Safer, more automated drilling and with greater capabilities for managing difficult pressure environments than the best we have today-in other words, a reach into the future-is making good progress. Even remotely operated drilling is possible.
Steinar Strøm, Mohsen Karimi Balov, Halvor Kjørholt, Rune Gaasø, StatoilHydro; Erlend H. Vefring, IRIS; Rolv Rommetveit, SINTEF Petroleum Research
StatoilHydro believes that a new, fully Automated Drilling System (ADS), while a major technological effort, is achievable in the relatively near future. The company is pursuing various sub-systems for incorporation into an all-inclusive integrated system. Two different solutions are the Drilltronics (IRIS/NOV) and the eControl/eDrilling (SINTEF /HPD/Aker Solutions) concepts.
The Drilltronics system is based on mathematical computer models for dynamic real-time analysis of drilling processes; critical limits for operational parameters, such as drilling fluid pump rate, trip velocity and optimal process parameters are calculated. The result is used to control drilling equipment in real time. The new system has been field tested on the Statfjord C platform. Combining the new system with wired pipe, decision support programs and continuous measurements of drilling fluid parameters give synergy effects that, in the future, may allow remotely operated drilling systems.
eDrilling is an innovative system for real-time drilling simulation, 3D visualization and control from a remote drilling expert center and is the technology basis for eControl, which is a rig supervision, optimization and control system that will integrate 3D visualization of the wellbore with advanced drilling process models.
This article gives an overview of field-tested, pilot-tested equipment and the synergy effect when combing different technical solutions in future drilling scenarios.
BACKGROUND
The technology, as such, is to a large extent at hand. It is a matter of applying the technology in an integrated manner. Our experience is that many drilling problems are related to human error, or rather, slow response with respect to corrective actions. The ADS has the capability, if designed correctly, to eliminate this type of misbehavior. It is mandatory to design the ADS such that the general progress in operation is not slowed.
The essential part in the future drilling concept is use of high-speed telemetry through drill pipe. The technology is regarded as an emerging commercial product that is now being applied. The ADS should have the function of optimizing operations; these are:
- Speeding up drilling/tripping operations when conditions permit
- Slowing down drilling/tripping operations when required
- Early kick detection, improved well control
- Automated pump startup/stop
- Automated mud checks
- Effective use of telemetric drill pipe; i.e., real-time downhole data from the well
- Automation of the drilling process-a great opportunity to minimize operational downtime by handling borehole problems correctly and consistently, thus significantly reducing human errors
- Establish drilling programs in a semi automatic manner.
AUTOMATED DRILLING PROCESS
There are several technologies involved in an ADS. These include:
We regard these as complementing technologies that all have the potential to contribute toward an automated drilling process. The general idea of how the future will look is shown in Fig. 1. It is of great importance that the interfaces between the various technologies are handled in a consistent manner by the operator. We, as an operator, need to define these interfaces to allow for future improvements and in particular allow for new innovations to be implemented. Hence, it is important to have open “plug-n-play” type interfaces based on Ethernet technology.
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Fig. 1. Flowchart of the fully automated drilling process.
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DRILLING CONTROL SYSTEM AUTOMATION
StatoilHydro is pursuing two different solutions: the Drilltronics (IRIS/NOV) and the eControl/eDrilling (SINTEF) concepts.
Drilltronics. This system applies dynamic process models for well flow and drillstring mechanics, using advanced dynamic rheological modeling with gelling, thermo-physical modeling, solids transport and equation-of-state modeling. The applied torque and drag modeling is based on a “soft string” model. Pre-processing of measured mechanical data through filtering and derivation of required model input is performed by a previously developed system for improvement of drilling data. The applied flow-model solver is a semi-implicit matrix solver, explicit with regards to mass transport, that enables solving complex flow situations in real-time. Model calibration is performed through application of Kalman filtering techniques, where a proportional flow-friction factor is applied for pressure calibration.
Limitations for tripping/reaming dynamics and pump dynamics are calculated through forward modeling based on the pressure limitations of the well and mechanical limits of the drill pipe. Through automatic enforcement of these dynamic limits, depletion and pipe sticking issues will be dealt with.
Diagnostics of wellbore stability and cuttings transportation is performed through trend analysis of the friction between wellbore and drillstring using a torque-and-drag model. The trend of the calculated friction will indicate the state of the hole with regard to cuttings and borehole condition. Through application of an automated pick-up and slack-off tests, the diagnostics may be improved, as the test will be identical each time it is run. Repeated testing combined with analysis of results will indicate whether the wellbore condition is deteriorating.
