bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-Dependent Matrix-Fracture Shape Factors for Partially and Completely Immersed Fractures
Authors: Rangel-German Edgar R. , Kovscek Anthony R. 
Published: December 2007

Abstract
Modeling multiphase flow in fractured porous media relies on the accurate description of matrix to fracture transfer of water. The rate of mass transfer between the rock matrix and fractures is significant, and calculation of this rate, within dual-continuum models, depends on matrix-fracture transfer functions incorporating the shape factor. Typically, matrix-to-fracture transfer functions are obtained by assuming all fractures to be instantaneously immersed in water (instantly-filled), with a uniform fracture pressure distribution under pseudo-steady state conditions. The result is constant, timeindependent, shape factors. Clearly, this is not necessarily true. Partially immersed fractures and other unsteady-state conditions do not lead to constant shape factors. The current formulations for modeling flow in fractured porous media need to be reconsidered.
A new time-dependent matrix-fracture transfer shape factor formulation and transfer functions for both filling- and instantly-filled fracture transfer are derived based on dimensional analysis of experimental data. The general shape factor is expressed as the area of the matrix block contacted by the wetting phase divided by the product of the bulk volume of the rock matrix times the distance between the saturation at the fracture and the matrix average saturation. These parameters are readily obtained. The dimensional analysis of full-physics data avoids simplifications that may lead to expressions that do not represent accurately matrix-fracture transfer. The new shape factor carries information of the transient behavior of the water saturation, Sw, and so it leads to more accurate description of the matrix-fracture transfer. Good agreement was found between experimental data, an analytical model, and a proposed modified dual-porosity formulation with the new time-dependent shape factor and transfer function.
Integration of Seismic Anisotropy and Reservoir Performance Data for Characterization of Naturally Fractured Reservoirs Using Discrete Feature Network Models
Authors: Will Robert , Archer Rosalind , Dershowitz Bill 
Published: December 2007

Abstract
This paper proposes a method for quantitative integration of seismic (elastic) anisotropy attributes with reservoir performance data as an aid in characterization of systems of natural fractures in hydrocarbon reservoirs. This method is demonstrated through application to history matching of reservoir performance using synthetic test cases.
Discrete Feature Network (DFN) modeling (Dershowitz et al.1) is a powerful tool for developing field-wide stochastic realizations of fracture networks in petroleum reservoirs. Such models are typically well conditioned in the vicinity of the wellbore through incorporation of core data, borehole imagery, and pressure transient data. Model uncertainty generally increases with distance from the borehole. Threedimensional seismic data provides uncalibrated information throughout the inter-well space. Some elementary seismic attributes such as horizon curvature and impedance anomalies have been used to guide estimates of fracture trend and intensity (P32) (Dershowitz and Herda2) in DFN modeling through geostatistical calibration with borehole and other data. However, these attributes often provide only weak statistical correlation with fracture system characteristics.
The presence of a system of natural fractures in a reservoir induces elastic anisotropy that can be observed in seismic data. Elastic attributes such as azimuthally dependent normal moveout velocity (ANMO), reflection amplitude versus azimuth (AVAZ), and shear wave bi-refringence can be inverted from 3D seismic data. Anisotropic elastic theory provides physical relationships among these attributes and fracture system properties such as trend and intensity. Effective elastic media models allow forward modeling of elastic properties for fractured media.
A technique has been developed in which both reservoir performance data and seismic anisotropic attributes are used in an objective function for gradient-based optimization of selected fracture system parameters. The proposed integration method involves parallel workflows for effective elastic and effective permeability media modeling from an initial DFN estimate of the fracture system. The objective function is minimized through systematic updates of selected fracture population parameters. Synthetic data cases show that 3D seismic attributes contribute significantly to reduction of ambiguity in estimates of fracture system characteristics in the inter-well rock mass. The method will benefit enhanced oil recovery (EOR) program planning and management, optimization of horizontal well trajectory and completion design, and borehole stability studies.
Case Study: Merging Modern Reservoir Characterization with Traditional Reservoir Engineering
Authors: Rothkopf Brian , Fredrickson Steve , Hermann Jeff 
Published: December 2007

