bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensitivity Analysis of Hole Cleaning Parameters in Directional Wells
Authors: Li Jeff , Walker Scott 
Published: December 2007

SummaryIn this study, 600 tests were conducted and a new computer program was developed for the prediction of cuttings transport in the multiphase system (gas+liquid+cuttings). The sensitivity of cuttings bed height with respect to liquid/gas volume flow rate ratio, in-situ liquid velocity, rate of penetration (ROP), inclination angle, and circulation fluid properties was conducted. The hole-cleaning time with both circulation mode and wiper trip is also discussed. The results from the sensitivity analysis presented in this paper indicate, first, that the fraction of the circulation liquid has a significant impact on the cuttings transport in underbalanced drilling with gasified fluids; second, that among different variables, the in-situ liquid velocity is the most important variable for cuttings transport; and, finally, the hole-cleaning time decreases nonlinearly with increasing fluid circulation rate.
Compositional Grading—Theory and Practice
Authors: Høier Lars , Whitson Curtis H. 
Published: December 2007

Summary
This paper quantifies the potential variation in composition and pressure/volume/temperature (PVT) properties with depth owing to gravity, chemical, and thermal forces. A wide range of reservoir fluid systems has been studied using all of the known published models for thermal diffusion in the nonisothermal mass-transport problem.
Previous studies dealing with the combined effects of gravity and vertical thermal gradients on compositional grading have been either (1) of a theoretical nature, without examples from reservoir fluid systems, or (2) proposing one particular thermal-diffusion model, usually for a specific reservoir, without comparing the results with other thermal-diffusion models.
We give a short review of gravity/nonisothermal models published to date. In particular, we show quantitative differences in the various models for a wide range of reservoir fluid systems. Solution algorithms and numerical stability problems are discussed for the nonisothermal models that require numerical discretization, unlike the exact analytical solution of the isothermal gradient problem.
We discuss the problems related to fluid initialization in reservoir models of complex fluid systems. This involves the synthesis of measured sample data and theoretical models. Specific recommendations are given for interpolation and extrapolation of vertical compositional gradients. The importance of dewpoint on the estimation of a gas/oil contact (GOC) is emphasized, particularly for newly discovered reservoirs in which only gas samples are available and the reservoirs are near-saturated.
Finally, we present two field case histories—one in which the isothermal gravity/chemical equilibrium model describes measured compositional gradients in a reservoir grading continuously from a rich gas condensate to a volatile oil, and another example in which the isothermal model is grossly inconsistent with measured data and convection or thermal diffusion has apparently resulted in a more-or-less constant composition over a vertical column of some 5,000 ft.
Critical Point and Saturation Pressure Calculations for Multipoint Systems
Authors: Baker Lee E. , Luks Kraemer D. 
Published: December 2007

Abstract
Calculation of fluid properties and phase equilibria is important as a general reservoir engineering tool and for simulation of the carbon dioxide or rich gas multiple-contact-miscibility (MCM) mechanisms. Of particular interest in such simulations is the near-critical region, through which the compositional path must go in an MCM process.
This paper describes two mathematical techniques that enhance the utility of an equation of state for phase equilibrium calculations. The first is an improved method of estimating starting parameters (pressure and phase compositions) for the iterative saturation pressure (bubble-point or dew-point) solution of the equation of state. Techniques previously have been presented for carrying out this iterative solution; however, the previously described procedure for obtaining initial parameter values was not satisfactory in all cases. The improved method utilizes the equation of state to estimate the parameter values. Since the same equation then is used to calculate the saturation pressure, the method is self-consistent and results in improved reliability.
The second development is the use of the equation of state to calculate directly the critical point of a fluid mixture, based on the rigorous thermodynamic criteria set forth by Gibbs. 1 The paper presents an iterative method for solving the highly nonlinear equations. Methods of obtaining initial estimates of the critical temperature and pressure also are presented.
The techniques described are illustrated with reference to a modified version of the Redlich-Kwong equation of state (R-K EOS); however, they are applicable to other equations of state. They have been used successfully for a wide variety of reservoir fluid systems, from a simple binary to complex reservoir oils.
Impact of Research on Oil Recovery
Authors: Sherborne John E. , McEwen C.R. 
Published: December 2007

