bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shortcomings in the Use of TGA/DSC Techniques to Evaluate In-Situ Combustion
Authors: Nickle S. K. , Meyers K. O. , Nash L. J. 
Published: December 2007

ABSTRACT
Combustion tubes are the classical laboratory tools for evaluating in-situ combustion. However, high operational, capital, and maintenance costs, as well as, extensive material and analytical requirements have restricted their application. Recently, inexpensive methods for evaluating in-situ combustion using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been described in the literature. TGA/DSC techniques have been used to determine combustion parameters such as fuel laydown and peak temperature and to quantify the kinetics of low temperature oxidation and combustion. The published TGA/DSC procedures often employ experimental conditions which are significantly dissimilar to those encountered in either a combustion tube or a reservoir process. Yet, limited data has been reported on the sensitivity of combustion parameters determined by TGA/DSC to experimental conditions such as heating rate, oxygen partial pressure and flow rate.
In this paper, the sensitivity of TGA/DSC procedures to experimental/operating conditions are evaluated. First, the operating conditions and techniques used in the literature are briefly reviewed. Next, the results of a laboratory study on the sensitivity of TGA/DSC procedures to heating rate (0.2 to 20°C/min), oxygen partial pressure (0 to 400 psia), purge gas flow rate (75 to 1000 ml/min), matrix materials (0 to 90 wt%), and sample size (20 to 100 mg) are presented. This study details not only the effects of the experimental conditions on the thermal curves but also on the combustion parameters/kinetics calculated from them (fuel laydown, peak combustion temperature, heats of reaction, Arrhenius constants, and the extent of low temperature oxidation [LTO]). The observed sensitivities are examined in terms of heat/mass transfer limitations and reaction kinetics. As a consequence of the sensitivity study, TGA/DSC procedures are proposed that mimic the experimental conditions typically encountered in a combustion tube. Application of these procedures to eight viscous and heavy oils is discussed.
A Review of Horizontal Well and Drainhole Technology
Authors: Joshi S. D. 
Published: December 2007

ABSTRACT
This paper reviews the state-of-the-art of horizontal well and drainhole technology, and provides guidelines for the initial evaluation of horizontal well and drainhole drilling prospects. The primary emphasis of the paper is reservoir engineering. Since drilling and completion methods influence a horizontal well's performance, a brief review of these aspects of technology is also included. The paper also reports the field production histories available in the literature.
Hydraulic Fracture Propagation in the Presence of Stress Variation
Authors: El Rabaa W. 
Published: December 2007

ABSTRACT
This paper presents results of a study regarding the effects of horizontal stress gradient as a barrier limiting vertical growth of an induced hydraulic fracture. Dry blocks (6 × 12 × 18 in.) of various rock materials were subjected to stresses by a polyaxial cell capable of delivering up to 3000 psi loads. Actual stress distribution inside the block and along fracturing planes was determined by a 3-D finite element model using elastic elements. Effects of stress magnitudes and stress profiles were investigated and fracturing pressure and fracture width were monitored at the center of the borehole during experiments. After splitting the block along the fractured plane, the final geometry was observed.
The study has shown that stress variation between different levels (zones) of the block can greatly modify the induced fracture shape. However, the magnitudes of stress difference between zones to contain a fracture were found to be rock type dependent. Tests on blocks of softer material (such as hydrostone) needed lower stress contrast to contain a fracture than if a stiffer rock (such as Carthage marble) was used. In tests where fractures were initiated at higher stress zones adjacent to lower stress zones, fractures extended into the lower zones. The ratio between fracture areas in both zones was dependent on the difference in stresses between the two zones. At a constant stress contrast between zones, the growth of fracture height into the higher stress zone was found to be a nonlinear function of the injection rates. Experiments have also indicated that the stress contrast needed for containment depends on the height of the middle zone (simulated pay zone height). The ISIP measured during the tests were 11% higher than those predicted by the 3-D finite element model.
Calculation of the fracture toughness values (K1c) of the rock from the experimental data were significantly higher than those obtained by standard fracture toughness testing.
An Evaluation of the Effects of Environmental Conditions and Fracturing Fluids Upon the Long-Term Conductivity of Proppants
Authors: Penny G. S. 
Published: December 2007

