bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of Well Productivity in a Reservoir Simulator (I)
Authors: Chen G. , Tehrani D. H. , Peden J. M. 
Published: December 2007

ABSTRACT
One of the objectives of reservoir performance prediction is to determine the number of wells needed for future development of a field. It is known that most of the wells are deviated, especially in offshore environment. It is also known that conventional simulators cannot simulate the performance of slanted wells with acceptable accuracy in many cases. Many simulators cannot calculate the flowing bottom hole pressure of the wells accurately, even for vertical and horizontal wells in which well block aspect ratios are far from unity or where the well completion interval is short or the well is close to the reservoir boundaries. This paper presents formulations with which the flowing bottom hole pressure of wells (hence their productivity) can be accurately calculated for all wells. These will include vertical, horizontal and slanted wells and generally any well whose trajectory is not parallel with the simulation grid.
A methodology is presented by which a conventional finite difference simulator can be used together with an analytical model that we have developed to calculate accurate well pressure and productivity for many types of wells. At this stage the solutions we offer cover a single well in an infinite slab reservoir or in a fixed boundary rectangular box shaped reservoir with a single phase fluid and only for homogeneous or anisotropic uniform permeability reservoirs. Research is in progress for other situations.
Sensitivity studies on variables such as reservoir rock and fluid properties, simulation gridding, reservoir geometry and well geometry have been conducted.
The validity of the new methodology is demonstrated by comparing the results of our analytical method with numerical solutions for cases in which there is no doubt on validity of the numerical results.
Comparison is made between our analytical method and those available in the literature. The results demonstrate the superiority of the method.
Furthermore, we have developed a new computer program which has coupled our analytical program with a numerical simulator in one package by which the necessary skin factor can be calculated in one run. It is demonstrated that the use of this program eliminates the need for a refined grid and it is less time consuming and much more economical than local grid refinement, where local grid refinement is used only to improve the numerical accuracy and not for inclusion of more detailed geological and petrophysical data.
New Well Models for Partially Penetrating Wells in Heterogeneous Reservoirs Using Non-Uniform Grids
Authors: Lin C. Y. 
Published: December 2007

ABSTRACT
This paper presents new models for partially penetrating wells with any number of perforated intervals in either layered, isotropic, anisotropic, or 3D, heterogeneous reservoirs. These models are applicable to both vertical and horizontal wells and are capable of accurately simulating non-uniform flux distributions along perforated intervals. For a partially penetrating well, the models generate a constant well index for each perforated layer based on the quasi-steady state conditions established early in unsteady state flows.
In general, the predicted flux distributions along the well in a coarse-grid simulation using the new models agree almost identically (within 1% error) with fine-grid solutions. It is shown that well indices depend only on the permeability distribution in the vicinity of the well, reservoir thickness, wellbore radius, and locations of perforated intervals. Finally, for a heterogeneous reservoir, the calculated well indices and the rate distribution along the well can be greatly influenced by the subgrid permeability distribution near the wellbore.
limitations in the Use of Pseudofunctions for Up-scaling Reservoir Simulation Models
Authors: Taggaif I. J. , Soedarmo E. , Paterson L. 
Published: December 2007

ABSTRACT
Pseudofunctions methods have been used to up-scale relative permeability data from the sub-grid scale typical of core data up to grid block sizes used in conventional reservoir simulation. In spite of the widespread use of pseudofunctions, such approaches can be inappropriate due to the use of implicit assumptions regarding the constancy of saturation velocities (as used in the Welge construction).
This work presents an alternative methodology of generating two-phase pseudo relative permeability and capillary pressure functions, using numerical simulation, when non-constant characteristic saturation curves exert a strong impact on the displacement process. The proposed length-dependent pseudofunction technique generates pseudofunctions from 2-dimensional cross-sectional black-oil simulations and later used in a 1-Dimensional reservoir model. The coarse model's simulation predictions are compared to those of the conventional Kyte and Berry method. In addition to this, a case example is given to validate the application of length-dependent pseudos in a 3-dimensional simulation. In this example, sets of length-dependent pseudofunctions were generated and used in a 2-dimensional areal study. Simulation results showed that: a) Curved saturation characteristic velocities occurred in most up-scaled representations and b) The introduction of length-dependent pseudofunctions could result in improved predictions using coarse simulation models.
Dynamical Upscaling Techniques Applied to Compositional Flows
Authors: Thibeau Sylvain , Barker J. W. , Souillard Philippe 
Published: December 2007

