bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accurate Subgrid Models for Two-Phase Flow in Heterogeneous Reservoirs
Authors: Efendiev Yalchin R. , Durlofsky Louis J. 
Published: December 2007

Abstract
Subgrid effects can have a strong influence on flow and transport in oil reservoirs. In this work a new model for the representation of subgrid terms is introduced and applied to two-phase reservoir flows. The model entails a generalized convection-diffusion treatment of the saturation equation as well as an extended representation for total mobility in the pressure equation. Motivation for the form of the model is provided through a consideration of volume averaging and homogenization results. The numerical computation of the subgrid terms and the implementation of the overall method are described. The accuracy of the new subgrid representation is compared to that of coarse scale models with no subgrid treatment and to coarse models based onpseudo relative permeabilities. The new model consistently provides more accurate overall coarse scale predictions, relative to reference fine scale results, than the other coarse scale models, particularly in cases when the global boundary conditions vary in time.
Dual Mesh Method in Upscaling
Authors: Audigane Pascal , Blunt Martin J 
Published: December 2007

Abstract
We develop and test a dual mesh approach to upscaling. A fine grid model is divided into coarse blocks, each of which contains many smaller cells. Pressure is computed first on the coarse grid using upscaled average transmissivities. These pressures are then used to compute the pressure at the small scale within each coarse block. In this way an approximation for the pressure is obtained without ever having to solve the full fine-grid problem, saving both CPU time and memory. The velocity is everywhere continuous and used to transport fluids on the fine grid - this step is no different from a conventional finite-difference approach once the pressure field is known.
We develop the method for multi-well two-phase incompressible flow with gravity in three dimensions - the method is an extension of the work of Verdière et al.1,2, and uses ideas developed by Gautier et al.3 in the context of streamline-based simulation. We discuss how this approach can be the platform for a fully decoupled dual mesh approach, where the fine grid transport problem is also decoupled into a series of coarse cell problems, resulting in a rapid but accurate method that can be applied in principle to grids with any number of cells.
We test the approach on two and three-dimensional problems with gravity. One of the test cases is a model from the SPE 10th Comparative Solution Project on upscaling4. The dual mesh method gives results that are very close to the fine grid results, but uses less CPU time and memory. The results are good even when a very coarse mesh is used and the method is more accurate than using standard single-phase upscaling techniques.
Locally Streamline-Pressure-Potential-Based PEBI Grids
Authors: Mlacnik Martin J. , Harrer Andreas W. , Heinemann Zoltan E. 
Published: December 2007

Abstract
Streamline pressure-potential (SPP) grids are a very promising tool for reservoir simulation, allowing to honor the actual path of flow. These grids represent a successful combination of streamline simulation and finite difference methods. One of the major challenges of this technique is that with changing flow conditions the grid needs to be altered over the period of a simulation run.
This paper presents the application of the windowing technique, introduced by Deimbacher and Heinemann1, to locally honor the changing directions of flow by modifying the grid during a simulation run. One or multiple parts of a reservoir model can be represented by windows with the objective to minimize the grid orientation effect and to enhance the CPU performance by locally incorporating time dependent streamline pressure-potential based PEBI grids.
In a first step the fully implicit solution for the full model will be calculated, but the inner blocks of the window, represented by a fine scale Cartesian grid, are solved for pressure only. Saturations and mole fractions will not be updated during this step. The solution of the first step provides the boundary influx for the windows and the pressure distribution that allows to determine the grid points of a streamline – pressure potential grid. Based on this point distribution a new window grid will be constructed using the PEBI algorithm. The new grid will then be solved in a second step, where the window is calculated for the same overall timestep, using the boundary flux determined during the first step.
The paper describes the generation of locally streamline based PEBI grids and presents results obtained from the application of this technique. A small scale example highlights the advantages of the proposed technique to handle the grid orientation effect. A further example demonstrate the application of the technique in full scale simulation models.
Upscaling Fluid-Flow and Geomechanical Properties in Coupled Matrix+Fractures+ Fluids Systems
Authors: Couples G. D. , Lewis H. , Reynolds M. A. , Pickup G. E. , Ma J. , Rouainia M. , Bicanic N. , Pearce C. J. 
Published: December 2007

Abstract
We have developed a coupled simulation approach, HYDRO-DDA, which calculates the fluid flow through, and geomechanical interactions within, a system of matrix blocks plus their bounding fractures. The flow and deformation behaviours of these simple, but realistic, systems do not agree with common "rules-of-thumb". The upscaled properties of these systems can potentially be used within large-cell reservoir simulations, but some of our models show severe non-linearities and bifurcations, suggesting that coupled hydrogeomechanical upscaling requires due consideration of the context.
Coupled Analysis of Geomechanics and Fluid Flow in Reservoir Simulfation
Authors: Samier P. , Onaisi Atef , Fontaine G 
Published: December 2007

