bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluating Productivity of a Horizontal Well
Authors: Michelevichius D. , Minijos Nafta , Zolotukhin A. B. 
Published: December 2007

Abstract
This paper discusses an alternative approach to a horizontal well (HW) productivity evaluation. The approach is based on the exact solution to a task of the horizontal well productivity evaluation in a 3D reservoir with correct evaluation of all boundary conditions including the no cross-flow conditions at the top and bottom of the reservoir.
Validation of the new equation for the HW productivity is made by means of special asymptotic analysis. In particular, it is shown that the obtained solution asymptotically approaches well-known solutions for cases of simple flow geometry.
However, comparison of the new equation with solutions available from the literature shows some differences between them. We believe that this is mostly due to a more accurate handling of boundary conditions in the new solution. For example, comparison with Joshi’s solution [1, 2] shows that a newly obtain solution gives higher production rates for short length of horizontal sections (L in the order of tens of meters) and lower rates for long horizontal wells in thin reservoirs (Lπh, L⊇re). In the latter case reduced production rate (as compared with [1]) was obtained with due regard for a no cross-flow conditions at the top and bottom of the pay interval. Higher production rates in case of short length of horizontal sections can be caused by a dominating effect of 3D flow in the vicinity of a well, especially in case of a thick pay interval. The highest discrepancy between solutions reported in the literature and proposed in this paper found to be up to 19% for long wells and can exceed 30% for short sidetracks (5-20 m). More detailed analysis of similarities and differences between several solutions is given in the next sections.
A generalized solution for the inflow performance of a HW accounting for the directional values of the reservoir permeability (an orthotropic reservoir) is also given in the paper. In particular, it is shown that in case of anisotropic reservoir orientation of a horizontal well in plane has a strong impact on its productivity
Pressure Pulse Workovers in Heavy Oil
Authors: Dusseault Maurice , Shand Darrell , Davidson Brett 
Published: December 2007

Abstract
Approximately 100 pressure pulse workovers have been performed on heavy oil wells in Canada since 1998. Analysis of a number of the wells shows varying degrees of success, but in general, the workovers have paid for themselves in almost all recent cases. Although there is insufficient information to fully prove hypotheses using statistical criteria, it appears that pressure pulse workovers have particular application in three situations: ▪In cases where the CHOPS well did not initially start producing sand during the primary completion attempts;▪In cases where the well became disconnected from the far-field pressure and gravity driving forces; and,▪In cases when it is desired to place a workover chemical in a well-dispersed fashion around a well.
This article will review the physical mechanisms and drive energy sources that are believed to be responsible for CHOPS production; it will also present the physical processes that we believe occur during aggressive pressure pulse workovers around a heavy oil well.
Determining Oil Sand Reservoir Properties from Logs and Core – The Controversy Continues
Authors: Donnelly John K. , Hitchner John 
Published: December 2007

Abstract
It has been 25 years since Zwicky and Eadc presented their paper on the subject. Now that the Steam Assisted Gravity Drainage (SAGD) process has made it possible to open much of the oil sand resource to commercial development the controversy is renewed. The key reservoir properties that must be determined from log and core data are porosity, permeability and initial water saturation. This paper will review an approach that has been successful for the authors. An example of the use of this method for predicting the performance of a SAGD application is given.
The Long Lake Project – The First Field Integration of SAGD and Upgrading
Authors: Kerr Rich , Birdgeneau John , Batt Bob , Yang Peter , Nieuwenburg Gary , Rettger Phil , Arnold Jim , Bronicki Yoram 
Published: December 2007

