bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure Transient Analysis for Single Well/Reservoir Configurations (Considering Partial Penetration, Mixed Boundary, Wellbore Storage, and Skin Effects)
Authors: Theuveny B. C. , Jack W. A. , Economides M. J.
Published: December 2007

This work presents a set of solutions for pressure transients analysis demonstrating the flexibility of Green's functions In solving a wide range of problems.

The Impact of partial completions and offoentered wells is presented along with a first-time Incorporation of wellbore storage and skin effects. Custom type-curves tailored to fit any well, reservoir and boundary configuration may be generated using the methods outlined here. An associated computer model is fully interactive and can be run on a small computer, readily available to most reservoir engineers.
Decline Curve Analysis for Double-Porosity Systems
Authors: Sageev A. , Da Prat G. , Ramey H. J.
Published: December 2007

A type curve matching method for analyzing constant pressure testing in a double-porosity system is presented. Both infinite systems and closed outer boundary systems are considered. Rate responses of constant pressure wells with and without wellbore skin are described.

Five type curves are presented for the rate response of the constant pressure active well. The first four curves describe: (1) An infinite system without wellbore skin, (2) a closed outer boundary system without wellbore skin, (3) an infinite system with wellbore skin, and (4) a closed outer boundary system with wellbore skin. In the fifth type curve, the first four type curves are assembled into one.

A log-log type curve matching method is presented, where the parameters λ, ω, reD, and S are estimated. The parameters λ and ω describe interporosity flow and relative fracture storativity respectively, and τeD and S are the dimensionless size of the system and the wellbore skin respectively. This paper considers only the estimation of these four parameters. The estimations of permeabilities and storativities have been described in the past, hence, are not described in this paper.

It is observed that the presence of wellbore skin has an important effect on the rate response of the double-porosity system. It is essential for the success of the analysis, especially in the determination of λ and reD, to include wellbore skin. The presented analysis method is valid for transient interporosity flow with fracture skin greater than 0.33, with slab-shaped matrix.

Three type curve matching examples are presented along with a discussion of the applicability and practicality of the analysis method.
Computerized Monitoring of Compliance with Environmental Regulations and Permits
Authors: Lyons C. E. , Svoboda L. , Harbert J. M.
Published: December 2007

The steady increase in the number and complexity of government regulations requires that oil and gas production companies find more efficient means to comply with environmental laws while maintaining profitable operations. One major production company has developed a comprehensive computer program to automate compliance with government environmental regulations. The highlights and advantages of this new computer system are described in the following paper.
Steam Quality Measurement in Flow Lines
Authors: Sinclair J. W. , Startzman R. A.
Published: December 2007

This paper presents the results of a small scale experimental program undertaken to investigate critical and subcritical flow correlations between steam quality and pressure. Subcritical flow tests indicate only a general trend exists between steam quality and pressure drop through a venturi. However, for the critical flow of a steam-water mixture in the pressure range of 26 to 69 psia, results indicate a suitable correlation exists between steam quality and upstream pressure. Unlike existing methods for measuring quality, this method is independent of mass flow rate, is insensitive to flow splitting and avoids problems associated with sampling.
Procedural Design Considerations Associated with Tubing-Conveyed Underbalanced Perforating
Authors: Young W. S. , Zaleski T. E.
Published: December 2007

Thirty-two tubing conveyed underbalanced perforating jobs conducted in the Gulf of Mexico between May, 1980, and May, 1982, have been carefully reviewed in order to draw correlations between procedural variations and trouble prone jobs. General procedural guidelines designed to avoid past problems were formulated and are presented. The procedures are designed for the generalized case where the perforating guns will be pulled out of the well in order to gravel pack and not for those run as part of a permanent completion. Careful application of these procedural guidelines has resulted in reducing rig time requirements by an average of 35% on 33 additional tubing conveyed underbalanced perforating jobs conducted subsequent to the establishment of the guidelines contained in this paper.
Design of an Effective Gravel Pack for Sand Control: A Numerical Approach
Authors: Peden J. M. , Russell J. , Oyeneyin M. B.
Published: December 2007

The production of sand associated with oil and gas developments has been a considerable problem in production operations in the recent past. Early investigative work on the subject concentrated upon the mechanisms by which sand production is initiated and in addition how the sand might be restrained from flow into the wellbore by a concentric lining of gravel in the wellbore across the production zone. This research has provided useful guidelines for the selection of gravel for the prevention of sand migration(1,2,3).
Continuous Fracture Probability Determination as Applied to the Monterey Formation
Authors: Grove G. P. , Whittaker J. L.
Published: December 2007

Most openhole logs can be used for fracture detection. Each petrophysical measurement responds to fractures in a different way, and there is a large amount of literature describing the effects of fractures on tool responses. Most fracture detection programs written to date have either used only one or two logs or displayed many fracture indicators, but made little attempt to tie them together.

