bluuebunny/crossref_metadata_2025 huggingface dataset:
A Model To Assess Economic Feasibility And Optimum Prod. Volume
Authors: MARKS R.
Published: December 2007

The State of Alaska's revenue forecasting model computes the economic rent of prospective fields to assess whether or not they are feasible to produce given price and volume scenarios. When economic rent is negative production is delayed until a start-up year generating a positive rent is found. If economic rent is positive the model finds the profit maximing amount of enhanced recovery.

Introduction

The Department of Revenue of the State of Alaska is responsible for forecasting the State's revenue for planning and budgeting purposes. Petroleum revenues. accounted for $2.7 billion in fiscal year (FY) 1985 (July 1984 – June 1985), 84 percent of the total State revenue. These took the form of severance taxes, royalties, corporate income taxes, property taxes, bonuses, rents, and intergovernmental receipts. Eighty-eight percent of these petroleum revenues were derived from either severance taxes (both production and conservation taxes, the latter being very small), or royalties.

Nearly all oil revenues accrue from the North Slope. The very mature Cook Inlet fields are relatively insignificant from a revenue standpoint.

The petroleum production revenue forecasting model is designed to calculate oil and gas severance taxes and royalty payments due each year to the State of Alaska under provisions of existing State laws and contracts.

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Analytic Two-Dimensional Models of Water Cresting Before Breakthrough for Horizontal Wells
Authors: Giger François M.
Published: December 2007

Production with horizontal wells offers a new approach to reducing water-coning effects during oil production. This paper evaluates what effect water cresting under a horizontal well will have and determines the critical flow rate by fully analytic, two-dimensional (2D) methods developed in a vertical plane perpendicular to the axis of the horizontal well. Three production mechanisms are considered: lateral edge drive, gas-cap drive, and bottomwater drive. The theory gives the critical flow rate value in each case. A major achievement of this theory is the proof of a decreasing critical flow rate value with cumulative production by the bottomwater-drive mechanism. Results are presented in graphs for quick use. Case studies exemplify a simple evaluation method to help solve practical engineering problems.
A Laboratory Evaluation of Core-Preservation Materials
Authors: Auman J. B.
Published: December 2007

This paper documents the results of a laboratory study of the effectiveness of available state-of-the-art core-preservation materials. The ability of the core-sealing material to prevent postpreservation changes in fluid saturations may have a profound effect on subsequent laboratory measurements. Considering the expense involved in obtaining, storing, and analyzing a native-state (oil-cut) core and the purpose for which it was cut, knowledge of exactly what materials can adequately preserve a core until laboratory measurements are made is critical and should not be overlooked. In this laboratory study, saturated Berea sandstone core plugs were preserved in a number of commonly used sealing materials. The sealed plugs were then stored in a humidity-controlled environment and periodically weighed to ascertain the degree of change that had occurred in the saturation of the plug. In addition, this paper discusses and suggests procedures for applying the recommended sealing material.
Effect of Overburden Pressure and the Nature and Microscopic Distribution of Fluids on Electrical Properties of Rock Samples
Authors: Longeron D. G. , Argaud M. J. , Feraud J. -P.
Published: December 2007

Laboratory equipment aimed at determining the exact correlation between resistivity and water saturation under stress, pressure, and temperature conditions is described in the first part of this paper. The porous-plate method adapted to reservoir conditions is used to obtain different saturation values during both drainage and imbibition. With this equipment, the influence of the effective stress on the porosity and formation resistivity factor can be studied before the test. In the second part of this paper, the values of the formation resistivity factor and resistivity index are compared for water-wet samples from sandstone and carbonate reservoirs. These measurements indicate that the influence of the effective stress depends on the nature of the rock sample. In addition, the resistivity/water-saturation law depends on the direction of the saturation change (drainage or imbibition) and on the nature of the fluids (water/oil or water/gas).
Performance Improvement of Direct- and Indirect-Fired Heaters
Authors: Sams G. W. , Hunter J. D.
Published: December 2007

The operating performance of direct and indirect heaters is discussed, and principles and guidelines that can be applied to effect improvements in efficiency are presented. This paper also discusses the associated heater efficiencies and several useful operating techniques to approach the maximum, steady-state heater efficiency. The techniques presented apply to all types of direct- and indirect-fired heaters: salt bath heaters, propane vaporizers, heater/treaters, production heaters, and glycol and amine regenerators.
Fluid Distribution and Reservoir Characteristics of the Big Piney Mesaverde Reservoir, Wyo.
Authors: Miles F.V. , Pedersen J.A.
Published: December 2007

The text presents an approach used to evaluate a productive reservoir whose hydrocarbon accumulation is under hydrodynamic control. The fluid, rock and structural factors that control the distribution of the fluids and their flow characteristics have been studied. Potentiometric and structural information have been utilized to determine the limits of the hydrocarbon accumulation and its qualitative relationship with structure. A comparison is made of predicted and actual gas-oil and oil-water contacts. The oil column was divided into two producing intervals, and capillary-pressure and relative-permeability data were utilized to evaluate their fluid distribution and transmissibility.

