bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Investigation of the Role of Capillary Forces in Laboratory Water Floods
Authors: Perkins F.M. 
Published: December 2007

Introduction
Capillary forces play a controlling role in waterdrive displacement processes both in laboratory experiments and in actual reservoirs, but their quantitative importance may be quite different in the two cases. Because of the importance of conducting laboratory experiments which are representative of field conditions, it is necessary to understand exactly the role of capillary forces in the displacement process. Though a number of experimental investigations related to this subject are contained in the literature, there appears to be a lack of information pertaining to unsteady-state experiments in water-wet media. This experimental study was conducted to obtain additional laboratory data to clarify further the role of capillary forces in both the macroscopic and microscopic flow of oil and water in porous materials.

Theoretical Considerations
The capillary pressure is defined as the difference in pressure between a continuous oil phase and a continuous water phase in a porous material. The magnitude of this pressure difference depends on the interfacial curvature and the interfacial tension. The interfacial curvature is determined by the geometry of the pore spaces, the wettability of the rock surfaces, and the quantity of each phase present. Capillary forces are involved in a water-drive displacement process in that they exert a controlling influence on the microscopic fluid distribution which in turn is reflected in the saturation or macroscopic flow behavior.

Microscopic Fluid Distribution
Because of the microscopic nature of the displacement of oil by water, it is necessary to consider the flow and the fluid distribution in individual pores. On this microscopic scale the capillary forces, which act over a distance of one or two sand grain diameters, control the distribution of oil and water under static equilibrium conditions. When an external force is applied to the fluids, such as in a water-injection experiment, the applied forces tend to distort the oil-water interfaces. However, in most fine-grained, water-wet sands, the applied pressure difference across one or two grain diameters is usually several orders of magnitude less than the capillary pressure difference.
Stability and Failure of Sand Arches
Authors: Bratli Rolf K. , Risnes Rasmus 
Published: December 2007

Abstract
When producing from an unconsolidated sand, sand arches may form behind the perforation opening. On the basis of a theoretical model, we have analyzed the stresses in the sand. The effect of flowing fluids has been studied, and criteria describing the stability and failure of the sand are given.
The arching phenomenon was studied in the laboratory. The experiments qualitatively reproduced the theoretical results. To the extent that comparison was possible, the quantitative agreement between theory and experiments was fairly good.
Taylor's Dispersion in Stratified Porous Media
Authors: Lake Larry W. , Hirasaki George J. 
Published: December 2007

Abstract
During 1953–54, Taylor showed that if a certain criterion is met the combined effects of the transverse profile of longitudinal velocity and transverse diffusion on a solvent slowly flowing through a tube will manifest themselves as a longitudinal diffusion phenomenon. A similar phenomenon exists in stratified porous media where the transverse profile of longitudinal velocity and transverse dispersion can produce an effective longitudinal dispersion, called Taylor's dispersion in this paper. Since this effective longitudinal dispersion is larger than the corresponding homogeneous longitudinal dispersion, the quantitative description of this phenomenon would be important to dispersion-sensitive EOR processes, such as surfactant or miscible flooding.
Taylor's dispersion will occur in two-layer porous media if a suitably defined dimensionless number is much greater than unity. When this condition holds, the effluent history of a constant-mobility equal-density miscible displacement is that of the same displacement in a homogeneous medium with increased dispersion. The resulting effective longitudinal dispersion may be derived analytically and verified numerically as a function of several media properties. The most important of these are system thickness and permeability contrast.
In multilayer media, when two adjacent layers have a large transverse dispersion number they behave as a single layer with suitably averaged properties. This observation suggests an algorithm whereby Taylor's dispersion may be extended to multilayer systems. The algorithm, or grouping procedure, gives effluent histories that are in agreement with numerical solutions to the continuity equation and allow properties of the resulting effective dispersion to be investigated. From the results of this work, Taylor's dispersion can offer an explanation for the large field-scale dispersion observed in tracer test studies. Moreover, it appears that the grouping procedure could indicate a method for obtaining layered reservoir models from core data.
Effects of Bit Hydraulics on Full-Scale Laboratory Drilled Shale
Authors: Tibbitts Gordon A. , Sandstrom John L. , Black Alan D. , Green Sidney J. 
Published: December 2007

