Requirements of Downhole Flow Control Valves
- H. Gai (BP)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 5-8 October, Denver, Colorado
- Publication Date
- Document Type
- Conference Paper
- 2003. Society of Petroleum Engineers
- 1.7.5 Well Control, 5.7.2 Recovery Factors, 4.5.7 Controls and Umbilicals, 2.2.2 Perforating, 4.1.5 Processing Equipment, 4.2.3 Materials and Corrosion, 3.1.6 Gas Lift, 4.3.4 Scale, 4.1.2 Separation and Treating, 4.6 Natural Gas, 7.3.3 Project Management, 5.3.2 Multiphase Flow, 2.3 Completion Monitoring Systems/Intelligent Wells
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A brief review of Down Hole Flow Control technology shows that it is still far from mature. Efforts on characterizing DHFC valves highlight some fundamental challenges, and indicate that DHFC valves are flow control devices, not pressure control devices as chokes are. The DHFC valve requirements are then detailed, including the functionality, mechanical, and reliability requirements and other considerations, and an attempt is made to dispel some of the misconceptions. Some simple guidelines for system/valve design and selection are also presented, providing a useful tool for the user. An example is given, demonstrating the complexity of the interactions of multiple well and reservoir parameters and some of the design basics, and the use of a simple spreadsheet simulator.
It is concluded that while the DHFC technology has proved itself as viable and capable of delivering huge value to the industry, there remain some serious technical challenges, which call for continued and concerted efforts. The complex requirements should be managed with a system approach not just focusing on discrete components. Analytical tools are needed for proper system design and validation in the given application environment to achieve success.
The IW (Intelligent Wells or Smart Wells) technologies have made significant progress in the past few years. Arguably the heart of the IW system, the DHFC valve, which directly effects the control whereby the well objectives can be met, is still one of the least understood parts. Comprehending what is required of it must be among the first things for a sound technical design. It is apparent that a systematic approach in design and validation of the valve and DHFC completion is still lacking. Because basic design steps are not carried out, wrong valves are selected as a result of misunderstanding.
This paper examines the fundamental issues related to design and selection of DHFC valves, and demonstrates some useful tools for application.
A brief review of DHFC valve technologies
The number of benefits and possible applications of the DHFC system is large, and growing. The common ones include:
Reduce intervention costs in subsea wells,
Reduce well count,
Increase RF (Recovery Factor),
* Control including shut-off unwanted water or gas,
Manage reservoir conformance,
Control Multi-Lateral Wells (MLW's),
Control hill draw-down of long horizontal wells,
Clean-up or fracture zones or laterals more effectively and economically,
Gather zonal information on pressure and flow more effectively and economically and so on.
There are now three categories of DHFC valves in terms of control style: On-off only, Stepwise and Infinitely Variable (IV). Although DHFC used in IW completions only started in 1997, mechanically operated (as opposed to automated type in IW) sliding sleeves and ported nipples etc. had been in use for decades. The discussions here are not limited to automated type, and will be self-evident when they are.
The Stepwise and IV types were introduced as key functions of IW technology and their controls are typically automated. However, the ported-nipple with replaceable inserts by wireline or coiled tubing can be viewed as a Stepwise DHFC valve. The main difference is that the inserts could be fine-tuned or designed at the time when needed, in a one-off manner, rather than predetermined with little chance of altering like the Stepwise DHFC valve. However, the automated valve can be reconfigured without intervention. Some earlier Stepwise valves are controlled in 4 or 5 (equal) steps from fully closed to fully open. Others have 10+ steps, and valves designed in the last three years have variable "spacing" instead of equal spacing to achieve more effective control. Most suppliers can tailor the flow-areas vs. steps-spacing of the valve positions for the user.
The IV valve is entirely flexible in its control of position between open and close, seemingly versatile in achieving any position. Notably such valves always require electronics for position monitoring/control although the power for the valves can be hydraulic as well as electric. By contrast, Stepwise DHFC valves are typically hydraulic only and do not necessarily need electronics for the position control.
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