Introduction

One of the main problems to be solved in evaluating a hydrocarbon reservoir is determining the fluid interfaces and their relationship with structure. This is especially vital in reservoirs where the hydrocarbon accumulation is under hydrodynamic control. The purpose of this paper is to report an approach used to determine the distribution and structural relationship of the gas, oil and water phases in the Big Piney Mesaverde reservoir, Sublette County, Wyo. In conjunction with this study, potentiometric data have been utilized to evaluate entrapment, and a study has been made of the rock and fluid properties of the reservoir which are related to saturation distributions and flow mechanics. The Big Piney Mesaverde reservoir lies approximately 100-miles northwest of Rock Springs, Wyo. The field was discovered in Aug., 1957, by the Gulf No. 1 Tresner State well located in the SW-NW Section 36–29N–113W (see Fig. 1) which produced gas and oil during drill-stem testing. Selective tests during completion in the gas and oil columns resulted in indicated capacities of 9.5 MMcf/D and 118 BOPD, respectively. The discovery was confirmed by Belco Petroleum Corp.'s completion in Jan., 1958, of Well B–34. Initial development in the field showed that the oil column possessed a low productive capacity; this subsequently was attributed to a combination of circumstances, including a low reservoir temperature, a relatively high pour-point oil and low matrix permeability. No particular difficulty was observed in producing free gas. Due to this situation, only 17 wells were completed within two years after discovery. In June, 1959, development was stimulated when Gulf Oil Corp. introduced notch-fracing, and 40 wells had penetrated the reservoir by the end of 1960. To date, production has been curtailed by market restrictions and the need of conserving gas-cap energy; however, as of Jan., 1961, the field had produced approximately 740,000 STB of oil, 1,760 MMcf of separator gas and negligible volumes of water. Fig. 1 is a plat of the producing area showing the limits of development drilling to Jan. 1, 1961, and the areal distribution of the hydrocarbons.

Geology

The Big Piney Mesaverde reservoir lies on the LaBarge Platform, a major structural feature on the west edge of the Green River basin.

JPT

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Effect of Cleavage Rate and Stress Level on Apparent Surface Energies of Rocks
Authors: Perkins T.K. , Krech W.W.
Published: December 2007

As fractures are propagated through rocks, energy is absorbed near the extending crack tip. Apparent surface energies for several rocks have been measured by cleavage under dynamic conditions. At nominal crack velocities from 0.5 to 500 in./min. measurements showed that fractures propagated in discrete jumps. Calculated surface energies and moduli were relatively insensitive to nominal rate of cleavage.

In another set of experiments, rocks were cleaved under high confining stresses. The rocks were submerged in low leak-off fluids which formed a filter cake on the freshly cleaved surfaces (similar to the hydraulic fracturing process). Apparent surface energies were increased substantially as the surrounding fluid pressure was increased. Moduli in bending increased significantly upon application of the first 1,000 psi but were insensitive to stress level at greater pressures.

INTRODUCTION

For almost 20 years, hydraulic fracturing processes have been utilized effectively to stimulate oil and gas wells. During this period, some process improvements have resulted from studies of fracture orientation, mechanics of fracturing, areas generated, conductivities of cracks, etc. Yet many questions remain concerning the conditions and pressures needed during fracture propagation.

In this paper we will report additional studies of the mechanics of fracture extension. It was shown previously3 that large rock samples could be cleaved under controlled conditions so as to measure the apparent surface energy (that amount of energy absorbed per unit area of new surface created). In this paper we consider the effects of two additional factors on surface energies, viz.:effect of cleavage rate andeffect of confining stress level.

THEORY

Cleavage experiments were conducted on rock samples similar to that illustrated in Fig. 1. Blocks of rock several inches wide, 2- to 3-in. thick, and up to 3 ft in length were grooved longitudinally with shallow guide slots. A crack was initiated and allowed to extend along the web as the top of the rock specimen was pulled (or pushed) apart. Auxiliary equipment permits the measurement offorce applied at the top,separation at the top andcrack length.

(Further experimental details will be given in the next section.) The rock beams created by the crack are considered to' be cantilever beams. The deflection (or separation of the rock beams) at any point is calculated4,5 by the beam Eq. 1.
A Polynomial Approach to the van Everdingen-Hurst Dimensionless Variables for Water Encroachment
Authors: Klins M. A. , Bouchard A. J. , Cable C. L.
Published: December 2007

Traditional water-influx calculations rely on accurate values of the van Everdingen and Hurst dimensionless variables pD and qD. We have presented six sets of simple polynomials that provide a fast, simple method to determine pD, pD’, and qD for finite or infinite radial aquifers. The results yield values as accurate as the original tables and are up to 15 times more efficient.
Mechanisms of Foam Generation in Glass-Bead Packs
Authors: Ransohoff T. C. , Radke C. J.
Published: December 2007

