How good are your models? Can they be used to improve your drilling processes? These are questions often posed in relation to real-time model applications, including models integrated with drilling control. Do the models fulfill requirements with regards to accuracy and calculation speed? Can the data be applied by the models to both interpret the state of the process and provide reliable input for calculations? Can the rig equipment be used safely and securely to control the processes? This paper seeks to answer these questions and further elaborate on current activities and near-term challenges in drilling automation. While static models are generally accepted, the use of dynamic models is emerging. In real-time model applications, it has been found that rig equipment analysis is necessary to assess applicability or upgrading requirements. Controlling machines for drilling operations using outputs from models has been successfully achieved. This paper provides examples of recent developments within drilling automation, drawing from applications of closed-loop control systems in the North Sea. Challenges regarding interpreting state-of-the-process are discussed, with respect to existing rig instrumentation, while examining the need for enhanced surface and downhole sensors. Mathematical models used with the drilling control system must communicate regularly with the drilling process to extract information from sensors and provide updated control commands for automation. How sensor data is applied through models to enable automation functionality is also illustrated.

Recent developments in drilling technology, such as increased sensory information, enhanced data processing and transmitting capacity and capability, and developments in computer controlled machinery, together with adaptation of already available process technology and know-how, are opening up new possibilities for drilling operations. Application of these combined technologies, together with advanced computer modeling, enables enhanced monitoring and increased optimization and control of drilling operations. This paper presents such an integrated system for monitoring and control of the drilling process, currently in the test phase. A key element in the methodology used here is that the models for fluid flow and drilling mechanics are continuously updated in real-time according to the measured data using Kalman filtering techniques. By comparing the calibrated models to real-time data, unwanted occurrences can be detected quickly, and mitigating actions may be taken, either through system control or through manual intervention. Using the calibrated models, safe limits for the drilling operation are computed and enforced, and procedures are optimized. The modules developed cover tripping and reaming, pump start up, friction tests, stick-slip prevention, bit load optimization and monitoring. The methodology may be applied to drilling operations where the drilling equipment is computer controlled. Surface and preferably downhole data must be available in real time. Rigorous testing with drilling data from offshore drilling operations has been performed, and several full-scale tests have been run on a test rig. The ability to maintain the drilling operation within critical limits has been demonstrated. The methodology may contribute to increased safety and reduced down time during drilling operations. Introduction A large part (25%, [1]) of the overall cost associated with drilling operations is a result of non-productive time due to unplanned well incidents. The main problems during drilling are related to events such as kick, stuck pipe, wellbore collapse, lost circulation and equipment failures, see [2]. Proper use of real time data has the potential to reduce the down time caused by these events significantly. Availability of real time drilling data is increasing, both from surface instruments and downhole gauges. Open standards for real time data access are being developed. Computer controlled drilling machinery like pumps, draw-work and top drive are available. High band-width communication between the rig sites and the office like fiber optic, high band width VHF and satellite are used. All these combined developments enable enhanced monitoring through data processing, and optimization and control of drilling operations through computer modelling and drilling machinery automation. For many years IRIS has developed advanced computer models for the oil industry. Among these are multiphase well flow models and torque and drag models. Testing and verification is done through studies with comparison to field data. Additional sub models have been incorporated to handle special effects and give the models special features. During the last few years the models have been developed in order to run real time and use available measurements of operational data such as flow rate, inlet temperature, surface torque and hook load. In order to run real time and to be a corner stone in a control system for the drilling operation, the models need to be fast and robust. Drilltronics - A Software System for Monitoring and Control IRIS (former RF-Rogaland Research) and National Oilwell Varco (NOV) have developed a new drilling, monitoring, control and prediction system called Drilltronics [3]. The main feature of the system is to combine existing hardware and software for monitoring and controlling the drilling process (system environment) with advanced mathematical models for the drilling process. In the implementation of the system we have used existing and upgraded system environment from NOV.

