Manipulation of the choke pressure during Managed Pressurized Drilling (MPD) operation

Master's thesis in Petroleum EngineeringIn the present investigation, the disturbance and its effect on the bottom hole pressure has been studied. After digging into the prior works, it’s figured out that the reason of their failure is oversimplification and ignoring some parameters that have considerable impact on the BHP like frictional forces resulting from fluid and drill string movements. Following the weakness of the last studies, the feasibility of applying new hydraulic model has been studying and new assumptions have been presented. The model is provided by a set of linked PDEs 1. the pressure dynamics of the well annulus during unsteady Couette flow with a pressure gradient; 2. The movement of the elastic drill string coupled with the pressure dynamic through viscous friction and displacement of drilling mud. It is shown how the model can be simplified to a linear system and under which assumption this simplification can be proceeded. By using the Laplace transformer and inserting appropriate boundary conditions, the transfer function is derived from the linear system. The resulting model uses heave disturbance and controlled flow into the wellbore as input, and the measured pressure at the top of the well, as well as the pressure at the bottom of the well as output. Based on the Hydraulic model developed, for the sake of simplification and faster running time, a lower order of the model with fewer control volumes have been introduced for the Model Predictive Controller (MPC). Two control algorithms for both normal and intervention operations have been evolved by application of PID and Model Predictive Controller (MPD). The Optimization of the PID controller has been done theoretically and validified by MATLAB

Control-Oriented Modeling for Managed Pressure Drilling Automation Using Model Order Reduction

Automation of Managed Pressure Drilling (MPD) enables fast and accurate pressure control in drilling operations. The performance that can be achieved by automated MPD is determined by, firstly, the controller design and, secondly, the hydraulics model that is used as a basis for controller design. On the one hand, such hydraulics model should be able to accurately capture essential flow dynamics, e.g., wave propagation effects, for which typically complex models are needed. On the other hand, a suitable model should be simple enough to allow for extensive simulation studies supporting well scenario analysis and high-performance controller design. In this paper, we develop a model order reduction approach for the derivation of such a control-oriented model for {single-phase flow} MPD {operations}. In particular, a nonlinear model order reduction procedure is presented that preserves key system properties such as stability and provides guaranteed (accuracy) bounds on the reduction error. To demonstrate the quality of the derived control-oriented model, {comparisons with field data and} both open-loop and closed-loop simulation-based case studies are presented

Simuleringsstudie ved bruk av "HeaveLock" for dempning av nedhullssvingninger som følge av hivbevegelser i rig

Lett anskaffet olje er i dag allerede produsert. Både nye og modne felt med muligheter finnes, men mange ligger i forhold som gjør dem vanskelig å bore. Det er også en lavere oljepris enn det har vært i lang tid, som resultat av den nåværende verdenssituasjonen, og dette også et insentiv til å øke lønnsomheten i felt. Ved boring i krevende forhold, kan Managed Pressure Drilling (MPD-teknikker) brukes for å unngå trykkrelaterte problemer. Et slikt problem er for eksempel når en flytende rigg må gjøre en forlengelse, altså å forlenge borestrengen. Da blir strengen festet til oljeriggen og eventuell hivbevegelse i riggen gjør at borestrengen fungerer som et stempel i brønnen, og skaper både høye og lave trykk. Riggbevegelser kan da ikke lenger frikoples matematisk fra strengens bevegelser, noe som gjør at konvensjonelle MPD-teknikker ikke kan brukes. Strategien i dag er å vente til at vær og vind er på et tilfredsstillende nivå, for og så gjenoppta driften. HeaveLockprosjektet er et forsøk på å løse dette problemet. HeaveLockaktuatoren er en ventil montert inne i borestrengen, over bitet, med formålet å regulere trykksvingninger i brønnen, spesielt nedihull. Denne avhandlingen er en simuleringstudie av HeaveLock i en oljebrønn. De viktigste parameterne i simulatoren, for funksjonen av HeaveLock når den skal gjøre en forlengelse, er identifisert. En prosedyre for fremgangsmåte er funnet, med en tilfredsstillende regulering av nedihulls trykksvingninger. Alle endringer av parametere som forbedrer prosedyren har derimot sin pris. En mindre nominell HeaveLock åpning krever et høyere pumpetrykk og skaper trykkforstyrrelse ved initialisering og terminering av HeaveLock. Tidsintervaller kan forlenges og skape bedre vilkår i forstyrrelser, men ettersom det er ønskelig å gjøre forlengelsen så effektiv som mulig, blir dette også sett som en ulempe. En forlengelsesprosedyre er imidlertid dokumentert, og viser best mulig konfigurasjon som er funnet i denne avhandlingen. For den aktive perioden av HeaveLock, så kan rundt 70% av nedihulls trykksvingninger dempes, med 3,2 bar og 3,7 bar i nedrampingsforstyrrelse av HeaveLock

