bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resistivity in Carbonates: New Insights
Authors: Fleury Marc 
Published: December 2007

Abstract
A detailed explanation of the non-Archie behavior of the resistivity index vs Sw curves in carbonates is proposed. The model is based on resistivity index (RI) curves measured at ambient and reservoir conditions, on double or triple porosity micritic and oolitic carbonates. We used the Fast Resistivity Index Measurement (FRIM) method to obtain accurate and continuous RI curves down to very low water saturation (5%). In general, the measured RI curves cannot be described by an Archie's law and the measurements at very low saturation are often a key observation to confirm a non-Archie behavior. A large variety of shapes is observed and the local saturation exponents can vary from 1 up to 3.
These shapes can be explained qualitatively and quantitatively using two new models (DPC and TPC) in which the different porosity systems are connected together either in series or in parallel, or a combination of both. The second key feature of the models is the use of NMR and mercury injection curves to estimate the pore volume fraction of each population and the sequence of invasion of each population by oil during the primary drainage process. Hence, only two of three adjustable parameters are needed to model the experimental results. In particular, the saturation exponent of the dominant pore system can be extracted from the analysis. For field applications, we also propose a simple procedure to calibrate resistivity logs with variable saturation exponent.
From the experimental results and the model, we conclude that the pore structure plays a key role. In particular, the microporosity can be responsible for the low resistivity contrast in carbonates, although it may represent less than 10% of the total pore volume. The water contained in the microporosity forms a continuous path for the current. When invaded by oil, the conductivity of the microporosity system is weakly modified.
A Novel Approach for Incorporating Physical Dispersion in Miscible Displacement
Authors: Shrivastava Vijay K. , Nghiem Long X. , Moore R. Gordon 
Published: December 2007

Abstract
Physical dispersion is one of the main mechanisms responsible for controlling the gas-oil mixing that occurs in a miscible flood process. Many conventional reservoir simulators do not explicitly account for the physical dispersion and presume that it may be compensated by numerical dispersion arising out of the finite difference scheme with single point upstream weighting of mobilities for the reservoir grid block sizes used in field-scale simulations. This assumption may lead to erroneous results.
The multi-point flux approximation (MPFA) schemes developed in recent years provide improved treatment of the convective flux and allow the handling of tensorial permeabilities for non-uniform and skewed grids. These grids are often required for proper representation of the reservoir geometry. The physical dispersion coefficient in the dispersive flux is tensorial in nature and amenable to a treatment similar to the permeability in the convective flux. We have applied a multipoint control-volume method together with a total variation diminishing (TVD) scheme to calculating the dispersive flux in a compositional simulator. The TVD scheme was used to minimize the effect of front smearing caused by numerical dispersion.
This paper presents a method for calculating the full physical dispersion tensor in a compositional simulator using corner-point grids. The proposed formulation accurately handles dispersive flux for non-orthogonal grids, and along with the TVD scheme provides a means for distinguishing physical dispersion from numerical dispersion.
A number of cases are presented to show the improvements in simulation results that could be obtained with the proposed method.
Use Of The Noise Log As A Downhole Diagnostic Tool
Authors: Koerner H.B. , Carroll J.C. 
Published: December 2007

Introduction
Flow of aquifer water into a dry oil production stream, contamination of fresh water aquifers production stream, contamination of fresh water aquifers due to casing leaks or crossflow behind pipe, and loss of oil, natural gas, or injection fluids due to downhole equipment failures are examples of everyday problems in a large oil producing operation. These problems must be detected, confirmed, diagnosed and solved - quickly and economically. Collection of useful downhole information is the key to meeting this requirement.
Conventional logging techniques such as temperature, flow-meter and radio-active tracer (RAT) are used effectively for detecting undesirable fluid flow in a wellbore. However, in ARAMCO operations, situations are frequently encountered where these techniques are partially or totally inadequate, for example:Oil producer waters out. Temperature profile is normal. Tubing is set to TD. Source of water is questionable.Producer with tubing run to TD develops pressure on a casing - casing annulus. Temperature profile shows no anomalies.Supply wells producing 120 MB/D of 170 deg. Saline aquifer water by electrically driven submersible pumps hung at 500 ft on a watercolumn must be monitored routinely to prevent contamination of fresh water aquifers.Power water injection well develops awell-bore obstruction. The obstruction is opposite the top of a large aquifer whose temperature is the same as that of the water being injected.
In all these cases the flow stream is in accessible, which rules out the use of a flowmeter or RAT. The temperature log is ineffective because either the flow rate is too small to effect a gradient change or the temperature of the flowing fluid is indistinguishable from the wellbore temperature. Since 1976, however, ARAMCO has been using a noise logging technique to successfully evaluate problems similar to these.