Abstract
Lean gas injection in reservoirs is more and more frequently encountered. This production strategy induces strong compositional gradients in the field. Accurate compositional simulations with a coarse grid have been obtained through the use of an upscaling technique based on three main features: the computation of pseudo rel perms upscaling molar, instead of volumetric, fluxes;the reproduction of the fine grid flow through ‘Dual Scale Simulations’ (DSS) which are an alternative to classical Representative Elements of Volume (REV) simulations;the correction, within each phase, of the flux of each component, with the ‘alpha-factor’ pseudo-functions.
Well Productivity for Arbitrarily Inclined Well
Authors: Mochizuki S. 
Published: December 2007

ABSTRACT
This work extends Peaceman's equation to a well areally and vertically inclined at arbitrary angles with respect to grid lines in anisotropic reservoirs. The method is based on the transformation of the anisotropic flow equation to a homogeneous equation, and interpolating the effective well block radius, wellbore radius, and equivalent well length as a function of angles.
3-D Discrete Fracture Flow Simulations Using Monterey Formation Fracture Data
Authors: Schaefer R. A. , Gale J. E. , Herbert Alan 
Published: December 2007

ABSTRACT
A 3-D discrete fracture flow simulator was employed to evaluate the impact of the variability in fracture orientation, fracture interconnectivity, and fracture aperture on rock mass permeability. The fracture data were collected for two distinct fracture scales from outcrops of the Monterey Formation located along the central coast of California using areal and scanline mapping techniques. Differences in structural position were accounted for and statistical methods were used to correct for biases, in trace length, spacing and orientation data, that are associated with scanline mapping. The statistics of trace length, density, and orientation obtained from the field data along with assumed aperture distributions were used in 3-D simulations of rock mass cubes with side lengths of 8 to 18 meters for the small-scale fracture data and 100 to 150 meters for the large-scale fracture data. At the modeled scales the fracture geometry was well connected and imparted a strong anisotropy to flow in the horizontal sections and less so in the vertical sections when the same aperture was assigned to each fracture. Varying fracture aperture logarithmically within fractures of the same set had a strong impact on the magnitude of directional permeabilities but only a slight affect on the direction of the principal permeabilities. This study shows that fracture network simulators can be used to integrate fracture geometry and hydraulic data to provide flow and transport input parameters for large scale 3-D reservoir simulators.
Scaling-up in the Vicinity of Wells in Heterogeneous Field
Authors: Ding Yu 
Published: December 2007

Abstract
It is well known that the equivalent gridblock permeability obtained by the scaling-up procedure from fine gridblocks depends on the boundary conditions. In the literature, most boundary conditions considered represent a "linear" flow pattern, while in reservoir simulation, "radial" flow plays an important role and is related directly to well production forecasts.
In this paper, we will show the need for a specific treatment of the scaling-up procedure in the vicinity of wells due to the "radial" flow pattern with a high pressure gradient. On reservoir field scale, two types of flow should be considered: (1) the "linear" flow pattern, which usually represents a low pressure gradient region; and (2) the "radial" flow pattern, which usually represents a high pressure gradient region. The determination of the equivalent absolute permeabilities by "radial" flow patterns is discussed in this paper. The scaled-up parameters consist of transmissibility and numerical productivity index (PI).
A Massively Parallel Reservoir Simulator
Authors: Kaarstad Terje , Frøyen Johnny , Bjørstad Petter , Espedal Magne 
Published: December 2007

