bluuebunny/crossref_metadata_2025 huggingface dataset:
Crossplot Technique for the Analysis of the Carbon/Oxygen Log
Authors: O'Brien William Jay , Brown Susan L. , Sanyal Subir K.
Published: December 2007

A graphical technique is presented to compute hydrocarbon saturation from induced gamma ray spectroscopy (IGS) logs. The technique is based on a linear equation that approximates the carbon-oxygen-ratio log response as a function of porosity, shale volume fraction, and hydrocarbon saturation. Coefficients of the equation are obtained from empirical crossplots. Porosity and shale volume fraction are computed from open hole logs.

IGS logs are often run in cased hole wells to monitor hydrocarbon saturation in low salinity reservoirs for enhanced oil recovery (EOR) projects. Two examples are given from an EOR project of the North Kern Front Field in Bakersfield, California. The examples illustrate the crossplot approach for a shaly-sand, heavy-oil reservoir under steam drive. Hydrocarbon saturations obtained using this technique are compared with core and Dresser Atlas' computed data. The results compare favorably with core data.
A Competent and Practical Approach to Well Testing and Analysis in Tight Gas Resevoirs
Authors: Branagan Paul , Cotner Gene
Published: December 2007

Well testing of low permeability gas formations generally concerns itself with acquiring quantitative information of a number of reservoir parameters including: initial reservoir pressurereservoir permeabilityskin effects or damagereservoir boundariespropped fracture lengthfracture conductivitydeliverability

These and other parameters are obtained from essentially the following three distinct types of pressure transient well tests: drill stem testspre-frac testspost-frac tests

These well tests involve both drawdown and buildup periods and the subsequent analysis is generally based on measured or derived bottomhole pressure data and surface flow rates. A great deal of literature has been written describing gas well testing and the various analytic techniques1–5. Although the basic assumptions and limitations for each type of technique are described, the fact is that most of these assumptions or limitations are difficult, if not impossible, to adhere to, particularly in a field environment. Numerous authors6–8 have fixed upon certain of these fundamental assumptions and proceeded to suggest alternative methods or variations in the analytic technique that would tend to compensate for the discrepancies and thus decrease the induced error.
Fracture Porosimeter — A New Tool for Determining Fracture Conductivity under Downhole Stress
Authors: Wendorff C. L.
Published: December 2007

This paper describes a new, fast, simplified procedure for determining fracture conductivity at downhole stresses. The embedment and crushing of proppant between rock samples from a specific formation are measured at closure stresses. The conductivities of fractures propped with various proppants can be determined rather quickly. As a result, the procedure can supply information useful in determining optimum fracture treatment for a specific well.

In the new procedure, samples of formation and proppants are placed in an appropriate confinement chamber. Closure stresses are applied and fracture conductivity can be calculated.

A proppant data base obtained using a modified Cooke2 conductivity test unit includes permeabilities, porosities and fracture widths measured over a range of closure stresses. These properties are dependent upon the type and amount of proppant tested and the stress applied.

Fracture porosity determinations can be made in a short time with a relatively small investment in equipment. Core preparation and testing time require a few manhours per test.

The paper includes examples of permeability and surface areas of conventional proppants. Fracture conductivity determinations, made with a variety of formations and proppants, indicate how this procedure can be useful when making decisions concerning fracture treatment design.

An improvement in equipment design is also presented. The use of a Hoek11 triaxial cell as a fracture porosimeter allows the application of both closure and confining stresses, thus more closely simulating downhole conditions.
Dispersion in Flow through Porous Media
Authors: Sahimi Muhammad , Heiba Adel A. , Hughes Barry D. , Davis H. Ted , Scriven L. E.
Published: December 2007

Dispersion is a consequence of flow. It results from the different paths and speeds and the consequent range of transit times available to tracer particles convected across a permeable medium. The kinematic mechanism stems from the connectivity structure of porespace; the dynamic mechanism, from the effect of pore shape and size on flow. Molecular diffusion can modify both. In many circumstances these mechanisms lead to distributions of macroscopic average solute or tracer concentration that are diffusive, i.e. that can be modeled by the convective diffusion equation, dispersion coefficients taking the role of diffusivity.

For cases of diffusive mixing locally at pore junctions and no appreciable diffusion between, a simple network approximation is appropriate. Square and simple cubic networks of variable pore segments, with average flow in one of the pore directions, are useful idealizations. Dispersion in one– and two–phase flow through these networks is studied here by the Monte Carlo strategy of replicated computer experiments. This strategy combined, with considerable computational savings, with the percolation theory of fluid distributions in two-phase flow. Network topology and pore geometry and thus the two basic mechanisms are precisely controlled.

