bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling-Up the Capillary Imbibition Process from Laboratory Experiments on Homogeneous and Heterogeneous Samples
Authors: Hamon G. , Vidal J.
Published: December 2007

Experimental and numerical studies investigating the validity of the prediction of reservoir matrix blocks performance from water-oil imbibition tests on small samples are reported.

The reliability of the numerical predictive method is confirmed. It was checked against a complete set of laboratory imbibitions tests on homogeneous synthetic samples and heterogeneous outcrop cores for water-wet conditions. The ability to simulate a wide range of blocks heights and several different experimental boundary conditions allowing counterflow is satisfactorily verified.

Experimental results highlight the effects of heterogeneity on oil recovery rate. Oil production cannot be matched when the simulation does not take the heterogeneity into account. Any attempt to use a modified capillary pressure curve in fitting experimental data can lead to large errors in recovery rate prediction. When spatial distributions of petrophysical parameters are introduced in the simulation, good agreement is obtained with the laboratory results. Finally, guidelines are proposed for scaling-up the imbibition process from laboratory to the field.
Theory and Application of a Measurement-While-Drilling Neutron Porosity Sensor
Authors: Roesler R. F. , Barnett W. C. , Paske W. C.
Published: December 2007

Until now, Measurement-While-Drilling (MWD) services providing formation evaluation information have been limited to natural gamma ray and resistivity measurements. A porosity sensor has been needed to complete the basic set of measurements required for quantitative formation evaluation. We describe the first MWD compensated neutron porosity measurement service (CNØSM)* which employs a dual-spaced, borehole-compensated detector system to measure neutron-capture gamma rays. CNØ service, when combined with existing MWD gamma ray and resistivity services, provides the basic data necessary for calculation of water saturation from MWD logs, making it possible to replace wireline logs in many situations with resulting savings in both logging costs and associated rig time. This is particularly cost effective when drilling high angle offshore development wells and in other high cost development drilling. Making the neutron porosity measurement while drilling also limits the adverse effects of borehole washout that often plague wireline porosity measurements.
An Analysis of the Design Loads Placed on a Well by a Diverter System
Authors: Beck F. E. , Langlinais J. P. , Bourgoyne A. T.
Published: December 2007

Diverter systems, used as an alternate means of well control while drilling surface hole, have a demonstrated history of failure. Of particular interest in this paper are failures related to excessive backpressure, such as mechanical failure of surface equipment or the loss of the rig due to foundation collapse. Critical flow effects, neglected by current design practices, are shown both experimentally and theoretically to have a significant effect on backpressure. Critical flow is modeled by quantifying exit pressures and by including fluid acceleration pressure losses in backpressure calculations.

"Systems analysis" of diverter operations is developed and applied to a field example, proving its effectiveness as a design method. In addition to incorporating critical flow effects, this analysis also considers wellbore and reservoir performance. Calculation methods developed to perform the systems analysis are discussed. Design procedures culminate in a method by which diverter vent line diameter, conductor depth, and drilling depth are related to identify a safe interval over which to operate the diverter system.
Microprocessor Control of Sand Concentration Improves the Quality and Versatility of Fracturing Operations
Authors: Handke W. A.
Published: December 2007

A microprocessor based control system has been developed which automatically controls sand delivery of a fracturing blender to help maintain a desired sand concentration setpoint in the fracturing fluid exiting the blender. The computational speed and input/output capabilities of the system's microprocessor have resulted in steady sand concentration traces and fast sand concentration step changes. Non-standard "ramping" sand concentration schedules have been performed routinely and without difficulty using this automatic control system.

Subject paper describes the theory of operation, details of the basic design, and blending capabilities of the automatic control system. Field test results are also presented.

Documentation of control system operation is presented in the form of strip chart data collected during several fracturing operations.
Optimum Power Cable Sizing for Electric Submersible Pumps
Authors: Vandevier J. E.
Published: December 2007

Electric Submersible Pumps are a major form of artificial lift in secondary and tertiary recovery operations. The optimum selection of pumping equipment involves both consideration for reliable operation, as well as minimizing the total cost for artificial lift. It has long been the practice in the industry to use "rules of thumb" for determining minimum conductor size in selecting power cables for electrical submersible pump (E.S.P.) installations. In addition, it has been the practice to generally select the smallest conductor size possible, thereby reducing the initial capital cost for the installation. These practices have, in many cases, led to false economic decisions which cost the operator a great deal more over the life of the pumping equipment.

It is important, then, to understand how power conductor sizing affects the reliable operation of E.S.P.'s, as well as understand the total economic considerations which must be recognized for optimum cable sizing. Once important factors for proper cable sizing are understood, then a personal computer can be effectively utilized to calculate and to print the necessary data for optimum cable sizing.