The fundamental, pore-level mechanisms of foam generation are investigated in monodisperse bead packs. First, direct visual observations identify the following generation mechanisms: lamella leave-behind, gas-bubble snap-off, and lamella division. Then, to ascertain the relative importance of these mechanisms, quantitative experiments are pursued on the role of bead- pack permeability (bead sizes from 0.25 to 1 mm [0.01 to 0.04 in.]), gas-phase velocity (0.001 to 0.8 cm/s [0.0004 to 0.3 in./sec]), gas-phase fractional flow (0.60 to 1.0), permeability variations, and surfactant type [sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), Chevron Chaser SD1000™, and Suntech IV 1035™]. We discover a critical velocity, above which a "strong" foam is generated and below which only "weak" foam is formed. The snap-off mechanism is the primary mechanism responsible for the formation of the strong foam. A simple model, based on the concept of a "germination site," is developed to predict the onset of snap-off at higher gas velocities. New experimental data obtained in the homogeneous glass-bead packs for the critical capillary number necessary to form a strong foam are in excellent agreement with the proposed germination- site model.
North Sea Development Drilling, South East Forties: A Case Study
Authors: Denholm J. M.
Published: December 2007

The development of the South East Forties field began in July 1984, when a 16-slot subsea template was transported to location and installed by the semisubmersible drilling vessel (SSDV) Sedco 707. Thereafter, 14 subsea development wells were drilled before the installation of a minimum-facilities jacket, to which the wells would be tied back and completed. This field development was identified as an ideal candidate for the optimization of the drilling operation. The result of this optimization campaign was a significant reduction in well-drilling times and associated costs.
Designing Well Paths to Reduce Drag and Torque
Authors: Sheppard M. C. , Wick C. , Burgess T.
Published: December 2007

A deviated well with an undersection trajectory (i.e., a trajectory lying below the conventional tangent section and constantly building to target) can exhibit lower drag and torque than a conventional well geometry in certain circumstances. The influence of well geometry on drag and torque is discussed, making use of the results of the theoretical model. Although an undersection well may have a reduced overall drag, the side forces in the drill collars will be increased. This can lead to a greater danger of sticking in the bottomhole assembly (BHA). Furthermore, because of the enhanced side forces near the bit, an undersection well may also exhibit greater torque. The relative merits of constant-build and catenary trajectories are discussed.
Analysis of Borehole Images and Their Application to Geologic Modeling of an Eolian Reservoir
Authors: Plumb Richard A. , Luthl Stefan M.
Published: December 2007

New wellbore imaging techniques significantly enhance geologic descriptions of reservoirs. These new techniques include electrical images formed by the Formation MicroScannerSM (FMS) tool and acoustic images made by a digital borehole televiewer tool (BTT). Quantitative image-analysis software is described that provides strike and dip measurements of tectonic and sedimentary structures and the orientation of the contemporary stress field. This software was used to map geologic features from images acquired in a North Sea reservoir. Quantitative geologic models constructed from these image data highlight the interrelated effects that fractures, anisotropic stress, and bedding may have on the directional permeability in this reservoir.
An Experimental Investigation of Fatigue-Crack Growth in Drillstring Tubulars
Authors: Dale B. A.
Published: December 2007

Drillstring failures continue to plague the oil industry, often costing millions of dollars each year. This problem is frequently intensified with the drilling of deep, deviated wellbores or "hard rock" drilling conditions. The drilling industry attempts to guard against these costly failures by performing periodic nondestructive inspections to remove damaged tubulars from service. This paper describes the results of full-scale fatigue-crack-growth tests of drill collars under rotating and bending loads. In addition, corrosion fatigue-crack-growth data are also presented for API drillpipe steels in air and in three representative water-based drilling-fluid environments. Based on this experimental investigation. the test data support the practical application of fatigue-crack-growth mechanics principles for the development of nondestructive inspection intervals to reduce drillstring failures.
A Study of Excitation Mechanisms and Resonances Inducing Bottomhole-Assembly Vibrations
Authors: Besaisow Amjad A. , Payne Mike L.
Published: December 2007

This paper presents a study of important excitation mechanisms and resonances that cause bottomhole assembly (BHA) vibrations during drilling operations. The study is based on dynamic vibration data gathered in a test well with our Advanced Drillstring Analysis and Measurement System (ADAMS) surface measurement system. The data were gathered while three different BHA's were used to drill portions of this well to 800 ft [244 m]. A case study for a large-diameter hole in an actual field well is also presented.

The data showed many velocity-dependent excitation mechanisms, including 1×ω, 2×ω, 3×ω, a drillstring walk mechanism, and drillstring whipping mechanisms that were dependent on the drillstring and hole geometries. The data also show important resonances that may be excited, including resonances with strong local contributions, and axial and torsional resonances. When the excitation mechanisms match these resonances, damaging vibrations can be induced.

