bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced Resolution Processing of Compensated Neutron Logs
Authors: Galford J. E. , Flaum C. , Gilchrist W. A. , Duckett S. W. 
Published: December 2007

Summary
Compensated neutron logging (CNLSM) uses a two-detector system that was developed to reduce borehole effects. The ratio of counting rates from the detectors provides the basic tool response from which a porosity index is obtained. Each detector in this system has a different vertical resolution because of its spacing. A new method of processing the counting rates has been developed to enhance the vertical resolution capabilities of the neutron porosity index by exploiting the better vertical resolution of the near detector. Because no additional or new measurements are required, data from older wells can easily be re-evaluated.
Results from the new method have been compared with microspherically focused logs (MicroSFLSM) and electromagnetic propagation logs (EPTSM). They show repeatable thin-bed resolution on the order of 1 ft [0.3 m] for data sampled at 6-in. [15-cm] intervals; the typical vertical resolution from ratio processing is approximately 2 ft [0.6 m]. The statistical precision of the high-resolution processing is superior to that of the standard ratio method.
An additional parameter, obtained with the new processing method, provides information about borehole effects. This parameter can be used for qualitative indications of gas when invasion is not deep and environmental effects are not large.
The new method has been applied successfully in carbonate and laminated sand formations. Studies show that thin beds can be detected in high-porosity formations where normal processing has significant statistical variations resulting from reduced counting rates.
An Experimental and Theoretical Study of a Coupling Mechanism Between Longitudinal and Torsional Drillstring Vibrations at the Bit
Authors: Aarrestad Thor Viggo , Kyllingstad Åge 
Published: December 2007

Summary
A mechanism that couples longitudinal and torsional drillstring vibrations at the bit was studied. Torsional vibrations are associated with dynamic variations of the rotational bit speed. When a roller bit runs over a multilobed pattern, these speed variations have been shown to affect the input of longitudinal vibrations. The theory for this coupling mechanism is verified experimentally by high-rate data of near-bit accelerations and torque recorded in a 1000-m [3,280-ft] -deep well.
Variable-Skin and Cleanup Effects in Well-Test Data
Authors: Larsen Leif , Kviljo Knut 
Published: December 2007

Summary
Methods to analyze well-test data influenced by variable-skin and cleanup effects are introduced, with emphasis on verifications of consistency in drawdown and buildup data. It is shown that a stable cleanup trend can be modeled by a simple hyperbolic skin factor in solutions for wells with constant skin. It is also shown that if the skin effect stabilizes at constant values within the general cleanup trend, then segments of data fitting a model with constant skin should be detectable. In some cases, repetitions of such segments can be used to estimate the formation flow capacity and the well cleanup rate. We also discuss how a gradual reduction in the skin effect in drawdown data can produce a false semilog straight line and lead to gross overestimation of flow capacity and skin. Well cleanup can produce constant or nearly constant bottomhole pressures (BHP's) during periods of constant-rate production, thus giving a false impression of pressure support in the reservoir. Methods presented will help to recognize whether a well is strongly influenced by either gradual or abrupt cleanup effects.
The Application of New Approaches for Shale Management in a Three-Dimensional Simulation Study of the Frigg Field
Authors: Hazeu Godard J.A , Krakstad Ole S. , Rian Dag T. , Skaug Mari 
Published: December 2007

Summary
The Frigg field is a major North Sea gas reservoir composed of turbiditic sediments. This paper describes the detailed geologic modeling and three-dimensional (3D) reservoir simulation of the field.
A geologic model containing sand lobes and intercalating shales has been defined from seismic and well data. Special attention was paid to the realistic modeling of the shales. The more continuous (deterministic) shales between the turbiditic sand lobes of the reservoir were directly implemented in the model as horizontal flow barriers. The more discontinuous shales within the lobes were modeled with the method of Haldorsen and Lake1 and Begg and King.2 This method uses statistical geologic information and well data to calculate effective vertical permeability. The simulator was built as a 3D, two-phase (gas/water) model. Field data for 8 years of production were matched. A good match of both fluid levels and pressures was obtained. This reservoir study demonstrates that the impact of the shales on the reservoir behavior in general and the movement of the gas/liquid contact (GLC) in particular is essential.
Total Organic Carbon Content Determined From Well Logs
Authors: Fertl Walter H. , Chilingar George V. 
Published: December 2007

