bluuebunny/crossref_metadata_2025_split huggingface dataset:
Eolian Sandstone Reservoirs: Bedding Facies and Production Geology Modeling
Authors: Nurmi R. D. 
Published: December 2007

ABSTRACT
The purpose of this discussion is to define the characteristics of eolian sandstones that are important for geometrical and. geological modeling. Although eolian sandstones are thick, widespread blankets of sandstone that are relatively free of shale, eolian sandstone reservoirs are far from being homogeneous and isotropic. Experience has shown that a sedimentological understanding of eolian facies is important for realistic reservoir analysis. Sedimentological knowledge can guide the study of reservoir geometry and/or performance characteristics of sandstone reservoirs of eolian origin.
The continuous measurement and evaluation of eolian bedding characteristics are critical to the evaluation of eolian reservoirs. By analyzing the bedding characteristics using continuously oriented cores and/or dipmeters, the internal and external characteristics of eolian reservoir units can be modeled. In simple cases where the reservoir unit is comprised of a single, thick crossbed set, the geometrical modeling of the depositional characteristics can be directly related to reservoir geometry. Geological modeling can also be done in complex cases where the reservoir units are comprised of vertical and lateral sequences of crossbed sets. Each of these crossbed sets is commonly underlain by an impermeable interdune deposit which results in a complex multi-layered reservoir; multi-layered because each of these crossbed sets may perform as an individual reservoir. Eventually each may even develop a separate gas cap. These crossbed reservoir units generally are elongated in the depositional transport direction; whereas, the pronounced directional permeability is perpendicular to this direction. Although the number of tests are limited, it appears that average crossbed thickness is related to areal extent of these reservoir units. In summary, the knowledge of bedding is a valuable tool for the analysis and modeling of eolian sandstone reservoirs.
Seismic Visibility of Stratigraphic Objectives
Authors: Neidell N. S. , Beard J. H. 
Published: December 2007

ABSTRACT
In the recent past it was well recognized that certain stratigraphic exploration objectives could be most subtle in seismic terms. The classic work by Bubb and Hatlelid1 illustrates this view in discussions concerning certain reefal developments and the requirements for their detection. Hence, some appreciation of limitation in the seismic perspective was an important element in the interpretive view.
Most recent works explored in some depth the question of seismic resolution potential. One of the earliest of such studies by Widdess2 considered detection of thin beds, and an in-depth method described by Neidell3 demonstrates not only detection of thin beds at substantial depth, but also their detailed mapping. Later published works document thin bed mapping at significant depths using more or less conventional seismic data.
The fact that reliable contouring of 5 ft. (9.5m) units at 12,000 ft. (3,658m) depths can be accomplished leads to an unwarranted confidence about the ultimate detection capability of usual seismic approaches. It is easy to demonstrate that where stratigraphie developments entail some subtlety in their geometry, the conventional seismic display can fail totally in presenting them. Carbonate banks of the order or 300 ft. (91m) thick having good velocity contrasts can be missed at depths of 12,000 ft. (3,658m) and 600 ft. (182m) thick channels again having good reflectivity contrast can be lost entirely at depths of 15,000 ft. (4,573m).
Even when the seismic display is refined far beyond the usual state-of-the-art, the limitations persist. They are in good measure a consequence of both the narrow dynamic range of a black and white presentation and inadequate handling of seismic velocities. We argue here for refined use of seismic data and color or other innovative displays. A short catalogue of noteworthly failures of the conventional procedure supports our case. Two conclusions follow: Effective stratigraphie exploration cannot be conducted without improved processing practices and enhanced displays which overcome the limitations cited here.Presently available seismic views very likely have caused us as an industry to miss a substantial number of stratigraphie targets and even in mature areas.
Substantial avenues for technological progress and economic success appear to be ahead in view of these findings.
The Prediction of Interpretation of Downhole Mud Temperature While Drilling
Authors: Thompson M. , Burgess T. M. 
Published: December 2007

ABSTRACT
The prediction of downhole mud temperature throughout all the operations of drilling has long been a clear objective, tackled by several previous authors. A method is given here for performing this prediction in an accurate yet rapid manner which differs from all previous methods used and is suitable for extension to the interpretation of measurements downhole.
The problem lies in the coupling of the heat conduction in the formation, which can involve a lengthy solution process, with the heat convection in the mud, the numerical solution of which can suffer from non-physical instabilities in response to some of the fast changing conditions of rig operation. A justifiable approximation to the formation conduction reduces it to analytical form and a space transformation yields a stable solution procedure for the convection problem. Details are given of the equations used, the approximation involved and the space transformation which result in a computer model which is simple and fast in execution. Despite the speed, the model is comprehensive in terms of the drilling, circulating and static operations modelled and the complete specification of evolving well geometry and constraints.
The prediction method is validated by checking against recent field data of temperature measured downhole during drilling.
The speed of the model makes it feasible to consider its use for realtime interpretation of measurements downhole and a promising application would be the continuous determination of geothermal gradient. Thus the model described includes both predictive and interpretative aspects.
A Simulator for Gas Kicks in Oil-Based Drilling Muds
Authors: Ekrann S. , Rommetveit R. 
Published: December 2007

