bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single-Phase Flow Through Natural Fractures
Authors: Jones T. A. , Wooten S. O. , Kaluza T. J. 
Published: December 2007

ABSTRACT
It is well known that for a single-phase fluid flowing between smooth parallel plates, the pressure drop is proportional to the cube of the aperture separating the plates. Some investigators2,3 have looked at the effect of surface roughness on flow using fabricated surfaces, induced fractures, or sawed surfaces and have found deviation from that law at small apertures. This paper presents new laboratory data for single-phase flow through open rough natural fractures.
Two types of petroleum reservoir rocks (sandstones and cherts) were used, each having a different surface roughness. Flow through both open and closed fractures is evaluated with apertures ranging between 0.002 to 0.0253 in. A technique for measuring apertures in-situ has been developed which avoids back-calculating apertures from flow data, as other investigators have had to do. Fluids with viscosities of about 1 and 18 cp were used.
At large apertures (0.0253 in), compared to the surface roughness, the cubic law is followed; at smaller apertures for rough fractures, deviation is seen. Transition from laminar to turbulent flow is smooth but is dependent on surface roughness for smaller fracture apertures. Critical Reynolds Number, the Reynolds Number where laminar flow ends, is seen to decrease with decreasing fracture aperture for rough fractures. Data are correlated using plots of friction factor versus Reynolds Number.
Techniques for Measuring the Electrical Properties of Sandstone Cores
Authors: Lewis M. G. , Sharma M. M. , Dunlap H. F. , Dorfman M. H. 
Published: December 2007

ABSTRACT
Methods currently being used to measure the electrical conductivity of fluid saturated porous media are highly sensitive to various capillary and electrical effects. If these effects are not taken into account when making electrical measurements on cores, large errors in the computed values of the resistivity index (I) and the Archie saturation exponent (n) can occur.
Resistivity was monitored at 1 inch [25.4 mm] and 2 inch [50.8 mm] intervals along 6 inch [152.4 mm] Berea cores in order to observe electrical and capillary end effects. Computerized Axial Tomography (CAT Scan) was utilized to examine fluid distributions within the sandstone cores under water-wet primary drainage conditions. When the CAT Scan data was combined with electrical resistivity data, the magnitude of electrical contact resistances between the current electrodes and the core can be estimated as well as the saturation variation due to the capillary end effect. It was found that the contact resistances are substantial at low water saturations and in oil-wet cores.
Field Evaluation of a New Gelant for Water Control in Production Wells
Authors: Avery M. R. , Wells T. A. , Chang P. W. , Millican J. D. 
Published: December 2007

ABSTRACT
A new chemical process for improving the performance of wells producing at high watercuts has been developed. This process is based on covalently bonding a medium molecular weight, cationic polyacrylamide with an organic crosslinking agent to form a three dimensional gel structure. Because the gel solution is hydrophilic, it is preferentially emplaced in the zones of high water saturation and high water permeability. Gelation rate is controlled by adjusting the pH of the gel solution. Once the gel structure has developed, effective water permeability is reduced with little impact on the effective oil permeability.
This paper reports on the results of over 30 wells treated using the new process. Substantial decreases in water production have been realized and, in some cases, significant amounts of incremental oil recovered. The evaluation of these treatments helps demonstrate the working mechanisms of the gelant and the optimum field application of the process.
A New Approach for Mathematical Modeling of Formation Damage Due to Invasion of Solid Suspensions
Authors: Kumar T. , Todd A. C. 
Published: December 2007

