Subsea controls systems can be either integrated or discrete from intelligent well completions.
Intelligent well completion (IWC) systems are proliferating rapidly offshore. As the market expands to the Gulf of Mexico, there is a question of who will provide the controls for these systems. In a market where subsea control pods are a common production solution, the question of control, responsibility, and ultimately standardization, is rapidly moving to the forefront of industry debate.
While companies like Kongsberg Offshore, which provides subsea controls systems, favor an integrated solution, IWC companies argue they must maintain control of the downhole systems for which they are responsible. Terje Skogen, Director of Technology for Kongsberg Offshore, said his company's control systems transport the data, power, and controls for IWCs, so it makes sense that they should control this data.
Most of the initial IWC solutions will require only low-density data transmission for measuring flow, temperature, and pressure. As the downhole power and data requirements increase, there will be a greater impact on the design of the subsea controls and wellhead system. In addition, if a subsea development is tied back to a remote host platform several miles away, a separate umbilical would be required to operate the subsea controls and IWC, if the two were developed as free-standing, discrete systems.
The IWC would also require its own subsea module and its own topside operator station to handle the electronics. This is expensive and results in a decoupled system of controls. The thinking is that if something malfuntions with the subsea controls system, the IWC would not be affected. The problem is that if something does go wrong with this system it would lead to a shut down in IWC operations, regardless of where the systems are coupled.
Skogen believes there are a number of advantages to sharing the control of this information. In addition to saving money by reducing the redundancies in power and data transmission lines, Kongsberg could benefit from the data collected by downhole sensors. Skogen said this information could be used to set and adjust the control system, and ultimately to design a more advanced "closed-loop system" that could manage production by integration of subsea and downhole technology.
Kongsberg has aligned with PES, now Halliburton, to integrate its controls system with the PES SCRAMs IWC system, for installation on the Gulfaks Satellite field in the North Sea this summer. Skogen said operator Statoil, who was interested in reducing the amount of topsides equipment, drove the alliance. This solution is illustrative of what many feel will be the ultimate driver in the evolution of subsea and IWC technology.
If the operator requires in its design that the subsea controls and IWC systems should be integrated, then there is much more incentive to produce such a system. Skogen said this is not always the approach taken by operators. Often, there is no requirement for such integration. On the contrary, because price is such a factor, it is critical that service companies compete in every aspect of the project, meaning the winner who gets to design the IWC must be sure its equipment can communicate with a wide range of controls systems.
In addition to communication, there are a number of other issues that dictate whether a controls system can communicate with an IWC.
The Three Ps
There are three major areas of potential standardization between controls systems and IWCs, according to Jack Angel, Director of Marketing and Technology for Intelligent Well Technologies at Baker Oil Tools. He refers to these as the three Ps: power, protocol, and plugs. Angel said there are several levels of power requirements depending on the IWC.
Power levels range from the limited power required to support sensor data to the high power needed to run electrical submersible pumps (ESPs). In the case of high power, not only is there an issue of delivering the power, but also dissipating the heat such power generates.
The protocol category also covers a variety of issues. It is not just a question of one company's control pod speaking to another company's IWC. Different generations of pods and wellheads have different capabilities. If an older pod is in place, it may not have the capability of supporting some of the communication and power requirements of the equipment the IWC needs.
There is also the question of research and development investment. If a company has devoted significant time and effort developing a protocol to support IWC, it cannot abandon this effort in favor of standardization. Such a move would mean the loss of the research and development investment, and additional work, time, and expense would be required to modify a state-of-the-art IWC system to work with another protocol. This is a very expensive and time-consuming proposition for companies already far along with this technology.
The answer, Angel said, could be a limited number of standardized protocols. Such an arrangement would protect the work done to this point and allow this work to progress, but at the same time offer some uniformity to future systems.
The option of a suite of standard protocols might be the way to go. Angel said this would allow the selection of a protocol to be based on the specific needs of a project. That way, older control pods would be able to operate with certain IWC systems depending on the needs of a field.
