Method for enhancing the operational life of production parts in the oil and gas industry

Abstract

A method for improving the operational life of production parts, such as steel sucker rods, couplings, pump parts, and tubes, for use in underground recovery or production of oil and gas, includes coating the steel production parts with a layer of corrosion resistant alloy (CRA) to reduce a loss rate of the steel by improving corrosion resistance and mitigate pitting. In one embodiment, the corrosion resistant alloy is a nickel-based alloy. In other embodiments, the steel production parts can either be coated with an epoxy / phenolic layer, or coupled with a sacrificial anode. The coating process can implemented by any one of the following processes: cold spray coating; electroless corrosion resistant coating; flow forming; and electrochemical machining.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit under 35 USC §119(e) of U.S. provisional patent application 61 / 980,174, filed on Apr. 16, 2014, which is co-pending herewith and which is hereby incorporated by reference in its entirety.GOVERNMENTAL INTEREST[0002]The invention described herein may be manufactured and used by, or for the Government of the United States for governmental purposes without the payment of any royalties thereon.FIELD OF THE INVENTION[0003]The present invention relates in general to the field of subterranean extraction oil and gas. More particularly, the present invention relates to a method for improving the operational life of sucker rods, couplings, pump parts and rods or similar down hole equipment (collected referred to herein as “production parts”) for use in the oil and gas industry, through novel coatings and manufacturing processes.BACKGROUND OF THE INVENTION[0004]Many working oil wells depends on the sucker rods and ...

AI Technical Summary

Benefits of technology

[0024]The present invention addresses the foregoing concerns and presents new processes for examining high corrosion rates on sucker rods in oil and gas wells, and to develop solutions to increase the operational life of production parts

[0026]A preferred process includes the use of electroless, corrosion resistant coatings technology. This process enables unique, functionally graded coatings that can be matched to the operational environment. The coatings are deposited at low processing temperatures and do not thermally alter the microstructure of substrate material. The process enables rapid deposition of conformal coatings with minimal subsequent processing needed. The coatings may be deposited with beneficial compressive residual stresses, which may enhance the operational performance of production parts, such as in sour well environments in which H2S cracking is an issue.

[0028]Still another preferred process includes the use of flow forming technology. The flow forming process enables near net shape manufacturing of difficult-to-machine corrosion resistant alloy (CRA) materials, such as nickel base alloys. Moreover, this process may impart beneficial compressive residual stresses to mitigate the operational performance when used in sour wells.

[0029]Yet another preferred process includes the use of the electrochemical machining technology. Electrochemical machining can be exploited for its rapid material removal rates, ability to machine complex geometries, superior surface finish, and ability to retain prior beneficial compressive residual stresses from previous processes.

Problems solved by technology

Many oil wells have been suffering from the reduction in the couplings, tube and pump parts operational life, which drives the oil production costs significantly, not only in materials costs to procure new rods, but also in labor costs to replace the rods.

In addition, while the rods are being replaced, the oil production is suspended, further exacerbating the costs.

Corrosion is known to be one of the major issues contributing to the degradation and failure of equipment, such as the sucker rods, in the oil industry.

Corrosion accounts for about two-thirds of all sucker rod and coupling failures.

However, if and when this scale is compromised, such as by cracking, abrasion, etc., then aggressive local corrosion occurs in the affected areas, and appears as deep corrosion pitting.

The pressure impacts of a 10,000-foot deep well are also a very significant factor in solubility.

If the FeCO3 layer is not intact (e.g., not contiguous) or is cracked, localized pitting corrosion occurs.

Pitting corrosion tends to form under low flow or stagnant conditions often found in the vertical portion of an oil well tube.

The microstructure of the steel may also influence the corrosion in a CO2 environment.

However, the presence of microstructures composed of ferrite and cementite, results in increased corrosion due to the formation of a micro-galvanic cell within the steel.

In addition, microbial corrosion may occur in sucker rods.

This corrosion is due to the presence of bacteria that can produce H2S and other detrimental by-products.

Stray current corrosion may occur in the rod string if the pump jack were improperly grounded.

This may lead to arcing and damage to the sucker rods.

Manufacturing defects may occur in sucker rods, couplings, pump parts and / or tubing, known as production parts, that lead to stress risers, premature damage, and failure.

Examples of manufacturing defects include folds, nicks, scale, and microstructural defects, such as grain boundary melting, hardness differences (e.g., untempered martensite), and inclusions.

If the sucker rods are not straight or are bent during operation, this can lead to unevenly distributed stresses and fatigue cracking.