Summary
The effects of bit hydraulics while drilling shale with a standard three-cone bit are examined in this paper. Tests were conducted by drilling into large-diameter, intact shale samples at simulated downhole conditions in Drilling Research Laboratory's wellbore simulator. The shale samples were recovered from massive surface outcroppings and preserved for laboratory use. The effects of hydraulic horsepower from 20 to 400 hhp and bit weights from 20,000 to 50,000 lbm on rate of penetration are presented.

Introduction
Most deep shales and some intermediate shales found in the U.S. are typically "slow" drilling formations. Efforts to improve rate of penetration in shale have been performed in both field tests and small-scale laboratory investigations. Until recently, laboratory drilling studies on shale have been confined to microbit1 or single-cutter2 studies because the ability to obtain and preserve large, intact shale samples had not been developed. In addition, laboratory facilities where full-scale drilling tests could be conducted at simulated deep-well conditions did not exist.
Massive surface shale formations have been located and techniques have been developed to extract and preserve large-diameter, intact samples. With these samples and the ability to simulate full-scale drilling conditions, a systematic, technical approach was taken where the effects of drill bit hydraulics were examined while drilling shale at simulated downhole conditions.

Background and Definitions
The in-situ conditions of a typical deep wellbore and surrounding rock formation are illustrated in Fig. 1. The formation is subjected to overburden stress, confining stress, wellbore pressure, and formation pressure. As previously demonstrated,3–5 rate of penetration is influenced strongly by the bottomhole conditions and appears to be most sensitive to the differential pressure between the wellbore and formation. These effects, however, can vary widely depending on rock properties such as rock type, strength, density, permeability, and mud properties such as composition, filtration rate, viscosity, solids content, and particle size.6 Bit hydraulics - i.e., the means of removing cuttings from the hole bottom and cleaning the bit with the drilling fluid - are a key factor in improved bit performance. Bottomhole cleaning theories,7 microbit studies,8 and full-scale laboratory drilling experiments in hard, impermeable rock9 have shown the need for adequate bit hydraulics to maximize rate of penetration and avoid bit balling. Field tests with extended nozzles10 also have demonstrated great potential for increasing rate of penetration in certain formations with improved bit hydraulics. Some nondrilling laboratory studies have shown the effects of nozzle size on pressure distribution at the hole bottom.11
Evaluation of Shaly Clastic Reservoir Rocks
Authors: Fertl Walter H. , Frost Elton 
Published: December 2007

Log-derived spectral gamma ray data have been correlated to core-derived Qv data (i.e., cation exchange capacity per total pore volume) in a Texas coast Tertiary sand, east Texas Jurassic sands, and an Alaskan elastic formation. Such correlations can be used to provide a continuous in-situ water saturation estimate in shaly sands based on the Waxman-Smits equation.

Introduction
Exceptionally few hydrocarbon-bearing clastic reservoir rocks are essentially free of clay minerals. The significant effect of the latter on important reservoir properties such as porosity, water saturation, and permeability and on most geophysical well log responses is well-established.In clastic reservoirs, various types of clay minerals may occur in dispersed, laminated, or structural form. The types of clay distribution, each with a differing effect on effective porosity, can be inferred from crossplots of well logs, visual study of cores, or detailed SEM investigations. The latter distinguish dispersed-clay occurrences such as discrete particles (patchy kaolinite), pore lining, and pore bridging (illite, chlorite, and smectite), each of which have a pronounced but different effect on reservoir permeability.Clay minerals may be characterized in several ways. Table 1 lists composition, density, hydrogen index, cation exchange capacity C ec, and distribution of potassium, thorium, and uranium based on spectral gamma ray information for some of the more common clay minerals.Furthermore, numerous log-derived clay content (shaliness) indicators are reviewed and discussed (Table 2). These techniques basically assume identical properties for clay present in clastic reservoir rocks and adjacent shales. However, this assumption is often unrealistic.With the advent of the Waxman-Smits model to calculate reliable water saturation in shaly sands, emphasis has been focused on log-derived evaluation of C ec per total pore volume, Qv. The novel application of spectral gamma ray data will be discussed in detail.