This study identifies the presence of more fundamental excitation mechanisms than the l×ω and 3×ω mechanisms. These should be used in models that predict drillstring and BHA vibrations. The study also shows important resonances that should be considered when BHA vibrations are predicted.
Rubber Drillpipe Protectors Reduce Rotary Torque
Authors: Corbett Kevin T. , Dawson Rapier
Published: December 2007

Rubber drillpipe protectors have very low friction coefficients when they rotate against smooth or polished casing surfaces in drilling mud. A polished casing surface can be obtained by placing one protector on each joint of drillpipe run inside the casing. In this situation, casing polishing will occur in the course of normal drilling, and the resultant low friction coefficients will lead to reduced drilling torque in directional wells.

The friction coefficient between casing and drillpipe protectors is controlled by the roughness of the casing surface. Coefficients range from 0.50 for badly rusted casing to 0.05 for a polished surface. The smooth casing surface needed for low friction will be obtained during 50 to 100 hours of rotation with drillpipe protectors inside the casing. A field test of this concept gave friction coefficients below 0.10 and a significant reduction in drilling torque.
Skjold Field, Danish North Sea: Early Evaluations of Oil Recovery Through Water Imbibition in a Fractured Reservoir
Authors: Oen P. M. , Engell-Jensen M. , Barendregt A. A.
Published: December 2007

This paper reviews the performance of a fractured chalk oil reservoir in its first 3 years of production and evaluates future development options. The relatively low degree of undersaturation of the oil required that evaluations of pressure-maintenance potential be made early in the field’s life. To this end, many performance data have been collected, primarily through the use of observation wells. The performance data [pressures and free-water level (FWL) in fractures] are presented and their evaluation is described. In particular, the evaluation of the oil production performance through water imbibition is discussed. This evaluation has led to the initiation of pressure maintenance through water injection.
Re-Evaluation of Solvent Requirements for a Hydrocarbon Miscible Flood
Authors: Asgarpour S. , Singhal A. K. , Card C. C. , Wong T. W. , Springer S.
Published: December 2007

The required slug size for a patterned hydrocarbon miscible flood in the Upper Devonian reef at Fenn-Big Valley, central Alberta, was computed on the basis of dispersion/diffusion calculations at the leading and trailing edges of the solvent slug. This slug size included consideration of microscopic heterogeneities and a safety factor so that sufficient slug remained to ensure miscibility. This calculated slug size formed the design basis for a pilot experiment in part of the pool. After 3 years of pilot operation, sufficient performance and tracer results were available to enable a re-evaluation of the design basis. The motivation behind re-evaluation was to extend the recovery process to a much larger part of the pool.

Whereas local heterogeneities and transport considerations indicated that a moderate slug size (6% HCPV) was required, regional and interwell heterogeneities, flooding patterns, and geometry of flood propagation indicated that about twjce this slug size was needed. Because of this, it was concluded that the realistic design basis for a field-scale project must fully consider regional and interwell heterogeneities. This paper deals with the supporting data and procedures used in developing the revised design basis for the project.
Fluid-Velocity and Reaction-Rate Effects During Carbonate Acidizing: Application of Network Model
Authors: Hoefner M. L. , Fogler H. S.
Published: December 2007

Coreflood experiments were performed and a network model developed to study flow and matrix dissolution in carbonates during acidizing treatments. Wormholing in carbonates is controlled by the relative rates of flow and dissolution, which are characterized by a Damköhler number, NDa, for the process. Acid penetrates only as a result of wormholing, and well-defined channels will not form if NDa is either very high or very low. Effects of acidizing differ markedly between limestone and dolomite because of differences in the mineral dissolution rates.
Interference Testing: Detecting a Circular Impermeable or Compressible Subregion
Authors: Grader Abraham S. , Horne Roland N.
Published: December 2007

A practical consideration of the effects of a single, circular, heterogeneous reservoir subregion on interference transient pressure testing is presented. The production well and the observation wells are external to the circular subregion. The internal circular boundary is considered as a constant-pressure source or as an impermeable subregion. The constant-pressure subregion has significant effects on interference pressure responses regardless of the size of the subregion. Ignoring the presence of a neighboring compressible portion of the reservoir, such as a gas or a steam cap, may yield erroneously high storativities and transmissivities. Multiple interference tests may suggest the probable location of the gas cap. The effects of an impermeable subregion are subtle, and in some cases, large, impermeable portions of the reservoir may not be detected by neighboring interference wells. Some interference tests in the presence of an impermeable subregion may yield high values of reservoir storativities, stemming from a pressure response similar in shape to the line-source response. A map of the positions of interference wells that do not permit the detection of an impermeable subregion is presented.
Design Criteria for Completion of Steam Injection Wells
Authors: Willhite G. Paul , Dietrich William K.
Published: December 2007

Casing failure in production wells stimulated with steam is a serious economic limitation in the application of steam injection to accelerate oil production from viscous reservoirs. This paper discusses the causes of casing failures and develops design criteria for completion and stimulation of new and existing wells. Casing failure occurs initially when temperature-generated compressive stresses exceed the yield strength of the casing. This forces the casing material or joint to permanently deform during the steam injection period. Subsequent cooling while the well is shut in or producing relieves the compressive stress. However, the deformation induced during steam injection creates a tensile stress as the casing temperature returns to its normal level. Often this tensile force buildup results ill joint failure by fracture or pullout. The mechanisms of casing failures are discussed in detail to provide a basis for selecting safe casing temperature changes for any well completion. Design criteria derived from these mechanisms are proposed as guidelines for the safe stimulation of old wells and the completion of new wells specifically for high temperature steam injection. Field experience is presented to confirm the utility of these guidelines for the protection of casing in productions wells stimulated with steam.

