bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Modeling of Foam Flooding
Authors: Fisher A. W. , Foulser R. W. S. , Goodyear S. G.
Published: December 2007

In studying the flow of foam in unconsolidated porous media Khatib et al have shown that the destruction of foam lamellae depends on the gas/surfactant solution flowrates, fluid mobilities, and rock capillary pressure. This paper examines this flow regime, which we call the coalescence regime, in more detail. We have found that all published data referring to foam flow in consolidated media are consistent with a generalisation of Khatib's model. This new model is described in this paper.

Two and three phase steady-state foam mobility models have been developed which exploit the dominant role of the foam coalescence mechanism. These models are based on published data for foam flow. The mobility models are then used in a finite difference, three phase, multi-component simulator. The simulator is applied to show that it can reproduce the generic transient foam behaviour observed in core floods. Calculations are then used to examine some of the important issues that have to be considered when designing field applications of foam flooding.
Steam Circulation in Horizontal Wellbores
Authors: Best D. A. , Lesage R. P. , Arthur J. E.
Published: December 2007

A model to evaluate heat losses, steam quality and pressure profiles during steam circulation in a wellbore has been developed. The model's unique ability to simulate countercurrent flow streams accounts for the interactions of heat transfer, fluid flow, phase changes, slippage between steam and water, and flow regime changes. It is based on the conservation equations of mass, momentum and energy. The energy conservation equations can account for heat transfer in a stagnant annular gas blanket as well as the transient heat loss to the overburden and the reservoir.

The mixture densities and frictional pressure drops were evaluated from two phase flow correlations. The heat transfer from the flowing streams was calculated from overall heat transfer coefficients involving thermal resistances and film condensation/vaporization coefficients. The conservation equations were solved iteratively by the Newton-Raphson method.

The development of this model arose from a need to determine the wellbore heatloss distribution during the warm-up phase in Mobil Oil Canada's horizontal well at Cold Lake. Results from the model are verified with actual field data.
Implications of Water-Alternate-Gas Injection for Profile Control and Injectivity
Authors: Gorell S. B.
Published: December 2007

Simulation results are presented which demonstrate that Water Alternate Gas (WAG) injection should not be expected to improve vertical distribution of solvent, relative to continuous slug injection, for tertiary processes in non-communicating layered systems. These results are explained by considering the way in which fluid mobilities within, and between, different layers vary with time. WAG injection reduces the effective mobility of fluids in the highest permeability layer compared with continuous injection. However, it also reduces the mobility of the fluids in all the other layers, which can actually increase the fraction of CO2 entering the highest permeability layer with WAG. Profile control with WAG should not be expected whenever the effective fluid mobility during solvent injection is higher than during water injection.

The effect of compressibility on follow-up water injectivity reductions are also considered. Reduced water injectivity can result from the high compressibility of CO2 and the redistribution of pressure profiles when the injectant is changed from CO2 to water. While this redistribution is occurring, the local injection pressure gradient, and therefore the injectivity, is lower than one would calculate if compressibility were ignored. Differences between pressure and rate constrained injection schemes and the effects of slug size are also discussed.
Effect of High Shear Rate on In-Situ Gelation of a Xanthan/Cr(III) System
Authors: Jousset F. , Green D. W. , Willhite G. P. , McCool C. S.
Published: December 2007

An experimental investigation of the effect of high shear rates on the mechanisms of in situ gelation and development of flow resistance of a xanthan/Cr(III) gel system in sandpacks was made to simulate the conditions around a wellbore during a gel treatment. Gel solutions were mixed in-line to give an injected solution concentration of 1,500 ppm xanthan and 50 ppm Cr(III). Such a gel system has a gel time in bulk in the neighborhood of 15 hours. A 15 foot length of unconsolidated sand was used as the porous medium. The effect of high shear rates was examined by varying the frontal velocity from 12 to 120 ft/d. During each gel displacement, pressure drops across sub-sections of the sandpack were recorded as well as data on the effluent. Gelation behavior and Cr(III) concentrations of effluent samples were measured.

In gel displacements conducted at linear velocities between 11 to 35 ft/d. a high flow resistance developed at a specific location in the sandpacks confirming earlier work of Hejri et al.1,5. The build-up in flow resistance (in situ gelation) was accompanied by a reduced polymer concentration downstream of this location, which was inferred from reduced pressure drops and reduced effluent viscosity. The location of this region of high flow resistance was correlated linearly as a function of frontal velocity. Studies performed on effluent samples indicated that a large amount of Cr(III) and polymer were retained in the sandpacks. Moreover, the high flow resistances developed at a location where the age of the flowing solution was around 10 hours, corresponding approximately to the point where the viscosity starts to increase for this gel system.1.