Testing in active mode. StatoilHydro performed a full scale offshore pilot test in January 2008 of a new control system enhancement for optimization of drilling control. The test was at the Statfjord C platform on the Norwegian Continental Shelf. The Drilltronics system was run in passive (advisory) mode in a previous test autumn 2007 and was run in active mode in the time frame from January 21 to January 29, 2008.
Feedback from the operations group indicated that the system worked satisfactory and as intended. No HSE incidents were encountered during the function test while in active control mode. Some modification of the system is required to optimize the man-machine interface. In addition, we learned that the sensors on the relatively old rig were not ideally located and, to a large extent, too inaccurate to serve as input to an ADS. Other active control modules were tested as follows.
The friction test module. This module consists of programmable automated tests of friction in the well in relation to pick-up and slack-off with and without rotation. The module may also be used to program an automatic reaming function. Automatic analysis of measured dynamics gives an indication of friction in the well. Trend analysis of the friction will give an indication on cuttings accumulation, well stability and quality. This module was used on every connection while drilling.
Tripping/reaming control. This module limits speed and acceleration of the string to avoid excessive surge and swab pressures, i.e., outside the pore/fracturing pressure window. The tripping control assists in avoiding influx, fracturing and mud loss to the formation. Reaming control limits the speed of the string to avoid pack-off/stuck pipe. In case of “full throttle” on the joystick, this module limits the tripping/reaming speed to an acceptable value. This module was used when tripping into and out of openhole and in combination with the automatic friction test.
Pump startup. This module limits the circulation step-up of the pump rate to an acceptable level to avoid a well pressure that exceeds the fracturing pressure (weak zone), resulting in loss of drilling mud. The module includes both semi-automatic and manual modes. The semi-automatic function comprises a small number of insteps to reach the predetermined flowrate, where pump-rate buildup phases are optimized and automatic. The manual function limits incremental circulation increase rate within a predefined window, where the driller must acknowledge incremental increase in pump rate. The semi-automatic optimized function was used on pipe connections in the pilot test.
Narrow pressure windows. To handle drilling through large pressure variations between individual layers or between the overburden and the reservoir, future drilling practice will continue to improve. Rotary steerable liner drilling systems will be available near the end of this year. StatoilHydro and one of StatoilHydro’s suppliers are developing a 95/8-in. and a 7-in. rotary, steerable liner drilling system. A full drilling-tool package can be included in the system. By combining steerable liner drilling with the expandable pipe technology and managed pressure drilling methods, many of today’s drilling challenges can be solved.
eControl/eDrilling. eDrilling is an innovative system for real time drilling simulation, 3D visualization and control from a remote drilling expert center and is the technology basis for eControl. eControl is a rig supervision, optimization and control system that integrates 3D visualization of the wellbore with the most advanced drilling process models. The concept uses all available real time drilling data (surface and downhole) in combination with real time modeling to monitor, optimize and control the drilling process. The system comprises the following elements, some of which are unique and ground-breaking:
- Automated pipe handling
- An advanced and fast Integrated Drilling Simulator, which has the capacity to model different drilling sub-processes dynamically, and also the interaction between these sub-processes in real time, used for automatic forward-looking during drilling, and can be used for “what-if” evaluations as well
- Automated drilling based on advanced simulator models and 3D visualization
- Automatic quality check and corrections of drilling data, making them suitable for processing by computer models
- Real time supervision methodology for the drilling process using time-based drilling data, as well as drilling models/the Integrated Drilling Simulator
- Methodology for diagnosis of the drilling state and conditions, which is obtained from comparing model predictions with measured data
- Advisory technology for more optimal drilling
- Data flow and computer infrastructure.
The combination of the various elements will make eDrilling very attractive to new people coming into the industry; the so-called “Game Boy generation.” Virtual Wellbore will be a key element in the system, with advanced visualization of the downhole process, i.e., a new, open 3D visualization motor that can visualize all drilling and well related operations involved. The next-generation visualization system is designed to collaborate with all participants involved, enabling enhanced integration of all drilling and well activities in a global environment. The open system architecture allows equipment suppliers, service companies, contractors and operators to connect via standard interfaces (i.e., WITSML, etc.). The system is designed to handle the expected high data rates as a result of the use of wired pipe and similar technologies.