ABSTRACT
The presented work is a compilation of efforts directed by 20 producing companies, service companies and suppliers to understand the effects of environmental conditions and fracturing fluids upon various classes of propping agents. In preliminary work the long-term effects of closure and temperature combinations ranging from 3000 psi and 150°F to 10,000 psi and 300°F are investigated on sands, resin coated sands and ceramic proppants between monel shims and medium-hard sandstone. This portion of the work sets the baseline for equilibrium permeabilities and conductivities taking into account time, closure stress, temperature and embedment. The work then focuses on the effects of common crosslinked fracturing fluids and fluid loss additives upon conductivity and permeability. Equipment is described and procedures are established using a fracturing treatment simulator that permits job-like fluid mixing, tubing shear history (1000-1500/sec), formation shear (40-50/sec), heat-up, dynamic fluid leakoff through formation core at 1000 psi to create filter cakes, and the placement of proppant. Leakoff rates during and after the treatment, and conductivities and permeabilities measured after cleanup, reveal relationships of additives and conditions that will be useful in the design of fracturing treatments and the prediction of well performance.
Development and Application of an Operator's Stimulation Monitoring System
Authors: Pearson C. M. 
Published: December 2007

ABSTRACT
The monitoring of stimulation treatments has traditionally been left to the service company providing the pumping service. This paper describes the development of a monitoring system by an operator that is capable of being used with all the major service companies. The benefits of the SMART (Stimulation Monitoring Analysis and Research Truck) system is shown from quality control information obtained during four massive hydraulic fracture treatments. Data previously not recorded continuously on-site is shown to be of importance. The instrumentation used is also discussed together with some of the limitations and successful applications from monitoring over fifty treatments.
Comparisons of Computational Efficiencies of Different Equations of State and Transport Property Correlations in a Compositional Simulator
Authors: Klara S. M. , Hemanth-Kumar K. 
Published: December 2007

ABSTRACT
Comparison of computational time requirements for four equations of state (Soavé-Redlich-Kwong equation, Peng-Robinson equation, Joffe-Zudkevitch modification of the Redlich-Kwong equation, and the higher-order Conformai Solution Model Benedict-Webb-Rubin-Starling equation) and two viscosity correlation sets (Dean and Stiel for computing gas viscosities; Lohrenz, Bray, and Clark for computing oil viscosities; and the more accurate Modified-Chung-Ajlan-Lee-Starling correlation for both the oil and gas viscosities) for several compositional simulation problems are presented. The results of this study indicate that when the reservoir oil is characterized using 3 components, 10 components, and 15 components, the computational time increases with the number of components. Furthermore, although no specific equation of state was the most efficient in all cases, a particular equation of state may show significant savings for a specific case. The higher-order equation of state requires much greater computational time for the same simulation problems. Comparisons between multicontact miscible and immiscible problems indicate a higher time requirement for the former problem due to time-consuming computations in the critical region. Comparisons between two viscosity correlation sets for several compositional simulation problems indicate negligible differences in computational time, and, hence, the more accurate correlation is recommended for compositional simulators.
Secondary Gas Recovery from a Water-Drive Gas Reservoir: A Case Study
Authors: Ancell K. L. , Manhart T. A. 
Published: December 2007

