Future drilling technology: Closer than you think
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.
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:
- Automated pipe handling
- Automated drilling operations, including drilling on bottom, reaming and tripping
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.
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