Since fracture systems appear to provide nearly all the permeability for production in the Monterey formation, fracture analysis is essential throughout the well. A new program has been written to give a continuous output of fracture probability using data from well logs. This method makes use of all the fracture information available from wireline logs, mud logs, and drilling data. Each indicator is used to give an individual probability of fracturing. The program then computes a Continuous Fracture Probability (CFP) log using all the available fracture indicators, where the probability of fracturing is a value between zero and one. It is easily adaptable to specific local conditions (particularly the Monterey formation) through log analyst input. Computed outputs illustrating the use of this method in the Monterey formation are shown, and parameters and data used for input into the program are discussed.
New Core Analysis Techniques for Naturally Fractured Reservoirs
Authors: Bergosh J. L. , Marks T. R. , Mitkus A. F.
Published: December 2007

This paper reviews existing core analysis technology and discusses its limitations when used for the evaluation of naturally fractured reservoirs like the Monterey Formation. New core analysis techniques and equipment are presented which can improve the quality of core analysis data and the results of a core study using these methods are reported.
Some New Techniques in Flow Metering of Steam Injection Rate and Quality in Thermal Recovery Processes
Authors: Pascal H.
Published: December 2007

This paper is a theoretical investigation of two new techniques to be used in metering the steam quality and flow rate in two phase flows of steam and water mixtures in pipelines of steam injection. The first technique is two orifices in series. The performance of this flow system as a possible flow meter in two phase flow is graphically illustrated with regard to the determination of steam quality and flow rate. The second technique is the two-phase critical flow in a convergent-divergent nozzle. The possibility of using a single device, i.e. a convergent-divergent nozzle operating in the critical flow, in determining both the steam quality and flow rate is theoretically demonstrated. The illustration of the critical flow performance, as a possible flow meter in two phase flows of compressible mixtures, steam and water, is shown and discussed. A comparison with experimental data is also shown.
Application of Computers in the Analysis of Well Tests From Fractured Reservoirs
Authors: Barua J. , Kucuk F. , Gomez-Angulo J.
Published: December 2007

Naturally fractured reservoirs have proved to be important in the petroleum industry because of their prolific production behavior. Over the years, considerable effort has gone into evaluating these reservoirs by well tests.

Well tests are particularly important in this case because the reservoir parameters are otherwise difficult or impossible to obtain.

Well tests on naturally fractured reservoirs are not very easy to analyze. However, in the rare case when two or three clear semilog straight lines are present, analysis is straightforward. More often, because of the wellbore storage, the first semilog or possibly all semilog straight lines are obscured. Under these circumstances, the common way to analyze the test at present is by log-log (type-curve) analysis. Log-log analysis always compares poorly with semilog analysis because the logarithm of the pressure drop varies very little as time increases. There are other disadvantages in log-log analysis; e.g., the limited number of curves available on a type-curve and the difficulty of matching buildups.

The pressure-derivative curves enhance the definition of early time data but only provide a limited means of estimating two-porosity reservoir parameters. Clearly, there is room for enhancement in the quality of parameter estimates. Especially now, with the simultaneous use of pressure and pressure-derivative, the need for a general improvement in estimation procedures is felt even more.

This study was directed towards the application of computers to semi-automatically matched field data with the appropriate mathematical models. It shows that even though the computer is a powerful tool, it is also necessary to put in a great deal of human effort in order to obtain good matches.

One published field case is analyzed semi-automatically using computers in the study.
Single-Well and Multiwell Pressure Interference Analysis
Authors: Economides M. J. , Ogbe D. O.
Published: December 2007

The purpose of an interference test analysis is to provide reservoir characteristics such as permeability, porosity and areal extent. Reservoir anisotropy may be identified and measured. A drawback of interference testing is that it requires one or more potentially productive wells to be shut-in. However, this well test is superior to single-well drawdown or buildup because it often supplies results that reflect the characteristics of a much larger region of the reservoir. This paper presents a comprehensive review of the available analytical models and is supplemented by several real field problems and the associated interpretations. Guidelines are provided for the selection of the appropriate model, and criteria for interference well test design are outlined.
Prediction of Liquid Hydrocarbon Recovery from a Gas Condensate Reservoir
Authors: Almarry J. A. , Al-Saadoon F. T.
Published: December 2007

A compositional model consisting of material balance (M-B) ‘equations and the Peng-Robinson (P-R) Equation of State (EOS), was developed starting with the work of Bergman, Tek, and Katz. The model simulates constant volume expansion (CVE) as obtained from experimental analyses of gas condensates.