Water Saturation Calculation Models and Associated Parameters
Archie, in his classic empirical equation, relates formation conductivity Ct, formation-water conductivity Cw, and the formation resistivity factor F (a function of porosity phi and cementation exponent m) to the formation-water saturation Sw.
Ct =Sw CwF(-1),
where F= phi (-m).
Archie's equation satisfactorily applies to clean sands. The presence of clay minerals, however, has a detrimental effect on Sw calculations. Since such Sw results are often too pessimistic, several clay/quartz distribution models and Sw calculation concepts have been proposed.
JPT
P. 1641＾
Meeting the Challenge To Extend Success at the Pikes Peak Steam Project to Areas With Bottomwater
Authors: Wong Frank Y. , Anderson Don B. , O'Rourke J. Cameron , Rea Harley Q. , Scheidt Keith A. 
Published: December 2007

Summary
This paper provides a field review of the Pikes Peak steam project, showing key performance indicators of cyclic steam stimulation (CSS) and steamdrive in non-bottomwater. To test development over relatively thin bottomwater (less than 5 m), various steam processes were given field trials. Field pilot results from vertical-well CSS, dual horizontal well gravity drainage, and a combination of vertical injectors/horizontal well producers are presented for comparison.
Based on field experience and numerical simulation input, CSS has been conducted successfully with economic steam/oil ratios (SORs) in areas with up to 4 m of bottomwater by injecting significantly larger steam slugs in what is termed a drive, block, and drain process. In thicker bottomwater, the ability to operate at constant pressure to prevent bottomwater influx confers an advantage on the horizontal well approach. Follow-up field-scale developments of some bottomwater areas are described. Numerical simulation results indicate that pressuring up of a depleted steamflooded zone is an optimum strategy for maximizing offset flank recovery. This is being implemented in the field by reinjecting produced vent gases.
Fractured-Well-Test Design and Analysis in the Presence of Non-Darcy Flow
Authors: Gil J. A. , Ozkan E. , Raghavan R. 
Published: December 2007

Summary
The objective of this paper is to discuss the design and analysis of fractured-gas-well tests to account for non-Darcy flow within the fracture. The results and discussions are based on a semianalytical model. Guidelines and correlations are presented to enable engineers to design fractured-well tests whereby the magnitude of non-Darcy flow may be estimated and its effect minimized, if necessary. The effect of non-Darcy flow skin (or rate-dependent skin) is discussed in detail. A method is also presented to analyze fractured-well tests under non-Darcy flow conditions to estimate the non-Darcy flow coefficient, fracture conductivity, and reservoir properties. Unlike the conventional methods, this method does not require two tests at different production rates.
IMPES Stability: Selection of Stable Timesteps
Authors: Coats K. H. 
Published: December 2007

SummaryAn IMPES stability criterion is derived for multidimensional three-phase flow for black-oil and compositional models. The grid may be structured or unstructured. Tensor considerations are neglected. The criterion can be used to set the time steps in an IMPES formulation or as a switching criterion in an adaptive implicit model.The criterion extends previous work by accounting for three-phase flow, including capillary, gravity, and viscous forces, with all the possible cocurrent and countercurrent flow configurations in a general grid. The criterion derivation uses stability theory to the limits of its applicability, augmented by numerical experimentation, including extensive 1D tests and numerous field study datasets.
Evaluation of Monte Carlo Methods for Assessing Uncertainty
Authors: Liu Ning , Oliver Dean S. 
Published: December 2007

