bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oil-Water Displacements in Microscopic Capillaries
Authors: Templeton C.C. , Rushing S.S. 
Published: December 2007

Abstract
Methods previously developed for the study of liquid displacements in microscopic capillaries (inner diameters of 3 to 40 microns) have been used to investigate oil-water displacements in capillaries initially filled with water. Displacement calculations assuming perfect displacement and no capillary pressure hysteresis yielded oil effective viscosities smaller than the macroscopic viscosities. For a given liquid pair, the oil effective viscosity decreased both with decreasing capillary size and with increasing oil-water viscosity ratio. This behavior can be explained by the existence of an annular water film (20 Å to 260 Å thick) on the capillary wall.
When the capillary was first filled with oil, the ratio of the oil effective viscosity to the normal oil viscosity was highest for the first water displacement and decreased with subsequent displacements. Sometimes the oil effective viscosity ratio during the initial water displacement was greater than unity.

Introduction
In a previous paper, a technique was described for studying air-liquid and liquid-liquid displacements in very small capillaries of uniform diameter, in the hope that such microscopic data would further the understanding of the nature of multiphase fluid flow through porous media. That paper contained comprehensive data for air-liquid displacements in Pyrex capillaries, with a few data for oil-water displacements in capillaries initially filled with water.
The purpose of this paper is to present more complete results for oil-water displacements in capillaries initially filled with water, and to describe for the first time such observations in capillaries initially filled with oil. In this way the effect of the wetting history of the system upon the displacement process may be studied.

Methods
The basic techniques employed were described in the previous paper. The measuring procedure and the working equations will be briefly summarized here and a few modifications will be pointed out. For the present study, temperature control within 0.1 degrees C was obtained by placing the microscope and its immediate accessories in a thermostated air bath made of a steel frame covered with plexiglas.
Evaluation of Frac and Pack Completions and Future Outlook
Authors: Ayoub J. A. , Barree R. D. , Chu W. C. 
Published: December 2007

Summary
Frac and pack introduced in the early 1990's in the Gulf of Mexico has become a well-established completion procedure aimed at enhancing the productivity of gravel packed wells. The technique consists of incorporating a "tip screenout"1 hydraulic fracturing treatment as part of the gravel packing procedure, thus stimulating the well. However, published well test data, although showing generally better productivity than classic gravel packs, presents positive skin values indicating near-wellbore damage and often questioning the existence of a fracture intersecting the wellbore.
This paper quickly reviews published data and outlines a methodology which integrates the analyses of the fracture placement data and the well test data. This integration results in a more realistic modeling of the system well and reservoir and characterizes the hydraulic fracture intersecting the wellbore.
It is shown that poor fracture conductivity and/or high fracture face skin damage coupled with wellbore storage can reproduce the behavior observed in well test data and commonly interpreted with a nonfractured model. The effects of additional pressure losses across the gravel pack can also be incorporated for a more realistic modeling. Field examples are discussed to illustrate the technique and a quick outlook of how completions of unconsolidated sandstones may evolve is presented.
Effect of Pressure Depletion on Fracture-Geometry Evolution and Production Performance
Authors: Mukherjee Hemanta , Poe B. D. , Heidt J. H. , Watson T. B. , Barree R. D. 
Published: December 2007

Summary
A fractured well performance evaluation study, in the Frontier formation of the Moxa Arch area (southwestern Wyoming), revealed pressure depletion due to older 640- and 320-acre-spaced producers along the NE-SW diagonal in 640-acre sections. This was confirmed by six buildup tests across these sections. Reservoir simulation also showed that the production decline of some of these old, 320-acre-spaced wells causes enough pore pressure depletion to affect the fracture geometry in the new 160-acre infill offsets on the other diagonal in the same section. This paper presents the simulated pore pressure distribution in the drainage area of these older wells validated by buildup tests and their effects on the principal effective stress field and consequent fracture-geometry evolution around the newer wells.
The present paper also shows that depending on the location of the new well in the depleted zone and the original azimuth of the induced fractures, the newly created fracture may be asymmetric with only one wing of the fracture extending into the depleted area developing significant length and conductivity. This happens at the cost of development of the other fracture wing. Such asymmetric development of fracture wings can negatively impact production, in addition to the production loss due to actual reservoir pressure depletion.
Stimulation of Water-Disposal Wells Using Acid-in-Diesel Emulsions: Case Histories
Authors: Nasr-El-Din H. A. , Al-Anazi H. A. , Mohamed S. K. 
Published: December 2007