ABSTRACT
Mathematical techniques used in a newly developed simulator for gas kicks in oil based drilling fluids are presented.
The simulator works in one spatial dimension. By deleting the material derivative term in the momentum equation, a quasi-stationary approximation is obtained, which does not contain (hyperbolic) pressure propagation effects.
The equations are solved using a finite difference predictor-corrector shooting technique. Simple front tracking is employed for mud fronts and gas front.
The simulator is very modular in its structure. For several effects, a number of alternative formulations are programmed. Effects included in the simulator are frictional pressure losses (one- and two-phase), pressure loss in bit and choke, rise velocity of free gas, dissolution of gas in mud (including non-equilibrium effects), pressure and temperature dependent densities.
The simulator is equipped with interactive graphics, allowing the process to be observed and controlled (BOP, choke, pump rate, mud type pumped).
The Effect of Dissolved Gas on Reservoir Brine Viscosity
Authors: Ostermann R. D. , Bloori A. , Dehghani K. 
Published: December 2007

ABSTRACT
Correlations are available in the literature for the prediction of reservoir brine viscosity as a function of temperature, pressure, and salinity. Despite the fact that natural gas is soluble in brines, little useful data has been published regarding the effect of dissolved gas on viscosity. In the current work, the effect of dissolved methane on the viscosity of pure water has been measured at 100, 150, and 250°F, over a saturation pressure range of 0-7500 psi. The viscosity was found to increase by up to 6% with gas saturation at moderate pressures. A correlation of this data is presented, along with a recommendation for the extension of the correlation to brine/natural gas systems. In addition, a simple modification to the standard electrical contact rolling ball viscoslmeter to allow its use with electrolyte solutions is described.
Mathematical Model of the Polycrystalline Diamond Bit Drilling Process and Its Practical Application
Authors: Ziaja M. B. 
Published: December 2007

ABSTRACT
Assuming that rock failure during cutting with a polycrystalline diamond compact (PDC) cutter is in progress to the theory of the pulverside zone, a mathe-matical model of PDC bit drilling process has been developed. Using this theory, expressions for bit torque and bit weight are obtained in terms of bit penetration rate. The model takes into account the reduction in penetration rate during drilling resulting from bit wear. Some tests in the field conditions have shown that theoretical results agree reasonably well with available experimental data. A graphical method for estimating so-called indexes of rock properties also has been established.
Implications of Thermal Wear Phenomena for PDC Bit Design and Operation
Authors: Glowka D. A. 
Published: December 2007

ABSTRACT
Previous work has suggested that thermal phenomena can greatly accelerate the wear of polycrystalline diamond compact (PDC) drag cutters under certain conditions. In this paper, the implications of that finding for PDC bit design and operation are examined. An abrasive wear model for cutters is developed and applied to rotary drilling applications to demonstrate the significance of thermally-accelerated wear on bit life. Under conditions where thermal effects are not important, it is concluded that in order to maximize bit life, greater bit weights and lower rotary speeds are preferable over shallow cuts and high speeds. It is found that even under normal abrasive wear conditions, a PDC cutter develops a significant wearflat before one-half its useful life is expended, suggesting that PDC bits should be designed to operate effectively in the worn condition. A cutter placement criterion is presented for designing bits for equal cutter wear. Through analysis of new experimental data, a technique is developed for approximating cutter penetrating forces in the presence of cutter interactions on a bit face and for estimating relative cutter wear. A hypothetical bit designed for equal rock removal volume per cutter is examined to determine the relationship between the equal volume and equal wear criteria for cutter placement. The complex role of thermal wear phenomena in this relationship is also examined for the hypothetical bit in three different rock types.
Case Study of a Low-Permeability Volatile Oil Field Using Individual-Well Advanced Decline Curve Analysis
Authors: Fetkovich M. J. , Vienot M. E. , Johnson R. D. , Bowman B. A. 
Published: December 2007