An electric submersible pumping' system converts electric energy to hydraulic energy. From an electrical point of view, the combination of the surface distribution transformers, power cable, and electric submersible motor make up an electrical circuit which defines the system'selectrical performance. The power cable conductor size plays an important role in determining motor starting and running characteristics, as well as contributes to system electrical losses for which the operator must pay as part of the monthly power utility bill.
Calculation of the Critical Oil Production Rate and Optimum Completion Interval
Authors: Piper L. D. , Gonzalez F. M.
Published: December 2007

This paper presents a method for calculating the critical oil production rate and optimum completion interval in a reservoir containing both bottom water and a gas cap. Our method is an extension of a method recently presented by Wheatley which accounts for the effect of the cone on fluid potential. Results indicate that previous methods, which neglect the effect of the cone, give rates which are 20 to 25 percent too high.
Success in Offshore Gravel Pack Methods
Authors: Stracke M. L.
Published: December 2007

From 1980 to mid 1986 ARCO Oil and Gas Company's Southern District has gravel packed over 140 Gulf of Mexico completions. Defining a successful completion as one which has no rate limitations due to sand production, ARCO has achieved a 91.3% success rate in these completions. To identify the cause of this high success rate and to optimize its gravel pack procedures further, ARCO studied the effects of various factors on the gravel packed wells' performance. We compiled a microcomputer database1 covering all the wells gravel packed since 1980. The data base considered over 50 operational factors such as drilling and completion fluid overbalance, surge volumes, perforation washing, and use of fluid loss pills. These factors are listed in Table I. Using this data base, ARCO has been able to compare the production performance of the gravel pack completions versus any single factor or combination of factors. A performance indicator representing "Completion Efficiency" was developed to permit analysis of completions. It also allows comparison of the effects of different operational factors even in wells with dissimilar production and reservoir parameters. Initial results of this study have shown that no single factor can ensure a high efficiency completion. Rather, it is a combination of several key factors that contributes to high completion efficiency.
Taking Control of Tubular Inspections
Authors: Mortensen J. H. , Stewart D. L.
Published: December 2007

Operating companies spend more money than necessary on tubular inspection due to the lack of a coordinated quality assurance program. A substantial percentage of previously inspected tubulars have rejectable defects that result in excessive expenditures due to failures. An inspection program is proposed to maximize efficiency and reduce costs. Supporting evidence is also presented indicating that operators should not be liable for a significant percentage of the damages marked on rental tubulars following use.
Application of Tubing-Conveyed Techniques in through-Tubing Operations
Authors: Jones C. M.
Published: December 2007

Tubing conveyed techniques have been successfully applied in through-tubing remedial operations where excessive hole deviation and/or helical buckling have prevented conventional wireline or electric line operations. Perforating and setting bridge plugs have been performed using a concentric work string and a pressure actuated firing head. Two case histories, in which remaining reserves would not support the cost of a conventional rig workover, are presented. These cases describe procedures which were used successfully in remedial operations.
Microcomputer-Based Lease Monitoring and Operating System Lowers Costs and Enhances Production
Authors: Podio A. L. , Dunn W. W. , Irving R. H.
Published: December 2007

A practical, affordable system has been developed and field tested that performs all the common lease operating functions normally undertaken by lease pumpers with the additional benefits of continuous surveillance and data storage and retrieval provided by computer systems.

The development of a computer monitoring and control system that can be used for low to marginal production leases, has been made possible by the reduction in cost and the increased capabilities afforded by modern microcomputer systems used in conjunction with specially designed, low cost and high accuracy monitoring devices and microwave data transmission. Lease operations which involve gun barrels and settling tanks, pumping wells on time clocks, and shipping of crude by truck are especially well suited for this application.

The system is based on a ruggedized field microcomputer which communicates with single board microcomputer units distributed at the various leases via microwave transmission. Typical ranges are 15 to 25 miles. The distributed units interface with a set of special sensors, applied to monitor the entire surface (and subsurface through polished rod load) production operation. The sensors include measurement of pumping unit load, stuffing box leaks, polished rod temperature, gun barrel water level, heater treater temperature and pressure as well as tank level and tank temperature. The sensors are monitored frequently and the data and any alarms are reported to the field computer. The data base thus accumulated at the field computer can be accessed by remote users via telephone, with a standard modem interface so that any PC with off-the-shelf communications software can retrieve the pertinent data. Of particular value are special programs developed to analyze the long term data on each well; to identify the trends and obtain the "signatures" of individual problems.

A prototype installation has been operated over a year in a two-county area in Texas, covering 23 leases and 28 wells. Operating experience shows that the operators have accepted the system and have successfully integrated its use into their operations. Results indicate that the system has been useful in determining the efficiency of beam pumping systems, detecting upsets and leaks at the tank batteries, detecting errors in volume of oil sales, flowline leaks and other operational difficulties.