ABSTRACT
The 9100 ft Frio Reservoir at Northeast Hitchcock Field is being produced as an enhanced gas production project after being produced to high water cuts during primary depletion of this partial water drive reservoir. Six wells are currently capable of producing large volumes of brine and the associated gas, condensate and oil. The primary history of the reservoir was described by Anderson et al1. Twelve wells produced 86 Bcf (2.44×l09 m3) from 1958 through mid 1983. Two new wells completed late in the life at the top of the structure soon produced high water cuts. This confirmed that the reservoir was fully invaded. Initial gas in place was about 131 Bcf (3.71×l09 m3) thus leaving 45 Bcf (1.27×l09 m3) in place as residual gas and as small pockets of mobile gas trapped in the very top of the structure.
The basic premise of the project is that the residual gas saturation trapped by encroaching water is independent of the pressure at which it is trapped. If the pressure is subsequently lowered, this residual gas will expand to a saturation greater than residual and a portion of the gas will be mobilized. Conversely, if the reservoir pressure increases, the gas will be compressed and occupy a saturation less than residual. In this case, the reservoir pressure must be lowered below the previous minimum before any gas can be mobilized. Boyd et al2 defines this minimum pressure the "entrapment pressure."
Since 1983, the reservoir has been produced as an enhanced production project with wells producing high volumes of brine. The large brine production volumes were used to draw the reservoir pressure down causing trapped gas to expand and become mobile. The production characteristics and equipment of this period have been described by Randolph, et al3. During this time an additional 2.05 Bcf (5.80×107 m3) of gas and 120,000 bbl (1.91×104 m3) of oil and condensate have been produced. This success has given the operators in the field confidence to expand the project and include more brine disposal capacity to increase the reservoir voidage rate.
This paper describes a reservoir simulation study of this field that assesses the gas recovery and economic viability of the project. The reservoir description is presented as well as the future performance projections under two different operating scenarios. These scenarios show that an ultimate recovery can be increased by between 7 and 29 Bcf (2.0×108 and 8.21×108 m3) depending on equipment ultimately installed. Economic calculations for the two cases are presented. Also presented is an investigation of the effect of converting wells to brine producers instead of plugging the wells when water cuts started to increase. This shows that an additional 13 Bcf (3.68×108 m3) could have been produced to date had only two wells been kept on production instead of being plugged.
Using the Inertial Coefficient, ß, To Characterize Heterogeneity in Reservoir Rock
Authors: Jones S. C. 
Published: December 2007

ABSTRACT
New data, relating the inertial coefficient, β, or the Klinkenberg slip factor, b, to the characteristic length, k/ϕ, are presented for core plugs from several reservoirs. These are useful for estimating flow performance of wells.
The group, βkϕ, which is the characteristic length dimension in a Reynolds number for porous media, should be proportional to the k/ϕ characteristic length. It approaches proportionality for the most permeable samples, but deviates badly for tighter plugs. A multi-layer flow model is developed that demonstrates that the departure is due to the non-linear dependence of inertial resistance on permeability variations in a core plug. Thus the measurement of β provides a very sensitive indication of permeability heterogeneity, on a core-plug level.
Immiscible Displacements in Porous Media: Testing Network Simulators by Micromodel Experiments
Authors: Touboul E. , Lenormand R. , Zarcone C. 
Published: December 2007

ABSTRACT
In the past, many network simulators have been presented to describe transport processes through porous media, such as deep filtration, immiscible or miscible displacements, blob mobilization, acidizing, etc. In this paper we compare the results of physical and stochastic network simulators with experiments in micromodels. We first describe the patterns obtained by displacing a wetting fluid by a non-wetting fluid in a 2-dimensional porous medium, when both viscosity ratio (M) and capillary number (Ca) are varied independently over many orders of magnitude. The main result is the good agreement between experimental and simulated patterns (trapping, fingering, connectivity…) even for extreme values of M and Ca (high viscosity contrast or very strong capillary effects, for instance). In the second part, both experiments and simulations are compared to the results of stochastic models. The classical models of "invasion percolation" and "diffusion limited aggregation" are shown to represent the limiting cases when the dimensionless numbers Ca (for I.P.) and 1/M (for DLA) tend to zero. Finally, some comments are presented on a recent model based on fluid compressibility and particle diffusion.
Pore Level Visual Investigation of Oil Recovery by Solution Gas Drive and Gas Injection
Authors: Danesh A. , Peden J. M. , Krinis D. , Henderson G. D. 
Published: December 2007