Abstract
A two-phase sequential IMPLICIT three dimensional reservoir simulator has been developed for massively parallel computer systems. The parallel algorithm is based on recently developed domain decomposition methods. The simulator has been tested using a 16384 processor MasPar MP-2.
The simulator building blocks are robust Krylov space iterations using Additive Schwarz as the preconditioner. This approach naturally supports a distributed data structure with overlapping subdomains. In the simulator each subdomain is treated as a small reservoir in its own right, and each subdomain communicates with the neighbouring subdomains through boundary conditions. Previous work has shown that the use of minimal overlap is sufficient and computationally nearly optimal for these problems.
To solve the pressure equation we use a two level Additive Schwarz preconditioner. The coarse grid problem is solved by a multigrid solver and each subdomain problem can be solved with a range of simple iterative or direct methods depending on time, space or robustness considerations. The saturation equation is solved by splitting the equation into one hyperbolic saturation equation and one elliptic saturation equation, The hyperbolic saturation equation is solved by the Modified Method of Characteristics. The solution of the (nonsymmet-ric) elliptic saturation equation is again obtained using an Additive Schwarz preconditioner.
An Asynchronous Parallel Linear Equation Solution Technique
Authors: Kohar Gil , Killough J. E. 
Published: December 2007

ABSTRACT
Key to the development of an efficient parallel reservoir simulator is the implementation of an efficient parallel linear equation solver. Although recent advances in distributed memory parallel computers have seen a significant improvement in communications overhead among the processors, increases in processor performance have kept the ratio of communications to node performance about the same. Previous published parallel linear equation solvers have emphasized the importance of reduced communications and increased granularity for the solver partitioning among the processors. This study investigates the implementation of asynchronous message-passing schemes to further reduce communications overhead for the parallel solver. The basic idea is for each processor to proceed with the linear solution without interruption from waiting to receive messages. If data is available in the buffer from other processors, however, it is utilized.
This study implements an asynchronous parallel preconditioner for ORTHOMIN(k). The preconditioner has two parts: Z-line relaxation and a block incomplete LU factorization (ILU(O)). Also included in the solution is the use of a reduced three-dimensional subproblem which is solved on one of the processors. Because of the asynchronous implementation of the solver, each of the nodes may perform a different number of iterations and converge to different tolerances; however, the overall tolerance for convergence is checked periodically to determine when the linear solution can be halted. This technique has been implemented on the IBM SP2, Intel IPSC/860 and Intel Paragon with problem sizes varying from 4096 to 184,320 grid blocks. For the largest problem significant performance improvements were observed.
For the range of problems investigated the linear solution technique showed excellent robustness and efficiencies. Number of iterations increased only slightly with increasing number of nodes. Moreover, speedups of up to 26 and 37 were observed for 32 and 64 nodes, respectively, for the largest problem investigated.
Application of Adaptive Mesh-Refinement With a New Higher-Order Method in Simulation of a North Sea Micellar/Polymer Flood
Authors: Khan S. A. , Trangenstein J. A. , Horning R. D. , Holing Kent , Schilling B. E. R. 
Published: December 2007

ABSTRACT
This paper demonstrates the application of a higher-order Godunov method and adaptive mesh-refinement to a three-phase, seven-component, micellar/polymer (MP) model and use in the simulation of an MP flood designed for North Sea conditions. Conventional one-point upstream weighting with globally fine mesh is too expensive for obtaining a reasonable level of accuracy for field-scale simulations. The use of higher-order Godunov method with adaptive mesh-refinement not only results in significant reduction in computational times but also reveals more numerical details of the displacement process due to higher-order accuracy. Comparisons are also made between the first- and second-order Godunov methods under field-scale design conditions with and without adaptive mesh-refinement.
Symmetric Flux Continuous Positive Definite Approximation of the Elliptic Full Tensor Pressure Equation in Local Conservation Form
Authors: Edwards Michael G. 
Published: December 2007