Abstract
The OPTI Canada Inc. (OPTI) / Nexen Inc. (Nexen) Long Lake integrated bitumen recovery and upgrading project is a unique solution to the three key problems associated with the development of thermally produced extra heavy oil resources: the low value of the produced oil, the high fuel cost associated with thermal production, and the need for diluents to transport the produced oil to markets. The Long Lake Project will produce a premium light sweet synthetic crude from steam assisted gravity drainage (SAGD) produced Athabasca bitumen, utilizing upgrader bottoms as the primary source for upgrader hydrogen and SAGD fuel.
The core of the Long Lake integrated upgrader is the patented OrCrude™ upgrading process that uses distillation, solvent deasphalting, and thermal cracking in a unique combination to partially upgrade bitumen into OrCrude product and produce an asphaltene by-product.
At the Long Lake Project the OrCrude process will be integrated with commercially proven technologies to hydrocrack the partially upgraded OrCrude product to premium synthetic crude. In addition, the asphaltenes will be fed to an asphaltene gasification system to produce hydrogen for the hydrocracker and syngas fuel for the SAGD process.
The result is an integrated project that will produce premium synthetic crude with quality characteristics that are superior to other synthetics, at an operating cost that is less than any other Canadian production and upgrading project. The capital cost for the integrated Long Lake Project is forecasted to be comparable to other integrated Athabasca bitumen and upgrading projects.
The OrCrude process has been demonstrated at a 500 bpsd commercial demonstration facility near Cold Lake, Alberta which has been operating since mid-2001 on Cold Lake and Athabasca bitumens. The Long Lake Project, currently in the regulatory review process, is proposed to have an initial size of 70,000 bpsd of SAGD production and 70,000 bpsd of upgrading. OPTI and Nexen have plans to subsequently expand the upgrader to 140,000 bpsd. Construction is planned to commence in late 2003 with production in 2006.
Good Engineering Practices Achieve a 30-Fold Increase in Injection Rates in Selected Niger Delta Reservoirs
Authors: Arukhe James , Nwoke Linus , Uchendu Chike 
Published: December 2007

Abstract
Key points of the successful implementation of a pressure maintenance scheme by water flooding in a major operator in Nigeria are presented.
The wells considered were completed in July / August 2001 and immediately put on stream. They were designed to dump circa 7,500 BW/D from the sands at ±6100 feet TVD to an aquifer nearby. An initial dump rate as low as 200 BW/D (average) at a maximum surface injection pressure of 1000 psi was recorded prior to the jobs. This was attributed to severe impairment from the pseudo-oilbased mud, incompletely removed with stimulation treatments following perforation. Low permeability or wellbore damage associated with the mud in the drilling phase may also have been responsible for limiting injection rates into these sands, especially if the perforation tunnels during completion, did not extend past the area of mud invasion.
The stimulation treatments used a xylene solvent pre-flush and a new HF acid treatment to remove the pseudo-oil and perforation debris damage, improving injection rates significantly. The more than 30-fold injectivity improvements that resulted may have been due to one or a combination of the following:A nitrified acid-aromatic pickle performed before pumping treatment fluid into formation.Pickle volume kept at approximately 25% tubing volumeTreatment performed in segments reciprocation across the perforationsInjection lines flushed to more than expected injection rates to ensure clean injection water.Circulation of tubing to clean water using foamed nitrified fluids during the pickle, helped to bring the spent pickle acid back to surface.
Remedial work to further improve the dump rate (and oil sweep) may only be considered if BHP surveys at a future date from closed in wells do not indicate reservoir pressure stabilization or an improvement over the decline previously observed.

Introduction
The KKK field is an areally extensive field located in a Swamp location in Niger Delta. The field was discovered by KKK-1 well in 1996 and completed in August 2000 as a dual string water injection well in two (2) major aquifer sands (upper and lower reservoirs), one on each (short and long) string. Following this, several other wells have been completed to develop the field. A reservoir study was conducted for the upper and lower reservoir sands to investigate the need for pressure maintenance and artificial lift to maximize oil recovery from the reservoir. This study, supported by the geological interpretation of limited aquifer extent, showed that pressure maintenance by means of peripheral water injection was required to maximize oil recovery efficiency. The water injection wells were therefore needed to restore reservoir pressure so that oil recovery is maximised and GORs are reduced.
Rigless Activities at Otumara in the Western Nigerian Swamp
Authors: Hijlkema Sjouke 
Published: December 2007

ABSTRACT
"Snubbing" and "Hydraulic Workover Unit (HWU)" are words not often heard in Shell operations, unless used for special projects. However, they do serve a good purpose when used correctly. In an environment where rigs are expensive and attract many "disturbances" by communities, they can be used as an effective alternative to well workovers.
The Hydraulic Workover Unit supplied by an indigenous contractor is in line with the drive to support local contractors in developing expertise in the areas of well completion, work over and abandonment. The current arrangement is for the indigenous contractors to work under the umbrella of a multinational company such that in time they can become autonomous.
These considerations were the main driving factors to initiate the "Otumara workover campaign", (to prepare wells for gas-lifting), with a HWU instead of a rig.
This has resulted in potential cost savings of about US6$ million, increased oil production potential by 30-40,000 bbl/day, increased indigenisation of the Nigerian Oil Service industry in Nigeria, and is a prime example of a paradigm shift on "how to do things differently".
Generation of Low-Order Reservoir Models Using System-Theoretical Concepts
Authors: Heijn T. , Markovinovic R. , Jansen J. D. 
Published: December 2007

