bluuebunny/crossref_metadata_2025_split huggingface dataset:
Practical Use of Scale Up and Parallel Reservoir Simulation Technologies in Field Studies
Authors: Tchelepi H. A. , Durlofsky L. J. , Chen W. H. , Bernath A. , Chien M. C. H. 
Published: December 2007

AbstractScale up and parallel reservoir simulation represent two distinct approaches for the simulation of highly detailed geological or geostatistical reservoir models. In this paper, we discuss the complementary use of these two approaches for practical, large scale reservoir simulation problems. We first review our recently developed approaches for upscaling and parallel reservoir simulation. Then, several practical large scale modeling problems, which include simulations of multiple realizations of a waterflood pattern element, a four well sector model, and a large, 130 well segment model, are addressed. It is shown that, for the pattern waterflood model, significantly coarsened models provide reliable results for many aspects of the reservoir flow. However, the simulation of at least some of the fine scale geostatistical realizations, accomplished using our parallel reservoir simulation technology, is useful in determining the appropriate level of scale up. For models with a large number of wells, the upscaled models can lose accuracy as the grid is coarsened. In these cases, although field-wide performance can still be predicted with reasonable accuracy, parallel reservoir simulation is required to maintain sufficiently refined models capable of accurate flow results on a well by well basis. Finally, some issues concerning the use of highly detailed models in practical simulation studies are discussed.
The New Law for California's Offshore Oil Development
Authors: Moroney Thomas C. 
Published: December 2007

Introduction
It is the purpose of this article to demonstrate the significance of the new law for California's offshore oil development; to explain its provisions; to praise and criticize it; to emphasize the responsibility of the petroleum industry in operating under it; and to offer some speculative comments.

Necessity for New State Law

Previous Inadequacy of Law
The people of California for six years waged a battle which was successfully culminated by the enactment of federal legislation in 1953 whereby Congress confirmed California's claim to ownership of the 3-mile submerged land belt lying offshore the coast of the state. During those six years, the people of the state had made two things clearthat they were attacking the philosophy of the Supreme Court, andthat the unwarranted expropriation by judicial decision of the state's oil resources and other property rights in the submerged land area was a matter for great alarm.
For nearly 2 1/2 years after the restoration of those rights, the State of California was still unable to permit the proper exploration and development of the oil and gas resources underlying that belt because of the inadequacy of the state's then existing law. What a strange predicament after such a long period during which public officials and private persons represented to the Congress and to the people of the nation that, among other things, we needed our tide and submerged lands in order to explore and develop them for oil and natural gas, not only to provide for civilian uses in peacetime, but for the protection of our country in time of war.

To Keep Faith With Congress
It was essential that California laws be amended to provide for the exploration and development of our petroleum resources in the ocean areas, if for no other reasons than to keep faith with our representations to the Congress and the nation, and to enable us to exercise the proprietary rights which we had so effectively and vigorously asserted.
California law, as it existed prior to Sept. 7, 1955, did not authorize the issuance by the State Lands Commission of oil and gas leases embracing the state-owned tide and submerged lands except in the limited instances where such lands were being drained or threatened with drainage by means of wells upon adjacent lands. Because there are only a few isolated instances in which such drainage or the threat thereof exists, most submerged land belt lying offshore the coast of California could not be opened to exploratory drilling until this provision of the law was repealed.
Fracture Width Logging While Drilling and Drilling Mud/Loss-Circulation-Material Selection Guidelines in Naturally Fractured Reservoirs
Authors: Liétard Olivier , Unwin Tessa , Guillo D. J. , Hodder M. H. 
Published: December 2007

Summary
In this article we discuss drilling mud losses in naturally fractured reservoirs with fracture permeability larger than 50 odd md and much larger than the matrix permeability.
Type curves are provided that describe mud loss volume vs. time and allow the determination of the hydraulic width of natural fractures through the usual type curve matching technique of log/log plots.
Real time logging while drilling of natural fracture width permits the proper selection of loss-circulation material (LCM) with respect to particle size distribution. Efficient (rapid) mud loss control is made possible, increasing the chances of minimizing fracture damage by the drilling mud, the cuttings and the LCMs themselves.
The total mud losses experienced when drilling a long horizontal section are shown to agree with reservoir properties (derived by well testing) in particularly well-documented examples of the central North Sea.
The equations provided can therefore be utilized as well by reservoir engineers to properly evaluate the contribution of natural fractures to the permeability and skin of any well, whether these fractures are clear or are invaded by drilling mud.
Formation-Damaging Characteristics of Mixed Metal Hydroxide Drill-In Fluids and a Comparison With Polymer-Base Fluids
Authors: Fraser L. J. , Reid P. I. , Williamson L. D. , Enriquez F. P. 
Published: December 2007