The results show that dispersion is diffusive in the cases simulated. Longitudinal (mean flow direction) dispersivity is an order of magnitude greater than dispersivity in transverse directions. In two-phase flow, longitudinal dispersivity in a given phase rises greatly as the saturation of that phase approaches residual, i.e. its percolation threshold; transverse dispersivity also increases, but more slowly. As the threshold is neared, the backbone of the subnetwork occupied by the phase becomes increasingly tortuous, with local mazes spotted along it that are highly effective dispersers.

All of the findings accord qualitatively with most available data, except that dispersivities in reality are not constant but increase slowly with macroscopic average flow rate, which may stem from molecular diffusion that is lost from the network approximation used.
Interpretation of Mixed Wettability States in Reservoir Rocks
Authors: Melrose J. C.
Published: December 2007

It has recently been noted that the diffuse electrical double layers which exist at (1) the oil/ brine and (2) the mineral/brine interfaces in sandstone reservoirs will in many cases be quite similar with respect to electric charge and potential. Extremely thin aqueous wetting films separating such interfaces are thus stabilized by the electrostatic repulsive force acting between the double layers. In the present paper the limits under which stable thin films can exist are examined in more detail. It is shown that there exists a lower limit to the pore size in which thin wetting films will occur and that this limiting size depends on the salinity of the brine. It is also shown that whether this limiting pore size becomes a factor in determining the wettability of the rock/brine/oil system depends on the pore size distribution curve and on the initial brine saturation of the rock. Geological factors which may come into play in establishing the initial water saturation in a given case are discussed.
Flow Mechanism of Forchheimer's Cubic Equation in High-Velocity Radial Gas Flow Through Porous Media
Authors: Ezeudembah Agodi S. , Dranchuk P. M.
Published: December 2007

Until recently, the visco-inertial flow equation, which is an adaptation of Forchheimer's quadratic equation, has been used to describe gas flow behavior at higher flow rates and pressures. The inability of this equation, in some cases, to fully describe high-velocity, high-pressure gas flow behavior, especially around the wellbore, led to the consideration of other empirical equations.

In this paper, formal derivation of Forchheimer's cubic equation is made by considering the kinetic energy equation of mean flow and dimensional relations for one-dimensional, linear, incompressible fluid flow. By the addition of the cubic term, this equation is regarded as a modified Forchheimer's quadratic equation which accounts for the flow rates obtained beyond the laminar flow condition. The cubic equation spans a wide range of flow rates and regimes, i.e. Darcy type, inertial type, and turbulent. For suitable use in gas flow studies, this equation has been adapted, modified, and corrected for the gas slippage effect.

The physical basis of the cubic term has been established by using boundary layer theory to explain the high-velocity, high-pressure flow behavior through a porous path. Gamma, the main parameter in the cubic term, is directly related to a characteristic, dimensionless shape factor which is significant at higher flow rates. It is inversely related to viscosity, but has no dependence on the gas slippage coefficient in the higher flow regime.
Errors in K-Values Prediction and Its Effect on Natural Gas Processings
Authors: Hemeida Adel M. , Desouky Saad Eldeen M.
Published: December 2007

Computer programs vere designed to calculate K-values and enthalpy by using different methods for multi-component system. Results show that, a variation of 9.91 percent in the K-value of methane causes a variation of 31.2 percent of the produced liquid, and a deviation in the range of 1.15% of the condensed liquid is obtained from Canfield1, M. G. Kesler and B. I. Lee2 equations. Also operating conditions can be determined from material and heat balance calculations by using modified Redlich-Kwong MRK3,4 equation with an average error of -2.683%
Response of the Deep Propagation Tool in Invaded Boreholes
Authors: Chew W. C.
Published: December 2007

The problem of the radiation of a current loop antenna in a multicylindrical medium is formulated exactly in terms of an integral and an iterative scheme making the integral more tenable to approximation. This closely approximates the response of the Deep Propagation Tool (DPT* tool) in invaded boreholes. To enhance the understanding of the wave due to the current loop antenna, the integral is approximated in the limit in which the antenna spacing is much greater than the diameter of invasion, or the frequency is low. The approximation shows that the wave, for the case of shallow invasion, resembles the response of a loop antenna in an unbounded medium. An iterative scheme is devised to systematically compute the approximation for an arbitrary number of cylindrical layers. The approximation to the response allows one to understand easily the present operating principle of the Deep Propagation Tool and provides better physical insight into the problem.
Reservoir Property Implications of Pore Geometry Modification Accompanying Sand Diagenesis: Anahuac Formation, Louisiana
Authors: Holland Michael T.
Published: December 2007

This paper represents a study of reservoir pore modification accompanying diagenetic secondary porosity development within a deep (13,400') overpressured Anahuac Formation sandstone in southern Louisiana. Such secondary porosity formed by dissolution of carbonate cement, detri-tal grains, and other soluble replacive minerals comprises a significant portion of porosity formed in U.S. Gulf Coast Tertiary reservoir sands. The primary pore system within this reservoir was significantly enlarged (up to 35% porosity) by selective dissolution of soluble material by acidic fluids generated during hydrocarbon maturation and shale dewatering. Subsurface secondary porosity development is significant in influencing: 1) the type, amount and rate of fluid to be produced, 2) the development of potential reservoir porosity after primary porosity has been destroyed by compaction, and 3) mechanical competence of the reservoir to compaction accompanying production.