Use of the system is especially advantageous for small independent operators who lack computer/electronics, as well as production engineering personnel. The system can be implemented as a lease service at a cost comparable to routine manual surveillance with dedicated pumping crews. The prototype applications have indicated that the use of the system has improved the efficiency of field personnel, reduced operating costs, reduced the possibility of major spills, provided lease security and near continuous engineering data.
Evaluation of Field Methods to Determine Crosslink Times of Fracturing Fluids
Authors: Hodge R. M. , Baranet S. E.
Published: December 2007

Operators using delayed crosslinkers in fracturing fluids often specify an exact "crosslink time" to avoid the detrimental effects of shear. However, the field methods currently used for determining "crosslink time" do not simulate mixing and pumping conditions. To measure viscosity development under simulated field conditions, laboratory tests were performed with four common crosslinked fracturing fluids using a capillary rheometer to control temperature and shear. The results of this study indicate 1) the on-site "crosslink time" tests do not accurately represent viscosity development under actual treating conditions and 2) accurate control of the "crosslink time" is not necessary to insure optimum fluid performance. Also, the use of specific composition dual crosslinker systems (which combine fast and slow crossl inkers) appeared to be the best way to obtain good performance both at the perforations and in the fracture.
The Development of Scale Inhibitors and Inhibitor Evaluation Techniques for Carbon Dioxide EOR Floods
Authors: Chesnut G. R. , Chappell G. D. , Emmons D. H.
Published: December 2007

The injection of carbon dioxide for enhanced oil recovery causes profound changes in reservoir brine chemistry. These changes directly impact on a downhole scale control program and in some cases may require new products to effectively control scale formation. Evaluation techniques are presented for scale inhibitors to be used in carbon dioxide floods. The results of tests on current inhibitor molecules are discussed as well as the development and evaluation of specialized polymers for scale inhibition in low pH environments.
A New Concept of Treating Surfaces Exposed to Oilfield Water Systems
Authors: Surinach P. P.
Published: December 2007

The use of scanning electron microscopy (SEM) and x-ray microanalysis to study seawater biofilms has contributed to acquiring a thorough understanding of sulphate-reducing bacteria (SRB) growth within deposits. The micro-environment created within fouling films is much more aggressive to metal than natural corrodents of fluids. The outcome of these findings has been the creation of a new generation of antibiofoulants (ABF's) and biofilm preventives. These products exhibit excellent removal of deposits, excellent biocidal properties on biofouled surfaces and prevention of biofouling-induced corrosion. By proper surface pre-conditioning, the minimum cidal concentration (MX) required to kill SRB's within standard biofilms has been decreased from 70–80 ppm to 10–20 ppm. Thereby, biocidal properties similar to those of acrolein have been obtained.
Core Flooding in Well-Characterized Heterogeneous Systems: An Experimental and Simulation Study
Authors: Sorbie K. S. , Wat R. M. S. , Rowe T. , Clifford P. J.
Published: December 2007

This paper presents results from a series of single phase stable displacement experiments in a heterogeneous core assembly. This system consists of a 0.5 m cylindrical sandstone core with a central core removed and replaced with high permeability ballotini. Displacements at unit, 2:1 and 10:1 viscosity ratio were performed which demonstrated the importance of crossflow mechanisms in polymer flooding processes.

The experiments were modelled using a curvilinear grid in a chemical flood simulator. All of the main features observed in these experiments were successfully reproduced and analysed in terms of viscous and dispersive crossflow effects. Some discussion is presented on the significance of crossflow at the reservoir scale.
Importance of Dissolution/Precipitation Mechanisms in Sandstone-Alkali Interactions
Authors: Bertaux J. , Lemanczyk Z. R.
Published: December 2007

The mechanisms of interaction between sandstone minerals, particularly clays, and two alkalis, NaOH and KOH, have been studied in order to better understand the response of sandstone reservoirs to alkaline treatments as a function of sandstone mineralogy and the nature of the alkaline solution. Such interactions are of primary importance in currently applied alkaline flooding and matrix stimulation processes.

The clay-alkali interaction can be described as an incongruent dissolution with the precipitation of new aluminosilicates. With NaOH. a crystalline zeolite precipitate appears at the tested temperatures (90, 150°C). With KOH, amorphous precipitates are present at these temperatures, followed by crystalline precipitates at 200°C

Response of Berea cores to NaOH and KOH treatments has been studied and is explained on the basis of the observed dissolution/precipitation mechanisms. Permeability changes and clay reactivity with fresh water are directly related to the amount of dissolved minerals and the extent of precipitation.
Beyond Alkaline Flooding: Design of Complete Chemical Systems
Authors: Krumrine P. H. , Falcone J. S.
Published: December 2007

The design of chemical flooding systems has been and remains quite complex due to the many interactions that can occur between not only the various constituents in the chemical slug but also with the reservoir itself. This paper discusses many of the interactions that occur between surfactants, polymers and alkalis in a mixed system design. Specific focus is directed towards the benefits mixed alkalis impart to the overall design such as 1) water and reservoir conditioning, 2) adsorption/retention reduction, 3) emulsification improvement, 4) wettability alteration, and 5) improved sweep efficiency and mobility control.