Abstract
Modern reservoir characterization-simulation studies integrate geology, seismic, petrophysics and engineering to build three-dimensional (3D) static geologic and dynamic fluid flow models. These models have repeatedly proven their worth through reduced risk and improved reservoir management decisions. Prior to the advent of modern computers and software, traditional reservoir engineering techniques served the industry well through analytic and graphical analysis techniques. It would seem that the modern characterization tools would make these traditional reservoir engineering techniques obsolete; however, this paper shows that integrating these traditional techniques can improve the quality of modern 3D models.
This paper describes a field example where traditional reservoir engineering techniques from 40 years of waterflooding history were integrated into the modern reservoir characterization-simulation workflow.
Underbalanced Perforating of Long Reach Horizontal Wells Using Coiled Tubing: Three North Sea Case Histories
Authors: Bayfield Ian , Murphy Stuart , Taylor Don 
Published: December 2007

Abstract
It is acknowledged that in many reservoirs, perforating in under-balanced conditions can bring significant and obvious production benefits. Under-balanced perforating in vertical or "near" vertical wells may be performed with wire-line, whilst perforating in highly deviated or horizontal wells through the completion tubing normally requires intervention with either a wire-line tractor, hydraulic work-over unit unit, or Coiled Tubing. Consideration of all parameters surrounding the choice of what method should be used to transport the guns into long reach horizontal wells will quite often direct the operator to choose Coiled Tubing as the optimum conveyance tool.
Achieving true under-balanced perforation of a long reservoir section(s) utilising coiled tubing in an offshore environment presents a collection of technical, logistical and financial challenges.
Three North Sea case histories of such operations are illustrated. These examples demonstrate how gun lengths of over 2,800 ft and 24,500 lb in weight can be deployed to a measured depth of 17,800 ft through a challenging well profile. Particular attention is paid to equipment challenges and selection, the use of friction reducers and techniques employed to maximise the operating window, hence achieving the operator's desired results and realise the benefits associated with under-balanced perforating.
Simulating Carbon Dioxide Sequestration/ECBM Production in Coal Seams: Effects of Permeability Anisotropies and Other Coal Properties
Authors: Smith Duane H. , Sams W. Neal , Bromhal Grant , Jikich Sinisha , Ertekin Turgay 
Published: December 2007

Abstract
Coalbed methane now accounts for a significant fraction of domestic natural gas production. Injection of carbon dioxide into coal seams is a promising technology for reducing anthropogenic greenhouse gas emissions and increasing ultimate production of coalbed methane. Reservoir simulations are an inexpensive method for designing field projects and predicting optimal tradeoffs between maximum sequestration and maximum methane production. Optimum project design and operation are expected to depend on the anisotropy of the permeability along the face-cleat and butt-cleat directions, the spacing between cleats, and the sorption isotherms for methane and carbon dioxide.
In this work PSU-COALCOMP, a dual-porosity coalbed methane simulator, is used to model primary and secondary production of methane from coal, for a variety of coal properties and operational parameters. It is assumed that the face and butt cleats are perpendicular to each other, with horizontal wells parallel to one type of cleat and perpendicular to the other. The well pattern consists of four horizontal production wells that form a rectangle, with four shorter horizontal wells centered within the rectangle. In the limiting case of no permeability anisotropy, the central wells form a "plus" sign within the square of production wells. All wells are operated as producers of methane and water until a specified reservoir pressure is reached, after which the central wells are operated as injectors for CO2. Production of methane continues until the CO2 concentration in the produced gas is too high.
The simulation results predict the optimum lengths of the injection wells along the face- and butt-cleat directions, and how these optimum lengths depend on the permeabilities in the two directions. If the cleat spacing is sufficiently small and diffusion of the gas through the pores to the cleats is sufficiently rapid, instantaneous sorption may be assumed. Otherwise, the field performance depends on the characteristic time for transport to the cleats. The pressures at which the injection wells are operated also affect the amounts of CO2 sequestered, through the pressure and volume constants of the sorption isotherms.
Coalbed Methane Reservoir Simulation: An Evolving Science
Authors: Hower T. L. 
Published: December 2007

Abstract
It wasn't always this complicated! In 1990, Seidle and Arri1 demonstrated how to easily adapt a conventional black oil simulation model for use in coalbed methane simulation. These days, when setting up a coalbed methane simulation model, one needs to worry about a single or multi-component gas description; depletion or enhanced coal bed methane recovery; single, dual or triple porosity; vertical, horizontal, or multi-lateral wells; coals only or a mix of coals and sands; and coalbed methane or coal mine methane? Correctly determining what to model is almost as daunting a task as the simulation work itself. All of these variations add complexity to the task and, in some cases, require specialized simulation models to adequately characterize the problem.
This paper discusses how the exploitation and development of coalbed resources throughout the world is changing, and with it how our approach to reservoir simulation of the process is changing as well. The paper will provide a valuable resource to engineers and geoscientists faced with developing predictive tools to assist them in evaluating the optimum strategy to exploit these valuable resources.
Africa Is Poised to Become the Next Energy Superpower
Authors: Oyewole Peter O. , Economides Micheal J. 
Published: December 2007