The contributions of this paper include the following: (1) evaluation of the phase behavior and fluid properties for an arbitrary mixture of components (2) development of the material balance equations to compute depletion performance, (3) investigation of P-R EOS as a tool for reproducing measured PVT data, and (4) analysis of the effect of component property estimation on EOS predictions.

The North Field Khaff reservoir, which is situated offshore northwest of the northern top of Qatar, and the specific K-4 reservoir description was used as the example in this work.

Laboratory measurements for constant volume depletion and phase separations of a condensate fluid sample were obtained from well No. NWD 5 in the K-4 reservoir of the North Field in Qatar. This experimental data was used as a basis for comparing results from the proposed compositional model. The data analysis was carried out up to C20+ group hydrocarbons.

The experimental data used for comparison with the calculated results were volume percent liquid (retrograde condensation), cumulative produced volume, molecular weight of heavy components (C7+) produced, and compressibility factor. In addition to the values calculated above constant composition expansion at different temperatures, a partial phase diagram for K-4 gas condensate, and viscosity were calculated by the model.
Role Of Gas In Global Energy Balance
Authors: Clegg M.W. , Middleton A.R.
Published: December 2007

1. Some Observations on the World Energy Scene

The difficulties of forecasting the behaviour of world energy and economic systems have led to persistent major revisions of energy forecasts during the last decade. However in the energy business where projects are highly capital intensive and lead times are long it is necessary to take a view of the future. The starting point for any energy forecast must be the economic environment and the structural changes in the world economy that may occur over the period considered - in the USA, for example, over the last decade they have led to a fall of 20% in the amount of primary energy needed to produce a unit of real income.

The consequences of these structural changes are exemplified by the growth in levels of conservation arising from the increase in absolute energy prices over the last decade. This trend towards greater efficiency can be prices over the last decade. This trend towards greater efficiency can be expected to continue. In Europe the increase in fuel prices led to significant falls in the amount of energy used for space heating; in Denmark energy use per dwelling fell by a third during the decade. A similarly large fall occurred in the US. All this took place through the installation of better insulation, double glazing and the reduction of waste; but the living standards and levels of comfort improved.

The forecast of higher prices in the long run coupled with an expected high level of technological advance suggests that structural change will continue, energy use will be less intensive and the ratio of energy to GDP will continue to fall. But there will be regional variations. As energy intensive industries are switched to the less developed countries where low cost hydrocarbon reserves exist the fall in the energy/GDP ratio will be more pronounced in the industrialized countries particularly the USA. The ratio for the less developed countries, by contrast, will not fall (Figure 1).
Saudi Arabian Computerized Log Analysis System
Authors: Asar H. K. , Saner S. , Amri T. S.
Published: December 2007

Saudi Arabian Well Log Analysis System (SARLOG) is a computerized open hole well log interpretation system developed locally for the Ministry of Petroleum and Minerals. This system consists of a total of forty subprograms. These subprograms will digitize and prepare data, perform chartbook environmental corrections and do level by level main calculations. Cross plotting subprograms are included for verification of log calibration, identification of lithology, differentiation of gas and oil and determination of all formation parameters.

As the equations and methods used in well logging depend on lithology type, shaliness and available log combination, optional methods have been included in SARLOG to allow the log analysts to put his own judgement when it becomes required. Six shale indicators are used to approach a more precise shale value, and seven water saturation methods are optional for shaly sandstones and complex carbonate lithologies.
Surface and Downhole Production Safety Systems for Sour Oil and Gas Wells
Authors: Morsi K. M.
Published: December 2007

The work on sour gas and oil wells by its nature is dangerous. Highly flamable and toxic sour gas and fluids under high pressure need to be handled by special equipment in a hostile environment.

Within ADCO, safety systems have been developed to protect the large investment, the environment and safety of operating personnel.

As a result of the high pressure and sour production involved, it is necessary to incorporate high – strength tubular materials and safety features such as surface controlled sub-surface safety valves, kill/dump valves, downhole packers and chemical injection systems into the completion design.

Several types of surface and sub-surface systems have been reviewed and tested for use in our onshore sour gas and oil wells in Abu Dhabi.
An Evaluation of Acid Frac/Matrix Stimulation of a Tight Limestone Formation in Exploratory Wells in Kuwait
Authors: Singh J. R.
Published: December 2007