Data are presented and discussed to show how such systems can be designed and what parameters to consider in maximizing chemical survivability, transport, and effectiveness. Effects such as consumption, ion exchange, precipitation, and propagation are discussed for a buffered mixed alkali that is tailored to a specific reservoir environment. This approach expands the horizon for alkaline chemicals and indicates one of the few remaining economically feasible directions for chemical recovery systems in todays oil market.
OPEC and Adam Smith: Part II
Authors: Roberts M. L.
Published: December 2007

OPEC's failure to discipline itself clearly suggests that that organization refuses to acknowledge that Adam Smith is alive and well. Thus, the pain of Economics 101 is making itself felt through lower crude prices and a competitive fight for market share. The current fight by OPEC for increased market share is a direct result of its two quantum jumps in energy prices during the decade of the 1970s. The ten to twenty fold increase in oil prices set in motion irreversible forces that have changed the structural demand for energy which reduced by about 50% the historic growth relationship of energy to economic activity. In addition, the quantum jump in energy prices has encouraged the incremental supply of non-OPEC oil and non-petroleum energy at an annual rate of 1.0–2.0 million BD per year.

Since the beginning of 1986, OPEC in general, and Saudi Arabia and the Gulf States in particular, have made a decision to flood the market with oil and thereby reduce prices (rather than prorate production and increase prices) in an attempt to regain their historic market share of 54%, up from the current 31%. The degree to which they are successful at this game will depend almost entirely on the following factors: (1) the rapidity with which existing non-OPEC oil production declines; (2) the degree to which non-OPEC oil reserves are replaced; and (3) the degree to which the structural changes in demand will be re-altered at current prices of some 50% less than those experienced in late 1985.

This paper will discuss these issues by focusing on the forces of supply, demand and pricing and how they are changing the characteristics of the industry.
Importance of Cost/Price Relationships for Least-Cost Oil and Gas Reserves
Authors: Kuuskraa V. A. , Morra F. , Godec M. L.
Published: December 2007

Traditional economic analysis suffers when oil and natural gas prices are on a roller coaster. On the ride up, there are expectations of massive profits. On the ride down, there are dire predictions of economic doom, of outflight of capital, and of collapse in drilling. However, a narrow focus on only oil prices misses the point that costs also rise and fall with prices.

This paper examines the interdependent roles of prices, costs, and efficiency on the economics of domestic oil and gas supplies by addressing three points:

Historical relationship of costs and prices since the early 1970's; Change in relative oil and gas supply economics since the "energy crises" through today; Implications of the cost/price relationship on "least-cost" strategies for oil and gas reserves and alternate fuels.

The paper concludes with several examples to show where proper use of cost/price relationships could improve industrial and public policy decision making in energy.
An Analysis of Supply and Demand for Crude Oil
Authors: Cecil R. E.
Published: December 2007

Valuation of oil and gas producing properties requires projections of production rates, product prices, taxes to be paid and operating expenses. Production forecasts are based on engineering analysis with considerations given to equipment capacity, well deliverability and demand. Current laws normally govern tax considerations, although legislation under consideration must also be recognized. Past expenses coupled with estimates relative to inflation provide the basis for estimates of future expenses. Price forecasts have been dependent upon current prices with estimates as to future inflation rates. Therefore, the appraiser of an oil and gas property must have not only a geotechnical background but also an understanding of economics and finance.

Until the early 1970's, the oil industry had primarily focused economic analysis on domestic supply and demand. As this demand exceeded the supply, resulting in increased levels of imports, attention turned to supplies outside the United States. Today our evaluations require analysis of worldwide economic factors when projecting production rates, prices and expenses. Estimates of crude oil supply relative to the price for the various producing nations have been made, thereby providing supply schedules with the attendant supply curves. Estimates of world demand were made to obtain demand schedules and demand curves. The supply and demand curves have been brought together to provide the estimated equilibrium price for oil.
Financing Projects via Turnkey Contractors
Authors: Marple G. T. , Ruley G. E.
Published: December 2007

Exploration for oil and gas is a capital intensive endeavor, and the sudden and severe change in environmental conditions has drastically reduced this necessary resource. The critical missing element in the oil and gas industry right now is not the lack of economically viable projects, rather, it is the lack of capital. However, by breaking with the traditional relationship between a service company and an oil company, projects can be "financed" today without the need for an intermediary such as a bank. Cox Oil & Gas, Inc., among others, has been successful at structuring a program which has achieved getting wells drilled for their account without having to allocate any of their own capital resources.
True Government Take (TGT): A Measurement of Fiscal Terms
Authors: Smith D. E.
Published: December 2007