Summary
Total organic-carbon (TOC) content present in potential source rocks significantly affects the response of various well logs. This paper discusses and illustrates well-log anomalies caused by TOC as observed on various wireline measurements, including resistivity (or conductivity), acoustic, nuclear (density and neutron), gamma ray, natural gamma ray spectra, and pulsed neutron [sigma and carbon/oxygen (C/O) ratio].
Field examples of these well-log responses in open and/or closed wellbores are presented from several countries. Several correlations between TOC and individual and/or combinations of various logging responses are also reviewed.
Application of Unconventional Techniques in Constructing an Integrated Reservoir Simulation Model for Troll Field
Authors: Kydland T. , Haugan P. M. , Bousquet G. , Havlg. S. O. 
Published: December 2007

Summary
A number of unconventional techniques were used for constructing an integrated three-dimensional (3D), three-phase numerical reservoir model of the huge Troll field. The selected techniques included corner-point geometry (CPG), non-neighbor connections between grid cells, local grid refinement, improved vertical equilibrium (VE) description, and oilwell coning functions. By combining these techniques, an efficient model, capable of handling several complex reservoir problems simultaneously, was developed. This model became a flexible tool for reservoir management planning.
Proppant-Pack and Formation Impairment During Gas-Well Hydraulic Fracturing
Authors: Roodhart L. P. , Kulper T. O. H. , Davies D. R. 
Published: December 2007

Summary
Equipment has been constructed to give a realistic laboratory simulation of the in-situ conditions during and after a hydraulic fracturing treatment of tight gas reservoirs (TIGRE). The equipment measures the permeability of both the "natural" core material and the proppant pack with gas under in-situ conditions before and after exposure to fracturing fluid. The rate of cleanup of the proppant pack and the core sample is measured after the fracturing fluid has broken.
Various fracturing fluids commercially available from the major service companies have been evaluated. Little damage to the proppant/rock interface has been measured, but massive damage to the proppant pack was observed. The damage is caused by fracturing-fluid residue, filter cake, and non-Darcy flow effects. This damage is observed only in the experiments described above and has not been reported in other less sophisticated laboratory simulations of the fracturing process.
The least damaging of the commercially available products tested has been identified. Procedures have been developed for placing "overdesigned" (or increased-conductivity) proppant packs during field hydraulic fracturing treatments. This has resulted in large increases in well productivity during field treatment, which is particularly noticeable during the early (transient) production phase. It is concluded that there is scope for the development of less damaging fracturing fluids to optimize economics.
New Pressure-Transient Analysis Model for Dual-Porosity Reservoirs
Authors: Olarewaju J. S. , Lee W. J. 
Published: December 2007

SummaryThis paper presents a new analytical model for interpreting pressure-transient tests for wells producing from dual-porosity reservoirs. This model includes unsteady-state matrix flow and incorporates the effects of wellbore storage, skin, and, for gas reservoirs, desorption. The model is applicable to bounded and infinite-acting reservoirs.
A Three-Part Study of NMR Longitudinal Relaxation Properties of Water-Saturated Sandstones
Authors: Kenyon W. E. , Day P. I. , Straley C. , Willemsen J. F. 
Published: December 2007