Abstract
Formation damage due to invasion of solid suspensions has been studied by several investigators and some modelling approaches have also been reported in the literature, most notably the application of effective medium theory and percolation theory in two and three dimensional capillary networks.
This paper presents a new mathematical model, which is based on mass balance of particles flowing through the porous media. The linear as well as radial forms of the model are described.
Although the differential equations derived take the general form of diffusion-convection equations, the marked difference is in terms of the suitability of the model to apply for variation of parameters such as particle concentration in the fluid, injection rate, density of solid particles, against the depth and time of invasion.
The results of the simulation run agree reasonably well with the experimental damage data obtained on 80mm sandstone core plugs using a multi-port pressure-tapped core holder.
The radial form of the model can be used to simulate formation damage in water injection wells whereas the linear model can simulate damage in filtration systems involving industrial water purification or oilfield water injection treatment.
The Effects of Fluid Preconditioning and Test Cell Design on the Measurement of Dynamic Fluid Loss Data
Authors: McGowen J. M. , McDaniel B. W. 
Published: December 2007

Abstract
Accurate modeling of dynamic fluid loss in the laboratory has increased in importance as the art of computer simulation of fracturing treatments reaches higher levels of sophistication. Three dimensional (3-D) design simulators often require fluid loss behavior of fracturing fluids to be described more explicitly than is achieved using most previous laboratory testing procedures. Even two dimensional (2-D) simulators can only be as valid as the data used in their calculations, and the prediction of fluid leak-off to the reservoir is one of the most critical calculations. Although the use of dynamic fluid loss equipment is not new, it has been found that often overlooked procedural conditions can alter the results obtained.
Some earlier investigators recognized the need for using representative fracture shear rates within the test cell, but failed to consider the importance of fluid shear history prior to entering the cell. This shear history (termed "fluid preconditioning") can significantly affect fluid loss data, even if other factors are held constant. Also cell entrance effects and flow patterns across the core face may lead to inconsistent results when compared to other cell designs. In the work reported in this paper, both test cell configuration and fluid preconditioning were investigated to determine their influence on fluid loss results. More than 200 dynamic fluid loss experiments using two different test cells and two types of preconditioning flow loops have been conducted to investigate the influence of fluid preconditioning and test cell design. The effect on fluid loss resulting from incorporating sand slurries (up to 5 lb/gal) was also investigated.
Field and Laboratory Experience in Stimulating Ekofisk Area North Sea Chalk Reservoirs
Authors: Snow S. E. , Hough E. V. 
Published: December 2007

ABSTRACT
This paper describes field and laboratory work carried out recently to better understand stimulation behavior in Ekofisk Area North Sea chalks. Laboratory work has been done to study chalk hardness, chalk mechanical properties, and the development and stability of propped and acid fracture conductivity. The laboratory work, combined with a review of available stimulation techniques for these formations, shows that stimulations in most of these reservoirs can be optimized with a pseudo limited entry acid fracture technique. Cased hole logging, pressure transient tests, and other field data have been utilized to optimize the design of these stimulations. The best treatments have resulted when several widely spaced clusters of perforations are treated in stages using ball sealers for diversion.
Use of Low-Density, Gravel-Pack Material Improves Placement Efficiency (Part 2)
Authors: Hudson T. E. , Martin J. W. 
Published: December 2007

ABSTRACT
The success of a gravel-pack completion depends on placement of gravel in the perforation tunnel area and the screen-casing annulus. Wellbore deviation is one of the predominant factors affecting gravel placement. As wellbore deviation increases, the gravitational forces and carrier fluid limitations may result in gravel settling (duning) and an incomplete packing of much of the perforation tunnel area, as well as a premature screenout of the screen-casing annulus.
A completion technique is introduced that eliminates problems associated with gravel settling. The technique uses buoyancy forces to counter the gravitational forces on the gravel particulate. Particulate settling is minimized by decreasing the ratio of the particulate density (Dp) to the base fluid density (Dc). Verification of the concept includes test results from a gravel-pack model. The model is 18 ft long with an inside diameter (ID) of 6.2 in., a screen and blank pipe size of 2-7/8 in., and a working pressure of 1,000 psi. The blank pipe length is 6 ft and the screen length is 12 ft. There are 20 perforations that include a chamber to simulate a void space behind the casing.
Test results include gravel-pack efficiency for variations in base fluid properties, wellbore deviation up to 90° (horizontal) and particulate density/ base fluid density ratios (Dp/Dc) from 2.65:1 to 0.8:1. Recommendations for a treatment technique and low-density particulate specifications also are included.
Effect of Concrete and Berea Strengths on Perforator Performance and Resulting Impact on the NEW API RP-43
Authors: Behrmann L. A. , Halleck P. M. 
Published: December 2007