Using scanning electron microscopy, petrographic examination, mercury injection and core testing at in-situ reservoir conditions, characteristics of the reservoir pore system were examined from core within this particular sand interval. Secondary pore size and distribution was found to be affected by: 1) sandstone mineralogy, 2) pore matrix content, and 3) sedimentary structures and resulting textural components hindering fluid flow.

Mechanical competence of secondary porosity to compaction in sandstone reservoirs is an important parameter when considering reservoir stress sensitivity. Keystone bridging relationships between grains and silica overgrowths can be established during the initial phases of compaction such that when leaching of cement and soluble grains occurs, the less soluble quartz grain matrix is supportive to porosity development. Special core tests were performed at simulated in-situ reservoir conditions of pressure and temperature to examine porosity and permeability reduction as a function of effective stress generated by reducing pore pressure (simulated fluid production). Observed mechanical resistance to uniaxial compaction at reservoir conditions was determined within portions of the sand containing high (~30%) secondary porosity. Volumetric strain measured during testing showed less than 2% reduction in total core volume accompanying a 6000 psi reduction in pore pressure. However, permeabilities were reduced by 26-89%. These data reflect how pore apertures connecting pores were affected by compaction.
Fracture Detection Techniques in the Georgetown and Austin Chalk Formations
Authors: Julian Preston J.
Published: December 2007

This study relates the success of detecting and analyzing naturally fractured systems in the Austin Chalk and Georgetown Formations from log evaluations. The Austin Chalk is composed principally of calcareous unicellular algal remains called cocospheres and their disunited, gear-shaped, skeletal remains called cocoliths. The Georgetown Formation is a hard, dense, and finely brittle limestone. Both formations contain matrix porosity, but are dependent on open fracture systems for economical hydrocarbon production. Hence, defining and evaluating the developed fracture systems before setting an expensive casing string is important. The Dual Induction Log and the Compensated Neutron-Formation Density Log offers an economical method of evaluating these fracture systems.

Case studies in Robertson, Milam, and Burleson Counties, Texas have shown that fracture systems near the wellbore can be detected. Attempts to determine the existence of hydrocarbons in fracture systems using logs were successful in the Austin Chalk and Georgetown Formations. Full core analyses were also successful in determining the existence of these fracture systems. However, obtaining core samples on all wells as a method of determining fracture systems is not recommended due to the high cost of coring.

Emphasis of this study is on the use of logs to determine the existence of economically recoverable hydrocarbons in fracture systems. Although this study concludes that logs were successful in detecting naturally fracture systems near the wellbore, they cannot predict the effects of mechanical fracturing on the formation. Hence geological trends in the area must also be considered.
Development of a Kinetic Model for In-Situ Combustion and Prediction of the Process Variables using TGA/DSC Techniques
Authors: Vossoughi Shapour , Barlett Gordon W. , Willhite G. Paul
Published: December 2007

This paper describes the development of a kinetic model of the in-situ combustion process from data obtained from Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The kinetic model was used to predict fuel deposition and combustion rate in a combustion tube. Good agreement was obtained between predicted and observed fuel deposition and combustion rate in two combustion tube runs.

A crude oil from Iola County, Kansas, was studied. This oil has a gravity of 19.8° API and a viscosity of 222 cp at 38°C and 89 cp at 54°C. Data from TGA experiments on Iola crude heated in the presence of air were obtained. Analysis of combustion gases from the TGA was done by gas chromatography to determine the nature of the reactions occurring during the TGA runs. Main reactions/transitions identified were distillation, low temperature oxidation, cracking and combustion.

A kinetic model of the TGA process was developed from thermograms. The model is based on the weight of crude oil components which undergo main reactions/transitions. The kinetic model was used to predict the percentage of the crude oil deposited as fuel in the combustion process as well as the time for consumption of the fuel within the combustion zone. By estimating the length of the combustion zone from an energy balance across the region where combustion reactions take place in a combustion tube, it was possible to predict the rate at which fuel was consumed during the process.

A combustion tube run was made with silica sand containing 8.0% by weight Iola crude oil in order to test the prediction by the kinetic model derived from thermal analysis techniques. Results of the combustion tube run were in good agreement with predicted values of this work and another run from the literature which was performed on the same crude oil.