Introduction

Steam stimulation of production wells can subject the casing to high thermal stresses. Casing failures after first-cycle steaming have been numerous, particularly in areas where the injection temperatures are greater than 500F. At least 30 casing failures have been verified in California steam stimulation projects. Failures have also occurred in the Mid-Continent area from Texas to Wyoming. Generally, failures are found in the joint, although a few instances of collapse have been reported.

Discussion

Joint failure is a symptom rather than the cause of mechanical problems in steam injection wells. As the caring is heated it will normally tend to elongate in direct proportion to the change in temperature. Since some length of casing in most wells is not free to elongate, the tendency to elongate is replaced by compressive stress buildup in the casing. What happens to the casing can be understood if the behavior of a typical casing during a steam injection-production cycle is considered. The pipe body and the joint are assumed indistinguishable and both will be termed "the casing". Fig. 1 is a stress-temperature change diagram for casing heated in a steam injection well assuming that the initial stress is zero. Path A-B is the elastic portion of the compressive stress T curve. For plain carbon steels the compressive stress generated by thermal expansion forces is about 200 T psi.
Drag-Bit Performance Modeling
Authors: Warren T. M. , Sinor A.
Published: December 2007

Models for the forces required to remove a fixed volume of rock with a single cutter have been applied to different polycrystalline-diamond-compact (PDC) bit designs. The integration of the forces for each cutter over the bit face gives the torque and weight on bit (WOB) required for a particular rate of penetration (ROP). This paper presents the results of comparing such a model to laboratory drilling tests for four radically different bit designs in four different rocks. The geometry of each cutter on the bit was determined by detailed measurements of the bit with a three-axis coordinate measuring machine. Drilling tests were conducted by "reaming" rock with an 8½-in. [21.6-cm] bit that was previously drilled with a 6¼-in. [15.9-cm] bit. Only the peripheral cutters engaged the rock during reaming. Additional tests were conducted in which the WOB and torque were recorded during drilling of a pilot hole into the top of a flat rock and during drilling through two different bed boundaries with constant ROP. The model predictions compared well to the measured data for both the reaming and pilot-hole tests.
A Material-Balance Method for Deriving Interblock Water/Oil Pseudofunctions for Coarse-Grid Reservoir Simulation
Authors: Starley G. P.
Published: December 2007

This paper describes a material-balance method for deriving interblock water/oil pseudofunctions for application in coarsely gridded areal reservoir models. The method is shown to be effective in pattern waterflood simulation. This technique differs from previous methods in (1) explicitly accounting for grid orientation by deriving directionally dependent pseudos, (2) combining a dispersion control scheme with the pseudofunction derivation, and (3) matching fractional flow in pattern models through a material balance. The pseudofunctions are derived from fine-grid pattern models and account for various effects, including anisotropic formation properties, dominant displacement forces (viscous or gravitational), and correction for preferential directional flow.
Steady-State and Unsteady-State Flow of Non~Newtonian Fluids Through Porous Media
Authors: Van Poollen H.K. , Jargon J.R.
Published: December 2007

Non-Newtonian fluids may be injected into a reservoir during secondary recovery operations. The non-Newtonian fluid used in this work is a power-law type of fluid; that is, the viscosity of the fluid decreases as the flow rate or rate of shear increases.

This paper presents equations for steady-state, linear and radial flow of such fluids, transient behavior results from a finite difference model of a radial system, and transient behavior results from a field test.

The equations that describe the flow of a non-Newtonian fluid are non-linear and are solved numerically. Finite difference solutions are presented as curves of dimensionless pressure drop at the wellbore vs dimensionless time for a constant injection rate. Solutions were obtained for 5-percent, 10-percent and 100-percent PV of a non-Newtonian fluid for injection rates of 1, 10, 100 and 1000 cc/sec and for a 5 percent PV of non-Newtonian fluid located at r = rw, 3, 10, 20, 50 and 100 ft for a flow rate of 1 cc/sec. The buildup curves do not exhibit a straight-line portion as is the case for Newtonian flow through porous media.

Correlations also are shown for the productivity index vs rate for the computer model study and the field tests.

INTRODUCTION

During various secondary recovery operations non-Newtonian fluids are injected. Such fluids, in general, include thickened water and gelled fluids. The term "non-Newtonian" implies that the viscosity is not only dependent upon temperature and pressure, but also on the rate of shear that is applied to the fluid. For example, water, which is a Newtonian fluid, will have essentially the same viscosity no matter what rate of shear is applied. A pseudoplastic fluid exhibits a decreasing viscosity when higher rates of shear are applied; a dilated fluid has an increasing viscosity with increasing rates of shear.