With the advent of Kuwait's intensive exploratory activities to locate and test deeper geologic structures, tighter and very low porosity limestone formations were progressively encountered. Most of these hydrocarbon bearing formations initially appeared to be very stubborn and hardly indicated any fluid influx into the well-bore. In certain cases the hydrostatic head was nearly completely removed by unloading the well practically down to perforations, thereby creating optimum draw-down but it either resulted in poor inflow or none at all. In the absence of currently available chemicals, equipment, job design engineering and better understanding of tight carbonate formations and their responses to various acid formulations, some of these could have slipped into unattractive categories. With the implementation of specially designed matrix and acid-frac treatments, these formation have, however, been unmasked and turned out to be highly potential finds now. This paper basically outlines the salient features of theoretical and operational aspects of stimulating and testing some of the very low porosity hard limestone formations in Kuwait recently.
A Novel Approach for Risk Assessment in Chemical EOR Projects
Authors: Gittler W. E. , Krumrine P. H.
Published: December 2007

In today's volatile economic climate, comprehensive evaluation of the technical and financial uncertainties associated with all phases of tertiary or Enhanced Oil Recovery (EOR) projects is essential. In the portfolio approach used by major and independent oil producers, various EOR methods are in competition with exploration, drilling and continued secondary operations for limited funds.

A micro-computer-based, Chemical EOR Economics Simulator, (CEES) Model was developed to aid in the evaluations of various chemicals either used individually, or in combination for chemical EOR flooding. Chemicals such as alkalis, polymers, surfactants, sacrificial agents, etc., can be utilized in different chemical slug compositions. The model uses an oil recovery simulator with the option of utilizing a unique Monte Carlo technique to financially quantify the uncertainties associated with various chemical EOR alternatives. Parameters such as: Oil pricingCapital and expense escalationOil production and decline curvesTotal incremental oil production

are allowed to vary in the model. A user, by choice, can select a standard deviation for chosen parameters and allow them to vary randomly along a standard normal distribution. By varying any of these parameters, a project's sensitivity to that key factor can be determined. A cash flow analysis for each year is completed over the duration of the project and is used to produce an internal rate of return. In addition, an incremental internal rate of return is determined when the revenues and expenses attributable to the continued water flood are subtracted from the tertiary project. A single case can be completed or, through the use of multiple runs (1,000+), confidence bands can be established to determine the impact of each key uncertainty factor on the profitability of a proposed chemical flood.

Examples are given to demonstrate the advantages provided by using this tool for initial screening of proposed projects and in evaluating the financial and technical risks associated with close alternatives.
Internal Rate of Return: Friend or Foe?
Authors: Terry R. E. , Ehman M. P.
Published: December 2007

Results of a recent survey of over 100 exploration, production, and transmission companies operating in the Rocky Mountain Region indicate that the internal rate of return (IRR) is extremely popular as an economic evaluation criterion. However, there still remains, in the views of many authors and evaluators, a question concerning the validity of the IRR calculation. The validity question involves the calculation procedure and whether a rate of reinvestment of incomes is implied or not. Some feel that inherent in the calculation procedure is a reinvestment of incomes at the computed IRR, while others argue that there is no reinvestment implied and that it doesn't matter what is done with the incomes. Because of the reinvestment question and other complications of the IRR calculation, some individuals have suggested that other evaluation criteria be used.

This paper contains two parts. The first part presents a review of a few of the evaluation criteria used in the industry and the results of a recent survey concerning those criteria. The second part of the paper will address the reinvestment question and attempt to prove that the IRR calculation procedure does indeed imply reinvestment of incomes at the IRR.
Acoustic Static Bottomhole Pressures
Authors: McCoy J. N. , Podio A. L. , Huddleston K. L. , Drake B.
Published: December 2007

Acoustic instruments have been used routinely for many years as an aid in analyzing well performance of normal-pressure oil producers.1

Recent developments in equipment and techniques now permit more-accurate calculations of acoustic static bottomhole pressures at surface pressures up to 15,000 psi in corrosive (CO2 and H2S) environments. Equations and charts are presented herein for determining static bottomhole pressures from acoustic and well data. Also, a special technique is recommended for shutting-in a well which in most cases will yield more-accurate results.

This method has been programmed for an inexpensive, portable notebook-size computer which can be used in the field to easily perform these calculations.
Hydraulic Fracture Evaluation in a Geopressured Reservoir
Authors: Sookprasong P. A. , Elbel J. L.
Published: December 2007

Frequently, it is seen that production rate and flowing tubing pressure decline rapidly on abnormally pressured wells following a hydraulic fracture stimulation. It is often thought that rapid decline in production rate is due to inadequate fracture characteristics. However, the rate of decline depends on many factors, such as formation permeability, fracture half-length, fracture conductivity, reservoir pressure and reservoir size. Also on deep, low-permeability, high-pressure wells, closure stress can play an important role on the rate of decline in production when large rapid pressure drawdown is required for economic production rates.

This paper utilizes pressure transient test data and production data to evaluate a hydraulically fractured well in a geopressured reservoir. A prefracture buildup test, type-curve techniques for fractured wells with boundary effect, and a two-dimensional, single-phase simulation program with closure stress on proppant are used to arrive at an explanation for the performance of a well. It was found that a small reservoir drainage area and a loss of fracture conductivity were major factors of rapid decline in productivity.

