Introduction
Erosion and corrosion problems cost petroleum and other industries hundreds of millions of dollars each year. Severe damage has occurred to tubing, flow lines, pipe fittings, headers, valves, pumps, and other production equipment. Erosion/corrosion problems are associated with production velocities. Erosion is most severe when production velocities are high. Erosion-corrosion problems of deep pitting occur at intermediate flow velocity ranges when protective scales are removed by sand impingement.
To date, the most effective countermeasures involve using special erosion/corrosion-resistant materials, inhibitors, coatings, or placing limitations on production and flow velocities. These solutions can be very costly, and considerable work has been directed toward helping producers control the costs and lost production associated with erosion/corrosion damage. However, only limited work has been directed toward understanding the effects of flow velocity and flow geometry on the removal of metal by erosion/corrosion.
Oil and gas companies seek design and operating guidelines that will allow them to economically maximize production rates. Current American Petroleum Institute (API) guidelines are based on a recommended "erosional velocity" limitation described by The API Recommended Practice 14E (API RP 14E), which does not recognize many of the important factors contributing to erosion and corrosion damage. For example, the RP 14E guideline does not account for solid particles contained in the flow (such as sand), corrosivity of the fluid, type and concentration of inhibitors used, formation and removal of corrosion scale, type of metal used in equipment or geometries of production equipment.
The overall goal of this research program is to generalize the "threshold velocity" concept embodied in RP 14E to account for these additional factors. To achieve this goal, experimental data relating the solid particle erosion, liquid-droplet erosion, corrosion, and erosion-corrosion damage to flow velocity and to the other key factors are needed. Computational models are needed to guide the experiments and to extend the experimental results. To date, results from experiments and modeling have been combined to develop procedures and user-friendly computer programs for sand erosion to generalize API RP 14E. The program is called SPPS for Sand Production Pipe Saver. User-friendly computer programs have also been developed for liquid-droplet erosion (LIES), CO2 corrosion (SPPS:CO2) and erosion-corrosion (SPPS:E-C). Currently, we are expanding the accuracy and capabilities of these programs. Parameters being investigated are additional pipe fittings, multiphase flow conditions and various particle sizes and pipe materials.
The following sections contain background information on the Erosion/Corrosion Research Center, the benefits of the program, research goals, and a description of the research performed at E/CRC.
Background & History
In July 1983, ten major oil and gas companies joined The University of Tulsa Erosion/Corrosion Research Center, a non-profit, cooperative program formed to address industry problems on erosion and corrosion in oil and gas production. The initial research program was directed at three tasks: (1) Conducting a literature review, visits and discussions with companies and summarizing the state-of-the-art, (2) Identifying the erosion/corrosion problems of the companies and the resources needed to address these problems, and (3) Preparing a research program to address these problems. Visits and discussions pointed toward an interest in the effects of flow velocity on corrosion and erosion and a need to improve the currently used guidelines for the "erosional velocity" given in API RP 14E.
To date, more than 50 major Oil and gas and service companies had or have been members of E/CRC. Experimental research topics for the Erosion/Corrosion Research Center are selected by Advisory Board Members from sponsoring companies through discussions and questionnaires and originally included topics such as velocity effects on the performance of inhibitors in two-phase flows, velocity effects on corrosion behavior in two-phase flows involving carbon dioxide corrosion, and velocity effects on liquid impingement and solid particle erosion. However, currently, nearly 100% of the research efforts are targeted toward sand erosion in pipelines and wellbores including multiphase flows in elbows and other geometries as outlined in this description. The tools being generated by E/CRC such as the SPPS model are utilized by oil and gas companies around the globe and are being improved and expanded based on continuation of research in these areas.
The Erosion/Corrosion Research Center is structured to be a continuing entity to excel the research needed to address industry issues related to problems that are caused by sand production, and other topics such as material performance comparisons for resistance to erosion/corrosion will be addressed according to the guidance of the Advisory Board Members.