ABSTRACT
A recent work advanced a simple and economical audit method for controlling the field performance of shaped charge perforators. Fundamental to the method are rigorous specifications which will assure reliable, consistent quality control targets which provide performance data translatable to API RP-43 data. Results of an extensive test program showed decreases in perforator penetration with increasing strength of the target materials. Furthermore, the rate of penetration decrease was observed to be dependent bn charge type, target material, and target boundary conditions. Implementation of the referenced perforator performance audit and proposed changes to API RP-43 have challenged past concepts with respect to Berea target consistency, specifications, and translation factors.
The objective of the proposed API RP-43 is to specify recommended test procedures for evaluating the performance of perforating equipment. The desire of the API is to test gun systems in a consistent surface target with properties similar to a sandstone reservoir rock. It is believed that the use of a Berea sandstone target will ease the translation between surface and downhole performance. Thus, the issue addressed in this paper is the determination of perforator performance versus quality control and API Berea properties, their resulting translation factors, and API target specifications.
The present work expands the earlier investigation and focuses on specific issues of: –Determination of the proper Berea property to correlate with penetration.–Selection procedures and specifications for API RP-43 Berea targets.–Translation of quality control Berea data to proposed API RP-43 Berea slab target data. – Translation of API Section I concrete data to proposed Berea slab target data.
Stability and Failure of Spherical Cavities in Unconsolidated Sand and Weakly Consolidated Rock
Authors: Perkins T. K. , Weingarten J. S. 
Published: December 2007

ABSTRACT
The conditions necessary for stability or failure of a spherical cavity in unconsolidated sand or weakly-cemented rocks have been studied. Experiments using physical models have utilized weakly-cemented synthetic, porous rocks. As external confining pressure was applied to the rock, a shear failure region was induced around the cavity. When fluid flowed through this system at increasing rates, the outer boundary of the shear failure zone was calculated to have increased, and a region of disaggregated solids was created adjacent to the cavity.
Equations for convergent flow of a fluid towards a cavity predict that tensile stresses tend to be induced near the cavity face. These tensile stresses pull the pack of disaggregated solids apart, causing it to dilate. A region of material at the limit of tensile stability will be formed. The radius of this zone will expand until the system becomes stable with no induced tensile stress being greater than the slight adhesion provided by an immobile phase, if present.
As the flow rate is increased, the shear failure zone and the zone of material at the limit of tensile stability propagate farther away from the cavity. To preserve stability, the permeability of the sand at the cavity face must progressively increase by further dilation. When the cavity face porosity has increased to some critical porosity, mechanical interaction of the particles is insufficient to keep the pack from becoming fluid-like and being produced into the cavity.
For low permeability models, pressure drop data indicated that average permeabilities in the shear failure zones were greater than the permeabilities of the cemented rock in the surrounding elastic regions. When flow rates increased sufficiently, the shear failure zones expanded to the outer boundary of the models; total collapse of the models ensued and large quantities of sand were produced.
Some data for cavity failure in unconsolidated sands, which are available in the literature, as well as the experimental data for weakly-cemented synthetic rocks, have been analyzed using the equations and concepts developed in this paper. For mixtures of fracture proppant sand, for some coarse natural sands, and for disaggregated solids created around a cavity in the weakly-cemented rocks, the critical porosities at the cavity face (when the cavities were barely stable) were estimated to be in the range of 40% to 53%. An apparent unit cohesive strength of a few tenths of a psi was manifested, perhaps due to mechanical interlocking of the individual grains.
The Effect of High-Pressure Gradients on Gas Flow
Authors: Temeng K. O. , Home R. N. 
Published: December 2007