Introduction
Production research, as it exists today, is a product of the past 25 years. That it is an important part of the oil business at the present time can be indicated by its scope. Twenty-five years ago the number of individuals performing production research could almost be counted on the fingers of one's hands; today it is estimated there are several thousand people working in production research. During the past five years, a number of multi-million dollar production research laboratories have been built and many sizeable additions have been made in the production research facilities of practically all the major oil companies. It is estimated that there is currently being spent on production research something over $20 million annually exclusive of research on oil finding.
The impact of production research on the recovery of petroleum can be considered in three parts. The first of these is the tremendous body of knowledge which has resulted from production research. The second has been the change in our concepts regarding the occurrence and recovery of petroleum and thereby the change in our operating procedures which has been brought about. The third has been the improvement in our ability to quantitatively evaluate various recovery procedures so that the optimum one can be chosen at an early time in the history of the oil field.
It would be difficult indeed to give credit to the very many individuals who have contributed by their research efforts to our knowledge concerning recovery processes. A number of review papers covering the major contributions have appeared from time to time in the literature. Some of the more recent of these are noted in the bibliography. For details of the contributions made with respect to increasing our knowledge, the reader is referred to these papers and to the selected items in the bibliography of this paper.
Rather than produce another such review, we should like to discuss the impact of production research on recovery by citing some specific examples of how our concepts have changed and how our ability to evaluate recovery processes has improved.
Improved Integrated Reservoir Interpretation Using Gas While Drilling Data
Authors: Kandel D. , Quagliaroli R. , Segalini G. , Barraud B. 
Published: December 2007

Summary
The acquisition of gas in mud data while drilling for geological surveillance and safety is an almost universal practice. This source of data is only rarely used for formation evaluation because of the widely accepted presumption that it is unreliable and unrepresentative. Recent developments in the mud-logging industry to improve gas data acquisition and analysis have led to the availability of better quality data.
Within a joint Elf/Eni-Agip Div. research program, a new interpretation method has been developed following the comprehensive analysis and interpretation of gas data from a wide range of wells covering different types of geological, petroleum, and drilling environments.
The results, validated by correlation and comparison with other data such as logs, well tests, and pressure/volume temperature (PVT) data, enable us to characterize lithological changes; porosity variations and permeability barriers; seal depth, thickness, and efficiency; gas diffusion or leakage; gas/oil and hydrocarbon/water contacts; vertical changes in fluid over a thick monolayer pay zone; vertical fluid differentiation in multilayer intervals; and biodegradation.
The comparison of surface gas, PVT, and geochemistry data clearly confirms the consistency between the drilling gas data (gas shows) and the corresponding reservoir fluid composition.
The near real-time availability, at no extra acquisition cost, of such data has led to:
The optimization of future well operations (such as logging and testing). A better integration of while-drilling data to the well evaluation process. Asignificant improvement in both early formation evaluation and reservoir studies, especially for the following applications, in which traditional log analysis often remains inconclusive: Very-low-porosity reservoirs. Thin beds. Dynamic barriers and seal efficiency. Low-resistivity pay. Light hydrocarbons.
Examples show gas while drilling (GWD) wellsite quicklook interpretations with simple lithological and fluid interpretations, as well as more complex reservoir and fluid characterization applications in varied geographical and geological contexts; both demonstrate how GWD data are integrated with more standard data sets.
A Novel Approach for Reservoir Forecasting Under Uncertainty
Authors: Mishra S. , Choudhary M. K. , Datta-Gupta A. 
Published: December 2007

Summary
This paper presents a novel approach for developing statistical estimates of uncertainty in reservoir performance from a limited number of simulations. The methodology involves ranking and weighting the full suite of geostatistical models on the basis of a surrogate performance measure, then estimating the mean/variance of the desired performance measure by using a weighted average of simulation results from a few selected realizations. The streamline time-of-flight-based volumetric sweep efficiency is used as the surrogate performance measure to rank geostatistical models, and their weights are determined from a moment-matching algorithm.
Improvements to Reservoir Material-Balance Methods
Authors: Pletcher J. L. 
Published: December 2007