The objective of studies performed and described in this report is to obtain relationships and mathematical and empirical descriptions of the flow of non- Newtonian fluids through porous media. Simple mathematical relationships, computer studies that include the unsteady- state behavior of such fluids, and field tests are used.

PREVIOUS LABORATORY STUDIES

Laboratory studies have been performed by several investigators. The fluids used in one investigation1 were surfactant-stabilized dispersions of water in hydrocarbons. Its Fig. 6 is reproduced as our Fig. 1. This effective-viscosity vs frontal-velocity diagram shows that this fluid is of the power-law type over a fairly large range of frontal velocities. Gogarty1 developed an equation for the effective viscosity as a function of shear rate that reduces to Eq. 2 for frontal velocities greater than about 2 ft/D. The fluid characteristics used in the present study are similar to those reported by Gogarty.
Comparative Study of Eight Equations of State for Predicting Hydrocarbon Volumetric Phase Behavior
Authors: Ahmed Tarek H.
Published: December 2007

The objective of this study is to present a review of eight equations of state (EOS’s) and compare their ability to predict the volumetric and phase equilibria of gas-condensate systems. Included in the study are the Peng-Robinson (PR), the Soave-Redlich-Kwong (SRK), the Schmidt-Wenzel (SW), the Usdin-McAuliffe (UM), the Heyen, the Kubic, the Adachi-Lu (AL), and the Patel-Teja (PT) EOS’s. The SW equation exhibits a superior predictive capability for volumetric properties of condensate systems. The PR equation is found to represent the phase equilibrium behavior of condensate systems accurately. In terms of compressibility factors, the SW and PT equations give better predictions than other equations.
EOS Predictions of Compressibility and Phase Behavior in Systems Containing Water, Hydrocarbons, and CO2
Authors: Flroozabadl A. , Nutakkl R. , Wong T. W. , Aziz K.
Published: December 2007

Two cubic equations of state (EOS) have been adopted to compute multicomponent two-phase compressibility, CO2/water and hydrocarbon/water phase behavior, and gas- and liquid-phase densities. The equations used in this paper are the Schmidt-Wenzel (SW) EOS and the Peng-Robinson (PR) EOS. While these cubic equations have the same form, the SW is reported to be more accurate for predicting hydrocarbon gas- and liquid-phase densities. Density predictions are compared with experimental data to confirm the superiority of the SW EOS.

The use of EOS to predict equilibrium phase compositions of water/hydrocarbon and water/CO2 systems is discussed. For the water/hydrocarbon systems, the aqueous-phase interaction coefficient between water and the dissolved component shows a strong temperature dependency, while in the gas phases, a constant value of interaction coefficient is adequate. In the case of the CO2/water systems, the interaction coefficients for both the aqueous and gas phases show temperature dependency.

A scheme to compute the two-phase compressibility of multicomponent reservoir fluid systems is also introduced. Our results show the expected sharp change in the compressibility during phase change. Such computations are required in some reservoir simulators.
Bottomwater Drive in Tarmat Reservoirs
Authors: Al-Kaabi Abdul Aziz , Menouar Habib , Al-Marhoun Muhammad Ali , Al-Hashim Hasan S.
Published: December 2007

This paper addresses the class of tarmat reservoirs subject to bottomwater drive. Different shapes of tar layers are simulated physically and numerically to study the behavior of WOR and oil recovery.

Four different cases were studied: a square barrier beneath the well, a disk beneath the well, a hollow square or disk beneath the well, and a half plane. The results showed that breakthrough time occurs earlier in the case of hollow tarmat barriers, while it is delayed considerably in the case of tarmat barriers shaped in the form of a disk beneath the well. Paradoxically, in this last case, the WOR increases more rapidly and becomes higher toward the end of the depletion than in any other case. Among all the cases studied, the no-barrier case gives the highest recovery, while the hollow-tarmat-barrier case leads to the lowest recovery.
Enhanced Water Recovery Improves Stimulation Results
Authors: Ford William G. F. , Penny Glenn S. , Briscoe James E.
Published: December 2007

The effects of capillary pressure, wettability, and relative permeability in controlling load water recovery following hydraulic-fracturing treatments have been examined. Laboratory studies have indicated that the alteration of wettability to control capillary pressure and/or relative permeability can promote a rapid, thorough cleanup of injected water. Field applications of these concepts have resulted in enhanced load water recoveries and higher production because of longer effective fracture lengths and/or higher effective fracture conductivities after treatment cleanup.
The Outlook for Louisiana's Offshore Production
Authors: McCollum S.V.
Published: December 2007

Statistics Reflect Erratic Growth

The offshore area offers more challenge, more promise, more problems, more heartaches and more disappointments than any other oil and gas producing region in the world.

The growth and development in the offshore area of Louisiana has been a series of ups and downs, as verified by figures on the active drilling rigs running in the Gulf of Mexico since 1947.

From 1947 until the early part of 1953, there was a period of "no leasing". In early 1953, there were approximately 10 rigs running seaward from the Chapman line. There was a steady increase in drilling operations up to the middle of 1956, when the U.S. Supreme Court issued its injunction that shut down everything within the disputed area.