NOISE LOGGING
The diagnostic value of downhole noise was recognized as early as 1955. It was not until 1972, however, that the results of an extensive laboratory investigation the nature of downhole noises were reported. Using these results two important conclusions were drawn:That order of magnitude flow rates can be estimated using peak noise; andThat certain flow situations can be distinguished from others if the frequency structure of the noise can be obtained.
The development of a downhole noise logging technique ins undertaken based on these conclusions. The groundwork has been laid for quantitative interpretation of downhole noise, but, to date, most interpretations are still qualitative.

ELEMENTS OF THE TECHNIQUE
Peak Noise Peak Noise Our observations indicate that absolute noise amplitude is the key to qualitative noise log interpretation, since noise peaks are usually detected opposite a noise source, and the energy levels of these peaks indicate the severity of the problem.
Phase Envelope Calculations for Hydrocarbon-Water Mixtures
Authors: Lindeloff Niels , Michelsen Michael L. 
Published: December 2007

Abstract
The present work describes how the pressure-temperature phase diagrams for hydrocarbon-water mixtures can be calculated. This requires a thermodynamic model that can account for the polar interactions caused by the aqueous compounds and an algorithm that can trace the two- and three-phase boundaries encountered is such systems. Models and algorithms that can handle this task are described. The paper further describes a number of examples where the methods are applied.
Primary and Secondary Porosity Estimation of Carbonate Formations Using Total Porosity and the Formation Factor
Authors: Kazatchenko Elena , Mousatov Aleksandr 
Published: December 2007

Abstract
A technique for the primary and secondary porosity estimation is proposed. This technique is based on a resistivity model of carbonate formations with double porosity and the analysis of numerous core data. The resistivity model consists of an isotropic conductive matrix with a primary porous system and inclusions, which represent secondary porosity (vugs and fractures). Fracture systems are described by oblate ellipsoids of different sizes (which have the same orientation and aspect ratio) or by thin plates. These rock structures are characterized by an anisotropy of electrical properties. The components of the resistivity tensor have a nonlinear relationship with the matrix porosity and parameters of fracture systems (orientation and porosity). The model with spherical inclusions (Maxwell-Garnett approach) is applied to obtain the resistivity of vugular formations. The fluid type, saturation of matrix and secondary pores influence significantly the formation resistivity and anisotropy coefficient. When both pore systems are completely saturated by the same conductive fluid (the case of core analysis), the effective formation factor depends only on the matrix formation factor and the secondary porosity value. The statistical analysis of core data has shown that Archie's equation with cementation exponent m=2, is the best approximation to describe the matrix formation factor for carbonate formations in Mexico. For verification of the porosity separation technique, the fracture and vuggy porosities have been estimated for core with detailed description of pore structure.
Scale Prevention, a Magentic Treatment Approach
Authors: Farshad Fred F. , Vargas Silvia M. 
Published: December 2007

Abstract
Sixty experiments have been conducted to study the effects of magnetic fields on calcium sulfate scale (also known as gypsum scale). For this purpose, three magnetic systems were designed using NdFeB (Neodymium Iron Boron) magnets of different geometry arranged in open and closed magnetic circuits. The statistical analysis of the data obtained indicates the potential effectiveness of this technology to prevent and treat scale formation problems.
Coaxing Information from Petrophysics and Integrated Data Analysis: The Menggala South Field Case History, Sumatra, Indonesia
Authors: Pederson John M. , Stewart William F. , Yuwono Ipung P. 
Published: December 2007

Summary
We developed a reservoir model for potential infill locations in this mature oil field. Prior to a 3D seismic survey expected recovery was over 60% and the field had a limited amount of reserves based on the old 2D seismic lines. The new seismic study showed the crest of the structure was missed during the initial field development. This study was commenced to delineate new well locations and determine if one or more horizontal wells were feasible.
This study consisted of revising the petrophysics data from 11 wells, building an earth model and making a simple simulation model. The field had wells drilled over a fifteen year period from 1972 to 1987. This paper outlines the efforts to obtain a usable log suite including permeability, Swi and Sorw. Information from nearby fields and the initial field simulation using average properties were included in this analysis. This information was included into the earth model and subsequently the simulation model.
Successful Application of ESP's in a Very Corrosive Environment, Gulf of Suez Area, Egypt (Case Study)
Authors: Naguib Mohamed , Iraki Hesham , Wilson Magued , Hussein Ahmed 
Published: December 2007