At frontal velocities of 83 and 118 ft/d no significant flow resistance developed in these sandpacks. The residence time was apparently too small and the shear rate too large for in situ gelation to occur. The results of the experiments indicate that in situ gelation is mainly controlled by the kinetics of the gelation reaction and gel/polymer retention.
The Low-Tension Polymer Flood Approach to Cost-Effective Chemical EOR
Authors: Kalpakci B. , Arf T. G. , Barker J. W. , Krupa A. S. , Morgan J. C. , Neira R. D.
Published: December 2007

The Low Tension Polymer Flood approach addresses the two EOR problems of cost and control. Coinjection of low concentration surfactant and a biopolymer, followed by a further mobility control buffer, leads to much reduced overall chemical consumption, even in relatively high clay content rock. Though the optimum chemical injection period is more prolonged, the oil recovery timescale is not unduly prolonged. The LTPF process moves chemical flooding surfactant a long way toward being a simple, low-level waterflood additive process, attractive for field operations. It uses surfactant-polymer interactions as an advantage rather than coping with them as a problem.

The chemical system described is based on a scleroglucan biopolymer (500 – 750 ppm) plus surfactant mixture (3000 ppm total surfactant). No cosolvent is used. This system was developed specifically for use with high salinity injection water (seawater) in a high temperature reservoir. The essential phase behavior description is given, together with other physical parameters and detailed coreflood performance.

Finally, we discuss the computer simulation approach used to predict reservoir performance and the results obtained.
Numerical Simulation of Single-Well Polymer Gel Treatments in Heterogeneous Formations
Authors: Hughes D. S. , Woods C. L. , Crofts H. J. , Dixon R. T.
Published: December 2007

High watercuts are a pressing problem in North Sea fields. The application of polymer gels to block-off the water producing layers has been judged successful in many American fields, and this established technology may be fairly readily extendable to the more demanding conditions offshore. A difficulty is that there is generally some vertical communication between the geological layers.

A radial, near-well bore model has been constructed for the Ness layers of the Upper Brent reservoir of a representative field. The pre- and post-production phases of gel treatments have been simulated, with the effects on fluid mobilities of polymer adsorption and gelation modelled directly. The effects of various degrees of vertical communication, and gel strategies and properties have been investigated.

Principal conclusions are:

Near-well bore gel treatments would be effective providing there is at least some restriction to vertical flow. Low concentration "thin" gels act mainly through the permeability-reducing property of the adsorbed gel, whereas higher concentration "thick" gels act mainly through the increased viscosity of the aqueous phase. It is more effective to inject gel into only the watered-out layers; and this strategy is favoured more for thicker gels. "Thick" gel treatments without selective completion block all except the highest-permeability layer. They should therefore only be considered if this layer still contains mobile oil, the watercut is high, and production is currently limited by handling capacity.
Field Studies of Microbial EOR
Authors: Sheehy A. J.
Published: December 2007

Microbiologically enhanced oil recovery (MEOR) is the use of microorganisms to facilitate, increase or extend oil production from a natural reservoir. The concept is more than 40 years old, however, early proposals were poorly conceived and in most instances of no practical value. Recent studies have developed microbial biotechnology to resolve specific production problems such as pressure depletion and sweep inefficiency in a target reservoir.

Field trials to determine and document the effectiveness of microbial process, and to assess the validity of laboratory studies and models have been conducted. The application of ME0R in these trials has resulted in a substantial and sustained increase in production compared to control operations on the same reservoir. Increased production has been sustained from a single treatment.

A field assessment of the new technology in the Alton field is described. Twelve months after treatment an approximate 40% increase in net oil production continues. The test is unique because of the stringent controls applied during the assessment.
Use of Eight Flux Streams Per Cell in a Two-Dimensional, Three-Phase, Unsteady-State Reservoir Simulation Model
Authors: Garrett J.E. , Osborne H.C.
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers Inc.

Conventional reservoir simulation models use four-directional flux calculating procedures and accordingly compute fluid injection procedures and accordingly compute fluid injection performance with an inherent inaccuracy that performance with an inherent inaccuracy that often is of substantial magnitude. Tests show that the velocity of frontal movements computed are too slow diagonal to the grid axes and too fast parallel to the grid axes. The magnitude of the inaccuracy was found to range from +42% to -32% when referenced to a more accurate eight-flux procedure herein described. The four-flux inaccuracy can lead to especially serious error when matching limited fluid injection performance.

The eight-flux concept presented requires that the model's grids be viewed as symmetrical octagons for the purpose of computing the resistance to fluid flow from one grid to another.

The conclusion is reached that a model using the eight-flux computational procedure calculates saturation fronts more accurately; results in better reservoir performance matching and flood performance predictions; and is computationally more stable. The alternating direction explicit-type computational procedures are well suited to handle the procedures are well suited to handle the eight flux calculations.