When the agreement between Louisiana and the Federal Government was reached, the number of rigs operating increased to 106. This peak period, with over 100 rigs operating, lasted until the latter part of 1957. The operators then decided that it would be wise to shut down and "look at their hole card"; maybe offshore drilling was not the "economic plum" they had thought. This offshore recession lasted until the latter part of 1958, when the operators began a cautious recovery climaxed by the sale in Feb., 1960.

As of April 1, 1960 (according to industry statistics), there had been 3,091 wells drilled in the offshore Louisiana area. Of these, 1,799 were completed as oil wells, 418 as gas wells and 874 (or 28.3 per cent) were dry. Production of oil and condensate is approximately 226,000 B/D, and gas production is averaging 909 MMcf/D.

At the present time, there are approximately 3,375,000 acres under lease, with an accumulative investment in this acreage of $616,266,000. At the last offshore lease sale held Feb. 24, 1960, 454,046 acres were sold for $246,379,283. Left on the table was $133,078,895.
Artificial Lift in the Montrose Field, North Sea
Authors: Jacobs E. G.
Published: December 2007

Electric submersible pumps (ESP's) have been in operation in the Montrose field since 1979. Initially, very low run lives were reported, but continued efforts have increased these run lives significantly. A hydraulic-jet-pump pilot scheme implemented in the field is operating satisfactorily.
Field Examples of Nuclear Magnetism Logging
Authors: Hull Paul , Coolidge John E.
Published: December 2007

Field examples are presented from various operating areas which demonstrate the capability of the nuclear magnetism log to operate under most drilling and formation conditions. On the basis of these examples, it is shown thatthe free fluid index of nuclear magnetism logging provides a superior means of reservoir rock definition, yields a measure of formation permeability and productivity and is an excellent correlation tool andhydrocarbon and water can be differentiated with good reliability.

Operational factors are discussed along with methods of interpretation of original data.

Introduction

In Sept., 1959, Brown and Gamson presented a paper concerning the application of nuclear magnetism to oil-well logging. Some early examples of field performance were discussed along with a detailed explanation of the basic phenomenon as it applies to down-hole operations.

It is the purpose of this paper to discuss the operations of nuclear magnetism logging (NML) and to present additional field results. As will be evident, NML is in the early stages of development, and its full significance is yet to be realized. Its ability to define fluid-bearing zones is well established. In addition, considerable evidence suggests its application as a permeability or productivity index, its ability to distinguish hydrocarbon and water zones, and its capability of operating in all borehole conditions.

Certain operational problems of a commercial NML must still be evaluated. Only a limited number of logs have been conducted with a recently completed prototype tool, and continuous changes are being made for more satisfactory operation.
A Career of Human Significance
Authors: Glenn Wayne E.
Published: December 2007

EDITOR'S NOTE: Although aimed toward graduating senior engineers and delivered as a commencement address, the following paper offers stimulating thoughts to all engineers on "technical obsolescence", community responsibility, budgeting of time and other important matters. A somewhat more detailed version of this paper was delivered at Montana School of Mines on June 6, at which time the author received his honorary doctorate degree.

The years immediately ahead - 1961, 1962, 1963 - will be critical years from every standpoint for the young engineer. In the next few years, he must learn to grow professionally. Most often, the rate and extent of this growth will be governed by his own initiative and perseverance. Habits and attitudes acquired during these early professional years relate very closely to, and even foreshadow, future accomplishments.

The future goal of the young engineer is a moving target. It will change with professional growth, family requirements, changes in predominant interest, general economic and business conditions and geographic location. However ambitious and steadfast in his goal he may be, the young engineer should not hesitate to adjust or change - for he really does not know initially what he is best fitted for and will not know until he has tried a number of things patiently and persistently.

Professional development in specific technical competence and, broadly, as an individual and as a citizen will have many facets. To achieve "A Career of Human Significance" will require a well conceived plan, properly timed and executed. The successful engineer will need to maintain a thirst for knowledge throughout his career, for one of his critical personal problems will be the constant pressure to keep up with the parade of advances and new findings in the profession-to escape what might be termed "technological obsolescence".

Technological Obsolescence

The problem can be stated as a paradox. The engineering graduate leaves college partially educated for his career. Nevertheless, at that time he may possess a wider range of detailed scientific and technical knowledge than he will at any later stage of his career. To maintain the highest level of technical "know-how" calls for a life-long study habit.
Analysis of Prestimulation Test Data in Devonian Shale Reservoirs
Authors: Holgate K. E. , Lancaster D. E. , Lee W. J.
Published: December 2007

Prestimulation testing in Devonian shales has proved to be complicated because of the long duration of wellbore storage distortion that must be exceeded during flow and shut-in periods to obtain an analyzable test. This paper presents field examples of four prestimulation well tests that illustrate the practical difficulties in obtaining analyzable data. We were not able to analyze these tests with conventional semilog and type-curve methods.