ABSTRACT
This paper presents a detailed case history study of a low permeability volatile oil field located in Campbell County, Wyoming. The field was analyzed on an individual well basis using advanced decline curve analysis for 40 individual well completions. Well permeabilities, skins and original oil in place are calculated for each well from rate-time analysis using constant wellbore pressure type curve analysis techniques.
Original oil in place values calculated from rate-time analysis for individual wells are used with recoverable reserve projections from the decline analysis to obtain fractional recoveries for each well. Gas-oil ratios versus fractional recovery curves are also made for each well using historical cumulative production and the calculated oil in place values. Ultimate fractional recovery numbers and GOR vs fractional recovery curves, plotted for each well, are shown to suggest different rock types and reservoir fluids. Multi-well decline curve analysis shows the validity of the variables s (skin), k, 00IP, ultimate fractional recovery and G0R vs fractional recovery evaluated from each well's type curve evaluation. These variables must all give consistent and reasonable numbers when compared with each other. A single well analysis can easily give results that are not recognized as being invalid unless compared with other wells in the field.
The study also illustrates flowing and pumping well backpressure changes in a well's decline, the method of handling such changes, and their effect on ultimate recoverable reserves predictions. Conventional decline curve analysis can not handle backpressure changes because of its constraint that what controls the decline in the past will also continue in the future.
Unified Relationship To Predict Future IPR Curves for Solution Gas-Drive Reservoirs
Authors: Kelkar B. G. , Cox R. 
Published: December 2007

ABSTRACT
Several methods have been proposed in the literature to predict future IPR curves for solution gas drive reservoirs. Apparently all of these methods require different types of data to predict these future curves. This paper presents a unifying relationship which can be applied to any of the referenced methods. The theoretical justification for the underlying uniformity is based on the assumption that the relation(kro/ µo Bo) varies linearly with the average reservoir pressure. The new technique requires two sets of data points (each at different average reservoir pressures) to predict future IPR curves.
A Simple Gravity Override Model of Steamdrive
Authors: Miller M. A. , Leung W. K. 
Published: December 2007

ABSTRACTA steamflood predictive model for horizontal reservoirs based on severe steam override is presented. Unlike previous models, the current model is based on Vogel's1 observation that oil production is not driven by the growth of the steam zone, but rather vice-versa. Oil production rate In the current model is determined by conductive heating of oil below the steam zone. An "effective" steam condensate zone size is used to match the model to field data. The model was tested with twenty-three field cases and against thermal simulator results reported in the literature. Acceptable results were obtained with eleven field cases and with simulator results.
Induced Fracture Orientation Determination in the Kuparuk Reservoir
Authors: Griffin K. W. 
Published: December 2007

SUMMARY
The orientation of hydraulic fractures is often a significant factor in the generation of an optimum fieldwide development plan. The ability to predict or determine fracture orientation allows evaluation of the impact of fracturing on drainage patterns and on waterflood performance, and planning of further development drilling. In the Kuparuk A Sand--a medium porosity, heavily mineralized, shaly sandstone--hydraulic fractures are required to achieve the necessary injection and production rates to sustain waterflood and peripheral development.
A program was developed to test the applicability of a variety of fracture orientation determination techniques, and also to provide information on the orientation of Kuparuk hydraulic fractures. Seven fracture orientation determination and prediction techniques were compared in a single wellbore: Calculation of wellbore ellipticity from four-arm dipmeter calipers; on-site measurement of core strain relaxation; laboratory measurement of differential strain on oriented core samples (DSA); laboratory measurement of sonic velocities through oriented core samples; analysis of triaxial borehole seismic data; evaluation of expandable packer impressions and evaluation of borehole acoustic televiewer results. Results from this, and other, single-wellbore tests were then compared with fieldwide DSA data, sonic velocity data, wellbore ellipticity data, and fault and structure mapping.
All of the techniques examined provided indications of fracture orientation. The downhole triaxial seismometer surveys proved to be both definitive and economical as a method of determining fracture orientation. The methods which require rock property measurements to infer stress orientation (on-site strain relaxation, differential strain, and sonic velocity), require careful orientation of the core samples, a homogeneous sand with low shale content, and multiple samplings to ensure a correct interpretation of the results. Wellbore ellipticity measurements provide fair to good approximations of stress field orientation. The quality of the data increases with an increasing degree of borehole spalling or eccentricity. The openhole techniques, while very useful for verification and diagnostic purposes, are too expensive for general use as fracture orientation determination tools.
Compressibility Factors for High-Molecular-Weight Reservoir Gases
Authors: Sutton R. P. 
Published: December 2007

