bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vinylsulfonate/Vinylamide Copolymers in Drilling Fluids for Deep, High-Temperature Wells
Authors: Hille M. 
Published: December 2007

ABSTRACT
In the past it was necessary to formulate predominantly oil based drilling fluids for temperatures in excess of approx. 140°C/284°F. More recently, when high temperatures have been encountered, styrene sulfonate, maleic acid anhydride, polyacrylate and modified polyacrylate baaed dispersants have been used in drilling muds intended for very high temperature applications. Such products work satisfactorily in freshwater drilling fluids, but their performance falls with increasing electrolyte concentration. Water loss in freshwater systems is only moderately controlled, and they show practically no effect at all in saline drilling fluids. At temperatures over 200°C the thermally stable acrylate/acrylamide copolymers have only a limited application in drilling fluid systems because of their high sensitivity to even low quantities of calcium ion. The new vinylsulfonate/vinylamide copolymers close this gap in additives suitable for water-based drilling fluids in high temperature applications. To temperatures well over 200°C they stabilize the rheological and water loss characteristics of the drilling fluids, while remaining entirely unimpaired by the electrolytic composition of the mud.
This paper discusses the performance limitations of presentday-drilling fluid additives, and drawing from laboratory and practical examples, demonstrates the effectiveness of vinylsulfonate/vinylamide copolymers under the twin adverse conditions of elevated temperatures and high electrolyte concentration.
Thermal Stability of Surfactants for Steamflood Applications
Authors: Maini B. B. , Ma V. 
Published: December 2007

ABSTRACT
The objectives of the study reported in this paper were to evaluate the thermal stability of commercially available surfactants at typical steam injection temperatures and to investigate the kinetics of the thermal degradation process. Surfactant stability tests were performed under conditions of high temperature (200 and 300°C) and pressures (6.9 and 10.35 MPa) for twelve different sulfonate surfactants.
Most of the tested surfactants displayed halflives of longer than 100 days at 200°C, while at 300°C halflives were typically less than 10 days. Alkyl benzene sulfonates were found to be superior to alpha olefin sulfonates for chemical stability at 300°C, while petroleum sulfonates were found to be the least stable. A comparison of alpha olefin sulfonates with different carbon chain lengths in the range of 14 to 28 carbon atoms showed that thermal stability did not vary with chain length. A comparison of the results obtained with solutions to which a small amount of KOH was added to increase the initial pH with those in which the pH was not adjusted, showed that the initial pH can have a significant effect on surfactant stability.
For complex mixtures such as petroleum sulfonates, the experimental data displayed an apparent second order behavior in sulfonate concentration. This was found, however, to be merely a reflection of a gradual shift from faster decaying components towards slower decaying components at the reaction front due to the more rapid depletion of the faster decaying components.
Extensional Viscosity Correlation With Mobility Control Buffer Flow Behavior in Berea Cores
Authors: Fernando R. H. , Glass J. E. , Burnett D. A. 
Published: December 2007

ABSTRACT
The shear thickening phenomenon of mobility control buffers in flow through porous media is adressed through the use of high molecular weight synthetic water-soluble polymers (W-SP) blended with carbohydrate W-SPs. This approach is necessary to separate shear and extensional reponses of thickened fluids under deformation. In previous studies in which the elastic contributions are an important part of the fluid response (i.e., where the dimensions of the fluid are approximate with the boundary conditions or the relaxation time of the fluid is approximate with the duration time of deformation) the shear viscosity response has been observed to contribute to the magnitude of the extensional response. The complementary interaction can be separated by employing blends of a flexible synthetic W-SP with carbohydrate polymers. In Berea core evaluation of such blends at practical frontal velocities the resistant factors observed were not proportional to the fluid's extensional viscosity. The permeabilities (160 mD) were only appproximate with the dimensions of the macromolecules and additional studies at lower permeabilities are in progress.
Interrelationships Between In-Situ Gas Hydrates and Heavy Oil Occurrences on the North Slope of Alaska
Authors: Collett T. S. 
Published: December 2007

Abstract
In 1973 during the drilling of the West Sak #1 well on the North Slope of Alaska, oil was first recovered from a shallow Cretaceous sand interval which was later informally named the West Sak sands by ARCO Alaska. Stratigraphically above the West Sak sands there are two additional oil bearing sands, and are informally referred to by ARCO as the Ugnu and the 2150 horizons. Oils in these shallow sands appear to have migrated from the nearby, more deeply buried Prudhoe Bay Sadlerochit reservoir and appear to have lost substantial amounts of light hydrocarbons as the deeper oil passed through the bubble point at approximately 1,219 m (4,000 ft) during updip migration, reducing the API gravity. In addition the shallow oil appears to have suffered biodegradation further lowering the API gravity. The updip portion of these three reservoir sands are within the gas hydrate stability field. Gas hydrates are interpreted to exist in the West Sak #6 well in conjunction with heavy oil and the physical properties of this oil may have been influenced by the gas hydrate. Prior to this work, only experimental evidence suggested that hydrates and oil could exist in the same reservoir.
Material Balance Depletion Models for Two-Phase and Vapor-Dominated Geothermal Reservoirs
Authors: Economides M. J. 
Published: December 2007