Summary
Borehole measurements of the nuclear magnetic resonance (NMR) properties of rocks have been of interest for many years, especially for estimating permeability. This paper presents laboratory measurements of the NMR properties of water-saturated rocks and shows that permeability can be estimated well with expressions of the form ϕ4T12, where T1 is the relaxation time constant of the longitudinal nuclear magnetization of hydrogen nuclei. Different methods of representing the laboratory-measured T1 curves are shown, including a new one called the stretched-exponential representation. An improved method for estimating T1 parameters from borehole measurements that can be used with either old or new representations is presented.
Effect of Temperature on Wave Velocities in Sands and Sandstones With Heavy Hydrocarbons
Authors: Wang Zhijing , Nur Amos 
Published: December 2007

Summary
A laboratory investigation was made of the effects of temperature on wave velocities in sandstones and unconsolidated sand saturated with heavy hydrocarbons. The large decreases of the compressional and shear velocities in such sandstones and sand with increasing temperature suggest that seismic methods may be very useful in detecting heat fronts in heavy hydrocarbon reservoirs undergoing steamflooding or in-siju combustion.
In-Situ Heat System Stimulates Paraffinic-Crude Producers in Gulf of Mexico
Authors: Ashton J. P. , Kirspel L. J. , Nguyen H. T. , Credeur D. J. 
Published: December 2007

Summary
A thermal stimulation process that generates downhole heat currently is being used to stimulate oil wells in the Gulf of Mexico. The crude produced from these shallow wells is highly paraffinic. Previous attempts to stimulate these wells with paraffin solvents and acid systems have been unsuccessful. The in-situ heat process has yielded 10-fold production rate increases and payout times of less than 1 week.
Effects of Spreading and Nonspreading Oils on Foam Propagation Through Porous Media
Authors: Lau H. C. , O’Brien S. M. 
Published: December 2007

Summary
Experiments show that a spreading oil increases the time for foam generation and decreases the speed of foam propagation in a porous medium. It also breaks a foam faster than a nonspreading oil. These findings may be important in interpreting results of different foam displacement experiments and therefore surfactant selection.
Minimum Miscibility Pressure Prediction With Equations of State
Authors: Benmekki E. H. , Mansoori G. A. 
Published: December 2007

Summary
Prediction of the minimum miscibility pressure (MMP) of the vaporizing gas drive (VGD) process is modeled by use of an equation of state (EOS) with different mixing rules joined with a newly formulated expression for the unlike three-body interactions between the injection gas and the reservoir fluid. The comparison of the numerical results with the available experimental data indicates that an EOS alone overestimates the MMP. When the EOS is joined with the correct version of the van der Waals mixing rules and the unlike three-body interaction term, however, the MMP will be predicted accurately.
Dog-Leg Control in Directionally Drilled Wells
Authors: Wilson G.J. 
Published: December 2007

WILSON, G.J., MEMBER AIME, CONTINENTAL OIL CO., HARVEY, LA.

Abstract
Review of difficulties experienced in drilling directional wells in the offshore Grand Isle Block 43 field showed most failures of drill pipe, drill collars and casing to have been associated with excessive dog-legs. Alleviation of difficulties was approached by synthesizing theoretical and practical concepts in a planned dog-leg control program. Preventive measures necessary to control dog-leg severity and corrective measures used to reduce unacceptable dog-legs are discussed. When other measures fail, deliberative measures as outlined can be employed alter the probable cumulative fatigue damage to be sustained by the drill pipe has been determined. Results of a program successful in virtually eliminating problems stemming from excessive dog-legs indicate that control of dog-leg severity in directional wells is feasible and will cause no decrease in the over-all drilling rate.