SummaryUncertainty in future reservoir performance is usually evaluated from the simulated performance of a small number of reservoir models. Unfortunately, most of the methods for generating reservoir models conditional to production data are known to create a distribution of realizations that is only approximately correct. In this paper, we evaluate the ability of the various sampling methods to correctly assess the uncertainty in reservoir predictions by comparing the distribution of realizations with a standard distribution from a Markov chain Monte Carlo method. The ensemble of realizations from five sampling algorithms for a synthetic, 1D, single-phase flow problem were compared in order to establish the best algorithm under controlled conditions. Five thousand realizations were generated from each of the approximate sampling algorithms. The distributions of realizations from the approximate methods were compared to the distributions from the exact methods. In general, the method of randomized maximum likelihood performed better than other approximate methods.
A Natural Polymer-Based Cross-Linker System for Conformance Gel Systems
Authors: Reddy B. R. , Eoff Larry , Dalrymple E. Dwyann , Black Kathy , Brown David , Rietjens Marcel 
Published: December 2007

SummaryThis paper describes a material derived from natural sources that can be used to crosslink a variety of acrylamide-based polymers over a broad temperature range to produce gels for conformance applications.Delayed crosslinked polymer systems have been used for many years in conformance applications. For the past decade, the most widely used system has been based on chromium (3+) crosslinked polyacrylamide. Organic crosslinkers, such as phenol/formaldehyde and polyethyleneimine (PEI) have also been used with a variety of polymers. However, these systems are being scrutinized by governmental agencies and have been scheduled for phaseout in some countries. Because of these issues, a single, environmentally friendly crosslinker that could be used with a variety of polymers over a broad temperature range was the focus of this study.This paper details the laboratory development of an environmentally friendly, natural polyamine crosslinker system. This crosslinker can be used with a variety of polymers, such as polyacrylamide, AMPS/acrylamide, or alkylacrylate polymers. Gels ranging from stiff and "ringing" type to "lipping" gels have been obtained. The data illustrate a simple, commercially available system that can be applied to field operations. Potential crosslinking mechanism(s) of the system will be discussed.
Thickening Carbon Dioxide With the Fluoroacrylate-Styrene Copolymer
Authors: Xu Jianhang , Wlaschin Aaron , Enick Robert M. 
Published: December 2007

Summary
The fluoroacrylate-styrene copolymer is the first associative thickener that has been identified for carbon dioxide. Fluoroacrylate is highly carbon dioxide-philic, enhancing the solubility of the copolymer in carbon dioxide. Styrene is relatively carbon dioxidephobic, but promotes viscosity-enhancing, intermolecular associations. The copolymer used in this study had a composition of 29 mol% styrene - 71 mol% fluoroacrylate, a number-average molecular weight of 540,000, and a polydispersity index of 1.63. The copolymer was sufficiently soluble in CO2 at typical reservoir flooding conditions to induce a significant increase in viscosity. Falling cylinder viscometry measurements at 298 K demonstrated that the viscosity enhancement of CO2 increased with increasing copolymer concentration, decreasing shear rate, and decreasing temperature. Mobility measurements of the fluoroacrylate-styrene copolymer-CO2 solutions flowing through 80 to 200 md Berea sandstone cores at superficial velocities of 0.00035 to 0.028 cm/s (1-80 ft/D) at 298 K also indicated that the copolymer was an effective thickener. At a superficial velocity of 0.00035 m/s (1ft/ D), the addition of 1.5 wt% copolymer increased the CO2 viscosity by a factor of 19 relative to neat CO2. Smaller increases in viscosity occurred at lower copolymer concentrations and higher velocities. These results demonstrate that it is possible to design a compound that can enhance the viscosity of dense carbon dioxide. Fluoropolymers are characterized by environmental persistence, high cost, and unavailability in bulk quantities, however. Therefore nonfluorous, inexpensive thickeners are currently being designed.
Mechanisms of Mineral Scale Inhibition
Authors: Tomson M. B. , Fu G. , Watson M. A. , Kan A. T. 
Published: December 2007

