Past, Present and Future Developments in CT ESP Technology in the Al Rayyan Field
Authors: Goddard Craig , Cuadros Ernesto 
Published: May 2016

This reference is for an abstract only. A full paper was not submitted for this conference.

Background

The Al Rayyan field came on production in 1996, and has from the outset been completed with coil tubing deployed ESPs (CT ESP). The drivers for this type of completion are several. Firstly economic, as these units are installed and pulled using coil tubing with a CT unit permanently located on the platform. This results in significant savings in not requiring a rig, and greatly reduces deferred production losses as no significant mobilization activity is required. Production rates are such that the necessary annular flow can be achieved in 9-5/8C_" casing. The fluid characteristics in the field, low temperature and GOR with no solids production, make this an ideal candidate for ESP artificial lift. Greater detail of these will be set out in the paper. Finally, reliable CT ESP systems were becoming available at the time of early field development, having overcome initial problems such as the optimum method of conveying the ESP cable to the motor. There are currently 14 such systems installed producing from 3500 bfpd to 17000 bfpd.

Applications

The paper will suggest where CT ESP technology may usefully be applied, either where ESPs are already (given necessary surface modifications), or can beneficially be installed as an alternative to tubing deployment. Where rig availability or cost may result in uneconomic production levels, CT ESPs will be shown to bring several advantages. Not least that workover duration is typically 2 C_- 3 days from pulling to installation and commissioning. The paper will give an overview of pull and run procedures and highlight improvements made in the technique over time. As a result of the necessity to produce via the annulus, there is a requirement for horizontal wellheads to accommodate the coil tubing, the design of which will be discussed. Limitations in terms of deviation, dog leg severity, coil strength and other physical limits will be considered. Particular operating conditions will be discussed, and measures applied to overcome obstacles to stable production explained.

Results and Conclusions

In lift performance terms, i.e. rate, lift and power demand, these units are identical to conventional ESPs of equivalent specification. The paper will explore the evolution of run life performance since first installation in 1996. Comparison will be made with run life performance of comparable conventional units. An estimate of comparative economics between CT and tubing deployment will be made, as will total number of production days estimated to have been saved over field life.

Technical Contributions

The paper will consider how, as a result of being one of the first CT ESP produced fields, developments in Al Rayyan led to advances in the technology generally for application elsewhere. This will refer to methods of suspending cable in the coil, a problem which affected the evolution of CT ESP technology for some time. Developments in high rate and high horsepower motors will be explained, as will recent modifications to the ESP intake design to accommodate high rates and velocities through the shroud assembly that is required in CT ESP where the pump is located below the motor. Future developments will be addressed. Continuing development of the technology in partnership with the vendor is an integral part of OccidentalC_'s run life development strategy. Part of this has been to focus on primary failure mode. Increasingly, ESP life has exceed coil tubing life, often associated with corrosion in an H2S environment. Possible R & D work to remedy this will be outlined. Optimum production depends on the availability of downhole data. Presently these wells are completed with a permanent gauge located below the packer which provides an effective measure of down hole flowing pressure. However, to date no ESP gauge, as is routinely installed in conventional ESP completions, has been run. The paper will outline the development of such a gauge and define the benefits in ESP protection and optimization that will result. Future technical developments that are not yet available but would add significant value to the CT ESP system will be outlined. A drawback of the technology as it exists at present is that it is not possible to conduct production logging operations due to the presence of a 7C_" packer below the ESP which the intake stabs into. As the field is comparatively high in water cut, the ability to perform PLTs in the horizontal lateral(s) with subsequent water shut off opportunity would free valuable capacity in separation and disposal systems.