Companies involved in international exploration/production are always faced with the question of which countries have the most favorable fiscal terms. The typical way of analyzing this problem is to compare tax rates or profit splits. This task becomes much more difficult though, when an attempt is made to compare the terms of countries which vary considerably in their fiscal methodology. The True Government Take (TGT) is a quantitative indicator that measures the overall effect of a particular fiscal system and thus allows more meaningful comparisons between countries.
The Impact of the New Tax Law on Internal Cash Flow Generation
Authors: Thompson R. S.
Published: December 2007

The impact of The Tax Reform Act of 1986 on the ability of the integrated oil producer and the independent oil producer to generate cash from internal sources is investigated. How did the oil industry fair in the most recent tax reform battle. Obviously, the impact of the new tax law will vary from company to company depending on the specific tax situation of the company. The changes affecting the oil industry appear at first glance to be relatively minor. However, changes in the alternative minimum tax calculations are significant and could add to the tax burden in some years. Each year tax reform manages to chip away at some of the preferential treatment that the oil industry receives for certain capital expenditures. The 1986 Tax Reform Act is not an exception. However, the oil industy probably would have been "hit" harder had it not been for the current weak economic condition of the industry.
Oil Futures and Options Increase in Importance in Volatile Industry Conditions
Authors: Hill J.
Published: December 2007

The oil market of the late 1980's and into the 1990's is likely to be characterized by price uncertainty and volatility. The oil futures and options markets have developed to meet the needs of the petroleum industry to find a supplementary vehicle to reduce some of the risk surrounding pricing. This paper provides an introduction to the use of crude oil futures and options hedging by oil and gas producers.
The Impact of the New Tax Law on Project Evaluation
Authors: Wright J. D. , Thompson R. S. , Shipley S. E.
Published: December 2007

The Tax Reform Act of 1986 contains few provisions aimed specifically at the oil and gas industry. It does, however, contain dramatic changes for both individuals and corporations as a whole. The effect of some of the major changes is discussed from the viewpoint of project evaluation. Three representative projects- a drilling deal, a field development and waterflood, and an acquisition were studied.

If the Alternative Minimum Tax is not included, it appears that the new tax law does not significantly change the present value of typical oil and gas projects. Compared to the old tax law, the new law increases the tax liability in the early years of a project and decreases it in later years.
Cyclic Steam Stimulation in a Tight Clay-Rich Reservoir
Authors: Watkins D. R. , Kalfayan L. J. , Blaser S. M.
Published: December 2007

During the past several years, two proprietary-fines stabilizing processes have been field tested in conjunction with cyclic steam stimulation at So. Tapo Canyon Field, Ventura County, California. The Fourth Sespe Formation, the producing zone, is a low-permeability sand (<35 md) containing an abundance of clay and non-clay fines. It is characterized by rapid production decline and extreme water sensitivity. Laboratory tests demonstrate the potential for damage by formation fines as well as the effectiveness of the experimental processes in preventing damage.

The field tests resulted in widely varying steam responses. This paper describes the differences in steam responses and provides an explanation for some of these differences. Factors that appear to affect steam response include reservoir pressure, changes in oil composition caused by steam injection and heat transfer efficiency. Two wells demonstrated long term stimulation beyond the thermal effects.

Overall, the field tests demonstrated that the Sespe can be steam stimulated without damage.
Numerical Model for Evaluating Concentric Steam Injection Wells
Authors: Griston S. , Willhite G. P.
Published: December 2007

A mathematical model was developed to evaluate wellbore heat losses and two-phase pressure drop in concentric-pipe steam injection wells. The model is based upon the equations for conservation of mass, momentum, and energy within each pipe, heat loss in the wellbore, and heat conduction to the formation.

In the model, pressure drop in each pipe is determined from momentum balance equations and include liquid hold-up and flow regime correlations for two-phase flow. Heat transfer between the concentric pipes is calculated based on the combined thermal resistance of vaporization/condensation on each surface of the inner pipe and conduction through the inner pipe wall. Additionally, heat is lost from the outer pipe to the formation at the cement-formation interface. Transient heat-conduction in the formation is also taken into account. The computation procedure consists of it-eratively solving two sets of momentum and energy balance equations in a stepwise manner over a specified length of the well.

The model has been verified for single-pipe injection wells with a dry casing annulus, by comparing predicted and actual field data. Predicted temperatures and pressures showed very good agreement with measured temperature and pressure profile data. Model calculations for concentric injection have not been validated against field data; however, the predicted boiloff problems have been qualitatively verified in the field by the severe scale buildup found in either the inner or outer pipe of many Chevron concentric wells used in the Kern River and Coalinga areas.