ABSTRACT
A classical finite volume scheme well known in computational aerodynamics [1] for solving the Transonic full potential equation is imported into reservoir simulation and applied to the full tensor pressure equation. Cell vertex discretisation is shown to be a natural framework for approximation. With permeability placed at the cell centres and potential at the vertices (cell corner points), of the grid the scheme is flux continuous and locally conservative. Analysis is presented which proves that the resulting discrete matrix is symmetric positive definite provided the full permeability tensor is symmetric elliptic. The discrete matrix is also diagonally dominant subject to a sufficient ellipticity condition. For a diagonal anisotropic tensor the discrete matrix is always symmetric positive definite and the scheme is upto 4th order accurate. A cell centred version of the scheme is indicated.
Different Pressure Grids for Reservoir Simulation in Heterogeneous Reservoirs
Authors: Guérillot D. R. , Verdiere Sophie 
Published: December 2007

Abstract
Petroleum reservoirs are made of highly heterogeneous rocks. These reservoirs could be described by geostatistical models composed of millions of cells. Currently, fluid flow simulations performed within these media need upscaling (or averaging) techniques. Hence, their results are given by averaging on cells which are much larger than the geological model cells.
To overcome this problem, the Dual Mesh Method is proposed here, whose purpose is to solve the pressure equation on a low resolution grid, and then to interpolate pressure over the fine mesh by taking into account small scale heterogeneities of the medium. The aim of this paper is this interpolation step; its implementation is presented and illustrated in a five-spot pattern for three different rock characteristics.
Gas Well De-Watering System and Hydraulic Gas Pump, New Designs and a Discussion on Their Economics
Authors: Amani Mahmood 
Published: December 2007

Abstract
The concepts for two new artificial lift systems were first presented in SPE paper 25422. In the present paper improved designs are presented. The application and the economics of the Hydraulic Gas Pump are compared to the gas lift method that was used in East Quito Fusselman Reservoir, Ward County, Texas. The author concludes that the Hydraulic Gas Pump can be a more economic artificial lift method than gas lift for East Quito Fusselman Reservoir.
Experimental and Analytical Study of Sinusoidal Buckling in Vertical Wells
Authors: Salies J. B. , Cunha J. C. S. , Azar J. J. , Soren J. R. 
Published: December 2007

ABSTRACT
This paper presents results from experimental data for sinusoidal buckling of tubulars in vertical wells and discusses some analytical solutions presented in the literature. An experimental apparatus 55 feet long was used in the tests. Several tests have been conducted and the results are presented and analyzed. The following aspects of sinusoidal buckling were observed during the tests: critical sinusoidal buckling force, contact point between pipe and wellbore, further buckling modes, effect of friction in the post buckling behavior.
History Matching Production Data Using Analytical Solutions for Linearly Varying Bottomhole Pressure
Authors: Spivey J. P. , Frantz J. H. 
Published: December 2007

ABSTRACT
Performance of gas wells is often modeled using analytical solutions which are based on the assumption of constant pressure production at the wellbore. A variable pressure history can be modeled by using superposition of these constant pressure solutions. Unfortunately, each pressure change results in a spike in the resulting production rate. In practice, wells are often operated such that pressure declines slowly and smoothly until line pressure is reached. Thus, superposition of constant pressure solutions does not accurately model production in real wells. In this paper we present a procedure for calculating production rate and cumulative production using superposition of solutions for bottomhole pressure which varies linearly with time. These solutions for linearly varying bottomhole pressure may be easily obtained from the constant pressure solution for the same reservoir geometry. Rates calculated using superposition of linear pressure solutions model actual production data more faithfully than do those calculated using superposition of constant pressure solutions.
Characterization of Michigan Antrim Shale Reservoirs Based on Analysis of Field-Level Data
Authors: Zuber M. D. , Voneiff G. W. , Frantz J. H. , Gatens J. M. 
Published: December 2007