To understand the cause of the difficulties, we simulated a prestimulation well test to verify that the actual wells had not been produced long enough to exceed wellbore storage distortion. We then history matched the actual test data from two wells using a finite-difference simulator. Because we lacked good estimates of many formation properties, we performed a sensitivity study that indicated that the calculated permeability-thickness product is only slightly affected by errors in porosity and net pay estimates. We conclude with guidelines to aid in the design and implementation of a prestimulation test in Devonian shales.
Reservoir and Stimulation Analysis of a Devonian Shale Gas Field
Authors: Shaw J. S. , Gatens J. M. , Lancaster D. E. , Lee W. J. , Avary K. L. , Terry D. P.
Published: December 2007

This paper presents a study of a shallow, low-productivity Devonian shale gas field consisting of 48 wells in Mason County, WV. Gas production from wells in the field was found to be associated with zones of substantial free-gas porosity in the presence of high kerogen (organic) content. Most wells are poor producers; the best wells are located in the northwest portion of the field, which corresponds to an area of natural fracturing identified by remote sensing imagery. We identified and mapped quality reservoir areas and predicted performance for all wells in the field. The stimulation treatments conducted on all wells in the field successfully initiated gas production from the shales, but these treatments generally failed to achieve the degree of stimulation expected from such jobs.
Effects of the Quadratic Gradient Term in Steady-State and Semisteady-State Solutions for Reservoir Pressure
Authors: Finjord J. , Aadnoy B. S.
Published: December 2007

Constant-rate analytical solutions of the one-phase radial-flow equation in two dimensions, including effects of the quadratic gradient term, are derived for an oil reservoir with constant diffusivity and compressibility. The combinations of compressibility contributions to the various terms are analyzed. It is shown that the standard condition allowing the quadratic gradient term to be neglected (cp≪1) is incorrect; pressure, p, should be replaced by a function of the production rate and other reservoir parameters except absolute pressure.

The effect of the quadratic gradient term, for which quantitative expressions are given for steady-state and semisteady-state flow, may amount to several percent of the pressure drawdown at the wellbore.
Effect of Directional Permeability on Sweep Efficiency and Production Capacity
Authors: Landrum Bobby L. , Crawford Paul B.
Published: December 2007

Theoretical and potentiometric model studies have been made of the effect of non-uniform lateral permeabilities on pattern sweep efficiency and production capacity in waterflood and gas-cycling programs.

It is shown that a difference in directional permeability by a factor of three may result in a sweep efficiency of only 43 per cent for a five-spot pattern or a sweep of either 79 or 38 per cent for a direct line-drive square pattern, depending on the direction of the line-drive flood. Changes in the pattern conductivity varied from about 0.8 to 1.34 over this same permeability variation, depending on the pattern used.

It is suggested that measurements be made to determine the possible magnitude and extent of the directional permeability phenomenon early in the field development and certainly prior to the initiation of any fluid-injection program.

Introduction

Irregularities in reservoir sand properties long have been a major difficulty to anyone attempting to explicitly describe the field characteristics of oil production. In particular, it is well known that vertical and lateral permeabilities often differ appreciably; however, the existence of large regions with lateral permeability variation is not widely recognized. A number of years ago, extensive studies were conducted by the Secondary Recovery Research Laboratory of the Pennsylvania Grade Crude Oil Association, primarily on the Bradford field. Johnson and Hughes reported a permeability trend in the northeast-southwest direction. They indicated that flow in the preferred direction may be 25 to 30 per cent greater in that direction than in the northwest-southeast direction. They also reported that similar effects may be found in other nearby fields. The origin of the permeability variation has been discussed by Griffith. Hutchinson described the results of laboratory tests on limestone cores, pointing out that preferential directional permeabilities were significant in one-half of 10 formations studied and that the average permeability ratio was 16:1.
Tarmat Behavior Under Water Injection in a Reservoir With Two Intersecting Faults
Authors: Osman Mohammed E.
Published: December 2007

Tarmat problems, which are present in many oil reservoirs, were investigated in a series of papers. Tarmat behavior under water injection by an injector away from faults was presented in the first study, and the second study treated the case of a water injection under tarmat by an injector near a single fault. This paper investigates the case where an injector near two intersecting faults is used and resulted in a technique that can be used, both analytically and graphically, to predict the behavior of tarmat anywhere in the reservoir. It was found that the effect of both faults lessens and becomes more linear with increasing distance of the injector from the two faults. Also, a set of equations is presented to predict the response time (after tarmat breakdown) at any observation well in the reservoir.
Detailed Validation of an Empirical Model for Viscous Fingering With Gravity Effects
Authors: Fayers F. John , Newley Trevor M. J.
Published: December 2007

This paper extends to two-dimensional (2D) flows the derivation and validation of an empirical model for viscous fingering previously developed. Fine-scale numerical simulations are used to provide basic data for validating the approximations, and these fingering results are also checked against a range of experiments. The flow rate dependence of gravity segregation in vertical section experiments conducted by van der Poel is examined, where the broadly acceptable agreement of the empirical model is limited by some identified additional features.