Abstract
The need for artificial lift is very common worldwide, nearly all reservoirs requires artificial lift at a certain stage of the field life. The decision of which artificial lift method to use is very important to the long-term profitability of the field. An improper decision of artificial lift can reduce production and increase the operating costs substantially. Once a decision has been made on the type to install on a well, it can rarely be altered whatever the method been selected.
Ras Fanar Field is located on the western side of the central part of the Gulf of Suez about 3 km east of the city of Ras Gharib. Production commenced in January 1984 and a peak production rate of 20 MSTB/D was achieved in May 1984. The field was produced naturally for 14 years and the produced fluid contains up to 15% H2S and 11 % Co2 in the associated gas phase.
It has been recognized that there is a need for artificial lift when water cuts increased and/or reservoir pressure decline. Studies carried out by SUCO concluded that ESP's are the most appropriate method and it was installed in 1996. The operating experience gained during the period 1996 to 1998 led to significant improvements, resulting in ESP run lives in excess of three years. The main problems during the initial phase of the project and the applied solutions, as well as critical operating factors will be described.
This paper presents and discusses the operational challenges of the ESP in such highly aggressive environment and documents the success and failures.
A Study of Wettability and Permeability Change Caused by Adsorption of Nanometer Structured Polysilicon on the Surface of Porous Media
Authors: Binshan Ju , Shugao Dai , Zhian Luan , Tiangao Zhu , Xiantao Su , Xiaofeng Qiu 
Published: December 2007

Abstract
A nanometer (10−9m) structured particle material, generally so defined that the diameter of the particle is no more than 100nm, has some special physical efficacy in its surface, small size and other properties. One kind of polysilicon with sizes ranging from 10~500nm, and considered as nanometer or sub nanometer sized powder, was used in oilfields to enhance water injection by changing wettability of porous media. The mechanism of enhancing water injection is through improving relative permeability of the water-phase by changing wettability induced by adsorption of polysilicon on the porous surface of sandstone. On the other hand, the adsorption on the porous surface and plugging at the small pore throats of the polysilicon may lead to reduction in porosity and absolute permeability (K) of porous media for pore sizes from 100 to 1000,000nm. Thus the degree of success in well treatment is determined by the improvement of effective permeability of the water-phase.
In this paper a mathematical model, which was combined with the study of experiments in the laboratory, is presented and a simulator is developed to simulate water injection dynamics under the conditions of polysilicon injection. The simulator can accurately simulate the process of migration and adsorption in the pore bodies and blocking at the pore throat of the polysilicon in the sandstone. A series of numerical simulation runs was conducted to study the effect of a wide range of parameters, such as the sandstone with different permeabilities, concentration of the polysilicon, injection volumes, and others. The effective permeabilities of the waterphase measured by a number of core flooding experiments are matched well by the numerical results. Since April 2000, nine well treatments with solvent slugs of suspended polysilicon particles in several oilfields in China was shown to be successful and the average injection rate increased 5 times after treatments.
Determination of Fracture Orientation by Multi-Well Interference Testing
Authors: Cherifi Mohamed , Tiab Djebbar , Escobar Freddy H. 
Published: December 2007

Abstract
It is often desirable to know patterns created after a number of wells in reservoir have been fractured. Interference testing is one of the best techniques that can be used for estimating some of the important formation properties (transmissibility and storativity) and fracture orientation.
Generalized correlations are presented relating (a) the dimensionless pressure response, PD, inter, at the intersection point of the pressure and the pressure derivative to the compass orientation, θ, and (b) the quotient of the dimensionless pressure and the ratio of dimensionless time to the square of the dimensionless radial distance, (tD/rD2)inter, at the intersection point to the compass orientation.
The correlations can be used for analyzing interference test pressure response at an unfractured shut-in well caused by a production of a vertically fractured well with a uniform flux, infinite or finite conductivity fracture provided that the half fracture length is known a priori.
Detailed procedures for the analysis of interference testing of a vertically fractured well are presented and demostrated through a simulated example.
Waterflooding Performance of Stratified Reservoirs with Bottom-Water Conditions
Authors: Shirif Ezeddin , Zao Gary 
Published: December 2007