Introduction

Normally, in grid-type reservoir simulation models, flux calculations are made in only four directions with respect to each cell. These flux streams run between each cell and the four abutting cells along lines perpendicular to the four faces. For fluids to move perpendicular to the four faces. For fluids to move diagonally with respect to the axes of the cells, it proceeds in a stair-step fashion, making a 90 degree turn at the center of each cell. As a result of this procedure the flood fronts resulting from model simulation are distorted.

One technique for improving flood front tracking in a numeric model is to compute flux into and out of each cell in eight directions rather than four. Thus, as far as flux calculations are concerned, the cells are treated as symmetrical-octagons.
Experimental and Theoretical Determination of Residual Saturations After a Water-Driven Carbon Dioxide Flood
Authors: Deo M. D. , Deans H. A.
Published: December 2007

An approach similar to the determination of residual gas saturation by single well injection/production technique has been investigated to determine saturations of trapped phases after a water-driven CO2-enhanced oil recovery process. Theoretically, the theory of multicomponent, multiphase flow in porous media was applied to the flow reversal situation to show that the interaction of phase behavior and flow reversal leads to nonreversing composition paths, which can be used to obtain meaningful information about the state of the reservoir before the test. Experimentally, a single residual phase of various compositions was first established in the core and the saturations determined by volumetric balance. The saturation so established was then measured by using the fluid injection/production test and was in good agreement with the saturations established by volumetric balances. Extensions of the method to determine two residual phases simultaneously in the pore space in the three- and four-component cases was explored theoretically.
Design and Results of a Shallow, Light Oilfield-Wide Application of CO2 Huff ‘n’ Puff Process
Authors: Miller B. J.
Published: December 2007

A CO2 huff and puff process has shown to be economic at current oil prices in. a shallow oil field in the Appalachian Basin. Design and field results are reviewed.

The project shows excellent results for a tight, light oil reservoir at immiscible conditions. The results of 200 treatments (340 to 4130 Mscf [9630 to 116,900 m3] each) over a four year period are investigated. The results of a second treatment on wells that had been treated over three years prior are also shown. Mechanical failures have been published as attributing to partial failure of other huff and puff projects; thus, prescreening and small treatments have been used to minimize this problem. The mechanics of the treatment will be reviewed with an emphasis on simplicity and safety.

The production response from the treatments have been from one to four years. The response developed from field tests of different sizes will be reviewed and correlated with reservoir parameters. The complex relationships among these factors leads to the need for modeling that will not only predict the ultimate recovery efficiency but also the response curve for specific wells for project optimization. The optimum treatment or combination of treatments for a well is not where the CO3 utilization efficiency for the total treatment is maximized but where the net revenue is maximized. With the high cash turnover rate, a project can be designed to minimize the working capital exposed and maximize the project cash flow.

The primary project area covers over 400 wells in the same reservoir with varying reservoir and production parameters. Initial treatments have been set up to test all the wells. Information from these treatments are helping to supply data for modeling and multiple linear regression analysis.
Simulation of Heat Flow in Porous Media Using Numerical Models
Authors: Nicholson F.R. , Jones W.W. , Schwabe Klaus
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers Inc.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Generalized heat and fluid flow models are useful in evaluating the effects of heat upon crude oils in a reservoir environment and more particularly that area immediately surrounding a wellbore. The model described allows fluid and heat flow in the two dimensions of a vertical plane. As in other numerical models, each cell is assumed to be homogeneous in pressure, viscosity, temperature, etc. This paper describes how the flow of heat from one cell to another has been superimposed upon the unsteady-state flow of oil, gas, water, and steam between cells. Solutions to problems using this reservoir simulator are shown.

Introduction

During the last several years the use of numerical models to simulate reservoir conditions have become very commonplace and simulators of several types and configurations have been developed for solution on high speed digital computers. During these same years, thermal recovery techniques have received a great deal of attention, and numerical simulator solutions applied also to this area. The broad term of thermal recovery covers a spectrum from in situ combustion to hot water alteration of fluid saturations around wellbores. Thermal recovery, like many other popular techniques, has a certain amount of "romance" surrounding it. The benefits can be very substantial; however, like any new technique it is subject to misapplication. The purpose of this paper is to describe a numerical simulator that accounts for both fluid and heat flow, and further to relate some of the observations that have evolved from its use.

