Abstract

This paper presents a review of a coiled tubing deployed, bottom intake (CTDBI) electrical submersible pump system (ESP) developed specifically for use in the Al Rayyan Field, offshore Qatar. The evolution of this technology to its present form will be reviewed along with the systematic approach used to enhance the original design and improve system run life. Also presented are workover, operational and economic considerations as compared to conventional ESP systems commonly run offshore. The review will also include the well completion design and how it functions and accommodates the ESP.

Introduction

Al Rayyan Field is located approximately 45 miles off the northern coast of Qatar in the Arabian Gulf. The field was discovered in 1976, however commercial development did not begin until 1996 through the application of horizontal drilling. Oil production is from carbonate reservoirs that require artificial lift. With its relatively low GOR and low bottom-hole temperature, Al Rayyan was an ideal candidate for ESP's.In order to be economically viable, the field development plan called for high production rates as well as a work over process that was more cost effective than conventionally deployed ESP systems requiring a drilling rig to pull and run. Al Rayyan Field currently has 13 producing horizontal wells, all equipped with CTDBI ESP's.

In 1996 the CTDBI ESP system was the first of its kind to be deployed. The key drivers behind developing this technology were to reduce workover cost and improve ESP availability with an ultimate goal being to achieve better overall project economics. In a typical conventional ESP system, the ESP string is run on jointed production tubing with a power cable strapped to the outside. The produced fluid reaches the surface via the conveyance tubing for which a drilling rig or pulling unit is required to run and pull. In the conventional ESP system the motor(s) are placed at the bottom of the ESP string, while in the CTDBI design the motor(s) are at the top. This difference makes the system unique and is why it is termed "bottom intake" (Figure 1).

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