Design, development and control of a managed pressure drilling setup

Drilling in challenging conditions require precise control over hydrodynamic parameters for safer and efficient operation in oil and gas industries. Automated managed pressure drilling (MPD) is one of such drilling solution which helps to maintain operational parameters effectively over conventional drilling technique. The main goal is to maintain bottomhole pressure between reservoir formation pressure and fracture pressure with kick mitigation ability. Real life MPD system has to confront nonlinearity induced by drilling fluid rheology and flow parameters. To obtain a better understanding of this operation, a lab scale experimental setup has been developed. Reynolds number and pressure drop per unit length were considered to obtain hydrodynamic similarity. A vertical concentric pipe arrangement has been used to represent the drill string and annular casing region. A linearized gain switching proportional integral (PI) controller and a nonlinear model predictive controller (NMPC) have been developed to automate the control operation in the experimental setup. A linearizer has been designed to address the choke nonlinearity. Based on the flow and pressure criteria, a gain switching PI controller has been developed which is able to control pressure and flow conditions during pipe extension, pump failure and influx attenuation cases. On the other hand, a nonlinear Hammerstein-Weiner model has been developed which assists in bottomhole pressure estimation using pump flow rate and choke opening. The identified model has been integrated with a NMPC algorithm to achieve effective control within predefined pressure and flow constraints. Lastly, a performance comparison has been provided between the linearized gain switching PI controller and NMPC controller

Mathematical Modelling of the Drilling Process for Real-time Applications in Drilling Simulation, Interpretation and Assistance