Abstract
Many reservoirs in North America contain a high water saturation zone "bottom-water" underlying the oil zone. Waterflooding under such conditions is typically ineffective because of chanelling of water through the bottom-water zone. However, in some cases, waterflooding such reservoirs may still be feasible and economically viable. While there is no doubt that some of the injected water bypasses the oil zone through the bottom-water zone, most of the injected water may still displace the oil, depending on the reservoir conditions. Therefore, a mechanistic understanding of oil displacement by a waterflood in the presence of a bottom-water zone is the basis for predicting recovery performance, and there is a need for developing a mathematical model to describe water channeling under bottom-water conditions.
In this paper, a new simple analytical model was developed to predict waterflood performance in stratified reservoirs when a water zone is present. Given the reservoir description, the new mathematical model can be used to describe the amount of water channeling into the bottom-water, calculate pressure distribution in each layer and together with a prediction of oil recovery. Results of the mathematical predictions are compared with experimental and simulation results, showing good agreement.
The Geological Application of Acoustic Images in Homogeneous Clastic Sediments; Examples from the Tertiary Hemlock Formation, Cook Inlet, Alaska
Authors: Johansson M. , Saltmarsh Art 
Published: December 2007

Abstract
The Cook Inlet is a major oil and gas province south-southwest of Anchorage, Alaska. It is located in a forearc basin setting, which developed as a result of plate motion. This plate motion caused the migration and accretion of the Chugach terrain. The overall tectonic regime is compressional with the principal maximum stress orientated northwest to southeast. Thirty thousand feet of Tertiary sediments occupy the basin, and this great thickness is a result of contemporaneous deposition and active tectonics.
The Hemlock formation is nonmarine in origin and comprises sandstone and conglomerates of Eocene and Oligocene age. The rocks include braided stream deposits, alluvial fans shed from the margins, and fluvial deposits that developed in the axis of the basin. The sandstones and conglomerate beds often stack to form large homogenous sedimentary units, which can reach thicknesses greater than 50 ft.
An acoustic imaging tool commonly used in wells drilled with oil-based mud or other highly resistive drilling fluids has been used in the evaluation of this formation. Homogenous rocks have acoustic properties similar to these fluids, resulting in the resolution of very little diagenetic detail. However, dipping surfaces and textural variations were observed on the image and these features contributed to the building of a sedimentological model. Additionally, borehole breakout orientation provided key information regarding borehole stress directions.
A Chemo-poroelastic Solution for Stress and Pore Pressure Distribution around a Wellbore in Transversely Isotropic Shale
Authors: Ghassemi A. , Diek A. 
Published: December 2007

Abstract
It is generally accepted that shale deterioration and borehole instability are significantly influenced by excessive pore pressure, ion exchange between drilling fluids and shale, and the anisotropy of the in-situ stress state as well as the formation. This paper describes a model for estimating the influence of elastic and chemo-mechanical anisotropy on the distribution of stress and pore pressure around a well in transversely isotropic shale. The model is based on a practical theory that couples ion diffusion, chemical osmosis, and hydraulic flow to stresses and pore pressure. The field equations of the model are derived within the framework of a continuum chemoporoelastic theory that linearly relates total stresses and variation of fluid content to the strains, pore pressure, and solute mass fraction through anisotropic material coefficients. The field equations are solved analytically for the problem of a wellbore in transversely isotropic shale to yield the solute mass fraction, pore pressure, and the stress distributions around the borehole. The solution has been applied to a typical field situation and the results indicate that the osmotic pressure tends to stabilize the borehole. However, osmotic pressure dissipates with time due to ion diffusion. Furthermore, it is found that the anisotropy in chemo-mechanical material coefficients strongly affects the effective stresses around the borehole and enhances the potential for borehole failure.
A Damage Mechanics Approach for the Modelling of Sand Production in Heavy Oil Reservoirs
Authors: Shao J. F. , Marchina P. 
Published: December 2007

Abstract
Allowing sand to be produced together with the oil is a field proven technique to economically produce heavy oil reservoirs. By doing this, the performance of the wells is increased owing to a number of factors including an increased near wellbore permeability and/or the development of cavities (wormholes) significantly improving the flow conditions in the reservoir. However, the combination of a limited understanding of the physically complex processes involved in this phenomenon and the economic drive to adopt a pragmatic approach has led to mixed rate of success for this type of projects.
One of the first issue to tackle in studying this phenomenon is the quantification of the sand production and, equally important, the impact it has on the well and reservoir behavior.
Building on already published work, a sand production model is proposed that accounts for the mechanical damage induced in the formation by the production of sand. This model has been deliberately kept simple to evaluate the potential of the approach for modelling sand production in heavy oil reservoirs. The framework of the model is that of elasto-plasticity including isotropic damage. Th emodel has been tested on a synhetic, though realistic, set of data and, despite the simplfying assumptions (single phase flow, constant fluid viscosity) could qualitatively reproduce the salient features of the behaviour of typical heavy oil wells.