Abstract
Generally, in classical reservoir studies, the geomechanical behavior of the porous media is taken into account by the rock compressibility. Inside the reservoir simulator, the rock compressibility is assumed to be constant or to vary with the pressure of the oil phase. It induces some changes in the porosity field.
During the depletion phase or the cold water injection of HP-HT reservoirs, the stress state in and around a reservoir can change dramatically. This process might result in rock movements such as compaction, induced fracturing, enhancement of natural fractures and/or fault activation, which continuously modify the reservoir properties such as the permeabilities and the fault transmissibilities.
Modifications of such parameters strongly affects the flow pattern in the reservoir and ultimately the recovery factor. To capture the link between flow and in situ stresses, it becomes essential to conduct coupled reservoir-geomechanical simulations.
This paper compares the use of 5 types of approach for the reservoir simulations: ▪A classical approach with rock compressibility using only a reservoir simulator,▪A loose coupled approach between a reservoir simulator (finite volumes) and a geomechanical simulator (finite elements). At given user-defined steps, the hydrocarbons pressures calculated by the reservoir simulator are transmitted to the geomechanical tool which computes the actual stresses and feeds back the modifications of the petrophysical properties (porosities and permeabilities) to the reservoir simulator.▪A one way coupling: this approach is a simplification of the loose coupled approach, the modifications are not fed back to the reservoir simulator.▪A simplified approach using permeability and porosity multipliers inside a reservoir simulator. These multipliers are user defined curves and vary with the pressure of the oil phase. This approach uses only a reservoir simulator.▪A fully coupled approach where the structural and the flow unknows (displacement, pressure, saturations) are solved simultaneously.
These approaches are compared for 2 field cases described below.
A General Purpose Controller for Coupling Multiple Reservoir Simulations and Surface Facility Networks
Authors: Ghorayeb Kassem , Holmes Jonathan , Torrens Richard , Grewal Balraj 
Published: December 2007

Abstract
Integrated surface-subsurface modeling has been shown to have a critical impact on field development and optimization. Integrated models are often necessary to analyze properly the pressure interaction between a reservoir and a constrained surface facility network, or to predict the behavior of several fields, which may have different fluid compositions, sharing a common surface facility. The latter is gaining a tremendous significance in recent deepwater field development.
These applications require an integrated solution with the following capabilities: To balance a surface network model with a reservoir simulation model in a robust and efficient manner.To couple multiple reservoir models, production and injection networks, synchronising their advancement through time.To allow the reservoir and surface network models to use their own independent fluid descriptions (black oil or compositional descriptions with differing sets of pseudo-components).To apply global production and injection constraints to the coupled system (including the transfer of re-injection fluids between reservoirs).
In this paper we describe a general-purpose multi-platform reservoir and network coupling controller having all the above features. The controller communicates with a selection of reservoir simulators and surface network simulators via an open message-passing interface. It manages the balancing of the reservoirs and surface networks, and synchronizes their advancement through time. The controller also applies the global production and injection constraints, and converts the hydrocarbon fluid streams between the different sets of pseudo-components used in the simulation models. The controller's coupling and synchronization algorithms are described, and example applications are provided. The flexibility of the controller's open interface makes it possible to plug in further modules (to perform optimization, for example) and additional simulators.
A Generalized Wellbore and Surface Facility Model, Fully Coupled to a Reservoir Simulator
Authors: Coats B. K. , Fleming G. C. , Watts J. W. , Ramé M. , Shiralkar G. S. 
Published: December 2007

Abstract
The formulation of a black oil or compositional fully coupled surface and subsurface simulator is described. It is based on replacing the well model in a conventional reservoir simulator with a generalized network model of the wells and facilities. This allows representation of complex wellbore geometry and downhole equipment. The global reservoir/network system is solved simultaneously at the end of each simulator Newton iteration. The method avoids inefficiencies of other coupled models in which wells and facilities are treated as separate domains, or in which the global system is not solved simultaneously. Example cases demonstrate the efficiency of the model for cases with simple and segmented wellbores, with and without facilities.
Intergrid Operations - Dynamic Gridding Techniques in Nonlinear Domain Decomposition Methods
Authors: Liu Wei , Mezzatesta Alberto G. , Hildebrand Margaret A. 
Published: December 2007