ABSTRACT
The flow of gases through homogenous porous media is governed by non-linear differential equations when expressed in squares of pressure. In the usual analysis the equations are linearized by assuming small changes in pressure, and thus in fluid properties. The results thus yield a linear relationship between pressure drop and flow rate.
At high flow rates, experiments and well tests show deviations from the behavior predicted by the linear theory. These deviations are usually attributed turbulence, inertial effects and other factors, all of which are usually thought to render Darcy's law invalid. Quadratic and higher order equations are then used to characterize this type of flow, with the nonlinear coefficients determined empirically. However, this study has found that an alternative to using empirically determined non-Darcy effects is to correctly account for the consequences of the assumptions used to linearize the flow equations.
In this study the flow of real gases through porous media was analyzed by incorporating some of the nonlinearities present in the flow equations. It is shown that deviations from linearity, of the form observed in field tests and in laboratory experiments, can result from the nonlinearities inherent in the basic formulation. Thus, a lack of proportionality between pressure drop and flow rate does not necessarily imply or indicate a deviation from Darcy flow.
In laboratory examples it has been possible to correctly determine the observed Forchheimer coefficients, based on the derivation from first principles. This is achieved with only Darcy's law, without reference to any non-Darcy effects.
A Method for Determination of Permeability, Skin, and Turbulence Factor From an Open-Flow Potential Test
Authors: Beck F. E. , Lee R. L. 
Published: December 2007

ABSTRACT
A method is presented by which permeability, skin, and turbulence can be analyzed by interpretation of an open flow potential test. The method is based on a variation in the method suggested by Odeh and Jones, and allows a direct calculation of the turbulence factor from well test data. The method also utilizes the continuous record of bottom hole pressure now recorded for many well tests.
To facilitate interpretation of high permeability data, an optimization scheme is used to arrive at values of permeability, skin, and turbulence factor. Data from an open flow potential test and subsequent build-up are presented; analysis results in a favorable comparison. The optimized permeability, skin, and turbulence values also predicted, with reasonable accuracy, the measured well performance.
Analysis of the Effect of Pressure Data Frequency and Accuracy on the Calculation of Aquifer Influence Functions
Authors: Eicks T. D. , Wattenbarger R. A. , Startzman R. A. 
Published: December 2007

ABSTRACT
The performance of many Gulf Coast gas reservoirs are influenced by water influx from aquifers of unknown size, shape, and properties. Gajdica, et al. (1987) developed an automatic method for computing the performance of an aquifer by determining an Aquifer Influence Function (AIF). The current work investigates the use of Gajdica's AIF method to analyze the scheduling of pressure buildup tests and the effect of errors in this pressure data.
Test cases were constructed in which the AIF was known. A series of computer runs showed that the AIF is more accurate if more pressure data are available. No conclusions were reached about the spacing of the pressure data, but it seems that evenly spaced pressure data is desirable.
More importantly, a technique for detecting and correcting errors in pressure data was developed with the AIF method. The technique clearly shows where pressure errors occurred. Corrections to these pressure errors can then be made. This technique was applied to an actual field case and shows promise as a method for correcting pressure errors for this type of gas reservoir/aquifer system.
A Complex PVT Modeling Study
Authors: Brakstad F. , Bu T. , Bjørlykke O. P. , Mykkeltvedt K. 
Published: December 2007