Costly failures will be reduced and better knowledge of the process will be obtained. Total visualization of the drilling process will be possible in real time. This includes the well path; geological horizons encountered; seismic information while drilling in real time (not complete); depth by visualizing the tally/BHA; “seeing” the bit or tool joint going through restricted areas like the BOP or casing shoe; and linking real time software models with real time data to analyze and optimize drilling performance, e.g., visualizing well pressure profile and prediction of pressure when drilling ahead; recording and backtracking of operations in 3D.
The system is also well suited for training. A typical eDrilling infrastructure is shown in Fig. 1.
Managed Pressure Drilling (MPD). MPD is a necessary building block for automated drilling. As we see it, MPD solutions will make a difference in specific areas of the world, especially the Gulf of Mexico (GOM). StatoilHydro does not have any ongoing development projects in GOM, but has a large portfolio of prospects.
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Fig. 2. MPD solutions process.
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Figure 2 shows the AGR and ORS solutions for dual-gradient MPD solutions in deep water. The AGR’s CMP system may be used with existing BOP and drilling riser systems, while the ORS’s LRRS system is intended to be used with, as we see it, the future slim BOP and HP riser system. Common for both solutions are:
- Well control issues:
- Well influx will be spotted much earlier than existing systems, primarily by increase in mud return pump power consumption, secondarily by pressure transducers in the riser string
- Well killed by a dynamic process, i.e., no shut-in to mix heavy mud, etc.
- More complex well killing operation, i.e., automation required.
- MPD action:
- Maintain constant bottomhole pressure through all phases of the drilling operation
- Utilize telemetric pipe, fallback option is the use of a simulation program to predict bottomhole pressure
- Automated process required to maintain constant bottomhole pressure.
As indicated above, automated MPD solution can avoid letting the “human factor” become an obstacle. We are also considering the available solutions for continuous circulation while making/breaking drill pipe connections. Typical for the existing dual-gradient systems is that a relatively large amount of fluid is moved to compensate for ECD effect on connections. Continuous circulation systems, such as CircSub, NOV’s CCV, or others, could reduce time spent on connections.
Continuous fluid/cuttings measurement. Real time monitoring and measuring of drilling fluid and drill cuttings properties (CMFP) is necessary in a fully automated system, since it affects all of the real time drilling parameters such as ROP, ECD, MPD, etc. and it improves decision making. Further, it is essential for remotely operated drilling.
Geoservices is developing an automated system as described above in cooperation with StatoilHydro. The intention is to take elements of the system into operation in 2008 to build confidence in them. This particular system will measure fluid: viscosity, electric stability, loss, density, H2S, pH, particle size distribution and particle content.
It will also measure: the volume of cuttings and cavings monitoring (shape characterization), and the mineralogy of cuttings (using Raman spectroscopy).
Drilling Operations Tracking System (DOTS). We are working with the company Trac ID Systems AS to develop a system for automatic tracking of drill pipe. Initially, the focus will be on tracking pipe in and out of the borehole. The next generation of the system will include the history for each individual joint. The company has configured an ATEX-certified DOTS, including a purpose-built RFID antenna system for integration in the drill floor of a conventional offshore drilling rig and supporting pipe tally software.
The RFID transponder mounting technique is a proven technology (Fig. 3), and is used and verified by a major drill pipe rental company. The transponders are certified according to governing ATEX regulations. Each transponder includes references to the ATEX certificate. The transponders are passive and are proven to withstand temperatures and pressures present in oil and gas exploration and production wells. A separate test rig has been acquired to perform testing and verification.
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Fig. 3. RFID antenna for tracking drill pipe.
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A software tool is also included in the DOTS to tie all technical data, documentation, historical data, administration codes, etc. to each joint of drill pipe, as well as automatic tally-book generation.
Liner drilling. Drilling through sections with large pressure variations, or narrow pressure windows, continues to be a challenge. Rotary steerable liner drilling systems will be available near year-end 2008. StatoilHydro and one of its suppliers are developing a 95/8-in. and a 7-in. system. A full drilling tool package can be included in the system. By combining steerable liner drilling with expandable pipe technology and managed pressure drilling methods, many of today’s drilling challenges can be solved.