Summary
Two wastewater disposal wells in a carbonate reservoir in Saudi Arabia suffered loss of injectivity due to severe formation damage. A thorough experimental study was conducted to evaluate the use of acid-in-diesel emulsions to stimulate these wells, which had several tight zones. The emulsified acid consisted of 70 vol% of 15 wt% HCl, 30 vol% diesel, and an emulsifier. This is the first time emulsified acid has been used to stimulate disposal wells.
Experimental results indicated that the acid-in-diesel emulsion behaved as a shear-thinning fluid. The stability and reaction rate of the acid with reservoir rocks were found to be a function of emulsifier concentration. Coreflood results showed that the emulsified acid formed wormholes in tight carbonate cores. Permeability ratio (final/initial) of reservoir cores increased exponentially with the acid injection rate.
The acid-in-diesel emulsion was used to acidize both disposal wells. The treatment included an in-situ gelled acid stage for acid diversion, and an emulsified acid stage to create deep wormholes in the reservoir. The treatment was very successful and the injectivity of both wells has significantly increased. Field data indicated that longer soaking times were needed to stimulate disposal wells. This is to ensure complete acid spending.
Prediction of Slug Frequency for Gas/Liquid Flows
Authors: Zabaras G. J. 
Published: December 2007

Summary
During slug flow, knowledge of the slug frequency is essential for the gas-liquid receiving facility design as well as for predicting various slug flow characteristics such as slug length and pressure drop. Various methods proposed in the literature for predicting the slugging frequency in horizontal and inclined pipes were examined. These included both empirical correlations as well as mechanistic models. Slug flow frequency data taken with an air-water system in a laboratory flow loop together with data from the published literature were compared to the predictions of the various methods. A total of 399 data points were collected covering pipe diameters from 1 to 8 in. and inclinations from 0 to 11° above the horizontal. A total of eight published methods were compared to the data but none was found satisfactory. For this reason, the mechanistic slug frequency model of Taitel and Dukler1 was investigated in detail as an alternative unbiased prediction method. This model required the solution of the unsteady-state equations for mass and momentum by a finite difference technique. This numerical model gave satisfactory results at the expense of considerable computer CPU time. For faster slug frequency calculations a new correlation was developed utilizing all 399 data points. This resulted in 0% average error (bias) and 60% average absolute error. This correlation represents a significant improvement in slug frequency prediction accuracy over the other methods studied.
Liquid Carry-Over in Gas/Liquid Cylindrical Cyclone Compact Separators
Authors: Chirinos W. A. , Gomez L. E. , Wang Shoubo , Mohan R. S. , Shoham Ovadia , Kouba G. E. 
Published: December 2007

SummaryThe liquid carry-over phenomenon in gas-liquid cylindrical cyclone (GLCC©**) compact separators has been studied experimentally and theoretically.Experimental data have been acquired including the operational envelope for liquid carry-over and percent liquid carry-over beyond the operational envelope. The data show that at low gas and high liquid flow rates, under churn flow conditions in the upper part of the cylindrical cyclone, a large amount of liquid can be carried over relatively easily. On the other hand, at high gas and low liquid flow rates, under annular flow conditions, one should exceed the operational envelope significantly in order to have large amount of liquid carry-over.A mechanistic model has been developed for the prediction of the percent liquid carry-over beyond the operational envelope for churn flow conditions. An existing model for the prediction of the operational envelope for liquid carry-over has been extended to high-pressure conditions, including improved models for zero-net liquid flow holdup, droplet region and blowout and critical velocities.Comparisons between the new mechanistic model predictions for percent liquid carry-over with the experimental data, under churn flow conditions, show good agreement. Also, considering the lack of experimental data, the predictions of the operational envelope for liquid carry-over at high-pressure conditions show reasonable trends.
Analysis of Post-Audits for Gulf of Mexico Gravel-Packed Oilwell Completions Leads to Continuous Improvement in Completion Practices
Authors: Pashen M. A. , McLeod H. O. 
Published: December 2007