ABSTRACT
This paper focuses on the production characteristics of the Antrim Shale in the Michigan Basin. We have used a large database of Antrim project-level data, including production data; information regarding completion, stimulation and operational practices; and the results of production forecasts for 42 producing projects to provide insights into the impact of various completion and operational practices on Antrim well productivity. We used a production indicator to map well performance and identify wells of above or below average well quality. We have found that advances in completion and operational practices have increased well productivity.
Modeling Multilayer Gas Reservoirs Including Sorption Effects
Authors: Gao Chao , Lee W. John , Spivey John P. , Semmelbeck Mark E. 
Published: December 2007

ABSTRACT
Many coalbed methane reservoirs and Devonian shale reservoirs are naturally fractured with part of the gas adsorbed in the low permeability matrix. The adsorption mechanism is controlled by reservoir pressure; during the depletion of the reservoirs, the adsorbed gas in the matrix is released as free gas flowing from the matrix to the fractures and then to the w'ellbore. In addition, these reservoirs are frequent layered. This paper presents an approximate analytical model for modeling commingled (multilayer) gas reservoir with sorption effects. Our work shows that this model can be developed based on an analytical model developed for slightly compressible liquid commingled systems. To take into account the nonlinearity of the total gas reservoir system, each layer has to be treated as a nonlinear system individually and combine all the individual single-layer solutions with the boundary condition at the wellbore. For this reason, we applied pseudopressure and pseudotime concepts in each layer. The pseudotime definitions take into account the nonlinearity coursed by both the pressure-dependent gas properties and the sorption effects in each layer, both of which we assume to be controlled by average pressure within the layer. We used a numerical simulator to verify our model. The results show that our model agrees well with the numerical simulator.
Evaluation of Height Growth Controlled Fractures With Placement of Artificial Barriers
Authors: Greener M. R. , Snead L. L. , Arbaugh R. M. , Sears S. M. 
Published: December 2007

Abstract
The use of artificial barriers placed at the top and bottom of the producing zones before fracture stimulating a formation can control excessive fracture height growth. The reason for such barrier placement is to contain the fracture treatment within the producing zone when the stress barriers above or below the zone cannot contain height growth. Two case studies are included in this paper on wells fractured in the Richfield formation in the Northern Michigan Basin and in the Codell and Sussex formations in the Denver-Julesburg Basin.
Analysis of Production Response to CO2/Sand Fracturing: A Case Study
Authors: Yost A. B. , Mazza R. L. , Remington R. E. 
Published: December 2007

ABSTRACT
The U.S. Department of Energy, Petroleum Consulting Services, Universal Well Services, and Canadian Fracmaster have recently performed eight CO2/sand stimulations on four Devonian Shale gas wells in the Appalachian Basin. Four two-stage CO2/sand stimulations were executed with two operators in the Pike and Martin County, Kentucky area. All stimulätions involved 120 tons of carbon dioxide (CO2) and up to 47,500 pounds of sand. In addition, there are eleven existing control wells stimulated with four two-stage foam fracs and seven two-stage nitrogen fracs. Production results from these fifteen wells are compared. After nine months of production, CO2/sand fractured wells in the Pike County, Kentucky study area are nearly twice as productive as nitrogen gas fraced wells and nearly five times better than the foam fraced wells in the study group. The per well incremental gas production after nine months ranged from 13.5-22.2 MMcf per well for nitrogen gas and foam fraced wells, respectively. Discussion of the CO2/sand treatment parameters, job execution, and a representative pressure/injection response are discussed in detail. As the operators begin to utilize the CO2/ sand frac process on more wells, the new stimulation process will become commercially available on a routine basis.