Summary
Horizontal wells are commonly completed without casing and the fluids used to drill said sections can have a significant effect on the production outcome. Mixed metal hydroxide (MMH)/bentonite-based fluids are compared to two commonly used reservoir drill-in fluids (DIFs) with respect to filter-cake characteristics and regain in permeability. The MMH fluids are found to produce filter cakes with unique features which result in efficient backflow without need for chemical treatment. Return permeability results which equal or exceed those for more commonly used DIFs raise questions over the conventional view that bentonite-containing DIFs are harmful to reservoirs.
Wettability Change Related to Adsorption of Organic Acids on Calcite: Experimental and Ab Initio Computational Studies
Authors: Legens Christelle , Toulhoat Hervé , Cuiec Louis , Villieras Frédéric , Palermo Thierry 
Published: December 2007

Summary
We have investigated the interactions between organic acids and a calcite powder by adsorption from an organic phase (benzoic acid and lauric acid in toluene) and from an aqueous phase (benzoic acid and lauric sodium salt).
In addition to the experimental study, ab initio quantum chemistry calculations were performed for cluster models, simulating the interactions of molecules with calcite surface sites.
At the toluene/calcite interface, acids chemisorb on surface calcium ions, replacing surface hydroxyls resulting from the previous surface hydration by water. This surface saponification phenomenon was predicted by ab initio calculations and confirmed by spectroscopic techniques. The adsorbed acids conferred a hydro-phobic character to calcite, with the higher contact angles in water for the longest alkyl chains in the organic acid.
At the water/calcite interface, organic acids do not displace water.
Our results support the possible existence of mixed wettability patterns, related to spatial distribution of pore sizes, in the specific case of organic acids with calcite.
A Buckling Criterion for Constant-Curvature Wellbores
Authors: Mitchell Robert F. 
Published: December 2007

Summary
This paper examines the effect of wellbore curvature on the buckling stability of casing. A large-displacement/small-strain analysis was used to obtain a general stability result, including all curvature effects. Two types of analysis are provided for comparison and contrast. The first analysis is an equilibrium analysis, which provides not only the stability criterion desired, but additional information, such as the contact force between the casing and the wellbore. The second analysis is an energy balance. This analysis was developed to provide a comparison with other stability results, some of which differ from the calculations presented here. Previous papers investigating this problem have produced conflicting results. This paper resolves the conflict.
Identification of Geological Shapes in Reservoir Engineering By History Matching Production Data
Authors: Rahon Daniel , Edoa Paul Francis , Masmoudi Mohamed 
Published: December 2007

Summary
This paper discusses a method which helps identify the geometry of geological features in an oil reservoir by history matching of production data. Following an initial study on single-phase flow and applied to well tests (Rahon, D., Edoa, P. F., and Masmoudi, M.: "Inversion of Geological Shapes in Reservoir Engineering Using Well Tests and History Matching of Production Data," paper SPE 38656 presented at the 1997 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 October.), the research presented here was conducted in a multiphase flow context.
This method provides information on the limits of a reservoir being explored, the position and size of faults, and the thickness and dimensions of channels.
The approach consists in matching numerical flow simulation results with production measurements. This is achieved by modifying the geometry of the geological model. The identification of geometric parameters is based on the solution of an inverse problem and boils down to minimizing an objective function integrating the production data.
The minimization algorithm is rendered very efficient by calculating the gradients of the objective function with respect to perturbations of these geometric parameters. This leads to a better characterization of the shape, the dimension, and the position of sedimentary bodies.
Several examples are presented in this paper, in particular, an application of the method in a two-phase water/oil case.
Influence of Thermal History on the Waxy Structure of Statically Cooled Waxy Crude Oil
Authors: Chang Cheng , Boger D. V. , Nguyen Q. D. 
Published: December 2007