ABSTRACT
This paper examines the effect of high concentrations of the heptanes-plus fraction in natural gases on the calculation of gas compressibility (Z) factors. Laboratory measured gas compositions and Z factors are used to evaluate the accuracy of the Standing-Katz chart. It was determined that the chart itself provides satisfactory accuracy; however, Kay's molar average combination rules or comparable gravity relationships for calculating pseudo-critical pressure and temperature result in unsatisfactory Z factors for high molecular weight reservoir gases. The contributions of this paper are two-fold. First, new pseudo-critical property – gas gravity relationships are developed, and second, alternate methods for calculating pseudo-critical properties from composition are established. By utilizing either of these methods to calculate pseudo-critical pressure and temperature, the overall accuracy of Z factors from the Standing-Katz chart is increased almost three-fold.
A Simple Statistical Method for Calculating the Effective Vertical Permeability of a Reservoir Containing Discontinuous Shales
Authors: Begg S. H. , Chang D. M. , Haldorsen H. H. 
Published: December 2007

ABSTRACT
This paper describes a quick, simple, easy to use method of calculating the effective vertical permeability of a reservoir region containing discontinuous shales. The method, which is derived in both two and three dimensions, can be applied to a layered medium in which the sand permeability anisotropies (in three mutually perpendicular directions) and the shale frequencies and dimensions can vary from layer to layer. The method is validated for specific cases by using numerical simulation and an analogue model of a real outcrop. The latter consists of conducting paper with slits cut in it to represent impermeable shales. Although strictly the method is only applicable to impermeable shales we show that it would appear to be generally valid when the real shale permeability is more than about two orders of magnitude lower than the effective permeability derived by assuming impermeable shales.
Using Sidewall Sample Thin Sections To Evaluate the Completion Potential of Low-Resistivity Pleistocene Sands, Offshore Louisiana
Authors: Morphy P. H. , Thomson A. 
Published: December 2007

ABSTRACT
The most common reason that low-resistivity completions in South Marsh Island 130 fail to pay out is a lack of reservoir permeability. The non-commercial low-resistivity zones have a clay matrix which has only microporosity, probably due to the reworking of the sediment by burrowing organisms (bioturbation). In contrast, the commercial low-resistivity zones have visible porosity with almost no clay. This distinction can be determined by evaluating sidewall samples with the pétrographie and scanning electron microscopes. The method is applicable whether or not the low-resnstivity pay is geopressured.
Measurement of Remaining Oil Saturation in Northern Michigan Using Nuclear Magnetism Log Data and Pressure Core
Authors: Setser G. , Williams M. R. 
Published: December 2007

ABSTRACT
Remaining oil saturation measurements were made in a pinnacle reef field of Northern Michigan. Pressure core was taken in the Al Carbonate and Niagaran formations. A Nuclear Magnetism Inject-Log procedure was used as an independent measure of remaining oil saturation. Using procedures outlined in this paper, the core-measured and log-derived remaining oil saturations agree, well within their error limits.
Wireline Coring Device Aids Evaluations of Complex Geologic Areas
Authors: Hashmy K. H. , Robinson K. A. , Rojas J. M. , Skopec R. A. 
Published: December 2007

ABSTRACT
A new wireline coring device which uses a diamond core bit to drill sidewall plugs is described. Sidewall cores thus obtained are not subject to mechanical damage, and even hard, indurated rocks are easily cored. A wellsite core analysis system has also been introduced which provides mineralogical information in addition to porosity and permeability, etc. Accurate reservoir characterization is possible by using core data and geological information with well log data in a computer program based on an error optimization technique. Results of log analysis are presented where core information has been extensively used.
Experimental and Simulation Studies of CO2 Flood Performance at High Water Saturation
Authors: Inoue S. , Yazawa N. , Arihara N. 
Published: December 2007

ABSTRACT
The objective of this study is to evaluate the effects of a high water saturation in the vicinity of the CO2 miscible displacement front on the oil displacement efficiencies of CO2 slug and water-alternating-gas (WAG) injection processes. The results of CO2-flood core displacement tests under high water saturations and compositional simulation studies are presented.
Core displacement tests were conducted with a water-wet Berea sandstone core to evaluate differences among continuous CO2 injection in the secondary recovery mode and CO2 slug and WAG injection in the tertiary mode. The results of core-flood tests were strongly characterized by fingering of CO2 into oil and waterblocking of oil from contact with invading CO2. The slug injection process appeared to be superior to the WAG injection process.
One-dimensional simulation studies were carried out to reproduce the experimental results with an equation-of-state (EOS) based compositional model. EOS parameters were first tuned by matching laboratory phase behavior data and slim tube results. The use of Koval K-factor and Todd's waterblocking function, to express the fingering and waterblocking phenomena respectively, successfully duplicated the results of the core displacement tests.
Finally, based on experimental data matching, two-dimensional, cross sectional simulation studies were conducted to predict oil displacement performance in a waterflooded, vertically heterogeneous reservoir. Although the WAG process mitigates the undesirable effect of crossflow, oil recovery of the WAG process remains lower than that of the CO2 slug process in the strongly water-wet reservoir.