A general dynamic model for any flow-related operation during well construction and interventions has been developed. The model is a basis for a new generation support tools and technologies needed in today's environment with advanced well designs, challenging drilling conditions and need for fast and reliable real-time decision support. The solution method uses a "divide and conquer" scheme, which computes the flow in each well segment separately, and then solves for the appropriate flow in the junctions. This simplifies greatly simulating complex flow networks, such as multilateral wells and jet subs. The flexibility allows incorporating additional pumps in the flow loop, as in Dual Gradient Systems. The model includes dynamic 2-D temperature calculations, covering the radial area affecting the well and assuming radial symmetry in the vicinity of the well. Other features: Flexible boundary conditions (which includes drilling, tripping) Non-Newtonian frictional pressure loss Transient well-reservoir interaction Slip between phases Advanced PVT relationship The reason for this new approach was to respond constructively to today's challenges (complex and difficult drilling conditions, need for reliable real time decision support). Our approach has been more flexibility, improved accuracy, reduced numerical diffusion and increased computational speed. The paper will present the basic model assumptions; the model architecture, and solution methods. Integration of the model into a real time system with links to real time databases and advanced visualization tools is currently ongoing. Thus the model may follow the whole work process through planning, training, execution, and post analysis. Examples of applications of the model so far will be presented, as well as visions for future applications. Introduction Alongside the advances in instrumentation and the more intelligent tools being developed today, there is a need for advanced numerical simulators that can bring all the technologies together to do intelligent drilling that will increase safety, reduce the costs, and make previously "impossible" fields "possible". The challenge in making the simulators lies in making the simulator kernel able to include all the important physical parameters; the important events; compute correct results; and fast enough to meet real time requirements. Examples of some of the recent improvements of the "events" that simulators are able to dynamically simulate are: control during underground blowout1; and hydrate formation2. In order to do this, the kernel needs to be able to change boundary conditions and connectivity during a single simulation. The simulator kernel presented here fulfills the needs of the present and many of the future challenges, as shown in the examples. The next chapters briefly explain the models used in the simulator, and the numerical methods used. The flexibility of the simulator is illustrated through a few examples, and the results of its use in real situation are presented.
fax 01-972-952-$435. AbstractBeing able to simulate drilling problems when operating within narrow margins between formation pressure gradients and fi-acture pressure gradients can cause great savings through improved planning. This is especially the case for HPHT and Deep Water wells. Lost circulation (i.e. underground flow) has in many cases proved to be a significant contributor to complex well control problems and drilling delays.The advanced kick simulator, RF-Kick, has recently been expanded to include the simulation of massive lost circulation. This tool allows the user to interactively investigate the problems of killing an influx while losses to formation occur. Kill procedures can thus be optimized through simulations.The fracturing is computed in a simple way. Only three numbers define the fracturing: the Fracture Initiation Pressure, the Fracture Propagation Pressure and the Fracture Closing Pressure. These pressures are supplied by the person using the simulator. The flow into (and out of) the fracture is determined by the flow needed to keep the fracture pressure at the fracture position. A user given fraction of fluid lost to the formation determines the amount of fluid recentering the well. This paper presents a description of the model, and a simulation of a 'representative' deep water well. The simulation starts with a well taking a kick. The well is shut in. As the pressure builds up the formation breaks down and an underground blowout develops. The influx is stopped while limiting the loss to the formation using sufficient flow rate and kill mud. The example describes actions done to lower the pressure at the fracture to stop the loss of fluid, and the careful well operations needed to handle a well with a closing fracture. reservoir fluid has exited the well. Such simulations show the operator what equipment is needed for a successful kill, pump capacity (volume and power), and kill mud (density and volume).Simulating kick with lost circulation scenarios is novel and a significant contribution. This will enable the industry to perform planning and engineering of complicated well control situations.