ABSTRACT
Oseberg, which is one of the major Norwegian North Sea oil fields, will be produced by injection of associated gas and gas supplied through a pipeline from the Troll field. The two gases have different compositions and neither of them is in thermodynamical equilibrium with the in situ oil. By static multiple contact experiments it has been demonstrated that large component exchanges will occur. Other factors of importance for the reservoir process is a pronounced compositional variation with depth in the oil zone and the existence of a gas cap.
A number of relevant measurements and PVT experiments (constant composition expansions and multiple contacts) have been performed in order to obtain data for tuning a qubic Equation of State (EOS) PVT program which is composed of a PVT model and a set of equations. The PVT model consists of a set of well defined pure and pseudo components. Since the PVT program will form the basis for dynamical compositional simulations all the fluids involved must be characterized within a fixed component system. Various approaches have been tried, among them a multivariate lumping scheme.
After regression upon 49 experimental data from 4 fluid samples, four PVT models were obtained; two with 6 and two with 22 components. The paper will discuss the choice of experiments and the ideas behind the selection of models, including the choice of pseudo components and regression variables.
Simplified Compositional Formulation for Modified Black-Oil Simulators
Authors: Whitson C. H. , da Silva F. , Søreide I. 
Published: December 2007

ABSTRACT
This paper gives an evaluation of simplified compositional PVT formulations presently being used in modified black-oil reservoir simulators. In particular we consider a promising four-component general black-oil (GBO) formulation. This formulation has been successfully used in full-field simulations of several North Sea reservoirs containing near-critical fluids with composition that varies areally and with depth. The four "components" used in the GBO formulation are:
non-volatile surface oil volatile surface oil surface hydrocarbon gas injection gas (e.g., N2)
This formulation also models revaporization in reservoirs undergoing dry gas and/or non-hydrocarbon gas injection.
We first review the standard black-oil (BO) model and the modified black-oil model (MBO) based on solution oil-gas ratio (rs). Next, the GBO is introduced for reservoirs where only depletion is considered and therefore the injection gas component is not present. Finally, the four-component GBO formulation is developed for reservoirs undergoing gas injection and where the initial fluid composition may vary throughout the reservoir.
The GBO model requires PVT properties of hypothetical "binary" mixtures which are used to obtain actual fluid behavior. In the appendices we give methods for calculating these binary PVT properties based on correlations, material balance equations, and non-linear regression.
Laboratory Investigation of Inertial Flow in High-Strength Fracture Proppants
Authors: Pursell D. A. , Holditch S. A. , Blakeley D. 
Published: December 2007

ABSTRACT
High velocity fluid flow down hydraulic fractures will create pressure gradients that are proportional to the square of the velocity. As such, Forchheimer's equation, rather than Darcy's law must be used to correctly' estimate the pressure gradients near the wellbore and, consequently, the flow behavior of the hydraulically fractured well. To properly use the Forchheimer equation, one must know the value of β, which is the inertial flow coefficient. Cooke measured values of β for various sizes of Brady sand at several different closure pressures.
Cooke's correlation has been widely used in the industry but we have found that the correlation did not span the permeability range needed for all situations. Specifically, data are needed to estimate the pressure gradients of gas flowing through high strength, high permeability, man-made proppants. We also need the inertial flow data for sand that has been severely crushed,
A laboratory system has been constructed to investigate high velocity flow through fracture proppants. From test data, both proppant permeability and the inertial flow coefficient can be computed. The proppants tested included 12–20 and 20–40 mesh samples of Brady sand, Interprop Plus, and Carbolite. An improved correlation of inertial flow coefficient as a function of proppant permeability and initial mesh size has been developed using our laboratory system. The results indicate that the inertial flow coefficient depends upon the initial mesh size of the proppant, and is independent of the proppant type.
Grain size distribution was found to be a factor controlling the inertial flow coefficient for a given fracture proppant. It was found that different samples with similar permeabilities and inertial flow coefficients also had similar grain size distributions.
A variation in the pore pressure of the nitrogen used in the experiments was shown to have a significant effect on the inertial flow coefficient. The permeabilities calculated from the Forchheimer equation exhibited the same trend of decreasing permeability with increasing pore pressure as the Klinkenberg relationship for Darcy flow. Slip flow was found to influence the results significantly at Reynolds Numbers below 0.1.