SummaryAn extensive study of adsorption and desorption isotherms of four phosphonates on barite or calcite are tested for a wide range of solution conditions (0 to 1 M NaCl, 0 to 0.1 M Ca, 0 to 0.33 M sulfate, and 4.6 to 6.4 pH). From these adsorption/desorption observations, it is proposed that the primary driving force for adsorption is related to simple hydrophobic repulsion from solution of a macroneutral molecule and not, as is generally presumed, some specific inhibitor-surface interaction. From the nucleation study, it is observed that the inhibitor needed to completely inhibit barite formation is approximately equal to 16% surface coverage. An equation to predict minimum inhibitor need is proposed based on this model and is compared with field observations. The range of predicted inhibitor concentrations is quite similar to what is observed in the field as a minimum effective dose even though it was derived by a completely independent calculation method.
Zero-Tolerance Program To Enhance Safety Awareness During Well-Service Jobs
Authors: Farooqui Mohammad A. , Saudi Mohamed M. , Al-Ghurairi Fadhel A. , Blanke Allen T. 
Published: December 2007

SummarySaudi Aramco has implemented an effective program to emphasize safety during the increasingly complex, rigless well-service jobs in its maturing oil fields and during development activities in its new gas fields. The need was heightened for a structured approach to safe execution of well-service jobs because of the increasing number of horizontal well completions, which pose a higher risk and require greater logistical support during rigless jobs, and the initiation of an aggressive deep gas development program.The objective of the Zero-Tolerance Program is to complete all well-service jobs without incident, injury, or loss of resources while maximizing benefits and gaining knowledge to sustain the process of continuous employee development.The program comprises four basic elements.Human resources development. Planning. Safe and effective job execution. Post-job evaluation for continued excellence.Although production engineers (PEs) generally follow various guidelines and procedures covered under these categories, the Zero-Tolerance Program has placed these critical factors in a formal, structured document to ensure effective and consistent implementation.This paper covers details of these elements and discusses tracking and accountability procedures that ensure the program is effectively implemented. Aggressive implementation of this structured program among field personnel has greatly enhanced the awareness of safety-related issues during rigless well-service operations.
A Rigorous Formation Damage Skin Factor and Reservoir Inflow Model for a Horizontal Well
Authors: Furui Kenji , Zhu D. , Hill A. D. 
Published: December 2007

Summary
In this paper, we present a new analytical model for formation damage skin factor and the resulting reservoir inflow, including the effect of reservoir anisotropy and damage heterogeneity. The shape of the damaged region perpendicular to the well is based on the pressure equation for an anisotropic medium and, thus, is circular near the well and elliptical far from the well. The new model can be used for various distributions of damage along the well, depending on the time of exposure during drilling and completion. The inflow equation for a damaged, parallel-piped-shape reservoir illustrates the importance of the ratio of the reservoir thickness to the drainage length perpendicular to the well on the influence of formation damage for horizontal well productivity. Our model gives a simple, analytical expression for determining this effect.
A Strategy for Attacking Excess Water Production
Authors: Seright R. S. , Lane R. H. , Sydansk R. D. 
Published: December 2007

SummaryThis paper describes a straightforward strategy for diagnosing and solving excess-water-production problems. The strategy advocates that the easiest problems should be attacked first and that diagnosis of water production problems should begin with the information already at hand. A listing of water-production problems is provided, along with a ranking of their relative ease of solution. Although a broad range of water-shutoff technologies is considered, the major focus of the paper is when and where gels can be effectively applied for water shutoff.