DISCUSSION OF THE THERMAL MODEL

The concept used in designing this thermal model was to combine fluid and heat flow into one model. The continuity equations written for each mobile phase (oil, gas, and water) were summed employing the method proposed by Fogin et al. The equations were arranged for an implicit solution of the potential distributions using the alternating direction procedure of Peaceman and Rachford. Following the calculation Peaceman and Rachford. Following the calculation of the potential distributions, the saturation distribution and temperature distribution are calculated explicitly. An iterative procedure of the entire calculation sequence permits the use of conductance and expansion coefficients calculated forward in time. This forward approximation is particularly important in the model discussed here because expansion and phase changes are not only functions of pressure but also of temperature. This approach permitted the use of relatively long time increments which are essential for the use of the simulator in the solution of practical engineering problems. problems.
General Computerized Well Control Kill Sheet for Drilling Operations with Graphical Display Capabilities
Authors: Leitão H. C. F. , Maidla E. E. , Bourgoyne A. T. , Negrão A. F.
Published: December 2007

A rigorous method of pressure calculations was used in a general well control procedure for drilling operations with the drillbit on bottom. A computer program was developed to handle the calculations and graphics interactively to allow speed and flexibility of choices throughout a kick situation. A well control procedure was developed to handle from vertical to horizontal wells for many drilling situations. All pertinent equations are presented and unlike other publications the computer source code is given in the Appendix.
Concepts of Directional Drilling Data Management
Authors: Winther A. , Roper D. J. , Sjaaholm A. J.
Published: December 2007

A breakthough in directional drilling data management for large, multiplatform field developments is introduced. The need for accurate directional surveying has been recognized throughout the oil industry and new practices of survey data acquisition and quality control introduced which have resulted in the proliferation of survey and related data. Aspects of this data, namely its safety critical nature, its longevity, its redundancy and its volume, are discussed. The importance of correct management of this information to safe drilling and the avoidance of well collision are stated. Additional justification is made through the examples of planning and execution of the drilling program.

To date operators have attempted to manage directional drilling data through routes including paper files, mainframe and personal computer systems and contracting to directional drilling service companies. The failure modes of each mechanism are outlined.

The concept of a distributed, networked system of high performance personal computers to support directional drilling operations is introduced. Using suitable software the operator stores field, structure and slot geometries together with target details, slot to target allocations and all well plans and directional surveys. This database and all relevant engineering tools, for example survey computation, projection ahead, bottom hole assembly simulations and inter well clearances, are provided both in the office and at the rigsite. The requirement for local data storage to support high performance graphics and the problems of data replication and currency control which this implies are mentioned.

Finally, the utility of extending the rig to office network to provide a data feed to directional drilling contractors and the importance of technical prequalification of contractors in ensuring they can use this data is stated.
Systems for Automated Drilling AFE Cost Estimating and Tracking
Authors: Shilling R. B. , Lowe D. E.
Published: December 2007

As part of a strategic effort in drilling computer technology1, ARCO Oil and Gas Company is developing automated systems to produce drilling AFE cost estimates and allow detailed tracking of actual booked costs. Retrievals of booked costs from mainframe accounting databases, along with retrievals of drilling performance data from ARCO's Drilling Database System2 (DDS) are used to provide "calibrated" input to an automated well planning and cost estimating system. All AFE documentation is automatically generated by the system.

Historically the preparation of drilling cost estimates, associated AFE documentation, and the verification of booked costs has required significant time and effort within drilling organizations. Moreover drilling costs are a major portion of total expenditures. A consistent, calibrated cost estimating tool combined with an efficient cost tracking program improves well planning, estimating accuracy and cost control. On a work load basis, these systems also increase productivity by reducing the time and effort required to review booked costs and produce drilling AFE's, thereby freeing time for other important engineering, operations and business tasks.
CASE Technology is Used in the Development of a General Completion Simulator
Authors: Ben-Naceur K.
Published: December 2007

The major cause of the increasingly higher software development costs resides in the lack of reuse of existing technology in new applications combined with the costs of maintaining existing codes. Related to these considerations, Computer Aided Software Engineering (CASE) was introduced in the software industry as a methodology aimed at improving the software productivity. Some of these concepts have been used in the development of a modular software architecture to simulate completion operations, such as cementing, gravel packing, and coiled tubing. The open architecture was designed to host, at a minimal cost, incremental developments in the physics of the underlying processes as well as major modifications. The methodology of the development and the choice of the software technology are discussed: this includes the language specifications, the steps in documenting the project and the actual implementation. Compromises between "quick prototyping" and maintenance considerations/code performance have often to be made. The criteria for selecting a given strategy are discussed in terms of software metric.
Customization is the Key to Successful CAD
Authors: Byrd C. S.
Published: December 2007