Planning offshore wells in deep water depths needs special tools to optimize operation and safety procedures. One of the many technical problems in deep-water operations is the possible formation of hydrates in the BOP or Kill/Choke line. Hydrates are ice type substances consisting of frozen mixtures of water and hydrocarbons which may plug the BOP stack and well circulation path and will be very difficult and time consuming to remove. An advanced dynamic kick simulator, developed at Rogaland Research, has recently been expanded to include the determination of the potential for hydrate formation. Using dynamic temperature simulation, detailed PVT computations of the hydrocarbon influx on the component level, and an advanced hydrate formation program it is possible to obtain the ‘distance’ in temperature from hydrate formation throughout the well at any time during a simulated operation. The simulator includes code that takes into consideration the effect of hydrate inhibitor chemicals such as salts and alcohols. Thus it is possible to make several trial runs with differently inhibited muds to compare the danger of running into hydrates. The paper briefly discusses the physical and chemical models used, and points out how to circulate in a way to minimize the chance of hydrate formation. Simulating kick with hydrate formation is a novel and significant contribution. This will enable the industry to perform planning and engineering of complicated well control situations. In particular it will allow the planning engineer to evaluate the risk of hydrate formation versus the cost of mud inhibition - this will be very useful for low mud weight situations where providing hydrate inhibition is very expensive. Introduction In recent years more challenging drilling conditions are being encountered. As operations move into deeper water we are moving into an environment where the well pressure and the ambient seabed temperature are in the region where influx gases produce hydrates. Hydrates are ice-like crystalline compounds formed by a hydrogen-bonded network of water molecules.1 In the oil industry hydrates formation is often viewed as a hazard since it can plug flowlines and severely interfere with well control operations. Advanced drilling simulators that are able to correctly predict the well conditions are recognized as critical tools required for planning such wells. Rogaland Research Kick Simulator (RF-Kick)2 is one such simulator which has continuously improved with both new features and accuracy due to extensive experimental work and improved numerical modeling. In recent years RF-Kick has incorporated deep water, horizontal well, advanced PVT, HPHT and lost circulation features3. The hydrate formation module adds the thermodynamical computations needed to determine the conditions of the influx gas in the well that is based upon the composition of hydrocarbon components as well as the temperature and the pressure in the well. The module also includes the contribution of salts and glycerol in the drilling mud to the determination of the hydrate formation condition. The main purpose of the hydrate formation module is to combine many effects of well control in order to determine the chance of hydrate formation during well operations. Most hydrate reports are investigations into hydrates formation under carefully controlled conditions. We saw a need to add this information into dynamic oil/gas well operations where pressures, temperatures and hydrocarbon compositions can vary dramatically within hours of operation. This paper briefly discusses the basic equations of the kick simulator, the dynamic temperature model, the hydrate model and the thermodynamic elements used in the simulator.
Outline: An advanced dynamic flow and temperature model was used to optimize and control MPD operations at Kvitebjørn. This paper describes in detail pre-simulations done to prepare for operations and develop detailed procedures, and post-analysis of real time data done to improve performance with respect to upcoming MPD operations at Kvitebjørn. The paper gives details on:Pre-simulations of drilling operations including temperature effectsExtra offline simulations during operationsPost-simulations with analysis of model-data deviations Results and observations: The paper discusses in details critical operations with main focus on sequences with multiple fluids in the well. These include setting of a balanced mud pill, tripping out and in with the pill in the hole, circulating out the pill, and cementing. Comparison with data taken when testing in cased hole is discussed, and it is described how good pressure control was obtained in real operations after having drilled into the reservoir. Applications and conclusions: The paper gives useful input to the use of advanced dynamic models for MPD operations. It gives a good impression of current status as well as possibilities and limitations for future operations. Introduction The Kvitebjørn field in the North Sea, close to Statfjord and Gullfaks, started production in 2004. Conventional drilling continued after this, but the increasing pressure depletion caused severe losses on the ninth well. This event put an end to conventional drilling at Kvitebjørn, and the development of a comprehensive managed pressure drilling setup started. Due to an operational window between pore and fracture pressure that was very small and uncertain, good control of all dynamic effects was addressed by using and advanced dynamic flow and temperature model both before, during and after operations on each well. By using calibrated dynamic software and detailed measurements of mud and fluid parameters as a function of pressure and temperature, it was possible to make procedures based on the best available data and the most reliable computations. A general overview of the first MPD operations at Kvitebjørn is given in Ref. 1, while more details on parts of the setup is given in Refs. 2–4. Earlier UBD/MPD experience offshore Norway is described in Refs. 5–8. Model overview The numerical model used in these computations has been thoroughly discussed in Petersen et al. (Ref. 9). Only a very brief discussion is included here, please go to Ref. 9 for a more detailed discussion.
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