Summary
The effect of the thermal history on the waxy structure of two statically cooled waxy crude oils is examined using a controlled stress rheometer for rheological measurements and a microscope to observe microstructure of wax crystals. A three-yield-stress model is used to describe the yielding of the samples at low temperatures. The elastic-limit, static, and dynamic yield stresses as a result of different static cooling processes were determined from controlled stress and oscillatory rheological measurements. The types of histories examined include the temperature, cooling rate (0.5 to 4°C/min), and isothermal holding time before testing (up to 15 hours). In addition, the reversibility over time of the waxy structure after yielding was investigated. The results from both yield stress measurements and microscopic observations show that the waxy structure strongly depends on both the temperature and the cooling rate. The isothermal holding time both before and after yielding was found to have no observable influence on the structure over the time period studied in these experiments.
Estimating the Pressure-Transient Response for a Horizontal or a Hydraulically Fractured Well at an Arbitrary Orientation in an Anisotropic Reservoir
Authors: Spivey J. P. , John Lee W. 
Published: December 2007

Summary
This article presents a method for finding the equivalent isotropic system for a horizontal well or a hydraulically fractured well at an arbitrary azimuth in an anisotropic reservoir. The equivalent isotropic system can then be used to calculate the pressure response of the original system.
The horizontal well solution is compared with previous solutions reported in the literature. The general hydraulically fractured well case has not, to our knowledge, been presented before.
This study confirms the observation by Yildiz and Ozkan1 that small deviations (up to 20°) from the optimal azimuth for a horizontal well do not have a major effect on the pressure response. Because this solution is obtained by finding an equivalent isotropic system, this study also confirms the observation by Earlougher2 that an anisotropic system cannot be identified from a single-well test.
Determination of the Orientation of a Vertical Fracture by Interference Tests
Authors: Uraiet A. , Raghavan R. , Thomas G.W. 
Published: December 2007

An analytic solution for the pressure distribution around a fractured well in a homogeneous, infinite reservoir is presented in terms of tabulated functions. This solution can be used to determine fracture orientation from interference tests.

Introduction
The advent of costly tertiary recovery programs has resulted in the need to determine flow patterns created by fractures intersecting wellbores. This requires a knowledge of the compass orientation and length of fractures. Several papers have discussed determination of fracture length by pressure analysis. However, methods for determining the compass orientation using pressure data have not received much attention. This paper pressure data have not received much attention. This paper discusses a method for determining the compass orientation using pressure data obtained at shut-in observation wells due to pressure data obtained at shut-in observation wells due to production or injection at the fractured well. production or injection at the fractured well. In 1960 Elkins and Skov reported a method for determining the orientation of natural fractures. They assumed the system of natural fractures to behave like an anisotropic system and used the classical line-source solution to analyze, pressure behavior. More recently, Pierce et al. demonstrated the use of pulse testing for calculating fracture length and orientation. Other studies on the determination of fracture orientation include (1) use of acoustic signals; (2) measurement of pressure response at observation wells during fracture initiation and propagation; and (3) use of inflation impression packers and television cameras.Even though the problem has been recognized for quite some time, no general method exists for determining pressure distribution in the area drained by a vertically fractured well. The objective of this paper is to present an analytic expression, in terms of simple tabulated functions, for the pressure distribution in a uniform, homogeneous, infinite reservoir drained by a vertically fractured well. This solution may be used to analyze pressure data in adjacent observation wells to determine fracture orientation in a manner analogous to standard interference tests. It also may be used to analyze test data obtained by pulsing a vertically fractured well. pulsing a vertically fractured well. Theory
The mathematical model considered in this study is identical to the uniform-flux fracture examined by Gringarten et al. We assume that a single vertical fracture intersects a wellbore located in an infinite, homogeneous, porous medium (Fig. 1). The surface production rate is assumed to be constant and all the production is obtained by means of the fracture. Fluid enters production is obtained by means of the fracture. Fluid enters the fracture at the same rate per unit area of the fracture (uniform-flux fracture).
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Fully Coupled Geomechanics and Fluid-Flow Analysis of Wells With Stress-Dependent Permeability
Authors: Chin L. Y. , Raghavan Rajagopal , Thomas L. K. 
Published: December 2007

Summary
A fully coupled geomechanics and fluid-flow model is developed to analyze pressure-transient problems in stress-sensitive reservoirs with nonlinear elastic and plastic constitutive behavior. For hydrocarbon reservoirs with stress-dependent permeability (stress-sensitive reservoirs), the coupled interaction between geomechanics and fluid production may significantly influence both the stress state and the fluid flow in the reservoir. Therefore, in general the coupling effect cannot be ignored when analyzing stress-sensitive reservoir problems. Detailed model formulations and the numerical implementation are presented. Practical applications illustrating various aspects of well behavior of stress-sensitive reservoirs are also demonstrated in this article.
Neural-Net Identification of Flow Regime With Band Spectra of Flow-Generated Sound
Authors: van der Spek Alex , Thomas Alix 
Published: December 2007