Rolling cutter bit design is an iterative process in which a designer must balance bearing and cutting structure components within the available space to satisfy specific service requirements. In the last ten years bit designers have exchanged then-drawing boards for CAD terminals. While traditional CAD has a positive effect on the design process, custom software written to address specific design functions has been the key to realizing maximum benefit of the technology. Utilizing programs written in a modem graphics interface language, bit designers are able to consider more design concepts in the initial design process, select from existing tooling for manufacture, and fine tune or revise designs quickly. Specific details of the implementation of CAD at one rock bit manufacturer are given. Problems in implementing the system described and their solutions are also discussed.
International Workstation Network Improves Drilling Tool Quality and Responsiveness
Authors: Clench M. , Spacek E. , Felton J. M.
Published: December 2007

This paper describes a sophisticated computer network which integrates drill bit design, manufacture and quality control on a global basis. This work station based system links Aberdeen (UK) and Houston (U.S.A.). Product quality, scrap rates, product competition times, costs, customizing and standardization, have all been improved by use of this system.
Theory of Lost Circulation Pressure
Authors: Morita N. , Black A. D. , Fuh G -F.
Published: December 2007

Conventional theories predicting borehole breakdown pressure assume breakdown occurs when the tangential stress at the borehole exceeds the tensile strength of the formation. Fracturing tests conducted during the DEA-13 joint industry project, however, showed that when drilling fluid was used as an injection fluid, borehole breakdown did not occur until the well pressure significantly exceeded the pressure which resulted in a tangential stress equal to the rock tensile strength even with a large surface flaw. The test results have shown that all drilling muds have a tendency to seal narrow natural fractures or fractures created by high borehole pressure. The sealing effect of the mud stabilizes fractures and prevents fracture propagation. This effect is one of the primary factors for controlling wellbore stability. In this paper, a theory of fracture initiation and fracture propagation around a borehole whose stability is enhanced by drilling fluid interaction, has been developed and shown to be consistent not only with all the DEA-13 laboratory results, but also with various field evidence. The results show that lost circulation pressure is highly dependent on the Young's modulus of the formation, wellbore size, and type of the drilling fluid, although the conventional theories have ignored these facts.
Unique Articulated Downhole Motor Holds Promising Future for Short Radius Horizontal Drilling
Authors: Trichel D. K. , Ohanian M. P.
Published: December 2007

This paper will introduce the industry to a unique articulated downhole motor system designed to drill lateral extensions out of a short radius build curve.1 For the sake of clarity, a short radius build curve will be defined as a curve having a radius between 19' - 60' (6m - 18m). This equates to build rates of 3°/ft - 1°/ft (9.8°/m - 3.2°/m).

The theoretical build radius of the articulated motor system is 39’ (12m), or a build rate of 1.467ft (4.79°/m). Lateral extensions up to 929 ft (283m) have been drilled using the system. With significant improvements in drilling efficiency and lateral lengths, the articulated motor system opens up a wide range of opportunities for short radius horizontal drilling.2

The paper discusses the industry needs that brought about the system's conception and design. The development of the articulated motor system is explained through a series of case histories so that the reader will gain a better understanding of the overall nature of short radius horizontal drilling. Important points from the overall learning curve will be detailed. The paper assumes that the reader is familiar with basic directional drilling terminology.1

The paper will discuss the different options associated with hole size and casing programs. Techniques for horizontal re-entries will be presented, along with project planning considerations for new and existing wells. Rig requirements and operating parameters will be outlined. Unusual mathematical survey and projection considerations unique to this system are presented as well as hole drag observations from the field.
The Offshore Directional Drilling Advisor: An Expert System for Directional Drilling Optimization
Authors: Amara M. H. , Martin B.
Published: December 2007

ODDA is an expert system designed to assist the drilling engineer, at the drilling site, in the engineering base or in the research center during the 4 functional phases of his work.

Early planning phase, for designing the number and position of the different platforms or well clusters. (Field planning expert system). During a well planning phase, for determining the optimum well trajectory in a single or multiwell environment. (Trajectory planning expert system). During the operational phase: 3-1) for designing the bottom hole assembly suited to drill a given well section while minimizing the BHA make up time and implying no restriction on the drilling parameters to be applied. 3-2) for deciding to pursue or interrupt the current bottom hole assembly run, ODDA will evaluate and extrapolate the assembly's trends, account for operational and geometrical constraints and eliminate unnecessary trips. (Drill Ahead/Pull Out Of Hole expert system). During the evaluation phase, for running queries and statistics, comparing actual and predicted behaviours and identifying trends in the effects of different formations and drilling parameters on bottom hole assemblies (Post Analysis Module).

The post analysis facility includes a survey validation process consisting in visually aided or fully automatic filtration of survey errors.

The drilling engineer can also design his own assemblies by accessing the mechanical analysis module. This module is an upgraded version or TOTAL’S BHA2 program, which includes an enhanced graphical interface, a link with the system's central database and the possibility to run batch calculations while working with other functionalities.