Projections on future well performance were made and compared with subsequent actual well performance.
Oilfield Theft
Authors: Moss K. E.
Published: December 2007

The cost of oil field theft to the Petroleum Industry and the ultimate consumer is tremendous. Oil field theft should be a concern of everyone connected with the industry. We are going to have to do a better job of protecting ourselves against theft. The successful manager will find and develop ways to avoid theft. The unsuccessful will continue to be "easy pickings" for the thief.

Conservative estimates indicate that oil field theft is costing the Petroleum Industry one and one-half billion dollars per year. Some think that the cost may be as high as 10 billion dollars or more per year. Oil field theft affects everyone of us. For one to assume that he is not touched by oil field crime, is to admit ignorance or that he has his head in the sand.

The problem is present in a small or large degree throughout the Petroleum Industry. There is no area that is immune. The cost to the industry and the consumer is tremendous. Best estimates by government, insurance companies and law enforcement personnel are that oil field theft costs the consumer seventeen cents ($.17) of every dollar that he spends at the pump! Statistical records pertaining to oil field theft are very skimpy. Because our operations are scattered throughout the world and because many of the thefts are not reported, we don't know just how big the problem really is.
Use of Proppant Selection Models To Optimize Fracturing Treatment Designs in Low-Permeability Reservoirs
Authors: Phillips A. M. , Anderson R. W.
Published: December 2007

Low permeability reservoirs are currently being propped with sand, resin coated sand, intermediate propped with sand, resin coated sand, intermediate density proppants and bauxite. This wide range of proppant cost and performance has resulted in the proppant cost and performance has resulted in the proliferation of proppant selection models. Initially, a rather vague relationship between well depth and proppant strength dictated the choice of proppant. More recently, computerized models of proppant. More recently, computerized models of varying complexity have become available which utilize net present value calculations. The input is based on the operator's performance goals for each well and specific reservoir properties. Simpler, non-computerized approaches also being used include cost/performance comparisons and nomographs. Each type of model, including several of the computerized models, will be examined.

Utilizing these models and net present value calculations, optimum fracturing treatment designs have been developed for low permeability reservoirs such as the Prue in Oklahoma. Typical well conditions are used in each of the selection models and the results are compared. The computerized models allow the operator to determine, prior to fracturing, how changes in proppant type, size, and quantity will affect post-frac production over time periods ranging from several months to many years. Thus the operator can choose the fracturing treatment design which best satisfies his economic performance goals for a particular well whether performance goals for a particular well whether those goals be long term or short term oriented.
Hydraulic Fracture Treatment Design of Wells With Multiple Zones
Authors: Ahmed U. , Newberry B. M. , Cannon D. E.
Published: December 2007

In recent years, there have been significant developments in the optimization of hydraulic fracture treatment of wells with one pay zone, but studies concerning treatment in wells with multiple zonesare virtually nonexistent. Because a significant portion, it not a majority, of hydraulic fracture treatments are done in wells with multiple pay zones, discussions are presented to show (1) the use of limited technology leads to uneconomical depletion of the formation and (2) a model for effectively designing fracture treatment for multiple pay zones.

Three field examples are presented to illustrate the various uses of the model in optimizing hydraulic fracturing treatment of wells with multiple zones.
Simulation of Three-Dimensional Propagation of a Vertical Hydraulic Fracture
Authors: Thiercelin M. J. , Ben-Naceur K. , Lemanczyk Z. R.
Published: December 2007

This paper describes a laboratory and numerical study of contained hydraulic fracture propagation via a preexisting stress gradient. This study was conducted in order to improve current knowledge of three-dimensional geometry. Laboratory tests were performed using prefractured polymethylmethacrylate (PMMA) beams which were subjected to a stress gradient in the minimum principal stress direction. The fracture propagation was studied as a function of fluid rheology, flow rate and state of stress. The numerical approach consisted of a pseudo-three-dimensional model, developed to handle any type of boundary condition.