Abstract
We present five methods to derive low-order numerical models of two-phase (oil-water) reservoir flow, and illustrate their features with numerical examples. Starting from a known high order model these methods apply system-theoretical concepts, originally developed in measurement and control theory, to reduce the model size. Using a simple but heterogeneous reservoir model, we illustrate that the essential information of the model can be captured by a very limited amount of state variables (pressures and saturations). Ultimately we aim at developing computationally efficient algorithms for history matching, optimization and in particular the design of control strategies for smart wells. In this study we applied 1) modal decomposition, 2) balanced realization, 3) a combination of these two methods, 4) subspace identification, and 5) proper orthogonal decomposition (POD), also known as principal component analysis or the method of empirical orthogonal functions. Methods 1 to 4 result in linear low-order models, which are only valid during a limited timespan. However, the 5th method (POD) results in a non-linear model that remains valid over a much longer period. Subspace identification requires only input-output data and no knowledge of the system itself, and could therefore, in theory, also be applied to measured data. In particular POD and identification are promising methods to generate low-order models.
Experimental Design as a Framework for Reservoir Studies
Authors: White Christopher D. , Royer Steve A. 
Published: December 2007

Summary
Numerical simulation integrates extensive geoscience and engineering data with complex process models to examine reservoir behavior. Reservoir studies commonly consider many scenarios, cases, and realizations. However, reservoir simulation can be expensive. Complexity, combinatorics, and expense motivate improved reservoir study methods. The experimental design framework selects relevant models, records factor settings for models, creates data files, controls execution, gathers summary data, and creates response models. Response surface models facilitate Monte Carlo simulation, uncertainty analysis, optimization, parameter estimation, upscaling, and performance forecasting. A predevelopment study of a Gulf of Mexico turbidite reservoir uses this framework to examine the sensitivity of oil production predictions to well location, absolute horizontal permeability, pore compressibility, aquifer size, skin, and vertical permeability. Well location is optimized for cases with uncertain parameters.
Higher Dimensional Wave-Oriented Upwind Schemes With Minimal Cross-Wind Diffusion
Authors: Edwards Michael G 
Published: December 2007

AbstractStandard single-point upstream weighting schemes are still the most common type of method in reservoir simulation for integrating the essentially hyperbolic components of the system. These schemes rely upon upwind information that is determined according to the grid geometry. As a consequence directional diffusion is introduced into the solution that is grid and geometry dependent. The effect can be particularly important for cases where flow is across grid co-ordinate lines and is known as cross-wind diffusion. A new type of upwind scheme is introduced to reservoir simulation that minimizes cross-wind diffusion, is free of spurious oscillations and remains locally conservative.
Coupled Geomechanical Simulation of Stress Dependent Reservoirs
Authors: Stone Terry W. , Xian Chenggang , Fang Zhi , Manalac Evangeline , Marsden Rob , Fuller John 
Published: December 2007

Abstract
A geomechanics option that features the three dimensional elastoplastic stress equations which are fully or partly coupled to a commercial reservoir simulator is applied to a field and a synthetic case. Sanding, fracturing and stress dependent flow are analysed.
First the basic formulation is discussed. Elastic stress equations and boundary conditions are described including their implementation in the finite difference simulator. Comparison is made with an industry standard finite element code with an option for coupled single phase flow. It is demonstrated that the finite difference implementation of the stress equations, which is second order, can produce acceptable accuracy when compared against finite element simulators. Non-orthogonal corner-point gridding is also reviewed in this context when the gridding is skewed. Some features of other gridding types including unstructured grids are also presented. Plasticity, stress dependent permeability and faults are available as options.
Two cases are presented which were designed to demonstrate the applications of sand management, simulation of tight gas reservoirs with stress dependent permeability and propped/etched fractures. The sand management case is based on an offshore gas field. Reservoir geometry, properties and geological (tectonic) details were provided by the operator. A case which simulates fracturing was designed as a tutorial. Although synthetic, it offers a workflow for the use of predicted stress and pore pressure as input to calculations of fracture conductivities/geometries whose output is returned to the simulator.
This geomechanics option is currently under development. Some areas of further work are mentioned.
An Efficient Discrete Fracture Model Applicable for General Purpose Reservoir Simulators
Authors: Karimi-Fard M. , Durlofsky L. J. , Aziz K. 
Published: December 2007