The fuel heating value and heat availability during the process were also estimated by DSC techniques. However, the estimated heating values were low. This was attributed to the Increase in heating value of the crude oil in the combustion tube due to low temperature oxidation and distillation effects downstream of the combustion front.
Application of Linear and Spherical Flow Analysis Techniques to Field Problems—Case Studies
Authors: Kohlhaas Charles A. , del Giudice Claudio , Abbott William A.
Published: December 2007

Most engineers examine well-test data only with techniques developed for flow in a horizontal cylindrical-radial pattern toward the wellbore. Spherical and linear flow have application in many reservoir situations. Spherical flow has been examined extensively by many authors as an intermediate period between two radial-flow periods for wells which have a short completion interval in thick formations. Linear flow situations develop early in the life of wells which have been fracture-treated: their early linear-flow periods are followed by radial flow. Linear flow may develop late in a well test after a period of early radial flow due to certain configurations of reservoir geometry.

Techniques for analyzing spherical and linear flow are summarized here. Data plots which should be prepared and diagnostic features for recognizing and. interpreting spherical and linear flow are outlined. These techniques are applied to three example cases to illustrate the methods of analysis and the types of information which can be developed from such analyses and cannot be obtained from the standard Horner-plot analysis.
Uncertainties About Future World Oil Prices
Authors: Kilgore W. Calvin , Sandoval A. David
Published: December 2007

Projections of world oil prices are made with the knowledge that circumstances surrounding the world market can change abruptly, often as the result of political considerations. The ability to produce oil and the overall demand for oil change less rapidly. Anticipated world developments in these areas suggest that prices, adjusted for inflation, could easily remain flat through 1985 and then rise steadily during the next 10 years, doubling by 1995.
Non-Darcy Compressible Flow of Real Gases in Propped Fracture
Authors: Ubani Ephraim A. , Evans Ronald D.
Published: December 2007

The development of a simple hyraulically fractured gas well model is presented. A one-dimensional fracture flow model is used to investigate the effects of non-Darcy flow of a real gas in a hydraulically induced, vertical, propped fracture. A sensitivity analysis was performed on the inertial resistance factor β, to determine how any variation in the value of β would affect performance predictions based on non-Darcy flow. It was observed that non-Darcy flow effects in the fracture may be significant especially at the vicinity of the wellbore. It was also noted that the accuracy of non-Darcy flow predictions is quite sensitive to the interial resistance factor. Test results of the model are presented.
Practical Applications for a Gas Well Model With a Fracture
Authors: Poundstone David J. , Crafton James W. , Brown Charles A.
Published: December 2007

Production and reservoir problems can be routinely evaluated from pressure-production history using an efficient model of an individual gas well with a fracture. The model can be used to predict long term performance and make ultimate reserve determinations. Predictions can be used to compare against actual performance to isolate reservoir and mechanical problems such as critical flow restrictions, water loading, sand fillup, or permeability degradation. The model's ability to handle vertical fractures enables evaluation and design of effective field-wide fracture treatments. Because it can develop realistic gas deliverability scenarios, it can be applied to production facilities design and field exploitation. These applications are addressed with case study examples.
Seeking Prospects for Enhanced Gas Recovery
Authors: Doherty Mark G. , Randolph Philip L.
Published: December 2007

As part of the Institute of Gas Technology's (IGT) ongoing research on unconventional natural gas sources, a methodology to locate gas wells that had watered-out under over-pressured conditions was developed and implemented. Each year several trillion cubic feet (Tcf) of gas are produced from reservoirs that are basically geopressured aquifers with large gas caps. As the gas is produced, the gas-water interface moves upward in the sandstone body trapping a portion of gas at the producing reservoir pressure. The methodology for identifying such formations consisted of a computer search of a large data base using a series of screening criteria to select or reject wells. The screening criteria consisted of depth cutoff, minimum production volume, minimum pressure gradient, and minimum water production. Wells chosen by the computer search were further screened manually to seek out those wells that exhibited rapid and large increases in water production with an associated quick decline in gas production indicating possible imbibition trapping of gas in the reservoir.

The search was performed in an attempt to characterize the watered-out geopressured gas cap resource. Over 475 wells in the Gulf Coast area of Louisiana and Texas were identified as possible candidates representing an estimated potential of up to about 1 Tcf (2.83 × 1010 m3) of gas production through enhanced recovery operations. In addition, several thousand wells appeared to have watered-out but not at high enough pressures or with what was considered a strong enough water drive. Furthermore, many thousands of normally pressured shallow gas reservoirs were eliminated by the first screen and no production history obtained. This implies that the potential resource base for enhanced gas recovery is substantially greater.