Results show that fracture-shape evolution is close to radial propagation at initiation, but becomes more and more contained as the length increases. A good prediction is achieved once the assumptions of the model are validated, i.e., once the fracture is sufficiently elongated.
Hydraulic Fracture Geometry Modeling, Prediction, and Comparisons
Authors: Advani S. H. , Khattab H. , Lee J. K.
Published: December 2007

Results from an on-going DOE sponsored program related to hydraulic fracture response modeling are presented. Finite element model formulations and the solution methodology associated with a pseudo-three-dimensional hydraulic fracture model coupling fracture fluid flow and leak-off on both horizontal and vertical cross-sections with the elastic response in vertical cross-sections are described. In addition, fracture geometry evaluations and selected comparisons with available results are revealed.
Comprehensive Well Testing and Modeling of Pre- and Post-Fracture Well Performance of the MWX Lenticular Tight Gas Sands
Authors: Branagan P. T. , Cipolla C. L. , Lee S. J. , Wilmer R. H.
Published: December 2007

Well testing and reservoir analysis results from the Department of Energy's Multiwell Experiment (MWX) are presented before and after a set of hydraulic fracturing treatments were performed in two naturally fractured, lenticular Paludal sands of the Mesaverde Group in the Rulison Field, Colorado. The well testing data combined with seismic, core, log, production, and special fracture diagnostics information was integrated into a reservoir model that was used to assess the effects of various reservoir parameters on well performance before and after each fracture treatment.

Production/interference testing and the subsequent reservoir modeling revealed that although hydraulic fracturing produced a highly conductive linear flow path to the wellbore, the productive fracture lengths appeared to be considerably shorter than designed lengths. Furthermore, a post-frac decline in overall production implied a degrading effect upon the flow capacity of the original natural fracture system that was adjacent to the propped fracture. The production/interference testing illustrates the gradual degradation in the near term production capacity of the reservoir from its initial state through two hydraulic fracture treatments.
Geology and Production Performance of the Niobrara Low-Permeability Reservoir in the Denver-Julesburg Basin
Authors: Hollberg J. E. , Dahm M. A. , Bath J.
Published: December 2007

This paper presents geologic and reservoir parameters of the Niobrara Formation in Weld County, Colorado. With the use of computer generated contour maps, it is possible to predict favorable areas of profitable Niobrara pay. This predictability is further enhanced when combined with Scanning Electron Microscopy (SEM) analysis and historical production analysis.

The SEM results show that the Niobrara in this region is a micrite and not a true chalk. The porosity is, therefore, lower than would be expected in a chalk.

The thickness of the second bench and the pore volume appear to have a better relationship to known faults in the Niobrara than present day structure. These parameters were analyzed in order to predict areas of faulting and fracturing, since these areas are known to have the best potential for Niobrara production. Use of these techniques indicates that the northern portion of the study area has the highest potential for successful Niobrara wells.

Based on the limited amount of production history available in this region and current market oil and gas prices, the average Niobrara well in this region appears to be uneconomic unless supported by additional production from other horizons. However, computer mapping suggests that current production is not located in the most promising areas. Greater Niobrara production potential may be found in local areas characterized by greater porosity, thicker benches, and proximity to faults.
The Use of Conventional Decline Curve Analysis in Tight Gas Well Applications
Authors: Maley S.
Published: December 2007

Standard decline curve equations can by used outside their normal range of application to give accurate and theoretically valid projections of tight gas well performance. This approach is preferable to the use of the reciprocal square-root of time as a tight gas well "type curve".
Wall Slip Evaluation in Steady Shear Viscosity Measurements of Hydraulic Fracturing Fluids
Authors: Knoll S. K.
Published: December 2007

The rheological properties of hydraulic fracturing fluids, commonly used in low permeability reservoirs, has been discussed extensively in recent years because of their importance in stimulation treatment design. Rheology of these systems is primarily determined in a coaxial cylinder viscometer and reported as apparent viscosity. However, many problems have been encountered in obtaining accurate measurements of crosslinked gels due to the fluid slipping at the solid boundaries of the bob and cup. This slip creates an unknown velocity profile across the flow field; in other words, the fluid experiences an unknown shear. Since viscosity, as well as job design parameters n' and K' are the direct result of shear rate and shear stress, determination of the actual shear rate experienced by the fluid is critical. Many instances have been observed where the steady shear measurements indicate that the fluid has little or no viscosity. Yet, accounting for slip at the walls, the fluid is still a viscous crosslinked gel. Only by determining the existence and extent of wall slip of fracturing systems and how to correct for it, can the steady shear data that are utilized in treatment design models be meaningful.

This paper presents the application of a theory to determine 1). wall slip velocities in a coaxial cylinder viscometer 2). corrected shear rate not based on power law parameters and 3). true viscosity of crosslinked fracturing fluids. Data have been taken over a wide shear rate range to distinquish if wall slip is more prevalent at low or high shear rates. Data also show, that for certain mixing conditions of the polymer and crosslinking reagent, wall slip is very significant and the shear experienced by the fluid is less than expected, resulting in higher viscosity values. Methods of gel testing and preparation have been examined and those methods that minimize wall slip will be discussed. In addition, oscillatory shear measurements, which describe gel structure, are shown to further explain rheological behavior in steady shear. Viscosity values corrected for slip will be compared with viscosity values obtained on a closed loop pipe viscometer.
Proppant Transport by Xanthan and Xanthan-Hydroxypropyl Guar Solutions: Alternatives to Crosslinked Fluids
Authors: Clark P. E. , Halvaci M. , Ghaeli H. , Parks C. F.
Published: December 2007