Summary
Experience with material-balance data sets from the field and from simulation has revealed some procedures that can be used to improve analysis of both oil and gas reservoirs:
Failure to account for a weak waterdrive can result in significant material-balance errors. The assertion of previous authors that weak waterdrive exhibits a negative slope on the Cole (gas) and Campbell (oil) plots has been confirmed. A weak waterdrive is much more unambiguous on these plots than on commonly used plots, such as the p/z plot for gas. A modified version of the Cole plot is proposed to account for formation compressibility. The reservoir drive indices are a useful tool for determining the correctness of the material-balance solution because they must sum to unity. The drive indices should never be normalized to sum to unity because this obscures their usefulness and leads to a false sense of security. A modified version of the Roach plot (for gas) is proposed that improves interpretation in some waterdrive situations. Material balance has not been replaced by reservoir simulation; rather, it is complementary to simulation and can provide valuable insights to reservoir performance that cannot be obtained by simulation.
Slowing Production Decline and Extending the Economic Life of an Oil Field: New MEOR Technology
Authors: Brown L. R. , Vadie A. A. , Stephens J. O. 
Published: December 2007

Summary
This project demonstrated the effectiveness of a microbial permeability profile modification (MPPM) technology for enhancing oil recovery by adding nitrogenous and phosphorus-containing nutrients to the injection water of a conventional waterflooding operation. The MPPM technology extended the economic life of the field by 60 to 137 months, with an expected recovery of 63 600 to 95 400 m3 (400,000 to 600,000 bbl) of additional oil. Chemical changes in the composition of the produced fluids proved the presence of oil from unswept areas of the reservoir. Proof of microbial involvement was shown by increased numbers of microbes in cores of wells drilled within the field 22 months after nutrient injection began.
Selective Plugging of Injection Wells by In Situ Reactions
Authors: Hower Wayne F. , Ramos Joe 
Published: December 2007

Introduction
Petroleum engineers have long realized that producing horizons are not homogeneous. Severe permeability variations have been proven through core analysis and electrical surveys. After obtaining initial flush production through waterflooding, operators have shown concern about the distribution of water in the zone being flooded. At first, the efficiency of most floods was often an unknown factor. But efforts were soon directed toward the development of a method of accurately determining the distribution of flood water. Initial attempts to obtain necessary data were frequently very time-consuming and depended upon a uniform hole size for accurate information. Since many wells that were undergoing flooding operations had been shot, data of this type were inaccurate and misleading.

Early Research
In the early spring of 1951, a research project was instigated to develop a method of effectively treating water injection wells to greatly reduce the permeability of the above described thief zones. It was soon realized that it would be extremely difficult, if not impractical, to hope to be able to actually equalize the permeability of the entire horizon. Past research and field applications reported singular success when the surface of the formation was selectively plugged. There is adequate proof that additional oil was recovered as the result of these treatments and the process was a definite contribution to the industry.
The procedure had two major drawbacks, however. One being that where there are no horizontal bedding planes to isolate the selectively plugged zone and where the vertical permeability is relatively high, the injection water quickly goes around the surface plug and again enters the zone of highest permeability. The other is that an injection well will develop a formation pressure which will cause a back flow of formation fluids when water injection is stopped. Such a back flow normally washes away the surface plugging chemicals and thus reopens the offending zone so that it may accept flood water again.
Development and Application of an In-Situ Combustion Reservoir Simulator
Authors: Youngren Gary K. 
Published: December 2007

Abstract
This paper describes a three-dimensional, three-phase in-situ combustion reservoir simulator that rigorously models fluid flow, heat transfer, and vaporization/condensation. It has five components: water, oxygen, nonvolatile oil, and two arbitrary volatile components. The volatile components partition between the oil and gas phases. The physical mechanisms modeled, the comprehensive mathematical solution method employed, and four applications of the simulator are presented. The applications demonstrate that the simulator can be used to interpret laboratory results and predict the effects of reservoir characteristics and operating strategy on field performance.
New View on Continuous-Removal Liquids From Gas Wells
Authors: Li M. , Li S. L. , Sun L. T. 
Published: December 2007

Summary
The paper adopts the view that the liquid droplets entrained in gas wells tend to be flat and deduces new formulas for the continuous removal of liquids from gas wells. The results calculated from the formulas are smaller than those of Turner et al. However, the predicted results are in accord with the practical production performance of China's gas wells with liquids. The paper also gives the simple forms of these formulas and shows the load-up and near load-up production performance as well as unloaded gas wells through the wellhead, producing performance figures.
A Method for Predicting Oil Recovery by Steamflooding Including the Effects of Distillation and Gravity Override
Authors: Rhee Shie W. , Doscher Todd M. 
Published: December 2007