Abstract
A simplified discrete fracture model suitable for use with general purpose reservoir simulators is presented. The model handles both two and three-dimensional systems and includes fracture-fracture, matrix-fracture and matrix-matrix connections. The formulation applies an unstructured control volume finite difference technique with a two-point flux approximation. The implementation is generally compatible with any simulator that represents grid connections via a connectivity list. A specialized treatment based on a "star-delta" transformation is introduced to eliminate control volumes at fracture intersections. These control volumes would otherwise act to reduce numerical stability and time step size. The performance of the method is demonstrated for several example cases including a simple two-dimensional system, a more complex three-dimensional fracture network, and a model of a strike-slip fault zone. The discrete fracture model is shown to provide results in close agreement with those of a reference finite difference simulator in cases where direct comparisons are possible.
Better Field Development Decisions from Multi-Scenario, Interdependent Reservoir, Well, and Facility Simulations
Authors: Narayanan Keshav , Cullick A. S. , Bennett Matthew 
Published: December 2007

Abstract
Making better decisions, which take into account uncertainty in all the components of an exploration and production (E&P) asset's value chain, continues to be a significant challenge for the industry. The literature of the last few years has emphasized the importance of workflows that integrate and include formal quantification of uncertainties across subsurface, well locations, well configurations and operations, surface interconnections, and economics. Much of the effort has focused on scenario and probabilistic analysis decision support techniques. The industry continues to make many field development decisions from flow simulation ‘sensitivity cases’ or from simplified models, which can have the effect of underestimating the full uncertainty and adding unnecessary constraints.
This paper presents an integrated system that can assist field development decisions. The complex relationships between the earth models, the development strategy and the economics are retained in the development decision process. A full-physics reservoir simulator is used to maintain high fidelity to the physics of both the subsurface and surface components. The interdependencies of underlying uncertainties can affect the choices to be made. The system described can be implemented for project decisions at any stage within an asset's life cycle.
In this paper, we illustrate the application of the system on a single, significant reservoir unit, taken through a development-planning exercise. The exercise includes coupled well and facility scenarios and evaluates economic outputs that are fully coupled with the flow simulation outputs. The reservoir is a faulted structure covering about 30 square miles and has around a 450 feet thick oil column. Uncertainties in the earth model were present in the static properties, faulting, and fluid-rock dynamic properties. Uncertainties included both distinct scenarios and continuous distributions. multiple choices around well placement, drainage strategies with and without injection, and scheduling are included. Ultimate recoveries, profiles, and ultimate economics for the range of possibilities are evaluated.
A Comparison of Techniques for Coupling Porous Flow and Geomechanics
Authors: Dean Rick H. , Gai Xiuli , Stone Charles M. , Minkoff Susan E. 
Published: December 2007

Abstract
This paper compares three techniques for coupling multiphase porous flow and geomechanics. Sample simulations are presented to highlight the similarities and differences in the techniques. One technique uses an explicit algorithm to couple porous flow and displacements where flow calculations are performed every time step and displacements are calculated only during selected time steps. A second technique uses an iteratively coupled algorithm where flow calculations and displacement calculations are performed sequentially for nonlinear iterations during time steps. The third technique uses a fully coupled approach where the program's linear solver must solve simultaneously for fluid flow variables and displacement variables. The techniques for coupling porous flow with displacements are described, and comparison problems are presented for single-phase and three-phase flow problems involving poroelastic deformations. All problems in this paper are described in detail so the results presented here may be used for comparison with other geomechanical/porous flow simulators.
Numerical Simulation with Input Consistency between Capillary Pressure and Relative Permeability
Authors: Li Kewen , Horne Roland N. 
Published: December 2007

Abstract
This study proposes a numerical simulation approach without direct specification of relative permeability functions. Using this approach, it is not necessary to impose relative permeability functions as input to the simulator in order to conduct the numerical simulations of two-phase fluid flow. Instead only capillary pressure data need to be imposed and the relative permeabilities can be calculated consistently using specific models. Example numerical simulations at both core and reservoir scales were conducted to test the technique without the direct input of relative permeability functions from experimental data. The results showed that the production performance calculating from the numerical simulations without the input of relative permeability functions was almost the same as the experimental data. Using the method proposed in this study, the effects of pore size distribution index and entry capillary pressure on oil recovery by gravity drainage were investigated at both core scale and reservoir scale. The technique may be especially suitable for reservoirs in which it is difficult to measure relative permeability curves. Such reservoirs include gas-condensate reservoirs, extremely low permeability reservoirs, and geothermal reservoirs. The proposed technique may also be useful to upscaling, numerical simulation while drilling, and other areas.