Submersible Pumping - Long Beach Unit of East Wilmington Field: A 17-Year Review
Authors: Allis D.H. , Capps W.M. 
Published: December 2007

The electric submersible pump (ESP) was selected as the primary form of lift when we initiated production operations in Aug. 1965. Deviated production operations in Aug. 1965. Deviated wells with ever increasing volumes resulting from water flooding required the flexibility offered by this lift method. Many problems have been solved in the 17 years of these operations to provide a respectable run life and a sound economic provide a respectable run life and a sound economic operational basis.

Introduction

The ESP has been the chief form of artificial lift in the Long Beach Unit of the East Wilmington field. From Aug. 1965 through May 1983, a total of 657wells have been produced by submersible pump, with 610 active submersibles currently pump, with 610 active submersibles currently producing 476,000 B/D[75 678 m3/d] gross fluid. producing 476,000 B/D [75 678 m3/d] gross fluid. A number of improvements have been implemented over this 17-year period. These improvements have contributed significantly to reducing the failure rate from a high of 71/month in Oct. 1969 (425 wells) to a low of 10/month in March 1980(503 wells). Failures during 1982 averaged 35 a month from approximately 590active submersible wells. Thirty-two failures (610 wells) were recorded for May1983 (Fig. 2). A recent survey showed an average run life of 800 days for wells in the Ranger zone (4,000 ft [1219 m] measured depth), which has 96% of the 610active submersibles as of May 1983. The improvements are reviewed next.

Feed through Mandrel and Pigtail System

It was obvious from the beginning that the normal method of packing off around a narmorless section of cable through the wellhead was unsatisfactory from a safety point of view, considering wellheads 6 ft [1.8 m] apart in urban operations. A gas-saturated cable jacket would permit migration of casing head gas into the cellar and also on through the jacket of the upper pigtail to the electrical junction box-both highly unsafe operating conditions. In May 1966, THUMS, in conjunction with a wellhead manufacturer and an electrical connector manufacturer, successfully designed and implemented the feed through mandrel and pigtail system shown in Fig. 1. The system consists of a lower pigtail spliced to the top end of the power cable, an O-ring sealed mandrel through the wellhead (rated at 3 kV AC and 5,000 psi [34.475 MPa]), and an upper pigtail from mandrel to junction box. This system provides complete blockage of gasmigration through the jacket. Mandrel pins are phase-identified for correctrotation, and provide a quick means of recording the electrical provide a quick means of recording the electrical readings of the downhole system. The system also greatly expedites well servicing operations. Fig. 1 shows a typicalpigtail mandrel system with instructions for proper banding. Care should betaken for proper banding and splicing to prevent creation of potential failure points at the splice and molded connector.

Solid-State Overload/Underload Controls

Our initial operations used submersible pump manufacturers' panels with cumbersome dash pots or meter relays as overload/underload (OL/UL) controls. In1967, we began to use our specially designed space saving pump motor control centers (PMCC). A more reliable OL/UL control device was needed for this PMCC. In May 1970, we, in conjunction with an electrical motor engineer and an electronic engineer, installed a 4- × 7- × 5-in. [102-× 178-× 127-mm] black box in the PMCC on Well J-547 for evaluation as an OL/UL control device. After 1year's evaluation with no problems, the unit was eventually phased into service on all our wells. Improved models currently are being installed on new wells. It is believed that the solid-state control device has accomplished as much as any single improvement in lengthening run time on these wells.

Isolation Transformers

Dry-type auto transformers were initially used and placed in each PMCC. The early high rate of phase-to-ground cable failures prompted an engineering study that resulted in the adoption of isolation transformers. Some of the first installations of this type of transformer extended the well's run life by 2 to3 years These favorable results led to complete changeover to isolation transformers.

Evaluation of Failed Equipment

With the increasing failure rate in the late 1960's, production engineers began reviewing the 20 most troublesome wells to detect failure trends and recommend methods for correction.

JPT

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