AbstractThis paper describes a semianalytical method for calculating oil recovery by steamflooding. It accounts for effects of steam distillation and gravity overlay of steam. First, the equations for the heat balance and the configuration of the steam/liquid interface1 are solved simultaneously to predict the volume of the overall heated zone and the volume and shape of the steam zone. Second, the approximate enthalpy and material balances are combined with the thermodynamics of differential vaporization to derive a fully compositional method for calculating the volume and composition of steam-distilled hydrocarbons. Finally, the results of the foregoing are combined with a fluid flow model, similar to Higgins and Leighton's2 cell model for waterflood analysis to calculate oil recovery.This semianalytical method can account for almost all the important recovery mechanisms involved in steamflooding with relatively small computation time. Good agreement has been obtained between available experimental data and calculations carried out in accord with this analysis.
A Laboratory Study of Low-Permeability Gas Sands
Authors: Jones F.O. , Owens W.W. 
Published: December 2007

Routine permeabilities of tight gas sands are shown to be greater than under reservoir conditions, often by more than a hundred-fold, because of the great relief of stress, absence of connate water, and increased gas slippage. Correlations are presented that can be used to estimate in-situ permeability from routine data.

Introduction
Yearly compilations of U.S. oil and gas reserves by the American Gas Assn.1 show that U.S. gas reserves reached a maximum in 1967 of nearly 290 Tcf (8×1012 m3). With the exception of the year 1970 when Prudhoe Bay reserves were added, gas reserves have declined at a near-constant rate of 10 Tcf (2.8×1011 m3) per year since then. To help moderate or reverse this trend, the industry is extending its exploration and development efforts to include horizons with permeabilities in about the same range as common cement - i.e., microdarcies. The design of stimulation treatments to achieve commercial rates of production and reliable assessment of potential reserves in such low-permeability rocks demands accurate knowledge of their permeability, porosity, and flow properties. Though meager, there is sufficient information already available in the literature to suggest that some of the flow properties of these rocks differ markedly from those of more permeable rocks and, thus, require closer study.
Results of several different studies of the properties of low-permeability gas-producing horizons have been published previously. A study by Thomas and Ward2 showed that the permeability of cores from the Pictured Cliffs and Fort Union formations were affected significantly by confining pressure. Porosities, however, were not altered greatly. They also reported that the presence of a simulated connate water saturation (about 500(0) reduced gas permeabilities to only 10% to 20% of the specific gas permeability. Vairogs et al.3 concluded that very low-permeability rocks are affected by stress to a greater degree than those having higher levels of permeability. This agreed with results reported earlier by McLatchie et al.4
Tannich5 mathematically studied liquid removal from fractured gas wells in low-permeability horizons and concluded that in very low-permeability rocks, cleanup times could be extensive but that permanent formation damage was not likely. The study, however, provided no measured experimental data of the flow properties of low-permeability rocks.
A Study of Oil Displacement by Microemulsion Systems – Mechanisms and Phase Behavior
Authors: Willhite G. P. , Green D. W. , Okoye D. M. , Looney M. D. 
Published: December 2007

Abstract
Microemulsions located in a narrow single-phase region on the phase diagram for the quaternary system consisting of nonane, isopropyl alcohol, Witco TRS 10-80 petroleum sulfonate, and brine were used to investigate the effect of phase behavior on displacement efficiency of the micellar flooding process. Microemulsion floods were conducted at reservoir rates in 4-ft (1.22-m) Berea cores containing brine and residual nonane. Two floods were made using large (1.0-PV) slugs. A third flood used a 0.1-PV slug followed by a mobility buffer of polyacrylamide. Extensive analyses of the core effluents were made for water, nonane, alcohol, and mono- and polysulfonates.
An oil bank developed which broke through at 0.08 to 0.1 PV, and 48 to 70% of the oil was recovered in this bank which preceeded breakthrough of monosulfonate and alcohol. Coincidental with the arrival of these components of the slug, the effluent became a milky white macroemulsion which partially separated upon standing. Additional oil was recovered with the macroemulsion. Ultimate recoveries were 90 to 100% of the residual oil. Low apparent interfacial tension was observed between the emulsion and nonane. Alcohol arrived in the effluent at the same time as monosulfonate even though there was extensive adsorption of the sulfonate. Further, alcohol appeared in the effluent well after sulfonate production had ceased, indicating retention of the alcohol in the core. A qualitative model describing the displacement process was inferred from the appearance of the produced fluids and the analyses of the effluents.