Abrasion Technology for Electric Submergible Pumps

Abstract

Abstract This paper describes the results of a five-year investigation of sand abrasion phenomena in conventional electrical submergible pumps (ESP). The investigation includes a review of the available literature on two body and three body wear processes in the presence of corrosive fluids, and the development of laboratory test methods from which baseline wear rates for conventional pumps can be established. These baseline wear rates are compared with performance data on pumps incorporating special wear resistant features. Preliminary field test results are also presented. Introduction In oilwells which produce significant quantities of sand, it is generally accepted that the run life of a conventional electrical submergible pump (ESP) is too short to be considered the pump (ESP) is too short to be considered the best economic choice of an artificial lift method. A large number of these wells, particularly in California and the Gulf Coast region of the United States, are now being gas lifted or are being produced at low rates with beam pumps. These produced at low rates with beam pumps. These could be economically produced at higher rates with centrifugal pumps if the run life of a conventional centrifugal pump could be increased Experience with sandy well production indicates that in a significant number of cases the sand production will drop to a nondestructive level after some period of sustained production. Unfortunately, period of sustained production. Unfortunately, an operator may be required to endure several expensive pump changeouts before this happens. Two methods of addressing the sand control problem can be considered. The first is gravel problem can be considered. The first is gravel packing. However, this is not an extensive practice packing. However, this is not an extensive practice with the use of pumps. Second, sand may be controlled by not drawing the well down below a certain bottomhole pressure but while reduced drawdowns may eliminate the need for sand control, it will result in decreased production. If sand is projected to be a problem, a submergible pump will usually not be considered. One severe application for ESP's has been in the North Sea in the Montrose and surrounding fields. The Montrose field was not expected to be a sand problem initially when ESP facilities were installed on the platforms. While the application was severe in many regards, sand has also been found to contribute to pump failure rates. Conventional gravel packs have not been tried due to the possibility of production decreases and the fact that only small amounts of sand per volume of fluid have been measured. Short run lives in submergible pumps in this offshore environment have led to pumps in this offshore environment have led to operating expenses far outweighing the cost of the pumping equipment per se. This paper also describes the initiation of controlled field tests in which actual wellhead sand rates are measured and performance between standard and abrasion resistant designs can be compared. These tests also are yielding a better understanding of how sandy wells perform with varying fluid production rate and with time. A number of design modifications involving both material and hydraulic enhancements have been tested in the laboratory under simulated downhole conditions. Results from these tests indicate that a 500% increase in pump life under abrasive wear conditions is achievable and practical. Uncontrolled field tests suggest the validity of these results and additional tightly controlled field tests are being conducted to confirm them totally. It is the authors' opinion that these advances will result in extending the use of ESP's in many more sandy wells. WEAR IN CENTRIFUGAL PUMPS The principal wear areas in a centrifugal pump are: 1) radial wear in journal and sleeve pump are:radial wear in journal and sleeve bearings,downthrust wear at thrust pads and washers, anderosion wear in the fluid passages. The location of each of these types of wear is illustrated in Figs. 1 and 2. Radial Wear Laboratory tests indicate that radial wear in low specific speed pumps is the most limiting to pump life.