Proppant transport is of primary importance in the design of new fracturing fluids. In the prediction of proppant settling rates, a wide variation has been found between measured proppant falling rates and those predicted using correlations based on apparent vicosity. Many fracture design computer programs calculate proppant settling rates using calculation procedures which are based on Stokes' Law or some type of power law settling velocity correlation. Much of the experimental data on which these correlations are based were derived from studies of guar, hydroxypropyl guar and hydroxyethyl cellulose. This type of correlation is inadequate to describe the settling behavior in xanthan solutions, foams, emulsions or crosslinked gels.

Data on the proppant settling velocity and rheology of xanthan polymer solutions and xanthan-hydroxypropyl guar mixtures have been gathered to use in the development of correlations for proppant transport. The xanthan-hydroxypropyl guar mixture has excellent proppant carrying capacity over a wide range of temperatures. In fact, a mixture of 15 lb/1000 gal of xanthan with 15 lb/1000 gal hydroxypropyl guar yields comparable particle settling velocities to a 40 lb/1000 gal hydroxypropyl guar solution at room temperature and superior behavior at 150° F. The exact mechanism of the enhanced particle transport by the mixture has not been determined. However, the rheological behavior of the mixture at shear rates of less than 10 s-1 is important and is a shear rate not often considered in current fluid evaluation studies.
The ‘British Argyll’ DSV Wirelining System
Authors: Huber D S , Turner W , Baxter C
Published: December 2007

The wireline servicing of subsea completed wells is expensive and time consuming, as even simple wireline work has always been carried out by semi-submersibles in the North Sea. This paper describes the development of a subsea wireline and surface support system which has been used on a test well in the Argyll Field by the mono-hull diving support vessel, the ‘British Argyll’. The design of the system has evolved over the last three years as a result of close co-operation between Hamilton Brothers, the DSV operator and a major wireline company. The use of such a vessel has the potential to save an oil producer several million dollars per year based on the historical frequency of wireline interventions in a subsea developed field.
Field Experience in the Bothamsall Surfactant Flood Project
Authors: Cooper M N , Southworth R A , Walsh D M , Morgan J C
Published: December 2007

A low concentration surfactant flood was initiated in the Bothamsall Field in July 1983. The test area is described and the design of the project is discussed. The methods used to control surfactant injection and the steps taken to monitor produced fluids to assess the performance of the flood are described. Valuable experience has been gained both in the handling and injection of surfactant solutions and in the treatment of surfactant-stabilised oil-in-water emulsions. The initial production profiles for the surfactant flood are presented. The data required to make a complete evaluation of the response of the test area to surfactant injection are still being gathered.
OREDA – The Reliability Data Reference for the Offshore Industry
Authors: Gjerstad T
Published: December 2007

Probabilistic risk assessment and production availability studies are being applied extensively to offshore development projects. The associated need for reliability data has led eight major oil companies to co-operate in the development of the OREDA Handbook – an offshore reliability data reference published in 1985.
Experience of Perforation Under Drawdown Using Tubing Conveyed Guns on the Beatrice Field
Authors: Allan J. C. , Moore P. C. , Weighill G. T.
Published: December 2007

This paper describes the perforation, under drawdown, of Beatrice production wells. In view of the long completion intervals, tubing conveyed perforating guns are used.

A technique has been developed which enables perforation to be carried out under controlled underbalance conditions and allows well clean-up by means of a subsequent free-flow period. This, together with a pressure build-up, enables the well productivity index to be determined, and hence aids sizing of the electrical submersible pump. This is necessary to ensure that the pump operates within its recommended range.

To date, nine production wells have been perforated using tubing conveyed guns. It is shown that this technique has resulted in a significant improvement in productivity when compared to wells which have been perforated overbalanced. It is likely that this also enhances the life of the electrical submersible pump by reducing the pump loading.
Underwater Inspection and Surveys Using Computer Management
Authors: Mills G. , Ball D.
Published: December 2007

Mandatory underwater inspection programmes are expensive and generate large volumes of report material. Computer based systems have been developed to provide more efficient and flexible planning of these programmes, to facilitate report production and, most significantly to allow the management of the results of such inspections including trend analysis, summary reports, defect or reading ranking and so forth.

This paper will briefly review current common inspection techniques used underwater and detail how a computer aided inspection planning and reporting system was designed to satisfy the needs of underwater inspection. The basic philosophy of the system has been incorporated into six systems which have now been specifically tailored to oil companies' requirements, including one system for pipeline surveys which incorporates automatic transfer of information from the pipeline survey data processing computer system.