Abstract
Material balance calculations often referred to as "zero-dimensional" reservoir evaluations have been used extensively in petroleum and geothermal engineering. This paper presents a Havlena and Odeh-type1 material balance depletion model for two-phase reservoirs incorporating adsorption phenomena. A straight line, formed between groups of thermodynamic and adsorption properties of water and the cumulative production history provides the initial-fluid-in-place and the size of the vapor-dominated "steam cap". Adsorption phenomena were found by Economides and Hiller as the controlling mechanism in the depletion of vapor-dominated geothermal reservoirs. A material balance for vapor-dominated geothermal reservoirs, demonstrating the importance of adsorption phenomena is also presented. A straight line provides the initial-fluid-in-place.
Green's Functions for Solving Unsteady Flow Problems in Naturally Fractured Reservoirs With Arbitrary Fracture Connectivity: Part I—Theory
Authors: Wijesinghe A. M. 
Published: December 2007

Abstract
A general theory of Green's functions for solving boundary-initial value problems governed by two linear pressure diffusion equations coupled through a fluid transfer term which depends on the pressure histories, is presented. The governing equations, developed previously by Wijesinghe and Culham [1984], describe the flow of fluid in naturally fractured reservoirs with arbitrary fracture connectivity simultaneously taking into account both fracture and pore system permeabilities and unsteady interporosity fluid transfer. In this study, the relationship between the Green's functions (ie. generalized source solutions) and the adjoint Green's functions is determined, and the boundary conditions which must be imposed on the adjoint Green's functions to obtain explicit solutions for the fracture and pore pressures, are presented. The fundamental Green's functions, which characterize the basic properties of the two coupled differential equations, are derived and examples of their application to reservoir fluid flow problems are given. As in the case of the classical diffusion equation for fluid flow in single porosity formations, the Green's functions based on the present theory enable solutions to complex fluid flow problems in naturally fractured reservoirs to be systematically constructed from simpler source solutions.
The Effect of Annulus Water on the Wellbore Heat Loss From a Steam Injection Well with Insulated Tubing
Authors: Aeschliman D. P. 
Published: December 2007

Abstract
Recently completed field experiments using an instrumented string and test well have verified that the presence of annulus water in injection well annuli introduces a real and economically important heat loss mechanism--wellbore refluxing--for surface-generated steam. Measured boiling heat transfer rates at local hot spots are sufficient to maintain steady refluxing over a realistic range of injection conditions and overburden properties. It is shown that with the wellbore wet, the thermal properties of the cement and overburden, not those of the insulated tubulars, control the magnitude of the wellbore heat loss.
Steady refluxing without venting at the wellhead has been observed; hence, oil field operators should not automatically assume that a nonventing annulus is dry. Insulated couplings have been demonstrated to reduce coupling heat loss by up to 35% in a dry well, and in wet wellbores to prevent significant boiling at the couplings, typically the primary source of refluxing.
Heat loss estimates for refluxing or flooded wellbores indicate large incremental economic penalties, of the order of $100 million annually in the U.S. alone. The successful demonstration of simple, easily implemented, insulated coupling designs, and the confirmation that wellbore heat loss in refluxing annuli scales with annulus pressure in a predictable manner, suggests that much of this loss is preventable.
Relative Permeability Functions for High- and Low-Tension Systems at Elevated Temperatures
Authors: Kumar S. , Torabzadeh S. J. , Handy L. L. 
Published: December 2007

ABSTRACT
Mathematical simulation of thermal oil recovery processes require relative permeability data at elevated temperatures. High-temperature, low-interfacial tension relative permeability functions are needed to predict the performance and efficiency of enhanced oil recovery methods in which chemicals are cohsidered for use with hot waterfloods or steamfloods. This paper presents empirical correlations based on experimental data that relate water-oil residual saturations and relative permeabilities to temperature, interfacial tension (IFT), and capillary number.
A new model has been found for relating residual saturation to capillary number. A modified capillary number is defined that better represents the low-tension, high-temperature systems. End point relative permeabilities have been related to residual oil/water saturations and the mobile water saturation range. The predicted values of residual saturations and relative permeabilities by these correlations are in good agreement with experimental data.
Two alternative approaches are presented for relating residual saturations to IFT reduction and temperature increase. The relationships are of necessity more involved than those discussed by earlier investigators who have studied only the individual effect of temperature or IFT reduction.
Economic Evaluation for Steam Injection Projects: A Simplified Model
Authors: Holcomb G. B. , Alcocer C. F. 
Published: December 2007