For the last thirty years, mathematical modelling has been used to develop software solutions that support drilling engineering activities at the planning stage of drilling operations. But it is only for the last decade that mathematical models have been used for the real-time support of drilling operations. Moving from a pure engineering perspective to having models that can respect real-time requirements, necessitates many improvements of the subjacent mathematical modelling of the drilling process. First, it is not anymore possible to ignore transient behaviors that were somewhat irrelevant at the planning stage. Second, there is a need for solutions that should be fast enough to cope with the real-time constraints of the drilling process. With the perspective of creating applications that can support the drilling process in real-time, the following mathematical models have been developed: • Drilling fluid behavior. The properties of drilling fluids depend on their composition and pressure-temperature conditions. For instance, the pressure-temperature dependence of the mass density of drilling fluids, depends on the individual PVT-properties (Pressure-Volume-Temperature) of each of the components and their relative volume fractions. Therefore, the addition of drill-cuttings in the drilling fluid also changes the drilling fluid PVT-behavior. Furthermore, the rheological behavior of drilling fluids depends also on its composition. We have found that the rheological behavior of a KCl/polymer water-based mud is simultaneously modified by the relative proportion of barite and sand. Furthermore, it is known that drilling fluids are thixotropic. Yet, we found that the thixotropic behavior of drilling fluids is different from the one of other thixotropic fluids and we have determined that one of the causes for the discrepancy is related to the presence of solids in the fluid mix. We have developed a method to estimate the rheological behavior and its associated uncertainty, as a function of the modification of the solid proportions. • Drill-string mechanical sub-models coupled with hydraulic effects. Hydraulic pressure has also an impact on drill-string mechanical forces not only because the fluid mass density modifies buoyancy but more generally because viscous pressure gradients generate net forces along the drill-string. These hydraulic related forces are superposed to those engendered by mechanical friction and elastic deformation. • Steady state and transient drill-string mechanical models. Steady state torque and drag models utilizing the above-mentioned drill-string mechanical sub-models can be used to assess some characteristics of the drilling process when constant velocities are prevalent. But, during a drilling operation, there are many moments during which the drill-string displacement is in transient mode. Therefore, it is also important to have access to transient torque and drag models with a fast response time. • Transient cuttings transport model. The transport of cuttings is obviously influenced by hydraulic circulation but also drill-string rotational speed, at least in the deviated parts of a well. On the other hand, the presence of drill-cuttings in suspension or settling on the low-side of the borehole, influences pressure losses and mechanical forces along the drill-string. Therefore, the estimation of the transient displacement of drill-cuttings plays an important role in the overall estimation of the actual drilling conditions during a drilling operation. However, a transient cuttings transport model shall also be sufficiently fast, especially when it is used in real-time applications. Equipped with such models of the drilling process that are compatible with real-time constraints, then it is possible to solve problems that are relevant for the assistance of drilling operations. A first domain of application is related to the estimation, in real-time, of surface and downhole sensor values as a function of external commands like the block position and speed, the top-drive rotational velocity and the pump rates. We will refer to this domain of application as “drilling simulation”. However, comparison of measured values with simulated ones, require the proper modelling of the sensors and the impact of their actual position on the readings. For instance, drilling fluid is retained in the flowline and mud treatment equipment. Therefore, to simulate pit volumes, it is important to model the retention mechanism. Transient hydraulic, mechanical and heat transfer models, associated with precise modelling of sensor measurements, can then be used to interpret the current actual drilling conditions, because if their estimated parameters differ from the measurements, then a possible reason is that something unexpected is happening downhole. However, such drilling symptom detection method necessitates two additional conditions to be fulfilled: • The models shall be calibrated. Regardless of the quality of the drilling models, the inputs to these models are always known with a limited degree of accuracy and therefore their outputs may differ from measurements for that simple reason. However, it is important to distinguish between uncertainties that are related to properties that do not change substantially during a given drilling operation, from those that can change at any time. To avoid influencing the calibration of time invariant properties with possible side effects of the deterioration of the drilling condition, it is important to utilize drilling conditions by which undesirable side effects have no or little influence on the measurements that are used to calibrate the property. • Uncertainty of the modelled outputs shall be estimated. Calibration may reduce the uncertainty on the model outputs, but it does not eliminate it completely. It is therefore important to estimate the uncertainty of the predicted values. To achieve this, it is necessary to capture the precision by which the inputs of the process are known and to propagate that uncertainty throughout the modelling of the outputs. With continuously calibrated models and an estimation of the current downhole conditions, then it is possible to address some preliminary drilling process assistance functions: • Safety triggers. During the execution of automation functions, the situation awareness of the driller is reduced as he does not drive the drilling machines himself. Therefore, it shall not be attempted to automate any functions before a minimum set of protection functions are in place. Such safety triggers shall detect and react to incidents related to the axial and rotational movement of the drill-string and, of course, associated with pressure. Example of such safety triggers are: o Reactions to overpulls and set-down weights. o Reactions to abnormal torques. o Reactions to abnormal pressures. • Safeguards. Any drill-string or drilling fluid movements shall not generate a drilling incident. Therefore, commands to the drilling machines shall be kept within safe operational envelopes. For instance, upward movement of the drill-string shall not decrease the downhole pressure below the pore pressure or the collapse pressure of the open hole formations. Similarly, the applied flowrate combined with a possible downward movement and rotation of the drill-string shall not overpass the fracturing pressure of open hole formation rocks. • Automated procedures. Protected by safety triggers and operating within acceptable safeguards, then it is possible to automate some standard procedures. However, such automatic procedures must continuously be adapted to the current drilling conditions. For instance, the length of a friction must be modified to account for the current drill-string length and mechanical friction, or the flowrate applied during the ream-down sequence of a reciprocation procedure shall be reduced as a function of the current potential surging risk