Such systems, which are in use today, could lead to fully automatic inspection surveys, from sensors to finally assembled report and this potential is discussed, together with other applications such as above water offshore inspection and inspection control during fabrication. The advantages of computer aided inspection reporting are explained, including the potential for cost savings during inspections and examples for where these have been achieved in reality.
The Simulation of Phase Behavior and Slim-Tube Displacements with Equations of State
Authors: Kossack C. A. , Hagen S.
Published: December 2007

In compositional reservoir simulation the ability of an Equation of State to accurately model the phase behavior is evaluated for both the Peng-Robinson and Soave-Redlich-Kwong Equations of State. The analysis was performed with pure component systems to circumvent the problem of pseudo-components and to allow a comparison of calculated ternary diagrams with literature values. The initial work was performed with the binary system of methane and n-decane. The relative permeability of the slim tube was determined by the history matching of an immiscible slim tube displacement. The Equations of State were able to simulate the two-component displacements. PVT experiments were run with the three-component system of methane-propane-n-decane to provide data for a phase match of the Equations of State. The Equations of State with these phase matches were not able to simulate the multiple contact miscibility displacements in a slim tube. The sensitivity of the calculated results to the binary interaction coefficients and to the number of numerical grid blocks was studied.
Oilfield Cashflow: The Independents' Lifeblood for Survival
Authors: Chan S. A.
Published: December 2007

Independent producers are under increasing pressure to seek out every available dollar of internally generated cashflow from otherwise idle assets or premature financial obligations. Many petroleum companies can better manage their existing operations to improve their performances through cash management, updated collection policies, cash processing and disbursements, short term investments, and more accurate planning. Using the analytical capabilities of micro-computers, examples of the benefits of applying financial management techniques are illustrated in terms of increased working capital, added profitability and strengthened cashflow.
Development of Field-Size Distribution for Undiscovered Hydrocarbon Resources in the Lower 48
Authors: Woods T. J. , Duleep K. G. , Vidas E. H.
Published: December 2007

Analyses of exploration history have indicated anomalous increases in finding rates for many field sizes as the resource base is depleted. The anomaly is a wide-spread phenomenon, and it cannot be explained in terms of the general form of the Arps-Roberts find-rate equation. A modified Arps-Roberts equation has been developed that replicates historical discovery patterns and provides a basis whereby the anomaly can be explained. Using the modified Arps-Roberts equation, we have developed estimates of the remaining undiscovered lower 48 hydrocarbon resource base, apportioned among field sizes. The resulting field size distributions provide some insights into lower 48 hydrocarbon resource estimates, such as those by the U.S. Geological Survey and the Potential Gas Committee. Some insights into general exploration success patterns can also be obtained.

Application of the modified Arps-Roberts find-rate equation to estimate the cost to discover and produce the remaining undiscovered hydrocarbon resource base indicates that a substantial part of the remaining resource would be uneconomic to discover and produce. The major part of this residual resource base is comprised of fields that are currently economic targets.
How the Portfolio Approach Aids Exploration Strategic Planning
Authors: Jones W. A.
Published: December 2007

The objective of this paper is to demonstrate the numerous advantages of the use of portfolio theory in the analysis of exploration opportunities and options. The principal benefits of the Portfolio Approach to Exploration Strategic Planning can be divided into two categories: those benefits in dealing with corporate management and those in developing the exploration strategies themselves.

A simple case study has been developed using a computer model. The study will follow an Exploration Program through the three stages of an annual cycle: evaluation, improvement, and tracking. The study will also be used to demonstrate the advantages of the Portfolio Approach in developing basin/play strategies.
A Simulation Approach to Viability Analysis
Authors: Garibaldi C. A. , Iskander F. F.
Published: December 2007

Two issues in risk analysis are studied. First, a simple method is developed for making consistent risk adjustments to the expected present value of profits, considering capital exposure and attitude toward risk. Next, a Monte-Carlo simulation model is developed to perform viability analysis and, thus, adjust for risk a realistic and operative distribution of results.
Recent Design, Placement, and Evaluation Techniques Lead to Improved Gravel Pack Performance
Authors: Ledlow L. B. , Sauer C. W. , Till M. V.
Published: December 2007

Gravel packing has been the method of choice for sand control for the last 40–50 years. Historically gravel packs have impaired the productivity of sand controlled well completions. Only recently through the use of Well Flow, Nodal or Systems Analysis1,2 has the technology from perforating, formation damage prevention, and gravel pack design been assembled in order to effectively understand these damage mechanisms. On-site supervision and execution of better designs is crucial to sand control success. Better gravel placement, downhole tools, and planning have enhanced our ability to execute, these designs.