of its discharge into the pipeline and lowering the position of the oil-water section in the apparatus and upon reaching NIJ predetermined minimum level reduced initial amount of oil withdrawn in conduit in the reset period of the machine oil accumulated phase introduced therein an oil soluble corrosion inhibitor, e.g., alkilimidoaminy rate of not less than 5% of the volume of oil.

The drawing shows a diagram of the implementation of the proposed method. The apparatus for the directional discharge of produced water 1 contains an inlet pipe 2 with a valve 3 for receiving well products, a pipe 4 with a valve 5 for discharging the main volume of incoming water from the device 1, a pipe 6 with a valve 7 for draining the oil phase from the device, pipeline 8 s valve 9 for the selection of the separated gas. An oil pipeline 10 for pumping oil is connected to the valve 7, having an inhibitor inlet (shown by an arrow) and a valve 11 at the entrance to the oil treatment point. At the final section of the pipeline 10, taps 12 and 13 are placed between which there is an insert control pipe 14 of the same diameter. In front of the valve 12 and after the valve 13, a bypass line 15 with a valve 16 is inserted into the pipeline. At the lower point of the pipe 14 there is a sampling valve 17. The circuit also includes the water line 4 and the oil line 6 connected by a pipe 18 with a valve 19.

The drawing also shows the extreme upper (I) and lower (II) positions of the oil-water interface in apparatus 1.

In the normal operation mode of the apparatus 1, the production of the group of wells is carried out through line 2 with the gate valve 3 open. In the apparatus, under the influence of gravitational forces, as well as in advance of the demulsifier introduced, oil and water are separated. The main volume of produced water is discharged into the RPM system through line 4 with the valve open 5. The remaining water is discharged into the pipeline 10 along with oil through line 6 with the valve open 7. Separated gas is discharged through the top of the apparatus via line 8 through the open valve 9 to the consumer or can be introduced into the pipeline 10. In this mode, the valves 16, 17, 19 are completely closed.

The residual amount of water in the oil stream forms an underlying water layer in the pipeline, causing corrosion of the metal. However, if you periodically completely cover the pipe surface with a film of a corrosion inhibitor oil solution, then due to its increased adhesion to the metal, it will protect the pipes from corrosion for a long time, until the flow gradually rinses it off the surface.

To apply a protective oil film to the inner surface of the pipeline 10 along its entire length, a shutter 19 is partially opened of the line 18 connecting the water 4 and oil 6 lines. Due to the fact that the hydrostatic pressure at the point of insertion of the line 18 into the water line 4 exceeds the pressure at the point of the insertion of the line 18 into the oil line 6 due to the presence of a column of water in the apparatus, the flow of part of the discharged water into the oil line 6 will begin.

As a result, less oil and more water will flow into pipeline 10. Due to this, the accumulation of the oil phase will begin in the apparatus with a decrease in level I of the oil-water interface. When this surface reaches level II, the valve 18 is completely closed. After that, the accumulated dehydrated oil will be diverted from the apparatus through the oil line 6 to pipeline 10 with continued discharge of water to line 4. At the same time, the interphase level will move upward from position II to position I. When it reaches position I, the residual amount will begin to flow into the oil outlet water and the unit will return to normal operation.

During the discharge of the oil phase in the pipeline 10, the corrosion inhibitor is dosed based on at least 5% of the oil volume accumulated in the apparatus. Given that the volume of the apparatus between levels I and II is large enough, the created plug of dehydrated oil in the pipeline 10 will be of considerable length. The movement of such a plug is accompanied by the displacement of the aqueous phase from the entire metal surface due to intensive turbulent mixing of the oil flow and an abundant coating of the surface of the pipeline 10 with an oil protective film. When oil moves through the pipeline, a corrosion inhibitor from the volume will be adsorbed at the oil – metal interface and provide long-term protection of the metal from corrosion. The concentration of the inhibitor in an amount of not less than 5% was determined experimentally in the laboratory. The introduction of a smaller amount of inhibitor into the oil did not lead to a significant improvement in corrosion protection due to the capture of particles of the inhibitor by oil.

As such a plug moves, its head and tail are eroded, and when approaching the final section in the pipeline, the length of the oil plug will significantly decrease. To prevent corrosion of the final section of the pipeline, it is necessary that the length of the uncleared portion of the plug on it be sufficient to form an oil film on the metal. The length of the uncleared portion is monitored by taking liquid from the lower point of the plug-in control pipe 14. If the length of the non-smeared portion of the oil plug is insufficient or its excess is adjusted, the amount of accumulated oil in apparatus 1 is adjusted and the minimum level II position is changed.

During the subsequent operation of the apparatus 1 and pipeline 10, the protective film state is periodically analyzed without stopping pumping by temporary dismantling of the control pipe 14 by closing the valves 12 and 13 and opening the valve 16. When the initial thickness of the oil film is significantly reduced or the process of its separation from the metal begins, the oil is re-pumped conduit plugs 10.

The technical and economic advantage of the proposed method is the absence of additional costs for applying a protective coating and time for ongoing operations to protect against corrosion.

Information sources

1. RF patent No. 2230594. Installation for preliminary water discharge / Golubev V.F., Khaziev N.N., Shaydullin F.D. et al. 08/14/2003. Publ. 06/20/2004.

2. RF patent No. 2238781. Water discharge installation / Khatmullin F.Kh., Shaydullin F.D., Nazmiev I.M. et al. 08/14/2003. Publ. 10/27/2004.

3. RF patent No. 2158786. A way to protect pipelines from corrosion / Garifullin F.S .; Kalimullin A.A .; Shilkova R.F. Claim 08.24.1999 Publ. 11/10/2000.

4. RF patent No. 2059145. The method of applying a protective coating to the inner surface of the pipeline / Bakiev A.V., Yusupov Kh.Z., Mubinov D.M. Claim 05/26/1992. Publ. 04/27/1996.

Claims (1)

A method of corrosion protection of pipelines of a system for collecting waterlogged oil, including preliminary discharge of the main volume of produced water in devices for its line discharge, transporting oil through a pipeline with a residual water content to a centralized oil treatment point, creating a protective coating in the pipeline of a movable liquid plug, characterized in that a liquid plug of a solution of an oil-insoluble corrosion inhibitor in the dehydrated pumped oil is formed in the pipeline, periodically produce the oil phase in the water discharge apparatus by reducing the amount of its discharge into the pipeline and lowering the position of the oil-water section in the apparatus and upon reaching the specified minimum level, the initial amount of oil discharged into the pipeline is restored, and during the period of discharge of the accumulated oil phase into it an oil-soluble corrosion inhibitor is introduced in the form of quaternary ammonium compounds of alkylimido amines based on at least 5% of the oil volume.

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