Abstract
Domain decomposition methods provide major advantages to large-scale and high-resolution reservoir simulation studies in terms of computer resource requirements. In this paper, a directional, intergrid mapping technique is introduced together with a nonlinear domain decomposition algorithm - the Fast Adaptive Composite Grid (FAC). Domain decomposition techniques have often been applied to solve the linear system of equations resulting from reservoir numerical models. However, a stronger, more efficient approach is to apply the domain decomposition techniques directly to the nonlinear problem. As a result, mapping dynamic reservoir properties from one grid scale to another one, a process also known as intergrid mapping, becomes a key operation in dealing with composite grid systems.
Normally, upscaling and downscaling techniques focus on geological structures and formation properties. The proposed intergrid mapping operations in the FAC method honor the static reservoir properties while preserving the properties of fluid flow dynamics between grids with different scales. Most importantly, the intergrid mapping operator in FAC can accurately represent local phenomena in much coarser domains, so that the composite grid residual, which can be viewed as the relative overall solution error, can be effectively minimized. Application of the FAC method brings significant reduction in CPU time and memory requirements when compared with simulations having the same level of global grid and timestep refinement, making it possible to attain large simulation scales and resolution with limited computer resources.
In this paper, the approximation of the differential conservation equations is based on the control volume approach and uses cell-centered finite difference methods. The composite grid solution is obtained through a defect-correction process of refinements. Unlike many domain decomposition algorithms, the proposed method provides full approximation storage (FAS) by computing and storing the whole coarse grid solution, including the grids for which a refinement exists.
Computational results from a model featuring local spacetime refinements are presented to illustrate that a rigorous intergrid mapping operation can significantly improve the efficiency of nonlinear domain decomposition algorithms, especially in cases of multiphase flow with irregular local timestepping. The presented numerical examples demonstrate the applicability of the proposed numerical method.
The Disc Bit – A Tool for Hard Rock Drilling
Authors: Placido J. C. R. , Friant J. E. 
Published: December 2007

Abstract
This paper traces the development of a radically different design of drill bit; its concept, laboratory work and the latest field trials are described.
The technology of the Disc-bit is based upon the single rolling disc cutter. This type of cutter was successfully used in rock for the first time on a tunnel boring machine in 1956. By the early 1970's, virtually every rock tunneling machine in the world had moved from picks, tungsten carbide button cones, or multi-row tapered cutters, to the single row disc. By then, the superior performance on tunneling machines had been demonstrated by practical experience in the field. Further, Colorado School of Mines (CSM) began scientific studies, and based on full scale laboratory testing, published data comparing the Specific Energy of Excavation of various tools. This clearly showed that the single row disc cutter required less energy to excavate a given volume of rock. With energy at the cutting face always a limited commodity, a lower energy requirement translated to higher penetration rate.
Not until the mid 1990's was the concept of the single rolling disc cutter applied to drill bits. Very small, 3 ¼" Mini-DiscTM cutters were evaluated at CSM and found to be extremely efficient and sufficiently robust to be used on drill bits as small as 7 7/8". The U.S. Gas Research Institute sponsored an effort to develop the concept by laboratory and field testing. Other field trials were sponsored by private and government grants including the most recent test funded by a JIP, managed by PETROBRAS. An evaluation of an 8 ½" Disc-Bit was performed at GRI Catoosa Test Facility, in Oklahoma, USA.
Deploying Dual Gradient Drilling Technology on a Purpose-Built Rig for Drilling Upper Hole Sections
Authors: Judge Robert A. , Thethi Ricky 
Published: December 2007

Abstract
The benefits of using dual gradient drilling (DGD) technology to drill complete wells in ultra-deep waters have been stated in several papers and industry presentations. However, a new opportunity to employ DGD to reduce overall drilling costs exists by concentrating on drilling upper hole sections. The support equipment, rig integration strategies, and deployment methodologies for using DGD in a "top-hole" configuration can differ significantly from a pure, full-function DGD implementation.
Risk associated with equipment failure is one hurdle that must be overcome before the use of DGD becomes commonplace in the industry. While laboratory and full scale prototype tests have been performed for several DGD system designs, full industry acceptance of the equipment and techniques may not be achieved until there is additional field experience to fall back on. One way to mitigate this risk is to develop strategies to run new equipment separate from the conventional riser. Doing so minimizes the round trip time required to pull the hardware and perform any equipment repairs that become necessary.
This paper presents options for integrating and deploying DGD equipment specifically for use in drilling upper hole sections. Included are discussions regarding the following: Deploying equipment before BOPs are setSetting equipment off to the side of the wellhead, with and without a dual activity rigDeploying equipment with a Multi-Service Vessel (MSV)Auxiliary equipment, such as a lightweight mini-riser or free-standing riser with subsea jumpers.
Utilizing this paper as a guide, operators and drilling contractors will be able to consider new field development strategies that include DGD, while minimizing the risk and expense normally associated with new technology deployment.
Field Evaluation of a Rotating Separator as an Alternative to Shale Shakers
Authors: Saasen A. , Botnmark K. , Mikalsen K. , Jensen O. D. , Dale J. F. 
Published: December 2007