The system's relational database allows the recording and processing of the well programs, the prognosed and actual geological data, the drilling parameters, the surveys and associated error parameters, the bits and bottom hole assemblies. Reports of predefined or customized format can be generated at any time.

Its graphics capabilities and user environment, together with the above functionalities, make the ODDA system an integrated tool covering most aspects of directional drilling engineering.
Design and Application of a High-Temperature Mud System for Hostile Environments
Authors: Mitchell R. K. , Bethke M. E. , Dearing H. L.
Published: December 2007

This paper deals with the design and field application of an environmentally safe water base mud system for hostile environments with bottom hole temperatures in excess of 400°F (204°C). The paper discusses the basic mud formulation and modifications to handle high temperatures and a variety of contaminants. Toxicity, thermal stability, reaction to contaminants, wellbore stability, formation damage, and system maintenance are also addressed in the paper. The significance of product quality assurance, importance of cooperative lab and field testing, and solids control equipment requirements are also highlighted. A case history utilizing this mud system is detailed throughout the paper that highlights its usage in a zero discharge, hostile environment area.
Evaluation of a CO2 Foam Field Trial: Rangely Weber Sand Unit
Authors: Jonas T. M. , Chou S. I. , Vasicek S. L.
Published: December 2007

A CO2 foam field trial was conducted in the Rangely Weber Sand Unit, located in northwestern Colorado. Chevron began the CO2 flood on a 1:1 water-alternating-gas, WAG, injection scheme in October 1986. Currently the project injects 250 MMCFD CO2. Forty percent of this is recycled CO2. CO2 production is a major concern and is caused by thief zones between injectors and producers. The objective of the field trial was to investigate whether foam may block some of the thief zones and thereby improve sweep efficiency and CO2 utilization.

A pattern exhibiting severe CO2 breakthrough was chosen for the field trial. The injector, Gray A 10, is in communication with several offset producers. One of these wells, A.C. McLaughlin 4, produced more than 2 MMCFD gas within 10 days of placing Gray A10 on a CO2 cycle with virtually no tertiary oil. Gray A 10 was hydraulically fractured twice while it was a producer in the 1950's, but the fracture is not believed to be the sole cause of breakthrough in the pattern.

The foam project started in April 1989 at the end of a water cycle. The treatment consisted of a 12,000 BBL surfactant slug followed by 55,000 BBL of 79% quality foam. Average surfactant concentration was about 0.46%, and Chevron Chaser CD1040 was used. Foam was emplaced by simultaneously injecting CO2 and surfactant solution through a coarse mixing device in the tubing.

Results are encouraging. Injectivity and pressure transient data indicated that foam was emplaced in the reservoir. CO2 production in McLaughlin 4 was much lower during the trial while oil production was slightly higher. In contrast, both CO2 and oil production in the other offset producers increased somewhat. This could be evidence of CO2 diversion and improved sweep efficiency. Finally, foam reduced CO2 injectivity for as long as two months in the subsequent C02 chase after foam.
A Recursive Method for Estimating Single and Multiphase Permeabilities
Authors: Mohanty S. , Sharma M. M.
Published: December 2007

A method is proposed for obtaining effective permeabilities of heterogeneous porous media at many length scales. The real space renormalization group method (RSRG) has been modified to determine the effective properties of both uncorrelated and correlated permeability fields. The model shows excellent sensitivity to directional permeabilities and to the type of heterogeneity. In addition to two component shale-sand sequences, the method is extended to calculate effective properties of as many as four components. The method is also applied to obtain the ‘effective’ two phase relative permeability curves for porous media that are heterogeneous at the macroscopic or megascopic length scales. These effective properties are inputs into numerical simulators and can be used to interpret log and core derived properties.
Application of Integrated Pore-to-Core Image Analysis to Study Fluid Distribution in Reservoir Rocks
Authors: Tomutsa L. , Mahmood S. M. , Brinkmeyer A. , Honarpour M.
Published: December 2007

Effects of small-scale variations in rock properties on fluid distribution was studied in a layered Berea and a glauconite-laminated Shannon sandstone using x-ray computed tomography (CT), thin-section analysis, and rock-slab micromodels.

Dry and partially saturated cores were CT scanned at different stages of imbibition and drainage cycles to determine the spatial variations of rock properties and fluid distributions. Tests with brine-mineral oil (of 6.5 and 20 cP viscosities) and miscible brine-brine systems were conducted.

Based on the CT images, locations of various degrees of oil trapping were identified, from which samples were cut for thin-section analysis. Fluorescent and transmitted light microscopy images from these thin-sections were analyzed using commercial petrographic image analyses (PIA) software. Statistical analyses of pore and throat sizes were used to delineate small-scale spatial distributions of porosity and permeability.