Abstract
In early 2002 Washington DC policy-makers suggested, that within a generation, Africa might supplant the Middle East as the United States most critically strategic energy supplier. This is a significant departure from the situation, which permeated the previous three decades when the Middle East was perceived as the singularly most important source of world energy. Such potential of Africa, if realized, would have a decided influence on future energy economics and geopolitics.
Grandiose statements notwithstanding, is Africa (and in this context this implies the Sub-Saharan regions) at the brink of becoming an energy superpower? Does Africa have the potential reserves, production capability and capacity for such a role? This is not just an issue of geology but also one that touches on the rest of the development of the continent, its economic and political future.
This paper presents an in-depth investigation of the true energy potential of Africa. One obvious focus is the potential of deep- and ultra-deep-water production, spanning almost the entire Western Coast of Africa. Areas of interest involve the deep waters off the Gulf of Guinea and the continental shelves and include the inland basins of Benin, Nigeria, Cameroon, Sao Tome and Principe, Equatorial Guinea, Gabon, Congo and Angola.
We are proposing here a number of mechanisms of potential production and couplets of exploitation, i.e., optimum and likely ways to link producers with consumers, taking into account distances and hydrocarbon volumes and incorporating regional integration and co-operation.
Finally, we are offering conclusions and recommendations that will enhance sustainable energy development in Africa, and continuous availability of uninterrupted global supply of oil and gas, which indeed will usher the era of Africa as an energy superpower.
Building a Dynamic Interactive Information Website with Limited Artificial Intelligence: A Case History
Authors: Shaw Andrew , McCracken Daryl 
Published: December 2007

Abstract
The systematic design process used and design logic behind building an interactive information management site is described. The site was planned for use by internal employees, as an information resource, and as an external technical and information resource for approved users. A third consideration was an efficient web-enabled business to business quotation mechanism for wireline services.
The initial design objectives centered on the need for a web based information management tool with an easy to use navigation and a strong visual component that facilitated information based productivity utilizing a web enabled database.
A number of design considerations will be discussed:
type and range of data components, and challenges of handling multimedia assets in the database (html, images, text, PDF) information content customizable to individual user capability
The complexity of the data types, the desire to provide easy navigation, and a way to match services and equipment to match reservoir problems and needs involved building limited artificial intelligence into the user interface. The logic and criteria considered during this phase of development is presented.
Several business considerations influenced the design and each will be presented.
A database interface that did not require high technical competence in a database language to input and manage data. reducing dependence on printed material providing customized reports and technical catalogues site and database maintenance criteria measurement of the success of the site in terms of return on investment and strategic value
The information site was field tested and launched during 2002. Conclusions relating to the design of the site and the methodology used will be presented in the context of current user and growth history statistics.
A Model for Borehole Oscillations
Authors: Pastusek Paul , Brackin Van 
Published: December 2007

Abstract
The presence of borehole rippling, spiraling, and hour-glassing have been known for many years in the drilling industry. Descriptions of these problems have become more precise with improved logging tools, yet the underlying mechanisms have not been mathematically formulated. Many directional models have been presented in the past that attempt to explain the steady state response of the bottom hole assembly, but little has been published on the non-equilibrium or dynamic response of the system.
A theoretical/analytical dynamic model is proposed to explain the conditions required for borehole oscillations to occur. This model is presented along with correlating data from laboratory and full scale field tests for a steerable motor with an 8-1/2" hole size. For different parameters the model correctly predicts the presence and absence of oscillations, the oscillation wavelength, and the effect of bit geometry on borehole oscillations. It also makes testable predictions for the effects of bit speed, penetration rate, and rock strength. From these test cases, general guidelines are presented for selecting the appropriate bit, BHA, and operating parameters for an application.
Utilization of a Tactical Grade FOG-Based Inertial Measurement Unit in Real-Time Downhole Surveying
Authors: Ledroz Adrián G. , Mintchev Martin P. 
Published: December 2007

Abstract
Fiber optic gyroscopes (FOG) in an inertial navigation setup have been proposed as an alternative to magnetometer-based downhole surveying. The aim of this work is to study the applicability of a tactical-grade FOG-based inertial measurement unit (IMU) as complete surveying sensor for measurement-while-drilling processes downhole. Complete navigation solution for downhole applications was tested in laboratory conditions, indicating the usefulness of FOG-based IMUs as possible surveying sensors for directional drilling.
Object-Based Global Optimization in Modeling Discrete-Fracture Network Map: A Case Study
Authors: Tran Nam H. , Chen Zhixi , Rahman Sheik S. 
Published: December 2007