In this paper we present new methods for coordinated control of pump rates and choke valve for compensating pressure fluctuations during surge and swab operations. In hydrocarbon well drilling, automatic control of the choke valve improves the control of the bottom-hole pressure. This has made it possible to drill wells where it previously was not possible to reach total depth, due to narrow pressure margins in the reservoir. This concept is developed further in this paper, to also include automatic control of pump rates, coordinated with the choke valve control. In configurations where the choke valve is fitted with a flow rate controllable annulus back-pressure pump, the situation calls for structured methods for automatic and coordinated control of the main mud pump, the back-pressure pump and the annulus return choke valve. In this paper, well known methods for multivariable control are applied to the drilling process. These methods are based on identification of coupling and interaction between system input (controllable variables), e.g. pump rates and choke valve settings, and output (measured or estimated variables), e.g. pressure at given depths. It is shown how the well pressure profile can be kept within tight margins, subject to disturbances such as drillstring movement in surge and swab operations. Automatic coordinated control is shown through numerical simulations on a detailed, space-discretized well model. Comparisons are made with the case of complete manual control and the intermediate case where only the annulus return choke line pump is automated, using a simple linear controller. The results with automatic coordinated control of pump rates and choke valve are very promising - the performance of such a solution, measured by variance in pressure fluctuations, is improved - compared to both the case of manual control and the case of only automated choke line pump control. Introduction During surge and swab operations the downhole pressure will be affected by volume changes in the well caused by insertion or extraction of the drillstring, in addition to friction effects between the drillstring and the fluid in the annulus. Multiple control variables are adjusted in order to maintain underbalanced conditions along the well section exposed to the reservoir. The most important control variables are drillstring fluid pump volume rate, qp, drilling fluid density, rho, the annulus back pressure pump, qc, and choke valve opening area, Ac. Multiple measurements are available for evaluating whether the required downhole pressure conditions are maintained. Typical measurements available are flow rates, pump pressure, choke valve differential pressure and downhole pressure. To avoid pressure fluctuations during the drilling operations, multivariable process control can be required. In Balchen 1 there are descriptions of several approaches for controlling such a multivariable process. Control methods such as decoupling, feed-forward, modal control, LQG-control and robust control could be used. In addition the available models of the drilling process should be utilized to improve the control system.

Summary A new system for real-time optimization and automated control of the drilling process has been tested successfully on the Statfjord C platform in the Norwegian sector of the North Sea. The demonstrated system uses continuously calibrated dynamic process models combined with real-time drilling-data input to calculate available parameter windows, and forward-model simulations are applied to provide optimized operational parameter sequences. The calculation results are applied directly in machine control. The system further applies automated testing combined with continuous diagnostics to provide process advisory. In the field test, pipe-movement control automation, pump-rate control automation, and automated wellbore-condition diagnostics were demonstrated, proving fail-safe application of process safeguard enforcement and optimization of operational procedures. Results from active and passive testing indicated that the new methodology has the ability to improve drilling-process reliability, safely increase drilling efficiency, and reduce the risk of human error. The authors provide a thorough description of the preparations and testing and present an evaluation of the test results, with reference to success criteria that were developed in cooperation with the field operator and drilling contractors involved in the test. Implications for the work organization are also discussed, particularly in relation to control of data input, decision making, and responsibility. The demonstrated technology applies direct integration of current know-how and best practices into the drilling-control system, and available real-time information is applied directly in controlling the drilling process.

Drilling Automation is a rapidly developing area of technology that is seeing growing interest within the drilling community. The SPE set up a new Technical Section devoted to the subject as it relates to downhole performance, and the IADC has created a committee with a focus on surface processes. As with any emerging technology, the associated jargon is evolving rapidly, and different terms are used by different groups to refer to similar concepts with the potential for confusion and misunderstanding. Automation efforts are being undertaken by numerous and diverse organizations and implementation of such interrelated offerings at the rig site need consistent interface criteria at each boundary to ensure efficient and safe operations. The purpose of the proposed paper is to describe some of the concepts already in operation and under development and to classify them into a number of key categories. The more significant interface requirements will be identified and key safety concerns will be highlighted. Parallels will be drawn with other industries to demonstrate analogues and suggest directions where and how further developments might be expected to lead. Introduction Recent developments in drilling machinery, sensor technology, control systems, computer and communications technology are leading to an explosion of development across the whole spectrum of control activities, from machine level to integrated operations. A number of companies have added specialized controls to drilling machines and integrated them on rigs or placed them in drillstrings. Some have developed models to better understand the drilling process or advise set points to optimise drilling performance; others have specialized use of advanced visualization techniques to improve the situational awareness of drilling teams and decision makers. The latest call is to integrate these enablers to automate the drilling process. This work will likely be incremental and iterative. In parallel with a major initiative spearheaded by the IADC, the SPE has formed a new technical section to help the industry understand the current state-of-the-art of controls and automation and to facilitate the development of safe, reliable and efficient automated processes. The aim of the section is to provide a forum for the exchange of ideas and fostering communication. Terminology With so many different players involved in the drilling community and the rapid development of technologies, the authors believe that the importance of defining and agreeing on the basic terms and concepts of drilling automation cannot be underestimated. Having a commonly understood language is critical not only for the development of the interoperable technologies that will be required, but also to develop the trust and organizational structure that is required amongst the various players (contractors, service and operating companies) during the execution of a drilling project.