A process to determine the suitability of a watered-out geopressured gas cap reservoir for application of enhanced recovery is outlined. Working from data available in the public domain this process was applied to ascertain the potential and risk involved in enhanced recovery for over 50 wells. It also was used to determine which ones appeared to be the better prospects.

This paper addresses the identification of a potential gas source that is considered an unconventional resource. The methodology developed to identify watered-out geopressured gas cap wells can be utilized in seeking other types of watere.d-out gas reservoirs with the appropriate changes in the screening criteria.
Enhanced Gas Recovery From Water-Drive Reservoirs—Methods and Economics
Authors: Akindele Femi M. , Tiab Djebbar
Published: December 2007

As the search for additional natural gas continues, recovery of known reserves must be improved if the goal of avoiding shortages is to be met. One area requiring further industry attention for enhanced gas recovery is the reservoir associated with an active aquifer. In reservoirs of this type, pressure maintenance and entrapment of gas by encroaching water greatly reduce recovery.

This paper discusses the mechanism by which the aquifer reduces gas recovery and the magnitude of gas possibly left in place. Three methods of improving recovery are analyzed including (1) planned water production, (2) accelerated gas production and (3) gas replacement/displacement by other gas of lower economic value. The study shows criteria for technical and economic feasibility of the methods. Examples are used to illustrate the evaluation procedures.
Mathematical Field Model Predicts Downhole Density Changes in Static Drilling Fluids
Authors: Sorelle Roland R. , Jardiolin Ricardo A. , Buckley Peter , Barrios John R.
Published: December 2007

A mathematical model requiring a minimum of input data can predict the variation of downhole density and hydrostatic pressure in static drilling fluids. It is a general model for oil and water base drilling fluids and completion fluids. Analysis of the model allows several important conclusions to be drawn about the density behavior of drilling fluids downhole.
Determination of Skin Factors and Flow Capacities of Individual Layers in Two-Layered Reservoirs
Authors: Larsen Leif
Published: December 2007

Methods to determine skin factors and flow capacities of individual layers in two-layered reservoirs are presented. The methods are based on infinite-acting approximations derived for systems without crossflow, but can also to some extent be used to analyze early data from systems with crossflow. Limitations arise if the vertical permeabilities are of the same magnitude as the horizontal permeabilities, or higher. In such cases the methods presented in this paper can be invalidated by effects of crossflow.

For drawdown and buildup analyses we introduce both direct computational procedures and procedures based on trial-and-error plotting. Which procedure to choose in a given situation will depend on the smoothness of the data and the type of analysis being used.
Deep Sea Drilling Instrumented Riser Joint
Authors: Tonda Henri
Published: December 2007

An Instrumented Riser Joint (IRJ) developped to measure critical riser parameters in real time during offshore drilling operations in 1000 m water depth, is described Some characteristical data, provided during drilling operations in 680, 800, 950 m water depth are shown. A second IRJ designed for the 1800 m water depth drilling campaign in the Mediterranean Sea, integrates two new sensors (tool-joint and gas). The 1800 m IRJ and a riser measurement system are discussed.
State of the Art Hydraulic Fracture Stimulation Treatment for a Western Tight Sand Reservoir
Authors: Ahmed Usman , Schatz John F. , Holland Michael T. , Jones Arfon H. , Greenfield Harvey
Published: December 2007

The Pinedale gas field is a tight sand reservoir in Sublette County, Wyoming. A number of wells have been drilled in this field since the 1930's. However, there has been no commercial production because of low initial flow rates and rapid production declines usually associated with low permeability. This field would become attractive if the technological problems impairing development could be overcome. This paper describes a resource evaluation and stimulation research program centered around the drilling of two new wells in the Pinedale Field. The resource evaluation involved a critical review of prior data, geological and geophysical work, laboratory testing of core samples from the new wells, and pre-stimulation and post-stimulation flow testing of the new wells. The stimulation research involved special core testing with candidate stimulation fluids and proppants, field in-situ stress testing for fracture geometry estimates, transient pressure testing for well and fracture evaluation, hydraulic fracture design and implementation, and well deliverability projection. Utilizing the state-of-the-art technology, a total recoverable reserve of 2.8 tcf is now possible from the 90,000 acres of Pinedale Field.
Modeling and Analysis of the CSAMT Geophysical Technique Results to Map Oil Recovery Processes
Authors: Bartel Lewis C.
Published: December 2007