Using this approach, the providers of wellheads, wellpods, umbilicals, and IWCs would have a limited number of specifications they may be held to. This also insures custom features and benefits developed by the service industry are not compromised through a single standard. Standardization by its nature requires compromise and consensus, which may limit the total potential of these systems to the operator.
The current situation is one in which operators are selecting the company that will provide the control pod and the company who will provide the IWC. Typically, the decision on an IWC is made after work has already begun on the control pod. This can limit the capabilities of the IWC and possibly change the design.
To avoid such problems, Angel said these choices must be made up front. This would allow the control pod team to know the capabilities required by the functional requirements of the IWC. For certain applications, the umbilical becomes the critical link and the umbilical characteristics must accommodate the IWC requirements and the completion architecture. Therefore, these choices need to be made early in the well/field design.
The final P, plugs, refers to the actual interface between the IWC and the controls system. The details of this interface alone are very complex. If the industry could agree on standardization for such specific areas as cabling and connectors, it would clear up a lot of the incompatibility in these systems. In addition to downhole and subsea equipment, there is the question of surface systems. The surface controls need to interface with the operator and wellhead protocols for the production system to be integrated. All of this compatibility imposes limitations on the types and number of features an IWC can include.
As an example, the basic question of how many penetrations a wellhead contains can dictate the level of complexity system functionality for the IWC. If there are not enough holes to run power and control lines through, or the holes are not large enough to meet the requirements, then the system must be redesigned or system functionality compromised.
Baker Hughes, for example, simplifies this issue by designing an all-electric IWC system that requires only a single 1/4-in. wellhead penetration to allow up to 12 zones of monitoring and control. Other companies use multiple penetrations. Each design has its pros and cons, but the point is - they are not interchangeable.
To head off such potentially costly incompatibility, Angel said it is important that everyone involved in the project meets early to discuss the design interface. Even if there was such a "meeting of the minds" Angel said it is not likely a wellhead company will want a service company to tell it how many penetrations to build into its design. Such customized changes drive up costs, which means the wellhead company will have to place a higher tender bid.
If a question is not raised until after the fact, the potential impact to the operator is most likely a significant delay in wellhead/wellpod delivery, coupled with a redesign charge to makeup for meeting the new specifications. Existing wellhead penetrations will simply have to be accommodated by the IWC and controls pod, without affecting the tender bid.
Angel said there is currently an initiative underway to establish standards for the interface between subsea controls and IWCs. The initiative is IWIS, which stands for Intelligent Well Instrumentation Standardization. Accord ing to Angel the initiative was started by Shell in 1995. The current, two-phase initiative is working to establish a standard for the instrumentation on control pods and then it would tackle the question of power and communication standardization. The IWIS initiative has support from a number of service companies and several operators including Shell, BP Amoco, Saga, and Statoil.
Mark Stearnes is a Senior Consultant with OTM and involved with the IWIS initiative. He said the goal of setting a standard is to open up the IWC market. The European-based project set a standard for downhole equipment about 18 months ago and is now addressing the question of integrating this equipment with a control pod. To do this, he said, it would be necessary to get the IWC people in the same room with the control pod people. This would avoid a situation where the operators are dictating a standard to the industry. He said standards for low-power applications have already been set and now the group is interested in medium power applications. In addition to operating companies, the IWIS has representation from the equipment providers who build control pods. The group meets every two months and the goal right now is to have the low power standards accepted by the group this month.
As the power requirements increase it is more difficult to standardize. The low power applications are limited mainly to data collection. In the areas of medium and high power there are a lot of field-specific applications that don't lend themselves to standardization. Even so, Stearnes insists that setting these standards now is not going to limit the growth of IWC technology. He said setting these standards anticipates the needs of wells in the future.
While IWIS is having some success in setting a standard in Europe, Stearnes said there has not been discussion of standards for the US. He said some US manufacturers are involved in the IWIS and other operators are considering joining the initiative.