Using a newly developed technique, micromodels containing 2 to 3 millimeter thick rock slabs were constructed. Multiphase displacement tests were performed, and pore-level behavior was observed.

The influence of layering resulting from variation in pore characteristics on front advancement, fluid distribution, and trapping was studied at core and microscopic scales using combination of CT and micromodel techniques. Presence of lower qualitylayers re-duced the effect of instability and inhibited oil intrusion in these layers.

This integrated use of images at different scales, as obtained by various imaging techniques, was found to be useful in providing an improved understanding of the effects of small-scale rock heterogeneities on fluid flow and trapping. Such integration can be helpful in proper interpretation of petrophysical data, such as relative permeability, capillary pressure, and electrical resistivity of core samples.
Feasibility of Reservoir Heating by Electromagnetic Irradiation
Authors: Fanchi J. R.
Published: December 2007

Conventional thermal EOR methods, such as fireflooding and steamflooding, are commercially viable when properly applied. Every conventional method has one or more limitations. Electromagnetic heating (EMH) has the potential for overcoming some of these limitations. The EMH process relies on preferential absorption of electromagnetic energy as the means for increasing the temperature of a material. An algorithm for estimating the temperature increase associated with reservoir irradiation is described. The algorithm accounts for heat loss to confining strata. It is useful for generating a temperature profile of an irradiated reservoir. Applications of the algorithm to hypothetical reservoirs illustrate typical data sources and computational results.
Computation of Drainage and Imbibition Capillary Pressure Curves from Centrifuge Experiments
Authors: Glotin G. , Genet J. , Klein P.
Published: December 2007

In this paper new methods to compute capillary pressure curves from centrifuge are developed for both drainage and imbibition. The methods are applied to experimental data. Results show that accurate determination of drainage capillary pressure curve can be obtained and negative capillary pressure in imbibition and residual oil saturation are also determined.
What is the Market Value of Long-Life Reserves?
Authors: David A. , Hickman T. S.
Published: December 2007

The value of long life reserves is greatly reduced by conventional discounted cash flow approaches due to the present worth effect. However, the prices often paid for such reserves indicate that some buyers use alternate evaluation techniques and/or give considerable weight to nonquantifiable aspects. The impact of various evaluation methods is investigated. While some methods are more representative than others, all fail to express the strategic considerations involved in the business decision to buy reserves. Some buyers are better positioned by virtue of their orientation and capital source to acquire long life reserves.
Capillary Continuity Between Blocks of a Fractured Reservoir
Authors: Labastie A.
Published: December 2007

The oil recovery by a gravity drainage process in a naturally fractured reservoir strongly depends on the total height in capillary continuity. The existence of a capillary continuity between blocks is critical for the computation of this height, but this problem is supported by very few reliable experimental data. We have performed both numerical and experimental investigations to determine under which conditions this continuity actually exists.

The experimental program, designed from a preliminary sensitivity study, includes several series of gravity drainage experiments with a stack of two matrix blocks in contact through bridges made either of:

– porous and permeable media, of various characteristics; – or non porous material, considering that the actual contact zone may be quite tight (stress concentration, recristallization...).

All the experiments have been simulated with a fine-grided model, in order to check the validity of the classical concepts.

The main results of the experiments and their simulation are:

– when the matrix blocks are in contact through porous material, the permeability of the contact area is the most important parameter; Darcy law is satisfactory to represent all the phenomena, as long as all the geometrical and petrophysical characteristics are correctly described; – when the matrix blocks are in contact through tight material, a capillary continuity may be established, depending on the geometry; this continuity cannot be represented by the classical concepts, and allows slow but significant flow rates.

The problem of capillary continuity between the matrix blocks of a fractured reservoir is still quite controversial; we believe this continuity very likely always exists, but flow rates may be small.
Interwell Residual Oil Saturation at Leduc Miscible Pilot
Authors: Wood K. N. , Tang J. S. , Luckasavitch R. J.
Published: December 2007

An interwell test for residual oil saturation to waterflood (Sorw) was successfully conducted at the Leduc miscible pilot during August of 1987. Although the principle of the test was first disclosed by Cooke in 1971, lack of suitable tracers and interpretative techniques would have hindered previous attempts to apply the test in the field. Recent advances in radioisotope tracing technology make it possible to use the test as a cost effective alternative to conventional techniques. The Leduc test appears to be the first successful interwell Sorw test to be reported in the literature. To verify the interwell method, two other independent measurements of Sorw were made at the pilot by well-established conventional methods, namely, single well test and sponge coring. The excellent agreement between the measurements strengthens the credibility of the interwell test for determining residual oil saturation. The paper describes and compares the three techniques, focussing on the design and interpretation of the interwell test.
A New Resistivity Measurement System for Deep Formation Imaging and High-Resolution Formation Evaluation
Authors: Hunka J. F. , Barber T. D. , Rosthal R. A. , Minerbo G. N. , Head E. A. , Howard A. Q. , Hazen G. A. , Chandler R. N.
Published: December 2007

A new induction logging system has been developed that represents a fundamental departure from the technology and application of previous induction-based resistivity tools. The AIT* Array Induction Imager tool abandons the concept of fixed-focused sensors and is constructed of several independent arrays with main coil spacings ranging from a few inches to several feet. The AIT tool is operated simultaneously at several frequencies; in-phase and quadrature signals are acquired from every array at the frequencies suitable for that array length.