Abstract
Occupational hygiene requirements for operations on the Norwegian continental shelf when drilling with oil based drilling fluids, favour the use of enclosed system for solids control. Personnel working with shale shakers are often exposed to a base oil mist and vapour at an unacceptable level. A concept using rotating separators as an alternative to shale shakers was developed to reduce this exposure. Drilling fluid with cuttings from the mud line is fed into a slowly rotating separator that forces the cuttings to move over a very large effective screen area with screens of selected sizes. The drilling fluid is efficiently removed from the cuttings since the area underneath the screen is slightly vacuumed. The improvements this treatment has on the occupational hygiene and the environmental impacts compared to use conventional shakers are illustrated.
The current paper focuses on a field test where the rotating separator efficiency was compared with the efficiency of conventional shakers while drilling. The drilling operation was conducted with both water based and oil based drilling fluids. The field tests are described in detail. An efficient, but still gentle separation of drilled cuttings from the drilling fluid was observed. The paper discusses if the rotating separator managed to produce proper cuttings dryness even though 60–100% of the total cuttings load produced by the drilling rig was directed through the rotating separator. After completion of the field tests, the separator was brought onshore for further improvements. The flow capacity was increased with more than 100% based on these improvements.
Uniquely Engineered Water-Base High-Temperature Drill-In Fluid Increases Production, Cuts Costs in Croatia Campaign
Authors: Soric Tomislav , Huelke Robert , Marinescu Pavel 
Published: December 2007

Abstract
Along with exorbitant costs and safety considerations, drilling in a high-temperature, high-pressure (HTHP) environment also poses the difficult challenge of protecting a reservoir that is all-too-often depleted. In areas where environmental restrictions and compatibility issues in gas fields prohibit the use of an oil-base drilling fluid, engineering a water-base fluid system that is free of potentially damaging solids, stable at very high temperatures, and able to withstand acid gases (CO2, H2S) or other contaminants is a very difficult proposition. The demands are compounded dramatically when drilling a deviated or a re-entry deviated slim hole well in an HTHP environment. Furthermore, since pressure and temperature heavily influences the rheological behavior, it is extremely difficult to calculate, predict and control pressure losses, ECD, and/or ESD in real time to avoid total losses or kicks.
This paper details the design of a unique water-base reservoir drill-in fluid and its successful application on five HTHP wells in the Kalinovac and Molve gas fields of Croatia. Four of the wells were high-angle re-entry slim holes. Using laboratory, field, reservoir investigation and computer data, the authors will demonstrate the effectiveness of the new fluid in delivering zero skin damage and subsequently higher production rates than other wells in the field. Further, the system significantly reduced operating costs by eliminating costly stimulations, while simplifying the generation of clear imaging logs. The system also remained stable at bottom hole temperatures of 180 – 200°C.
During the drilling operations, a unique software program was employed that accurately predicted the rheological behavior, pressure losses, ECD and ESD, which contributed heavily to the wells being drilled trouble-free. The authors will detail the formulation of the new system, along with the coordination and pre-planning that contributed to its success in Croatia. The new water-base system has shown the effectiveness in drilling HTHP wells in areas where invert-emulsion drilling fluid systems are prohibited.
Low Risk/High Reward Strategy Drives Underbalanced Drilling Implementation in PDO
Authors: Francis P. A. , Davidson I. A. , Harthi S. , Geldof W. , Culen M. S. , Jenkins T. 
Published: December 2007

AbstractUnderbalanced Drilling (UBD) is a drilling technology capable of delivering substantial increases in initial well productivity and ultimate recovery from oil and gas wells, as well as a host of other benefits. Petroleum Development Oman (PDO) is exploiting a variety of reservoir types that could benefit from this technology. The difficulty in assessing the performance of a well drilled underbalanced compared to a conventional (overbalanced) well, however, is compounded by reservoir heterogeneity such that even two conventionally drilled wells relatively close together may deliver substantially different well initials. Single well trials of UBD in the past in PDO have been expensive, in terms of the relative cost of mobilising equipment to the Arabian Peninsula, and the results inconclusive. A strategy of ‘Zero Cost Implementation’ was formulated to avoid these problems. The business benefits necessary to ‘pay’ for the increased cost of UBD were determined. As the risk of those returns not being met were low then a sufficiently long campaign of UBD could be justified to assess the benefits. The result of this policy was the implementation of one and a half string years of UBD (some 20 wells) in two fields (one carbonate, one clastic), which makes it one of the largest campaigns of UBD outside North America. Two UBD packages have been employed from two different contractors and the campaign started in May 2002. Not only have both projects delivered significant increases in productivity but they have also shown the benefits of real-time assessment of reservoir productivity while drilling allowing real-time decisions on well operations and completion design.