Introduction
Prompted by an increasing frequency of drill pipe, drill collar and casing failures, a study of 50 directional wells representing 592,000 ft of hole, including 444,000 ft of deviated hole, drilled in the offshore Grand Isle Block 43 field was conducted in early 1965. A number of drill pipe washouts and six keyseating problems were recorded and a detailed review was made of 16 failures which had required fishing effort in 10 of the 50 directional wells drilled prior to June, 1965. These problem wells are exemplified by Wells G and F for which pertinent data are shown in Figs. 1 and 2. Data pertaining to all of the 16 failures are summarized in Table 1. Inspection of these data shows most of the problems to have been associated with dog-legs in excess of theoretical limits suggested by Lubinski and excessive dog-legging is indicated to have been concomitant with whipstocking in several of the problem wells. Results of the investigation agreed with those reported by Schenck who had concluded that problems could be expected when dog-leg severity exceeded limits proposed by Lubinski. Since Schenck had demonstrated the desirability and feasibility of drilling directional wells without excessive dog-legging, a dog-leg control program was established in June, 1965 for wells drilled in the Grand Isle Block 43 field. This paper reviews the methods by which theoretical and practical concepts were synthesized to develop a program of preventive, corrective and deliberative measures which virtually eliminated problems stemming from excessive dog-legs in directional wells. Dog-legs of a magnitude causing no damage are referred to as permissible dog-legs and larger dog-legs are referred to as excessive or severe dog-legs.
JPT
P. 107ˆ
Effect of Cyclic Formation-Pressure Changes on Permeability
Authors: Aggour M. A. , Malik S. A. , Harari Z. Y. 
Published: December 2007

Summary
Unconsolidated sandpacks of various mesh sizes and consolidated Berea sandstone cores were subjected to repeated pressurization/depressurization cycles under constant confining pressure, after which their absolute and relative permeabilities were measured during the relaxation periods. The permeabilities of the sandpacks decreased as a result of the pressurization, and the reduction in permeability increased as the magnitude and duration of the applied net core pressure increased. The permeabilities continued to decrease with successive pressurization/depressurization cycles, albeit at a decreasing rate. After a finite number of cycles, no further reduction was observed. The number of cycles needed for stabilization was inversely proportional to the duration of the pressurization cycles and was found to be lower for fine sand than for coarser sand. Some recovery in permeability was achieved after the cores were allowed to relax; however, the cores were permanently damaged.
Berea sandstone cores also exhibited reductions in permeability as a result of pressurization/depressurization cycling. The reduction increased in direct proportion to the magnitude and duration of net core pressure. However, no reduction in permeability was observed below peak net core pressure levels of &lt;3,500 psi [&lt;24.1 MPa]. It was found that no significant recovery of permeability had taken place after the cores were allowed to relax at low pressure, indicating that the cores were permanently damaged.
Two models are proposed for explaining the mechanisms of permeability reduction under the present test conditions for both unconsolidated sand and consolidated cores.
Reaction Kinetics of Fuel Formation for In-Situ Combustion
Authors: Abu-Khamsin Sidql A. , Brigham William E. , Ramey Henry J. 
Published: December 2007

Summary
Chemical reactions believed to cause fuel formation for in-situ combustion have been studied and modeled. A thin, packed bed of sand/oil mixture is heated under nitrogen flow at linearly increasing temperatures, simulating the approach of a combustion front. Analysis of gases produced from the reaction cell revealed that pyrolysis of crude oil in porous media goes through three overlapping stages: distillation, mild cracking (visbreaking), and severe cracking (coking). Expressions that govern the rates of the two cracking reactions are derived, and a technique is outlined to obtain initial estimates for their parameters from the experimental data. The parameters of a proposed distillation function, as well as refined estimates for the cracking reaction parameters, are obtained by non-linear regression methods based on an overall kinetic model.
Successful matching of the experimental data, including the total amount of fuel deposited, was achieved with this model. It was found that fuel formation was a result of two successive cracking reactions that the oil undergoes at temperatures above 280° C [536°F]. Also, distillation of crude oil at temperatures below 280°C [536°F] played an important role in shaping the nature and extent of the cracking reactions. The operating pressure and the rate of heating of the sand/oil sample were found to affect the fuel-formation process only through the influence exerted on distillation. Clay minerals showed a catalytic effect on the cracking reactions, especially coking. Finally, the asphaltene fraction of a crude oil was found to correlate with the fuel content of that oil.
Coastal Barrier Reservoirs
Authors: Richardson J.G. , Sangree J.B. , Sneider R.M. 
Published: December 2007

