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.
Summary Placing properly balanced cement plugs in wells has been a serious problem to the drilling industry for decades. The cement plug is rarely found at the desired depth. Because of the fact that the cement slurry usually is more dense than the well fluid, the cement plugs are found deeper than anticipated, and the quality of the cement plug further down may be doubtful. This often results in setting a new cement plug to proceed with operations such as kickoff in the wellbore, abandonment, or pulling the blowout preventer. In the North Sea area cement plugs fail in more than 25% of the cases. Several techniques have been developed to keep the cement in place, but they are either very time consuming or they have a low degree of success. A tool has been developed that is deployed below the cement plug, preventing the cement slurry from escaping down the well. This tool is very easy to install, does not take extra rig time and covers all sizes of hole diameters, from 152.4 to 584.2 mm(6 to 23 in.), with one tool. Before field application, the system was tested in full scale, where cement plugs were set in casings both with and without the new tool. The result from this testing showed that the new tool had a very high degree of efficiency compared to the reference tests that were performed without the tool. This paper presents the results from the tests and case histories where the tool was used. Introduction Balanced cement plugs in oil and gas wells are used for several reasons, including the following. To sidetrack above a fish or to initiate directional drilling. To plug back a zone or a well. To solve a lost-circulation problem during drilling operation. . To provide an anchor for an openhole test. For other remedial work. Such work often demands a cement plug at a specific place in the well, and rarely at the bottom of the wellbore. As the well fluid commonly has a lower density than the cement slurry, it has been experienced that the cement slurry tends to fall or flow down through the well-fluid column, leaving the top of cement (TOC) deeper in the well than anticipated. Smith et al. studied plug cementing in detail and made excellent recommendations for setting successful cement plugs. These recommendations included the placement of a gelled fluid underneath the cement plug and use of a diverter tool. Bour et al. recommend using a reactive fluid system placed in the well before pumping cement. This fluid develops a rapid gel structure upon contact with the cement slurry. The objective of this gel is to keep the cement slurry in place. These practices have been further improved by Heathman et al. by optimal management planning.
A new drilling control system enhancement for real-time optimization and automation control has been installed on the rig and tested in passive mode in preparation for a full-scale drilling test. The testing has been performed on the Statfjord C platform in the Norwegian sector of the North Sea. The aim of the field test is to demonstrate that the incorporation of real time calibrated process models in drilling control can make the drilling process more reliable, increase efficiency, and improve safety for the drilling crew and with regards to control of the drilling process. The system, described previously, performs continuous optimization of operational parameters using calibrated dynamic process models. Safe operational windows are calculated, and operational sequences are automatically optimized through forward model simulations. The results are applied to machine control in real-time, providing process safe-guards and increasing process efficiency. A thorough description of the preparations and passive testing is given. The final test results are to be evaluated based on success criteria developed prior to the test in cooperation with field operator and drilling contractors. The implications for the work organization are also discussed, particularly in relation to control of data input, decision making and responsibility. This technology will allow for direct integration of the know-how and best current practices into the drilling control system. Automated procedures and tests are to provide improved control of well conditions. Direct integration of process models shall enable safe optimization in the short time scale. And coupling the system to remote input will enable optimization in the long time scale, while built-in monitoring and diagnostics may ensure safe application of optimised parameters. Introduction A full scale off-shore pilot test of a new control system enhancement for optimisation of drilling control is currently being performed on the Statfjord C platform on the Tampen basin in the Norwegian part of the North Sea. The system has been developed to assist in particular drilling challenges experienced in this area, which include such challenges as unstable formations leading to packoff situations and stuck pipe, regions of shale between sandstone layers leading to increased risk of fracturing during drilling, hole cleaning issues, hydraulics management and tripping control issues due to depletion in the producing formations, as this is a field which has been in production since 1979. Also, some sections may be drilled at high inclinations, leading to potential issues with barite sag. In the current drilling process, stress-cage technology, using CaCO3, is applied in order to achieve a larger pressure window to drill in, and standardisations of procedures have been developed to deal with the existing challenges, which are to be enforced by the drilling crews. The system developed is primarily to aid the crew in such enforcement.
Many oil and gas operators around the world are faced with drilling operational risks when entering the matured field phase. Narrow drilling margins, hole collapse and lost circulation are among the challenges that must be dealt with safely and economically.This paper describes a successful approach to overcoming these challenges developed through close cooperation between the operator and the oilfield services company. By providing an overview of the concept, technology and operating principles of the 9 ⅝ in and 7 in advanced steerable drilling liner system, the paper highlights the development and the testing process leading to the successful execution of the world's first steerable drilling liner application in the Norwegian sector of the North Sea.The paper also discuss description of the testing and qualification of the two liner drilling sizes (9 ⅝ in and 7 in) at the service company's experimental test rig.
To place a proper balanced cement plug in a well has been a severe problem to the drilling industry for decades. The cement plug is rarely found at the desired depth. Due to the fact that the cement slurry usually is more dense than the well fluid, the cement plug is found deeper than anticipated, and the quality of the cement plug further down may be doubtful. This often results in setting a new cement plug in order to proceed with operations such as kick off in the wellbore, abandonment or pulling the Blowout Preventer. In the North sea area it is seen that cement plugs fail in > 25 % of the cases. Several techniques have been developed to keep the cement in place, but they are either very time consuming or have a low degree of success. A new tool has been developed which is deployed below the cement plug, preventing the cement slurry from escaping down the well. This tool is easy to install, does not take extra rig time and covers all sizes from 152.4 mm to 584.2 mm (6 to 23 in.) of hole diameters with one tool. Before field application, the system was tested in full scale, where cement plugs were set in casings both with and without the new tool. The result from this testing showed that the new tool had a very high degree of efficiency compared to the reference tests which were performed without tool. This paper will present the results from the testing and case histories where the tool has been used.
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