ABSTRACT
Economic evaluations serve as the policeman of the petroleum industry. They determine whether or not a project will be undertaken. However, due to the complexity and nature of each petroleum project, an evaluation used in conjunction with one type of project may not be necessarily suitable for another.
This paper will introduce a computer program of a simplified model that deals with the economic evaluation of steam injection projects only. Steam injection ecompasses a large variety of methods, but all methods do have several economic factors in common. They include present and future cost of oil, taxes and operating costs. Other factors include past and present production, lease cost, discounted cash flows, as well as inflation.
The program also contains several features not usually found in the petroleum industry: It is user friendly, no user manual is required.Alterations may be easily made in the program, therefore, tailoring it to the project.It can be used with different steam injection performance models with minimum modifications.
As the need for oil increases, the implementation of steam injection projects will in turn grow proportionately. This trend will call for fast, efficient methods for analyzing such projects. This program fulfills that need. This paper provides a means for economic evaluation in thermal recovery projects.
Comparison of Alternatives for Deepwater Development in the Gulf of Mexico
Authors: Johnston D. 
Published: December 2007

Abstract
Significant attention is being given to exploration on the Continental Slope of the Gulf of Mexico. There are over 2.7 million acres under lease in water depths over 1,000 ft. Conventional fixed-platform developments become very expensive as water depths exceed 1,000 ft., and in some situations the recoverable reserves will not economically justify a fixed platform. Due to technical and economic constraints imposed by this environment, development systems and techniques other than the fixed platform are being seriously considered.
Present unconventional offshore installations, which were developed for marginal fields in the North Sea and other areas of the world, provide field-proven alternatives in the selection of a development system for deep water. A comparison is made here of the technical and economic aspects of such alternatives.
Exploration Decision Strategy
Authors: Smith M. D. 
Published: December 2007

Abstract
Investing in exploration for oil and gas reserves is very attractive when it can be demonstrated that the risk adjusted returns exceed the investment by a 2-4:1 margin.
To realize this type of margin the explorationist must focus on opportunities that demonstrate – by analysis of historical data – that these types of financial rewards are reasonable. The process for identifying exploration opportunities that fit this criteria is generally referred to as "trend" or "basis" analysis. The objective of the analysis is to identify the geologic trends offering the highest probability of achieving a company's desired risk adjusted return on invested capital.
The author will present a process for conducting a trend analysis that is quick, efficient, and complements the explorationist's judgment about screening areas for investment. The process and support computer software consist of the following.
Build a historical database of well drilling and production information. Commercial sources for this database include the Texas Railroad Commission, Petroleum Information and DWIGHT'S Energy Data. Compute trend drilling statistics to estimate success ratios. Compute reserves added by recent exploration discoveries and set up a distribution of reserves by trend. Compute a distribution of development economics for reserve discoveries in a trend. Simulate drilling multiple exploration wells in each trend and calculate the risk adjusted return per trend. Rank trends by a financial indicator such as discounted or undiscounted cash flow to investment ratio. Simulate an exploration program where financial resources are allocated over several attractive trends and compute an allocation of funds to develop prospects and drill wells in each trend.
After the analysis process is complete, an allocation of funds is made to trends based on the combined effects of the probability of success and the probability of finding reserves of a given value. An exploration strategy is then developed which allocates personnel to prospect generation in the trends of interest or to analysis of investment opportunities with other companies.
The author intends to use a South Texas trend to illustrate the analysis process, to demonstrate the computer models and statistical techniques, and to show typical results.
The Demand for Exploratory Drilling: A Theoretical and Empirical Investigation
Authors: Rankin M. D. 
Published: December 2007

Abstract
The contract drilliing industry, on dry land and offshore, is by far, the most capital-intensive of the industries which comprise the upstream petroleum service sector. A drilling rig, once assembled, has a usable life of 10 to 20 years and has little value in any use other than that of petroleum exploration and development. The typical land rig employs an average of 18 individuals and an offshore unit will provide year-round employment for 60–100 personnel. These numbers do not account for the multitude of operator and service company positions which are linked to each working rig.
In 1783 there were an average of 1,700 fewer rigs (land and offshore) were active in the U.S. compared to the peak drilling year of 1981. This decrease in activity represents at least 34,000 workers who were forced to look for other employment. Taking into account "ripple effects") a more realistic estimate of displaced workers might be on the order of 70)000. At an average of $10 million per rig in plant and equipment) the slump accounted for $17 billion in idle capital; easily $3.7 million per day in unsatisfied depreciation charges.
Average rotary rig activity for 1983 represented 36 percent of the level reported for 1981 yet the A.P.I's tabulation of exploratory wells drilled in 1983 was 92% of the 1981 number and the similar statistic for development wells was virtually 99%. Over the same period) crude prices dropped some 18% in nominal terms – a 20% reduction in real value.
Evaluation of Production Loans for Gas Properties in Today's Economic Climate
Authors: Watson S. L. 
Published: December 2007