SUMMARY
StatoilHydro’s intention is to tie all of the technologies briefly discussed above together into an Automated Drilling System. Flexibility is a key issue. One of the major challenges is to specify a solution that enables future developments for new suppliers in the market, overlapping systems, and so forth. It is obvious that the system must be based on Ethernet-type interfaces to a central computer, where all the data and information are handled correctly. We are in the process of specifying such a system. A pilot is planned in 2009 where integration of different systems is the key issue.
Fully Automated Drilling Systems are now about ready to “take off.” There are several independent sub-systems being developed and others that are now commercial. The key issue for StatoilHydro is to tie all these sub-systems into a larger, all-inclusive system for the future. We, as an operator, realize that the market does not solve this challenge on its own. We must actively search for and qualify the sub-systems as part of a larger system. When the solutions are deemed qualified, the last step will be to include the system in our rig specifications. 
ACKNOWLEDGEMENTS
The authors thank the management and technical staff in StatoilHydro, IRIS, NOV, SINTEF, Aker MH, Trac ID, ORS, HPD and AGR for permission to publish and assistance during preparation of this article. This article was derived from a presentation (OTC 19409) at the 2008 Offshore Technology Conference held in Houston, Texas, U.S.A., May 5-8, 2008.
BIBLIOGRAPHY
Iversen, F. P., Cayeux, E., Dvergsnes, E. W., Ervik, R., Byrkjeland, M., Welmer, M., Torsvoll, A., Karimi Balov, M., Haugstad, E. and A. Merlo, “Offshore field test of a new integrated system for real-time optimization of the drilling process. IADC/SPE 112744, IADC/SPE Annual Conference, Orlando, Florida, March 2008.
Zacny, K., Paulsen, G. and G. Cooper, “Drill automation for the space environment: Lessons learned,” SPE 111126.
Eustes, A. W. III, “The evolution of automation in drilling,” SPE 111125.
Saasen, A., Omland, T. H., Ekrene, S., Breviere, J., Villard, E., Kaageson-Loe, N., Tehrani, A., Cameron, J., Freeman, M., Growcock, F., Patrick, A., Stock, T., Jørgensen, T., Reinholt, F., Scholz, N., Amundsen, H.E.F., Steele, A. and G. Meeten, “Automatic measurement of drilling fluid and drill cuttings properties,” IADC/SPE 112687.
Rommetveit, R., Bjørkevoll, K. S., Halsey, G. W., Fjær, E., Ødegård, S. I., Herbert, M., Sandve, O. and B. Larsen, “eDrilling: A system for real-time drilling simulation, 3D visualization and control,” SPE 106903.
Mathis, W. and G. Thonhauser, “Sensor data quality control-A challenge for real-time (rig) data transmission and usage,” Oil and gas Europe, March 2007.
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THE AUTHORS
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Steinar Strøm is a Project Manager with StatoilHydro in the R&D project called Increased Oil Recovery. He has held several positions within the company, mainly operational, starting with R&D in 2002. He began his career with Mobil Exploration Norway as a Drilling Engineer in 1984, and joined Statoil in 1987. He earned a Masters Degree from NTNU (former NTH) in 1984.
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Mohsen Karimi Balov is a researcher at the Rotvoll Research Center and is an Activity Leader in Automated Drilling Systems in the Increased Oil Recovery R&D program in StatoilHydro, where he has held various drilling related engineering and research positions. He earned an MSc in petroleum exploration, Chalmers University and an MSc in Earth Sciences from Stockholm University. Before joining StatoilHydro, he was a research scientist at SINTEF Petroleum Research and a Geologist for Baker Hughes Inteq, Norway.
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Halvor Kjørholt is a Chief Researcher within drilling and completion at StatoilHydro. He joined the company in 1994 and has mainly been involved in research within rock mechanics, sand management and drilling.
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Erlend H. Vefring is a Vice President in IRIS Petroleum. He has held several positions within IRIS since 1990, including Chief Scientist and Manager for several projects within drilling and well technology, and reservoir technology. He earned an MSc in applied mathematics in 1986 and a PhD in applied mathematics in 1989, both from the University of Bergen, where he was a professor.
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Rolv Rommetveit is Research Director for Drilling and Well Construction at SINTEF Petroleum Research. He has more than 20 years’ experience from research and development in drilling and well technology. He has authored more than 60 papers and is a member of the Program Committee for the SPE/IADC Drilling Conference. He has generated and managed several research programs in drilling. His main areas of interest are drilling hydraulics, well control and managed pressure drilling as well as remote real time drilling simulations and control.
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