Abstract
Modeling of fracture network is an essential step for developing naturally fractured reservoirs study. It helps to develop a best scenario for hydraulic fracture treatment, to design an optimum production method and to evaluate reservoir potential. This paper presents an integrated methodology for modeling fracture network by utilizing object modeling and global optimization. It also describes a field study to evaluate the methodology's effectiveness. Firstly, as an object-based model, each fracture is presented and treated as a discrete object, characterized by its centre location, orientation and size. Object-based modeling allows the output of spatial distribution and details of discrete fracture network. From observed data sources such as seismics, outcrops, well logs and images, etc., we characterize fracture and field attributes, including fracture density, fracture parameters' statistics. Then, we perform a statistical analysis on fracture properties to identify density functions and distribution patterns. The essential feature of this approach is the formulation of the objective function. Various variogram measurements, modified multi histograms and other statistical properties are selected, so that the objective function is able to adequately describe the representative field data. In the next step, we use global optimization (simulated annealing algorithm) to produce result fracture network, by optimizing the objective function. This network matches the field characterized fracture attributes and characteristics. A global optimization method such as simulated annealing is able to honor more data than conventional geo-statistical simulation techniques. Case study shows that the modeling methodology mapped discrete fracture network very closely to the observed fracture distribution and properties.
Seismically Driven Integrated Fracture Modeling
Authors: Shen F. , Ouenes A. 
Published: December 2007

Abstract
Given the importance of fractured reservoirs in the world, and the ever-increasing availability of 3D seismic data, this paper reviews existing fracture modeling approaches that use 3D seismic data. Two major approaches appear to provide efficient ways to use directly and effectively 3D seismic data. The first approach uses mostly post-stack data in an integrated computational framework where 3D seismic attributes are used along with other geologic and geomechanical information to provide reliable 3D fracture models. The second approach relies on the use of pre-stack seismic data along with other geologic and production information to provide an accurate description of the fracture density and orientation. Although these technologies are well proven and have been tested in many basins, they remain underutilized by most oil and gas companies, with the exception of a few companies that have been using them extensively to drill very successful wells.
Application of Advanced History Matching Techniques to an Integrated Field Case Study
Authors: Feraille M. , Roggero F. , Manceau E. , Hu L. Y. , Zabalza-Mezghani I. , Reis L. Costa 
Published: December 2007

Abstract
This paper presents an innovative integrated methodology for constraining 3-D stochastic reservoir models to well data and production history as well as a successful application to a real field case. The proposed approach allows to history match complex reservoir models in a consistent way by updating the entire simulation workflow. Advanced parameterization techniques are used to modify either the geostatistical model directly or the fluid flow simulation parameters in the same inversion loop. In a first step, the relevant inversion parameters are selected according to a sensitivity study based on the experimental design technique. In a second step, history matching is performed with the most significant parameters using an automated inversion procedure. In this step, the Gradual Deformation Method (GDM) is used to constrain the geostatistical model while respecting the global model properties. This technique may be combined with gradient based inversion methods in order to history match other deterministic parameters simultaneously.
A successful application to a real field case located offshore Brazil, named PBR, is presented. The lithofacies reservoir model was built using geostatistical simulations with the non-stationary truncated Gaussian method. The fluid flow model includes about 40 wells and 15 years of production history. The entire simulation workflow was integrated in one history matching loop in order to update the geostatistical lithofacies model and the fluid flow model simultaneously. The mismatch between simulated and real production data was quantified by the calculation of an Objective Function (OF). A sensitivity study based on the experimental design technique was performed to determine the most influential parameters within the workflow and to capture the possible reasons of the mismatch. Based on these observations, an automatic history matching was performed with the key parameters. A set of deterministic parameters, including the facies permeabilities, vertical anisotropy ratios, correlation lengths, relative permeability end points and Corey exponents was used first to improve the global match. Then, the GDM was applied to modify the geostatistical model itself. The GDM proved efficient in history matching to modify the spatial facies distribution of the geostatistical model. Moreover, the repetition of this history matching procedure with several model realizations confirmed the reduction of uncertainty on production forecasts.
Results on this real oil field case showed that this innovative approach, which combines both the experimental design technique and the GDM, enables detailed analysis of the mismatch and significantly increases the predictive quality of reservoir models, using a limited number of simulations.