The mapping of enhanced oil recovery (EOR) processes is important to predict process behavior and to be able to exhibit some control of the process for maximizing the stimulation of oil reservoirs. The controlled source audio-frequency magnetotelluric (CSAMT) electromagnetic geophysical technique shows promise for mapping steamfloods and firefloods. Two field trials were conducted, one at a steamflood tar sand oil recovery experiment and one at a fireflood heavy oil recovery process. An initial report of the results was given previously. In this paper, an analysis will be given of the CSAMT results for the two floods along with a comparison with production and post-test results. The result of this work is that the CSAMT technique is a viable technique for mapping these thermal EOR processes. In addition, a discussion of mathematical modeling will be given.
A Statistical Approach for Combining Reservoir Fluids Into Pseudo Components for Compositional Model Studies
Authors: Mehra Rakesh K. , Heidemann Robert A. , Aziz Khalid , Donnelly John K.
Published: December 2007

This paper describes a scheme for combining reservoir constituents into fewer pseudo components for compositional studies. The algorithm is based upon the minimization of the errors introduced in the predicted phase saturations. It requires the generation of a second derivative matrix of the phase saturation with respect to moles present at various expected reservoir conditions, which are then used to calculate the simple correlation coefficient matrix and to establish the criterion for combining the reservoir constituents.

Once determined, the properties of pseudo components are calculated using Lee and Kesler's mixing rule. The interaction parameters required for the two constant equation of state models are calculated using simple mixing rules.

The utility of the proposed scheme is demonstrated by comparing predicted phase saturations for the lumped scheme with the saturations obtained using the full original compositions for three widely different reservoir oils. A one dimensional gas cycling process is also simulated to show that the lumped scheme gives an adequate description of the process.
Compositional Effects on the Adsorption of Surfactant From Aqueous Phases in Equilibrium With a Middle Phase Microemulsion
Authors: Vernet Marc R. M. , Truchetet Remy , Schechter Robert S.
Published: December 2007

Adsorption onto nonporous alumina from an excess aqueous phase in equilibrium with an optimum middle phase microemulsion and the corresponding solubilization have been measured as a function of isopentanol concentration, sodium chloride concentration, and alkane molecular weight for 4-dodecyl benzene sulfonate and 4-tridecyl benzene sulfonate. The concentration of isopentanol was adjusted so that each system was optimal.

A multilinear regression analysis and a designed set of experiments were used to construct contours in the optimal plane--coordinate axes represented by the logarithm of salinity and hydrocarbon alkane carbon number (ACN).

These contour plots showed that at a constant ACN, the solubilization parameter exhibits a maximum and adsorption a minimum when the electrolyte concentration is increased.

Two different surfactants were studied. It was found that the one having the longer hydrocarbon tail yielded a larger solubilization and a smaller adsorption.
Field Facilities for CO2 Tertiary Floods—A Conceptual Design
Authors: Alderman David H. , McFarland Ray M. , McIntyre Jim W. , Minissale Joseph D. , Roye J. E.
Published: December 2007

Amoco Production Company is currently evaluating the economics associated with CO2 flooding in West Texas. In order to complete the economic evaluations, field facilities were designed to provide operational reliability, low maintenance, and a minimum investment cost. This paper will focus on the concepts involved in developing designs for the following major field systems: CO2 DistributionInjection wellsProduction WellsFlowlines and Fluid GatheringSatellite BatteriesGas Gathering

Each of these systems, as well as others, such as water disposal and electrical systems, was the subject of a detailed design study.

The CO2 injection system was designed to distribute dry, dense phase CO2 to the injection wells from a central supply point, using API X-grade pipe in a trunkline network. Surface and downhole injection well equipment was evaluated, as were methods of switching CO2 and water injection.

The major areas of study for the production systems were corrosion control and methods of producing a high gas-liquid ratio (GLR) fluid. Flowlines and fluid gathering systems were evaluated for possible replacement with fiberglass pipe. Satellite batteries were designed to meter and separate gas and liquid production. Conventional separator designs were modified for CO2 service. Comparisons between steel and plastic pipe were made for gas gathering systems.
Dynamics of Moving Interfaces in Porous Media: III. Extension of Buckley-Leverett Theory
Authors: Kale Dilip M.
Published: December 2007

In this paper Buckley-Leverett frontal advance theory is extended to two dimensional flows. Two dimensional analog of the front is a closed curve c across which the water saturation changes abruptly. Behind the front water saturation increases monotonically towards the injection well. Equisaturation contours behind the front are also closed curves. The continuous change in water saturation is approximated by several small steps. Then we get several equisaturation zones behind the front separated by contours across which water saturation changes abruptly in small steps. We shall refer to these contours as fronts. This approximation corresponds to linearizing the fractional flow curve beyond the frontal saturation by several linear segments.