Coastal barriers are long, narrow, wave-built, sandy islands parallel to the shore. Part of the island has a beach, but may parallel to the shore. Part of the island has a beach, but may have sand dunes and areas of vegetation above the high-tide line. A lagoon or estuary is behind the barrier on the protected side away from the ocean, as shown in Fig. 1. Coastal barrier reservoirs can hold major accumulations of oil and gas. Coastal barriers can build by three major processes: addition of sand washed onto the beach from breaker bars, addition on one end by sand washed from the other end and moved by riptides, and deposition of sand into the lagoon by waves breaking over the barrier during storms. Tidal channels that form at the ends of the barriers tend to migrate laterally and fill with sand from the barriers (see Fig. 1). Wind-blown (aeolean) dunes are usually minor parts of the barrier deposits. Galveston Island, offshore Texas, is a good example of a modern coastal barrier. Waves in the Gulf of Mexico have sufficient energy to transport and deposit fine-grained sand on Galveston Island. (Fine-grained sand is the coarsest sand available in upper Texas coastal waters.) Other examples of modern coastal barriers are found in the Gulf of California, where medium-sized sands are deposited. An example of an ancient deposit was found in the Elk City field, where the barrier beach was composed of well-sorted gravel and coarse sand.
P. 1127
Sand-Rich Deltas
Authors: Richardson J.G. , Sangree J.B. , Sneider R.M. 
Published: December 2007

Technology Today Series articles provide useful summary informationon both classic and emerging concepts in petroleum engineering. Purpose: To provide the general reader with a basic understanding of a significantconcept, technique, or development within a specific area of technology.
The preceding article in the Technology Today Series (Jan. 1989 JPT. Pages12–13) described the general processes of building deltas. The present articlefocuses on the reservoir characteristics of high-energy sand-rich deltas. Theseform when the wave and tidal action is sufficiently strong to rework thedeposits brought in by distributary channels before their burial. The principaltypes of sand bodies and highest-quality reservoir rocks in a delta arechannels and stream-mouth bars. Also present are the sheet sands deposited on adelta front and localized sand bodies left in minor crevasse deposits adjacentto channels during floods. While these bodies have definite areal relationshipsto one another during the process of building a lobe on the delta, theirthree-dimensional relationships become complex as the deltas build seaward orshift positions along the shoreline. Thus, a channel active during a laterbuilding cycle may cut into or may lie over stream-mouth bars, delta-frontsheets, or crevasse sands left earlier. Fortunately, the various sand bodieshave different distributions of permeability and different responses to logs sothat they can be identified. The coarsest sand is left at the base of a channeland silt and clays are left at the top. Typical gamma ray log responses andpermeabilities measured in cores show depth profiles in Fig. permeabilitiesmeasured in cores show depth profiles in Fig. 1a through c in sands leftupstream, onshore, and near mouths of distributary channels, respectively. Thelow gamma ray log responses at the bases show that little clay or shale ispresent. The increased gamma ray log response toward the tops of the channelsreflects the presence of more clay and shale. Similarly, the largest grainsizes and highest permeabilities are measured in cores from the base anddecrease upward.
p. 89
Treatment-Fluid Selection for Sandstone Acidizing: Permeability Impairment in Potassic Mineral Sandstones
Authors: Bertaux J. 
Published: December 2007

Summary
Drastic formation permeability reduction can result from certain rock-mineral/treating-fluid reactions. In potassic mineral sandstones, conventional HCl/HF acid treatments are proved to induce damage from byproduct precipitation, contrary to fluoboric acid (HBF4) treatments. Laboratory tests are described that provide a methodology for selecting the appropriate treatment fluid on the basis of formation/treating-fluid compatibility and damage removal.