ABB Offshore Systems is a bit unusual in that the company is building its own IWC called ADMARC (Advanced Downhole Monitoring and Reservoir Control), but is also a major provider of subsea control pods. Brian Drakeley with ABB said his company builds all its control modules with IWC in mind, since the popularity of this technology is growing. The integration of the two systems is not simple, even for a company doing the whole thing in house. The question of communication protocols is just one aspect of the design. He said the major question ABB faces is predicting how much power the IWC will need. The controls pod can only deliver so much power down hole. Without knowing what the IWC will be required to do, it is difficult to predict how much power will be needed. If high power is needed then this affects the design of the umbilicals, among a number of other components. Also accommodations must be made to deal with the heat generated by these systems. All of this is very expensive so if such accommodations are not needed on a particular well then it is cost effective to leave them off.
If a control pod is used with an IWC from a different company then there is a wide range of variables to consider. Drakeley said his company has identified 2,300 separate interface questions that should be addressed when mating different systems. The number of questions applicable to a particular system varies depending on the requirements of the system, but the interface affects everything from subsea controls, to tubing hangers. If there is to be a separate umbilical to control and power the IWC, then this must be built into the entire design from the Christmas tree, up.
In some cases, not only do the controls system and the IWC have to communicate, but they both must conform to the proprietary protocols of the operator who is running his own reservoir management software package on the surface. Drakeley said, from his experience, that it appears the industry is moving toward a number of systems that will be able to interface, rather than one uniform standard. Such standardization would be difficult to achieve because there are so many different IWC applications ABB is the only company to offer a fully integrated subsea/downhole controls system as opposed to interfacing the two.
The Production Engineering Association held an Intelligent Well Completion Forum Meeting in London in March of this year to address the issues of subsea and downhole interfaces. This oil company initiative is separate from IWIS, but the goals are the same. Among those who spoke in front of the PEA was Dick Rubbo, Group Technology Director for Halliburton PES.
Efficiency not standardization
When he addressed this industry group Rubbo emphasized the difficulty standardization would present as a goal in itself. He said PES is looking at increasing efficiency and reliability rather than standardization across the board. To achieve this their IWC systems must be versatile enough to work with a variety of control pods. In addition to being adaptive, Rubbo said PES wants to offer the operator the option of an integrated or discrete IWC system.
While there have been attempts to standardize downhole communications and power, Rubbo said premature standardization of down-hole systems could be detrimental to the future development of IWC. Because this technology is in its infancy, various competing approaches to IWC have been developed and are being proposed. No one can predict which will ultimately provide the most value. If there are too many standards for a design it could put an undue burden on the IWC provider. He gives the example of limited space downhole. Because IWCs work inside the well bore, challenging environmental conditions such as space and high temperature are major considerations, every component added to one of these systems in the name of standardization negatively affects reliability. PES is focused on producing a robust system that will remain reliable for years to come. Such systems may not be able to deliver information as fast as some proposed standards might require because of the design limitations.
Because there will be such a variety in the IWC systems of the future, Rubbo said he would like to see the emphasis put on a versatile downhole system and more discussion between the IWC provider and the controls provider early in the project. Currently he said the typical completion has the controls system in place long before the operator considers an IWC. This means the capabilities of the downhole system are dictated by the limitations of the controls system. If the well were initially designed with an IWC in mind the controls system could be robust enough to accommodate an IWC.
As for the future of IWCs and controls systems, Rubbo said increasing bandwidth for the communication of information to and from the well will allow IWCs to do a lot more. When PES designs new systems it designs in an architecture that is flexible enough to adapt to a variety of controls systems. This allows for the use of the same downhole components regardless of whether it is an integrated or discrete system. In many cases the two systems may not be fully integrated but they will share some infrastructure, such as electric or hydraulic power sources, while retaining control of their different components. This type of integration results in a more efficient system, but gives PES and the controls company the freedom to focus on their areas of expertise.
Maximum benefits from such a system would rely on the high bandwidth communications, which are just now becoming available in the subsea control world. Until high bandwidth communications are the standard, PES will continue to provide discrete system for applications where rapid and reliable data transfer is required.