The progress of the fronts with time depends upon the well configuration and the fractional flow curve. The total mobility changes across each front giving rise to a vortex sheet. A complex velocity potential for the instantaneous velocity field is constructed by the method developed in the earlier papers and the efflux vector is found out everywhere in the flow region. The velocity with which the fronts advance is in the same direction as the efflux vector, but the magnitude of the former differs from the latter by a factor Fw' = dFw/dSw evaluated at the corresponding water saturation. Knowing the velocity of the front it can be traced in time. In other words, after finding the efflux vector in the flow region, in an infinitesimal portion of the flow region we can apply the theory of frontal advance by assuming the flow to be linear there. The procedure of calculations is demonstrated for a typical fractional flow curve with some simple well patterns.
An Engine Concept for a Viable Transition Into the Future
Authors: Eng K. D.
Published: December 2007

Syncrudes and synfuels will be introduced in the future to supplement or replace petroleum based transportation fuels. Initial synfuels may have qualitites considerably different from present fuels and may cause operational problems in engines. Instead of further treating the synfuels to meet current fuel specifications, thus increasing the production costs, it is entirely viable to introduce an engine which has the capability of operating on a broad range of fuels. This type of engine, with its ability to run on petroleum based fuels and synfuels, could provide a smooth transition into the future.

The Texaco Controlled-Combustion System (TCCS) is a direct-injection, stratified-charge, engine concept. It has demonstrated the ability to run on a broad range of fuels including gasoline, diesel, broadcut fuels, low octane shale derived gasoline and alcohols. Performance of an engine modified to employ the TCCS concept, operating on different fuels, is discussed in this paper.
Exploration for Natural Gas in Northern Germany and in the Alpine Area
Authors: Hedemann Hans-Adolf
Published: December 2007

During the sixties, natural gas fields in carbonate reservoirs of the Sechstein formation (Upper Permian), in particular, were developed in the North German basin at depths of 2 000 - 4 000 m (about 6 500′ - 13 0001). Current exploration is focussed on Rotliegendes sandstones (Lower Permian) at about 5 000 m (16 400′). Successful discoveries are being developed. In some places natural gas has been discovered below the Permian in sandstones of the Upper Carboniferous (Pennsylvanian), the coalbearing source formation for the gas. With the development of gasbearing Paleozoic and deeply buried sandstones, the problems of tight reservoir rocks became evident. Stimulation of these rocks requires super-frac operations.

Throughout the present phase of active development, exploration geologists have in mind that exploration in future decades will be looking out for potential natural gas prospects in Devonian and/or Lower Carboniferous (Mississippian) of the North German basin. This has already happened in the eastern part of Germany. Such targets occur at depths of about 7-8 000 m (23 000′ - 27 000′). Geophysical surveys and some wildcat drilling, partly supported by governmental funds, have been carried out, some of which by major joint ventures.

Similar subsidies are given for exploration of deep targets (6 - 8 000 m, 20 - 27 000′) in the area of the Northern Alpine thrust zone in Bavaria. In the Northern Alpine Foreland, however, only small to medium natural gas fields at depths of between 1 000 and 3 000 m (About 3 000 - 10 000′) have so far been developed. Below the intermountane Alpine basins (Austria) and in the Southern Alpine Foreland (Italy) discoveries have been made at depths of up to 7 000 m (23 000′).
Project Financing for the Small Independent Company
Authors: Ramsay H. J.
Published: December 2007

This paper is written for the independent operator considering project financing in his operations. What the operator can expect in making these financial arrangements and how project financing compares to other financing methods is discussed.

Within the past decade, large amounts of capital have been needed by the petroleum industry to finance projects worldwide, especially in the North Sea area. In this area project financing has been used by companies having different objectives which include at least one of the following: raising capital, reducing financial exposure, or reducing capital costs1. In project financing the source of repayment is limited to the cash flow stream provided by a particular project. It can be used alone or in conjunction with other types of financing to provide a desired result relative to the corporate balance sheet and to the relative assumption of risks in the project between the borrower and the lender2,3.

Historically, financing for the small, independent company active in exploration and production involves oil production loans from commercial banks when the company has proved producing reserves to provide collateral for these loans. When such reserves are not available or the capital requirements outstrip the collateral value for conventional bank financing, the operator will resort to equity financing. Equity financing for the independent operator can include public and private limited partnerships, farmouts, and/or sale of a portion of the independent's interest at a promoted price. These types of equity financing are used by both public and private independent companies. Equity financing provides for spreading the risk and sharing the available capital within the industry, and also provides an important source of capital from outside the industry.
New Thoughts on an Old Topic: Reservoir Integration (Volumetrics)
Authors: Banks R. B.
Published: December 2007

Although planimetering of contour maps to determine reservoir volumes is widely-accepted, it can be shown mathematically that planimetering always is less rigorous than numerical integration when integrating net volume, net porous volume or hydrocarbon pore volume. This is true whether a) individual variables (such as porosity and thickness) are contoured, planimetered and multiplied, or b) combined variables (such as porosity * thickness) are contoured and planimetered. Numerical integration is shown to be the most mathematically rigorous method of determining reservoir volumes.
The Log Analysis 8K ROM Module
Authors: Bateman R. M. , Hall F. D. , Beers T. W.
Published: December 2007

Recent advances in computer technology have allowed ever larger computer circuits to occupy ever smaller physical dimensions. As a result, it is now possible to include a large body of detailed log analysis logic on a small Read-Only-Memory chip (ROM). The Log Analysis ROM, which weighs 7 grams and occupies less than 7 ccs, plugs into a widely used programmable pocket calculator. The Log Analyst is thus afforded easy access to a library of complex interpretation routines equivalent to those found heretofore only on mainframe computers.