Numerous test cases were run to study the effects of injection rate, injection pressure, injection quality, pipe sizes, and insulation on concentric steam injection. The results of this study indicate that heat transfer between the concentric pipes is very high, resulting in an unintended distribution of heat, steam quality, and pressure exiting each pipe and often causes steam boiloff (100% vaporization) in one of the pipes. Insulated tubing can effectively reduce the heat transfer, but certain practical limitations require close evaluation of its use.
Three-Phase PVT and CO2 Partitioning
Authors: Vetter O. J. , Bent M. , Kandarpa V. , Salzman D. , Williams R.
Published: December 2007

Flashing of reservoir liquids and their associated PVT behavior is critical for many oil field operations. Conventional PVT work considers only the reservoir oil and its gas flash behavior. The presence of a water phase in the reservoir is normally neglected. It is assumed that water does not flash below its boiling point. This assumption is justified to some degree if the system contains no components which are soluble both in the water and oil such as CO2 and other gases. Most reservoir fluids contain such gases. Therefore, the conventional bubble point considerations as used for field operations are conceptually wrong. Using only two-phase PVT data in petroleum operations when in reality a three-phase system exists in the field as commonly done could conceivably generate various problems related not only to the proper reservoir management but also to handling of carbonate or sulfide scale problems.

The experimental data on (a) three-phase PVT work and (b) CO2 partitioning effects between oil and water under various conditions are discussed. Actual and different oil/water/gas systems from three California reservoirs were examined.

The results of this work show that the three-phase PVT data are extremely important under the following field conditions: The WOR is varying and high.The GOR is varying and high.The concentration of CO2 and/or other gases which can dissolve in both oil and water phases is high.The water breakthrough occurs in a waterflooded reservoir.During CO2 flood operations.A carbonate or sulfide scale problem exists anywhere in the field.Application of inhibitors to prevent the formation of various types of scale.

In principle, the phase behavior of reservoir and/or produced fluids as well as.the associated CO2 partitioning effects between the various phases depend upon the following variables: Pressure and pressure changes.Temperature and temperature changes.CO2 concentration in any of the three fluid phases potentially existing in the reservoir prior and anywhere in the system, during and after flashing of the reservoir fluids.Composition of reservoir brine (including pH), oil and gas.WOP, GOR and GWE under any set of pressure and temperature conditions.

The present paper discusses the importance of three-phase PVT data (including bubble point and flash behavior in the presence of CO2) and CO2 partitioning data for oilfield operations. Sampling, testing and computational procedures are described. All the discussions are supported through three-phase PVT data generated in the laboratory for three different types of reservoir fluids from California fields.
Case History of Hydraulic Fracture Performance in the Naturally Fractured Paludal Zone: The Transitory Effects of Damage
Authors: Branagan P. T. , Cipolla C. L. , Lee S. J. , Yan L.
Published: December 2007

The pre- and post-stimulation reservoir performance of two naturally fractured Paludal sandstones in the Mesaverde Group were thoroughly tested and evaluated. The transitory nature and effects of natural fracture damage caused by two stimulation experiments are illustrated. These two sandstone reservoirs, located at the Department of Energy (DOE) Multiwell Experiment (MWX) site, designated Paludal sands 3 and 4, were initially characterized by integrating a comprehensive set of core, log, seismic, geological, well testing and production data. The data set indicated that the dominant production mechanism in Paludal sands 3 and 4 was a set of anisotropic natural fractures. The identification, quantification and incorporation of this anisotropic natural fracture system is critical to the subsequent post-fracture production and well test analysis.

These reservoirs were modeled using a finite difference naturally fractured reservoir simulator. This simulator is capable of modeling transient matrix flow and provides the proper coupling of the propped hydraulic fracture with the anisotropic natural fracture system. The initial postfracture well tests and production data indicated that although these fracture treatments had been carefully designed and monitored, they did not properly achieve the desired enhancement. Subsequent reservoir modeling illustrated that these treatments had probably decreased the flow capacity of the natural fracture system near the hydraulic fracture, thus limiting the production capacity of the well.

The natural fracture damage was assumed to be the result of residual treatment liquids and/or fracturing fluid blockage. The magnitude of these damage mechanisms should decrease with time. Paludal sands 3 and 4 were subsequently isolated for 18 months and then re-tested. The reentry testing and production indicated that the initial post-fracture damage was no longer present. This paper details the genesis of reservoir behavior from the initial pre-fracture well tests through the period of poor post-fracture production to the current period of enhanced reservoir performance.
Pressure Transient Response in Multilayer Gas Reservoirs Containing Hydraulic Fractures
Authors: Sullivan R. B. , Lee W. J. , Holditch S. A.
Published: December 2007

This paper presents a method to estimate induced fracture properties and reservoir geometry in multilayered gas reservoirs similar to the Travis Peak formation in East Texas. The Travis Peak is characterized by commingled production from small, high-permeability channel sands and blanket low permeability formations. Our specific objectives are to estimate fracture half-length, fracture conductivity, and area of the small, high-permeability layer in a two-layer reservoir system similar to the Travis Peak.