SummaryFinal production rate alone is not an adequate measure of the success of a well completion. Rather, we must estimate the "po-tential" of a reservoir and judge the ultimate success of a completion on how close we come to achieving this potential. Specific productivity indexes (SPI's) [(BFPD/ft)/psi], specific injectivity indexes (SII'S) [(BFPD/ft)/psi], and completion efficiencies (CE's) (percent of Darcy radial flow) can be calculated at various times throughout a well completion. Analysis of these data quantifies the efficiency of the completion after each individual completion operation, allowing a determination of the effects of each completion practice to be made. In addition to completion efficiency data, a comparison of gravel placement volumes behind casing helps quantify optimum gravel packing procedures.Twenty-two Gulf of Mexico completions have been analyzed using this technique. In this paper we will give details of the results of this analysis, in particular the productivity effects of various methods of underbalanced perforating, gravel packing, and well control. Items of discussion include the effects of underbalanced perforating on well performance, the effects of flowback after perforating on perforation tunnel cleaning, productivity impacts of various types of well control methods following perforating and gravel packing, and comparisons of gravel pack design parameters and gravel placement behind casing.
Experimental Investigation of the Influence of Perforating on Gravel-Pack Impairment
Authors: Blok R. H. J. , Welling R. W. F. , Behrmann L. A. , Venkitaraman Aadinathan 
Published: December 2007

SummaryAnalysis of the performance of perforated, gravel-packed wells compared with openhole gravel-packed wells has indicated that the perforation could be responsible for the low productivity of internally gravel-packed wells. A series of laboratory experiments on weak rock [unconfined compressive strength (UCS) = 1,200 psi] was conducted to quantify this. Castlegate sandstone rock samples, 7-in. diameter and 18-in. long, were perforated with shaped charges under downhole conditions. The perforations were gravel packed by circulating a gravel slurry past the tunnel entrance while applying a differential pressure. The pre-perforation, post-perforation and post-gravel-pack productivities of the core samples were monitored at different flow rates (5 to 20 B/D/perf). Sectional photographs of the core samples were taken at post-gravel-pack conditions for qualitative analysis. Performance evaluation of gravel-packed "realistic perforations" (debris and loose sand in the tunnel removed by drawdown-induced flow) vs. "ideal perforations" (debris and loose sand removed by external means) showed the post-gravel-pack productivities of realistic perforations to be much lower than ideal perforations in oil-phase as well as water-phase experiments. Injection of fluid after gravel packing only temporarily unplugged the perforation tunnel. The study shows the importance of fines- and debris-free perforation tunnels in maintaining the productivities of gravel-packed completions.
Heterogeneity, Permeability Patterns, and Permeability Upscaling: Physical Characterization of a Block of Massillon Sandstone Exhibiting Nested Scales of Heterogeneity
Authors: Tidwell V. C. , Wilson J. L. 
Published: December 2007