This paper describes the evolution of the log analysis ROM from a technical viewpoint including the general procedure for building a ROM and then details the architecture of the log analysis routines available. Methods used to make the system "user friendly" are described including the plain english prompting for input, computation options, and formatting of outputs together with audible cues.

Suggestions are offered to the practical log analyst for both wellsite and office formation evaluation using the log analysis ROM and related calculator and peripherals. These include shaly sand analysis, complex lithology solutions, dip and bore hole geometry related transforms, cased hole evaluation, and many utilities such as solution resistivity and concentration conversions.

The paper is illustrated with examples of the application of the Log Analysis ROM to practical formation evaluation problems.
Why Rig Efficiencies have Decreased—Solutions
Authors: Kortlang W. F.
Published: December 2007

For the past five or six years, the drilling industry has experienced growth at a dramatic rate, beginning with the 1974–75 lease sales. During this period, contractors have increased the mobile rig fleet in the Gulf of Mexico by 116 percent, and have enjoyed 100 percent utilization. Although the rig population has exhibited this drastic rate of growth, an unexpected decline in the number of wells drilled has become evident, with the average number of wells decreasing from 8.23 wells per mobile rig to 3.8 wells per mobile rig. This behavior can be directly related to rig and/or drilling inefficiency. This paper will outline this phenomena, and will analyze it on the basis of the following criteria:

Relationship between rig production/operator expenditure/drilling efficiency. Causative factors attributable to decreasing rig efficiencies. Prospectus for the future concerning operator requirements with regard to contractor operations. Possible solutions to increase contractor and drilling efficiency.
Field Experience with PDC Bits in Northeast Texas
Authors: Arceneaux M. A. , Fielder J. L.
Published: December 2007

In an effort to improve penetration rates of infill drilling in northeast Texas, Sun Gas Division, Sun Exploration and Production initiated a program to evaluate the performance of polycrystalline diamond cutter (PDC) bits. Numerous bit runs were made in a selected interval in an attempt to determine which style PDC bit to use. Steel body and tungsten matrix body bits with various cutter configurations were evaluated. These bits were run under different parameters, i.e. weight on bit, rotary speed (RPM), hydraulics and mud type. Each bit run was reviewed, problems identified and corrective measures recommended for future runs. Results varied with the style PDC bit used. A cost per foot savings of 15% to 30% and a penetration rate increase of 45% to 75% were realized with the style PDC bit eventually selected when compared to rock bit drilling.

This paper will describe the style PDC bit, the geologic interval and the operating parameters under which the best performance was obtained. It is concluded that the use of these bits may be beneficial to other operators in this area and other areas of similar lithology.
Riser Collapse—A Unique Problem in Deep-Water Drilling
Authors: Erb P. R. , Ma Tien-Chi , Stockinger M. P.
Published: December 2007

While drilling an exploratory well in 1750 feet of water, a large kick emptied the marine riser. The two lowest joints collapsed due to the external pressure. A diverter failure also occurred. The equipment damage caused by this incident is described, and collapse calculations for the riser are presented. It is concluded that, if a kick is taken in deepwater after the subsea blowout preventers (BOPs) have been run, the subsea BOPs should be closed instead of activating the diverter, even if only shallow conductor casing is set. Diverter systems remain a must for shallow water operations, but their strength should be reevaluated and perhaps upgraded.
Cementing—Simultaneous Rotation—Reciprocating Technique (ROTO-TEK System)
Authors: Lee W. T. , Dorge W. D.
Published: December 2007

This paper presents an improved cementing technique which is called ROTO-TEK. This is a method of combining rotation and reciprocation of the casing string or liner during the cementing operation to give the best possible cement job. The design and application of the equipment is discussed giving the basic features of this equipment. The results of actual cementing jobs are discussed, showing the great improvement in cementing even in very difficult fields.
The Offshore Drilling Contract—Operator and Contractor Perspectives
Authors: Rankin M. D. , Richardson D. R.
Published: December 2007

This paper reports the results of a survey conducted as a means of accessing the factors which most often constitute points of conflict between operators and drilling contractors during offshore drilling contract negotiations.