In this study, we developed constant rate drawdown type curves applicable for analyzing pressure buildup tests which follow production at constant bottomhole pressure. The results obtained from our type curves are used only as a starting point for a more rigorous numerical simulation (history-matching) study.

Our type curves assume the small, high permeability sand is a "channel" deposit, which is modeled with a 2×1 rectangle, whereas we assume the larger, lower permeability layer is a blanket-like deposit which can be modeled as a 160-acre square. A single vertical fracture of finite conductivity intercepts the wellbore and completely penetrates each layer, extending down the short side of the 2×1 rectangle.

Even though this paper presents a specific solution for a specific type of layered reservoir, it illustrates a general approach for analyzing other layered reservoirs with induced fractures and known geometry in the layers.
Quantitative Model of Overpressured Gas Resources of the Pinedale Anticline, Wyoming
Authors: Charpentier R. R. , Law B. E. , Prensky S. E.
Published: December 2007

The Pinedale anticline, located in the northern part of the Green River basin of Wyoming, contains a large accumulation of overpressured natural gas within a low-permeability sequence of Upper Cretaceous rocks. The geologic factors which control the gas accumulation can be used to create a quantitative model of the accumulation. Such a model was constructed for the Pinedale anticline and used for a resource estimation. Within this 197 mi2 [317 km2] structure, the 10,000 ft [3048 m] section of overpressured rock is estimated to contain 159 tcf [4.50x1012 m3] of in-place natural gas in the sandstone reservoirs, although only a small part of this resource may be recoverable.
Application of Horizontal Drainhole Drilling Technology for Coalbed Methane Recovery
Authors: Logan T. L. , Schwoebel J. J. , Horner D. M.
Published: December 2007

Methane gas contained in coal represents a potential new gas supply. Transformation of this large gas-in-place resource to reserves will depend on developments of modified and/or new completion methods to achieve long-term economic production. Coal reservoirs typically have very low matrix permeability with gas being desorbed from the matrix to the wellbore through a system of natural fractures or cleats. Due to low permeability, coal reservoirs usually require hydraulic fracture stimulation to achieve economic production. Investigations have shown that hydraulic fractures usually propagate parallel to the maximum stress or face cleat direction, and therefore may not adequately access an anisotropic reservoir. A more effective stimulation technique may be a horizontal borehole placed perpendicular to the maximum permeability direction. This paper discusses the application of drilling horizontal boreholes for coalbed methane recovery in two different situations: i) in a coal seam associated with an active underground coal mine, and ii) in a deeply buried unmineable coal seam.
Modified Fracture Pressure Decline Analysis Including Pressure-Dependent Leakoff
Authors: Castillo J. L.
Published: December 2007

Nolte developed an analysis of the pressure decline following a fracturing treatment to provide an estimate of fluid efficiency, fluid loss coefficient, and fracture geometry. This analysis has become an industry standard for evaluating and improving the design of fracturing treatments. The derivations by Nolte assume the leakoff coefficient is a pressure-independent constant. This assumption is valid when leakoff is controlled by a compressible filter cake.

In cases where leakoff is primarily controlled by filtrate viscosity, by an incompressible filter cake, or by reservoir permeability and compressibility, the leakoff coefficient is pressure dependent, and, therefore, declines during the closure period. Under these circumstances, direct application of the Nolte technique may not be appropriate, and could cause an optimistic estimate of fluid efficiency and leakoff coefficient.

This paper introduces a new plot for fracture pressure decline analysis that determines the pressure parameters (ISIP, Pc, P*) required in the Nolte leakoff calculations. The derivative of this plot may be used to identify the extension period, the closure period, and to assess the influence of pressure dependent leakoff on fracture pressure decline. In order to account for pressure dependent leakoff, equations are presented where the leakoff coefficient is treated as a mathematical variable. The equations describe simple linear relations applicable to the fracture closure period. When these relations are plotted on Cartesian coordinates, the closure period is recognized by a straight line with slope proportional to the leakoff coefficient. As shown in the examples, this modified approach is easily applied and provides new insight to the fracture closure period.
Gas Recovery from Deep Millidarcy Layered Gas Formations with Nonlinear Elastic Deformation Characteristics
Authors: John P. W.
Published: December 2007

Starting from Rotliegend well evaluation in parts of the European Southern Permian Basin this paper is adressed to a main problem of stimulation design in deep layered gas bearing formations:

Advanced in situ analysis discloses a gap in the approach of conventional theory to in situ reality of complex multilayersystems. Uniaxial strain tests on cores prove the presence of layers with non linear elastic deformation characteristics.