Summary
Over 75,000 permeability measurements were collected from a meter-scale block of Massillon sandstone, characterized by conspicuous crossbedding that forms two distinct nested scales of heterogeneity. With the aid of a gas minipermeameter, spatially exhaustive fields of permeability data were acquired at each of five different sample supports (i.e., sample volumes) from each block face. These data provide a unique opportunity to physically investigate the relationship between the multiscale cross-stratified attributes of the sandstone and the corresponding statistical characteristics of the permeability. These data also provide quantitative physical information concerning the permeability upscaling of a complex heterogeneous medium. Here, a portion of the data taken from a single block face cut normal to stratification is analyzed. The results indicate a strong relationship between the calculated summary statistics and the cross-stratified structural features visibly evident in the sandstone sample. Specifically, the permeability fields and semivariograms are characterized by two nested scales of heterogeneity, including a large-scale structure defined by the cross-stratified sets (delineated by distinct bounding surfaces) and a small-scale structure defined by the low-angle cross-stratification within each set. The permeability data also provide clear evidence of upscaling. That is, each calculated summary statistic exhibits distinct and consistent trends with increasing sample support. Among these trends are an increasing mean, decreasing variance, and an increasing semivariogram range. The results also clearly indicate that the different scales of heterogeneity upscale differently, with the small-scale structure being preferentially filtered from the data while the large-scale structure is preserved. Finally, the statistical and upscaling characteristics of individual cross-stratified sets were found to be very similar because of their shared depositional environment; however, some differences were noted that are likely the result of minor variations in the sediment load and/or flow conditions between depositional events.
Lessons Learned From 4D Projects
Authors: Waggoner J. R. 
Published: December 2007

Summary
Time-lapse three-dimensional, or four-dimensional (4D), seismic has been under consideration by the industry for reservoir monitoring for more than a decade. It offers the possibility of identifying the interwell distribution of bypassed and untapped oil, of monitoring displacement heterogeneity, and of detecting uneven pressure depletion away from wells. If obtained, these detailed observations could be used to increase ultimate recovery, reduce production costs, and prevent surprises such as unexpectedly early breakthrough.
But these benefits are not easily obtained, and are certainly not guaranteed. There are a number of factors that impact whether a 4D project will be successful, and a careful study of these is required to give a realistic expectation of what 4D can do for a specific reservoir. Numerous 4D seismic projects have been active over oil fields world wide, and successes, relative to each project's objectives, have been realized by field operators using a wide variety of data acquisition techniques (land, streamer, and seabed methods), and over a variety of field types, including both clastics and carbonates.
This paper draws from this experience to present a generalized 4D project workflow, and reviews results from some of these recent projects as illustrations. In general, sufficient software tools, rock physics data, and experience now exist to conclude that 4D is a low-risk/high-benefit reservoir management tool. The key to a successful project, however, is determining what 4D can do in a specific field, which requires a careful feasibility study, clear reservoir management objectives, and high-quality and experienced seismic processing and interpretation.
Two-Phase Isentropic Compressibility and Two-Phase Sonic Velocity for Multicomponent-Hydrocarbon Mixtures
Authors: Firoozabadi Abbas , Pan Huanquan 
Published: December 2007

Summary
Two-phase compressibility and two-phase sonic velocity of hydrocarbon mixtures are needed for a variety of applications in well testing, metering, and seismic exploration. In this work, a thermodynamic model is presented to estimate the two-phase isentropic compressibility and two-phase sonic velocity. The model accounts for the mass transfer between the equilibrium phases and the effect of capillary pressure. The results reveal that isothermal and isentropic compressibilities can be different by a factor of 20 in the two-phase near the retrograde dewpoint. With the exception of the retrograde dewpoint, the difference between the isentropic compressibility in the single phase and two phase is less than the corresponding difference for the isothermal compressibility.
The sonic velocity in the two phase can be either less or more than the single phase. For the hydrocarbon mixtures that the sonic velocity decreases in the two phase, the decrease is much less pronounced than in nonhydrocarbon systems such as water-steam and water-air.
Upscaling, Gridding, and Simulating Using Streamtubes
Authors: Portella R. C. M. , Hewett T. A. 
Published: December 2007