ABSTRACT
The evaluation of gas producing properties is made more difficult by increased market competition from fuel oil, random production curtailments and the abrogation of contracts. The bank engineer must construct a cash flow projection which incorporates a combination of technical and market factors from incomplete information in a rapidly changing market. By using a technical determination of the reserves as a target, he can forecast production rates that are consistent with anticipated market conditions.
Predictions of Size and Orientations of Lenticular Reservoirs in the Mesaverde Group, Northwestern Colorado
Authors: Lorenz J. C. 
Published: December 2007

ABSTRACT
Reservoirs deposited in a delta plain environment as part of the Mesaverde Formation have been penetrated by the three wells of the U.S. Department of Energy's Multiwell Experiment (MWX) in the east-central Piceance Creek basin, northwestern Colorado. These reservoirs are gas-bearing, low-permeability, sandy channel and splay deposits. Tight well spacing and an abundance of quality data from the MWX project make it possible to estimate reservoir width and orientation. Estimates of lens width were made independently by two techniques: 1) a well-to-well correlation/ probability method, and 2) by analogy to height-to-width ratios of similar lenses exposed in surface outcrops. Estimates of lens trends were made using a combination of crossbedding in oriented core, crossbedding indicated by experimental high resolution dipmeter tool, and the spatial arrangements of lens thicknesses and channel subenvironments as recognized in core and logs. Splay deposits, recognized as a different suite of lithologies and sedimentary structures in core, have less easily defined boundaries, but limits can be placed on their general position.
Mini-Frac Pressure Decline Analysis for Fractures Evolving From Long Perforated Intervals and Unaffected by Confining Strata
Authors: Martins J. P. , Harper T. R. 
Published: December 2007

ABSTRACT
When hydraulic fracturing operations are conducted in thick reservoir sections, it is common for the perforated interval to be long but yet still significantly shorter than the distance between reliable barriers to fracture propagation. Under these circumstances the fracture shape will change continuously as it evolves from the perforated interval, thus complicating the interpretation of pressure decline data measured during prestimulation mini-frac tests.
This paper presents a pressure decline analysis which assumes the fracture to have evolved as a family of confocal ellipses, which thereby ensures a smooth transition between the simpler fixed geometries which correspond to the injection of either very small or very large volumes of fluid (KGD and penny, respectively). The analysis enables the fracture shape and dimensions to be estimated, together with the fracture fluid-loss coefficient. An example is given of the application of this method, and a comparison is made with values determined assuming simpler, fixed shape models. The influence of injected fluid volume is considered. A rapid method for determining the Nolte "match pressure", P*, is also described.
A Review of the Long-Term Performance of Hydraulic Fracture Treatments in the Muddy "J" Sand, Wattenberg Field
Authors: Zahner R. L. , Crafton J. W. 
Published: December 2007

Abstract
A data base of production, fracture treatment, and volumetric data of wells in T2N/R65W, Wattenberg gas field, is used to evaluate the long-term (eight year) performance of hydraulic fracture treatments. Fracture dimensions are calculated using the procedure proposed by H. 0. McLeod, with modifications. proposed by H. 0. McLeod, with modifications.
Fracture design optimization must consider several variables in light of the general uncertainty of formation properties and created fracture shape and dimensions. Operators with limited leasehold positions generally cannot justify the expense of positions generally cannot justify the expense of rigorous optimization methods incorporating finite difference simulators. However, the results presented here strongly suggest that some type of optimization procedure is required to reduce the economic risk procedure is required to reduce the economic risk in drilling and completing wells in the Muddy "J" formation.
Horizontal Radial Drilling System
Authors: Dickinson W. , Dickinson R. W. 
Published: December 2007

ABSTRACT
A high pressure, water jet drilling system has been developed using a new force system to concurrently drill a bore hole and place a metal tube in the bore hole.
The first commercial application has been horizontal radials for shallow heavy oil reservoirs. Many radials may be placed at the same elevation. Logging, and completion techniques have been developed.
New Technology for the Development of Deepwater Offshore Gas Fields Exemplified by the Troll Module Concept
Authors: Varvin K , Sollie L P 
Published: December 2007

ABSTRACT
The Troll Module concept is one of several concepts under consideration for development of the Troll East field in the Norwegian sector of the North Sea. The concept is based on a direct transfer of unprocessed gas from subsea wells to shore or shallow water. A Troll Module base case for full field development of Troll East (PL 085) is described. The concept is considered feasible. However, some elements will have to be improved or better qualified to meet the standards required by a commercial project.