The impact of a hydraulic treatment on a strata-system comprising layerproperties beyond LEFM behaviour is not covered by conventional assumptions. Consequently it is neccessary to review basic treatment design approaches.

As a result this paper tries an analysis of sandstone-shale multilayersystems.

A layerspecific deformation characteristic supported from experiments is applied to quantify the interaction between the impact of a treatment and the layerindividual response due to timedependent in situ status and rock properties. The resulting reaction is expressed by parametervariations as a variabel function of stress status.

The consequence of these investigations leads to a new approach of an extended fracture criterium to cover multilayersystems including non linear elastic rockdeformation. This permits advanced modelling of multilayersystems, is important for realistic fracture geometry calculations, improved treatment design, selective access to gas accumulations and effective packed fracture systems.
Developing a PC-Controlled Digitizing Program
Authors: Brown S. L. , Walsh J. W. , Gibson M. M.
Published: December 2007

The digitizing tablet offers PC users the ability to input data from a strip chart or from printed graphs directly into disk files. To connect the digitizing tablet to the computer and to interpret correctly the stream of numbers output from the tablet, a driver program must be designed and implemented. This paper discusses digitizers for PCs and the design of driver programs for different applications.
Well Log Analysis Spreadsheet
Authors: Heemink G. H. , Bryant W. T. , Langenbuch T. L.
Published: December 2007

Log analysis without the aid of taped or digitized data, and a mini-computer, is a tedious chore. A typical desk top interpretation may consist of manual data extraction from log prints, hand plotting the appropriate crossplots for parameter selection, and then processing the data level by level in a hand held programmable calculator13. Fine tuning the calculations and documenting the results is very time consuming if the evaluation involves multiple zones and many levels.

This paper presents a spreadsheet log analysis program for the purpose of organizing pertinent well information and log data, minimizing computation time, fine tuning results, and producing documentation.

The program is very flexible, easy to use, and includes sophisticated techniques and industry standard logic. The program is open ended and is a suitable model for other similar applications.

Well log data is processed over multiple runs and includes zoning of log parameters, water saturation, porosity, and shale models.

Custom menu options are provided for easy use.

The program requires a 640K personal computer and was developed in LOTUS 1-2-3* version 2.01.
Enhanced Reservoir Evaluation System Analyzes Data From a Wide Range of Sources
Authors: Shuman J. L. , Ulloa K. , Wilkinson B. C. , Petak K. R.
Published: December 2007

Drill stem and well test data from surface readout instruments, mechanical gauges, memory gauges, or any combination of these can be acquired, analyzed, processed and displayed at the well site using a recently developed interactive system.

Data acquired from one or more of the sources is stored on disc, from which it can be used to produce any known conventional plot while the data is being analyzed. In the case of surface readout operations, analysis can be conducted during data collection, and an operator can interact directly with the computer to perform the analysis. Conventional, pressure derivative, and non-linear regression analysis techniques are provided. One microcomputer, printer, plotter, and appropriate data acquisition interface comprise the hardware of the system. Training requirements are minimal due to simplicity of software, hardware, and procedure.

Decisions regarding the well can be made on the rig floor, based on complete information available from the system. Time required to acquire data from memory gauges is reduced to a few minutes, so that analysis from these sources can also be made at the well site.

Subject paper presents conceptual and operational details of the system and explains its application in a variety of field conditions. Buildups, drawdowns and surge tests have been conducted on the Gulf Coast, the North Sea and other locations around the world using this data acquisition system. Several techniques of analysis are demonstrated, based on data collected on actual jobs. Plots available from the system are presented.
Cost Effectiveness of Oil-Based Drilling Muds in the UKCS
Authors: Bailey T J , Henderson J D , Schofield T R
Published: December 2007

Over the last five years the use of oil based mud in the North Sea has increased. This is principally for drilling the Tertiary and Cretaceous mudstones in the Central and Northern sectors and the massive salts in the Southern sector. The technical reasons behind this increase have been examined as has the cost effectiveness of using an oil based mud system.

To compare the performance between oil based and water based mud, operations in six distinct zones on the UKCS were evaluated; these included areas where several exploration or production wells had been drilled using both mud types. Only drilling operations which could be affected by the mud system were selected for comparison. This evaluation was done for the 17 1/2" and 12 1/4" hole sections of each well: the operations selected for consideration were drilling, tripping, reaming, conditioning mud and hole, and any instances of stuck pipe. Performance was compared using a time per metre drilled standard.

Analysis of the data shows that well sections drilled with oil based mud require fewer wiper trips, well costs are lower, average drilling rates are higher, there is a reduced need for reaming and mud conditioning, and mud related problems are fewer. Additionally the risk of stuck pipe in 12 1/4" hole is significantly reduced with the use of oil based mud. Overall, the cost effectiveness of using oil based mud is shown to be significant. In some instances significant savings are being realised; such savings could make marginal field developments economically viable from reduced drilling costs alone.