The presented log curves range in median depth of investigation from 10 in. to 90 in. Each log uses all the measured channels, combined with a nonlinear processing algorithm, to virtually eliminate environmental effects such as cave effect, shoulder effect, and skin effect. Reliable logs can be obtained even in difficult cases of bad borehole and extreme invasion. These logs are available at resolution widths of 6 ft and 2 ft.

Because of the large number of measurements made by the AIT tool, deep two-dimensional quantitative imaging of formation resistivity is possible. These images expose bedding and invasion features in a clear and quantitative manner. The resistivity in the part of the formation undisturbed by fluid invasion is accurately obtained without making any prior assumptions about the invasion profile. New invasion description parameters conveying more meaningful information about the presence of transition zones and annuli are a result of this imaging capability. Using established interpretation principles, this quantitative information about the invasion can be converted into a two-dimensional image of water saturation.
Deep Saturation in Low Salinity Reservoirs from Dual Laterolog Quadrature Signals
Authors: Saxena Vimal , Sibbit A. M.
Published: December 2007

In slialy sands with low salinity brines, resistivity logs show little contrast between oil and water zones. The phase angle computed from the quadrature signals of the Dual Laterolog, is significantly reduced in front of oil zones, even in very shaly reservoirs.

This phenomenon is used as a basis to estimate deep water saturation.
The Well Response in a Naturally Fractured Reservoir: Arbitrary Fracture Connectivity and Unsteady Fluid Transfer
Authors: Chen Her-Yuan , Poston S. W. , Raghavan R.
Published: December 2007

This work presents the development of a dual-permeability transient interporosity formulation for naturally fractured reservoirs that offers engineers considerable flexibility in analyzing transient pressure data. The chief advantages of our model are: (i) it permits communication of the matrix system with the wellbore, and (ii) it admits transient interporosity flow behavior in the matrix system. Presently available models can be derived as special cases of our formulation. New insights into "pseudosteady behavior" that is often attributed to naturally fractured reservoirs are provided. Alternate interpretations to the fracture skin concept are also discussed.
Workstation-Based Fracture Evaluation Using Borehole Images and Wireline Logs
Authors: Cheung P. S-Y. , Heliot D.
Published: December 2007

Wireline images and logs can be processed effectively to derive quantitative information relating to fracture orientation, density, aperture and porosity. A methodology based on analyses at the levels of individual fractures and fracture sets is presented. A program has been implemented on a workstation allowing a flexible blend of expert-user input and machine processing power.
Experimental Pulsed Neutron Porosity for Gas-Filled Boreholes in the Gulf Coast
Authors: Butsch R. J. , Vacca H. L.
Published: December 2007

Determination of formation porosities in cased holes becomes necessary when no other porosity information is available, such as openhole logs or core data.

Within the pulsed neutron generations of logging tools, there have been various hybrids of "neutron" porosity computations made. The porosity has primarily been derived from a ratio of the count rate data obtained from selected gating and or detector combinations. Success has varied, depending on tool type and the composition of the formation encountered.

A technique has been developed for the Gulf Coast which has much less sensitivity to the environmental effects of gas in the borehole. Over the period of a year, numerous tests were made with data from wells with various borehole conditions.

The results to date indicate that this new technique will have application in eliminating or minimizing wellbore environmental effects due to gas in the wellbore. Gulf Coast and other examples are included which illustrate comparisons of this new technique with other porosity measurements.
3-D Acoustic Scanner
Authors: Aas M. , Bacri J-C. , Frenois C. , Salin D. , Woumeni R.
Published: December 2007

The sound velocity in a porous medium varies with the concentrations of, liquids, miscible or immiscible, that saturate the medium. The sensitivity of acoustic measurements lead to accuracies in fluid concentration better than 1 %. This technique is used to design a 3D acoustic scanner. Compared to X-ray or NMR computerized tomography, the acoustic scanner has poorer spatial resolution (3×3×3 mm3) but it is less expensive, faster and do not require any dopant. Most liquids and solids being transparent to acoustic waves, this technique is well suited for a wide range of sample coating, for example for studies under pressure.