Advanced control of managed pressure drilling

Automation of managed pressure drilling (MPD) enhances the safety and increases efficiency of drilling and that drives the development of controllers and observers for MPD. The objective is to maintain the bottom hole pressure (BHP) within the pressure window formed by the reservoir pressure and fracture pressure and also to reject kicks. Practical MPD automation solutions must address the nonlinearities and uncertainties caused by the variations in mud flow rate, choke opening, friction factor, mud density, etc. It is also desired that if pressure constraints are violated the controller must take appropriate actions to reject the ensuing kick. The objectives are addressed by developing two controllers: a gain switching robust controller and a nonlinear model predictive controller (NMPC). The robust gain switching controller is designed using H1 loop shaping technique, which was implemented using high gain bumpless transfer and 2D look up table. Six candidate controllers were designed in such a way they preserve robustness and performance for different choke openings and flow rates. It is demonstrated that uniform performance is maintained under different operating conditions and the controllers are able to reject kicks using pressure control and maintain BHP during drill pipe extension. The NMPC was designed to regulate the BHP and contain the outlet flow rate within certain tunable threshold. The important feature of that controller is that it can reject kicks without requiring any switching and thus there is no scope for shattering due to switching between pressure and flow control. That is achieved by exploiting the constraint handling capability of NMPC. Active set method was used for computing control inputs. It is demonstrated that NMPC is able to contain kicks and maintain BHP during drill pipe extension

Dynamic Positioning System as Dynamic Energy Storage on Diesel-Electric Ships

Abstract-A dynamic positioning (DP) system on a dieselelectric ship applies electric power to keep the positioning and heading of the ship subject to dynamic disturbances due to the winds, waves and other external forces using electric thrusters. Vice versa, position and heading errors can be allowed in order to implement energy storage in the kinetic and potential energy of the ship motion using the DP control system to convert between mechanical and electrical power. New simple formulas are derived in order to relate the dynamic energy storage capacity to the maximum allowed ship position deviation, as a function of the frequency of the requested dynamic energy storage. The benefits of DP dynamic energy storage are found to be reduced diesel-generator maintenance need, reduced fuel consumption and emissions, reduced risk for blackout, and increased operational flexibility allowing power-consuming operations such as drilling and lifting to be safely prioritized over DP for short periods of time

Sustainable seabed mining: guidelines and a new concept for Atlantis II Deep

The feasibility of exploiting seabed resources is subject to the engineering solutions, and economic prospects. Due to rising metal prices, predicted mineral scarcities and unequal allocations of resources in the world, vast research programmes on the exploration and exploitation of seabed minerals are presented in 1970s. Very few studies have been published after the 1980s, when predictions were not fulfilled. The attention grew back in the last decade with marine mineral mining being in research and commercial focus again and the first seabed mining license for massive sulphides being granted in Papua New Guinea’s Exclusive Economic Zone.Research on seabed exploitation and seabed mining is a complex transdisciplinary field that demands for further attention and development. Since the field links engineering, economics, environmental, legal and supply chain research, it demands for research from a systems point of view. This implies the application of a holistic sustainability framework of to analyse the feasibility of engineering systems. The research at hand aims to close this gap by developing such a framework and providing a review of seabed resources. Based on this review it identifies a significant potential for massive sulphides in inactive hydrothermal vents and sediments to solve global resource scarcities. The research aims to provide background on seabed exploitation and to apply a holistic systems engineering approach to develop general guidelines for sustainable seabed mining of polymetallic sulphides and a new concept and solutions for the Atlantis II Deep deposit in the Red Sea.The research methodology will start with acquiring a broader academic and industrial view on sustainable seabed mining through an online survey and expert interviews on seabed mining. In addition, the Nautilus Minerals case is reviewed for lessons learned and identification of challenges. Thereafter, a new concept for Atlantis II Deep is developed that based on a site specific assessment.The research undertaken in this study provides a new perspective regarding sustainable seabed mining. The main contributions of this research are the development of extensive guidelines for key issues in sustainable seabed mining as well as a new concept for seabed mining involving engineering systems, environmental risk mitigation, economic feasibility, logistics and legal aspects