SummaryThis paper presents an innovative upscaling methodology based on a semianalytical streamtube technique. The methodology generates a coarse grid based on streamtubes and isobars, whose up-scaled properties are accurately calculated using the properties of each streamtube that constitutes the coarse block. Beyond the calculation of upscaled static properties of the grid, the methodology also calculates upscaled relative permeability curves, or pseudofunctions, using a semianalytical streamtube method to perform this without requiring any significant additional time. Tests showed that the results from the streamtube coarse grid had a good agreement with the fine grid solution. In contrast, simulations with a coarse grid upscaled with conventional techniques had a bad performance in many situations. Although this upscaling methodology is heavily based on a fixed streamtube simulation method, it provided good results even for situations in which streamtube simulation techniques are not supposed to work well, such as displacements that consider gravity and compressibility.
Precipitation of Chromium Acetate Solutions
Authors: Zou Bin , McCool C. S. , Green D. W. , Willhite G. P. , Michnick M. J. 
Published: December 2007

SummaryChromium(III)-polymer systems are often used in permeability modification treatments. The transport of chromium(III) in-depth in porous rocks is sometimes limited due to precipitation. Precipitation is caused by the increase in the solution pH because of fluid-rock interactions, particularly in carbonate rocks. This paper presents experimental data on the rate of precipitation of chromium from chromium(III) acetate solutions. Experimental data were obtained for the precipitation of chromium from chromium acetate solution at constant pH. Data were obtained as a function of pH, temperature, salinity, and OAc/Cr mole ratio. The pH range studied was between 7 and 10, and the temperature range was between 25 and 45°C. Precipitation of chromium was preceded by an induction period where there was no change in concentration. The induction period decreased from 1,200 minutes at pH 7 to less than 200 minutes at pH 10 at 25°C. A higher temperature increased the precipitation rate. Precipitation is delayed by the addition of acetate ion. Both the salinity and salt type have significant effects on the rate of precipitation. A kinetic model was developed to describe both the induction period and the rate of precipitation of chromium from a chromium acetate solution in 1% KCl at 25°C for a pH range of 7 to 10 with OAc/Cr mole ratios between 3 and 9.
Shallow Water Flow Planning and Operations: Titan No. 1 Exploration Well, Deepwater Gulf of Mexico
Authors: Schuberth P. C. , Walker M. W. 
Published: December 2007

SummaryShallow water flows (SWF) from overpressured aquifers have been a persistent problem in the deepwater Gulf of Mexico (GOM) and can create significant financial and operational risks for exploration and development drilling programs. For the GOM, SWF intervals typically occur between 300 and 2,500 ft below mudline (BML) and in water depths greater than 1,500 ft. If left unchecked, the disturbance from the water flow can cause loss of soil strength surrounding the wellbore, thereby compromising the structural integrity of the well. In industry, extreme cases have led to collapsed casing and/or total loss of wellbores.This paper details the up-front planning efforts implemented and the operational procedures utilized to successfully mitigate a SWF event experienced at the Titan No. 1 exploration well drilled in Garden Banks Block 785 (GOM), in 4,640 ft of water. Operations at Titan were based on the philosophy that performing a shallow hazards assessment, preparing and implementing SWF contingency plans, drilling a 9|-?. pilot hole (for dynamic kill), identifying a SWF zone quickly, controlling a water-flow zone with weighted mud (while drilling riserless), and using nitrified foam cement to seal off a water flow behind 20-in. conductor pipe, were all critical in successfully containing and drilling through a SWF occurrence.
The Development of Heavy Oil Fields in the United Kingdom Continental Shelf: Past, Present, and Future
Authors: Jayasekera A. J. , Goodyear S. G. 
Published: December 2007

Summary
In this paper we review progress made in developing United Kingdom Continental Shelf (UKCS) heavy oil fields. Reservoir productivity is compared with existing light oil developments and three categories of heavy oil reservoir are identified, which require the application of different well technologies to achieve acceptable offshore production rates. Case histories from existing developments and fields under appraisal are used to illustrate how advances in technology and effective risk management allow increasingly difficult heavy oil fields to be developed. Finally, the future direction for these heavy oil developments is discussed, looking at the scope for improved oil recovery (IOR) techniques and further technology developments to drive down costs and to increase reserves in fields currently under waterflood or to improve the economics of hitherto subeconomic fields.