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Article Citation - WoS: 25Citation - Scopus: 34Modelling and Controlling of Drill String Stick Slip Vibrations in an Oil Well Drilling Rig(Elsevier, 2022) Sadeghi, Amir Noabahar; Arikan, Kutluk Bilge; Ozbek, Mehmet EfeMitigating of drill string vibrations, plays a distinctive role in increase of rate of penetration and consequently decrease of the operation costs, prevent of severe damages to drill string and bit, increase of drilling operation quality and safety, and enhance the performances of the controllers. This study deals with modelling and controlling of drill string vibrations with focus on stick slip vibrations in vertical wells. The approach taken to subdivide the drill string into smaller torsional sections and model the complete system dynamically and employ the extracted torsional model to model the stick slip vibrations mathematically. To mitigate and or active control of stick slip vibrations, three architectures are developed and proposed, manipulation of the rotational speed, manipulation of the weight on bit, and increasing of the damping in the bottom of the drill string. The performance of each strategy is analysed individually as well as relative to each other, using a mathematical measure when the drill string length is divided into smaller torsional sections. By the aid of the simulations and mathematical measures, it is shown that manipulation of rotational speeds at the surface may not be an effective solution to reduce the stick slip vibrations, however manipulation of weight on bit and increasing of damping at the bottom of string can be two effective solutions to mitigate these kinds of vibrations. As a general conclusion, it is proved that the manipulation of bottom side drilling parameters is more effective than the manipulation of surface drilling parameters.Article Citation - WoS: 1Citation - Scopus: 1Performance Assessment of Tripping and Drilling Operations Controllers on an Experimental Drilling Rig Prototype(Elsevier, 2023) Nobahar, Amir; Arikan, Kutluk Bilge; Ozbek, Mehmet Efe; Naseri, BabekOil well drilling towers have different operating modes during a real operation, each mode involves certain external disturbances and uncertainties. Performance evaluation of robust or adaptive Cascade PID, Active Disturbance Rejection, Loop Shaping, Feedback Error Learning, and Sliding Mode torque controllers, during the tripping and drilling operations, and their practical comparison are studied and evaluated by constructing a drilling rig prototype. The modeling of the experimental setup is extracted by mathematical modeling, and system identification. The practical performance of the controllers and their stabilities against the uncertain forces including the parametric uncertainties and the external disturbances are studied during the operations, by loading and unloading a disturbance weight. It has been shown that the effects of uncertain forces are successfully eliminated by the controllers. The Loop Shaping controller has the best performance among all the designed controllers, and all of them roughly consume the same control energy. A desired speed profile is designed to shape the vertical speed reference during the tripping operation, then its effect on the system behavior is analyzed to prevent the slackening problem in the drilling cable. Also, the behavior of control architectures in two modes of autonomous drilling is studied and analyzed. By analyzing and optimizing the performance efficiency in a controlled environment, along with enhancing the performances of the controllers, what we learn in this research could presumably be applicable in the field to have an accurate and safe operation.Article Citation - WoS: 7Citation - Scopus: 7Torsional Model of the Drill String, and Real-Time Prediction of the Bit Rotational Speed and the Torque on Bit, in an Oil Well Drilling Tower(Elsevier, 2020) Sadeghi, Amir Noabahar; Arikan, Kutluk Bilge; Ozbek, Mehmet EfeIn an oil well drilling tower, the Bottom Hole Assembly (BHA) data is needed to optimize the controllable variables such as weight on bit and bit rotational speed for obtaining the optimum drilling rate. In order to acquire the data of the BHA, a simple and low-cost method, can be predicting of these parameters. In this study, first the torsional modelling of the drill string is implemented by dividing its length to some equal sections, then the effects of dividing on the estimation accuracy are evaluated. Using an ADRC (Active Disturbance Rejection Controller) in the vertical and rotational motions dynamics, some proper observers to predict the bit rotational speed, rock stiffness and torque on bit, in real-time are designed and presented. Dividing the drill string length to more sections, leads to design high order observer, so the performance of the designed observers with different orders, are compared and analysed. Employing the integral square error analysis, it is revealed, dividing the drill string length to more sections, leads more accurate in the prediction of bit rotational speed, but not more effect on the estimated rock stiffness, and torque on bit. Also it is shown that increasing of the observer bandwidth, leads to more accurate in the estimation, but concludes the estimation be more sensitive to the sensor noise. Employing the presented observers in this study to estimate the BHA data, in addition to enhance the drill quality and safety, the controllable variables are optimized, and consequently the whole drilling process can be robustly controlled, with no needs to the expensive measurement systems at the BHA.