SummaryMultiphase production log interpretation requires that the flow regime along hole in the wellbore is known. Flow regime is the cased-hole analog of lithology. Knowledge of the flow regime will help to interpret tool signals, will help to evaluate the flow rate on a per phase basis, and will reduce post-processing load. The flow regime can be classified correctly by a neural net in up to 87% of all cases using 1/3 octave band spectra of flow-generated sound plus the pipe inclination angle. Without the inclination an 88% correct classification can be achieved. A neural net trained on commercially available tool data (noise cuts) appears to be too sensitive to the wellbore inclination. Hence, application of automated neural net interpretation of noise logs requires a new generation of noise logging tools.
Modeling Porosity Distribution in the A'nan Oilfield: Use of Geological Quantification, Neural Networks, and Geostatistics
Authors: Wang L. , Wong P. M. , Shibli S. A. R. 
Published: December 2007

Summary
A'nan Oilfield is located in the northeast of the Erlian Basin in North China. The porosity distribution of the oil-bearing stratum is primarily controlled by complex distribution patterns of sedimentary lithofacies and diagenetic facies. This paper describes a methodology to provide a porosity model for the A'nan Oilfield using limited well porosity data, with the incorporation of the conceptual reservoir architecture. Neural network residual kriging or simulation is employed to tackle the problem. The integrated technique is developed based on a combined use of radial basis function neural networks and geostatistics. It has the flexibility of neural networks in handling high-dimensional data, the exactitude property of kriging and the ability to perform stochastic simulation via the use of kriging variance. The results of this study show that the integrated technique provides a realistic description of porosity honoring both the well data and the conceptual framework of the geological interpretations. The technique is fast, straightforward and does not require any tedious cross-correlation modeling. It is of great benefit to reservoir geologists and engineers.
Ejectors for Boosting Low-Pressure Oil Wells
Authors: Villa Marco , De Ghetto Giambattista , Paone Francesco , Giacchetta Giancarlo , Bevilacqua Maurizio 
Published: December 2007

Summary
The first field installation of a multiphase surface ejector was successfully accomplished in the Villafortuna oilfield (Italy) in 1996. The ejector increased the oil production rate by 30% and demonstrated the viability ofthe system as a reliable low cost-small size boosting system that had minimal impact on existing facilities, and is suitable for applications in existing fields or for new development both onshore and offshore.
The article describes the main steps ofthe R&D project, developed in collaboration with the University of Ancona, as well as the testing process in which different ejector geometries were extensively tested with crude oil and gas in the Agip's multiphase loop of Trecate.
The article describes the installation in the Villafortuna field as well as other studies under development.
Fracturing Horizontal Wells in Gas Reservoirs
Authors: Soliman M. Y. , Hunt J. L. , Azari Mehdi 
Published: December 2007

Summary
The fracturing of horizontal wells has recently gained wide acceptance as a viable completion option to maximize the return on investment. This is especially true in the case of tight gas formations.
Horizontal wells have unique rock mechanics and operational aspects that affect fracture creation and propagation and control fracture orientation with respect to the horizontal well. It has been well documented that fracture orientation greatly affects the productivity and well testing aspects of the fractured horizontal wells. Depending on stress orientation relative to the wellbore, the fractures may be transverse or longitudinal.
This paper presents a model for fractured horizontal wells operating under constant pressure conditions. This condition is most suitable for producing tight gas reservoirs. The model considers the presence of either transverse or longitudinal fractures.
In this paper, we examine the factors involved in determining the optimum number of transverse fractures for both finite and infinite reservoirs. For a group of transverse fractures, the rate distribution for each fracture is presented and analyzed. The effect of uneven fracture length is briefly presented.
The performance of a longitudinal fracture is examined and compared to a fractured vertical well and a transverse-fractured horizontal well. A comparison of longitudinal versus transverse fractures from reservoir and operational points of view is presented. Also included is a short discussion of field examples.
Because performance of a highly conductive longitudinal fracture is almost identical to that of a fractured vertical well, the existing solutions for fractured vertical wells may be applied to longitudinal fractures with a high degree of confidence. This approximation is valid for moderate to high dimensionless conductivity. In the case of transverse fractures, the outer fractures outperform the inner fractures. However, in most practical cases, more than two fractures are necessary to efficiently produce the reservoir. A simplified economic analysis supports this conclusion.