ABSTRACT
The mechanisms of oil recovery by solution gas drive and by gas injection have been studied. The flow visualisation experiments were performed in a high pressure heterogeneous micromodel reproduced from real rock micrographs. The micromodel was also employed in series with a compatible glass bead pack. Pressure depletion and displacement experiments by methane, propane and water flooding were conducted on a live North Sea crude. The video observations and the measurements made are reported.
The pore level investigation of solution gas drive revealed the mechanisms of nucleation, and the growth of gas bubbles at different pressure levels. The spontaneous movements of large bubble-oil interfaces contribute to the oil recovery process during the early stages of production. The recovery mechanisms at the higher gas saturations were found to be similar to the immiscible gas drive behaviour observed with experiments of methane injection at low capillary numbers.
The asphaltenes flocculation under dynamic conditions of oil displacement was studied by propane slug injection. The miscible displacement of oil by propane did not induce any significant asphaltene precipitation within the pores.
Material Balance Calculations for Solution-Gas-Drive Reservoirs With Gravity Segregation
Authors: Ambastha A. K. , Aziz K. 
Published: December 2007

ABSTRACT
In this work, a reservoir simulator is used to study the phenomena of gas percolation and gravity segregation, and their effects on reservoir performances. The sensitivity study of reservoir performance to block and time-step sizes shows that for typical solution-gas-drive reservoirs, large errors in average reservoir pressure may result from improper control of time-step in the simulator. The comparison of simulation results with the Tamer's1 method shows that the latter predicts faster reservoir pressure and oil saturation decline, and thus, underpredicts the reservoir producing life and recovery.
We propose a new material balance method for predicting the performance of thick, homogeneous, depletion-drive reservoirs. This method accounts for the vertical pressure and saturation gradients, and the secondary gas cap. The thickness of the secondary gas cap can be estimated with good accuracy using an idealized saturation profile. An iterative procedure relates average reservoir pressure to well pressure. The pressure and saturation at the well are then used to calculate the producing gas-oil ratio. The idealized saturation profile is also used to develop pseudo-functions to simplify the simulation of solution-gas-drive reservoir with gravity segregation.
Imbibition-Dominated Matrix-Fracture Fluid Transfer in Dual Porosity Simulators
Authors: Beckner B. L. , Ishimoto K. , Yamaguchi S. , Firoozabadi A. , Aziz K. 
Published: December 2007

ABSTRACT
Published imbibition experiments of an advancing fracture water level surrounding a single matrix block are simulated using a fine grid single porosity model and various double porosity models. The fine grid simulations show that a stationary water saturation profile quickly develops and advances in the matrix at the same rate as the fracture water level.
A new double porosity transfer function for imbibition dominated matrix/fracture fluid exchange is presented based on stationary profile solutions of the fractional flow equation. This transfer function models the imbibition recovery for these advancing water level experiments better than the conventional double porosity imbibition formulations. It is shown that the stationary profile transfer function is best suited to systems where the time to develop the stationary profile is short relative to the length of the waterflood.
The experimental data was also simulated using a diffusion equation with a nonlinear diffusion coefficient in combination with a moving boundary condition as the imbibition model. A constant diffusion coefficient based upon water relative permeability and capillary pressure gradient values at 1 − Sor matched the experimental results as well as the nonlinear diffusion coefficient, but required much less computer time. From analyzing two different diffusion type equations as imbibition models, we show that countercurrent imbibition is not a likely recovery mechanism for this type of advancing water level imbibition experiment.
Calcium Carbonate Scale Considerations: A Practical Approach
Authors: Vetter O. J. , Farone W. A. , Veith E. , Lankford S. 
Published: December 2007

ABSTRACT
Calcium carbonate scale, the most common oil field scale, normally forms from three-phase fluid systems at various downhole locations. The basic scale formation mechanism of CaCO3 in oil field operations was explained in a recent publication [1]. However, only the very basic model considerations and only a few field application details were given in this recent publication related to CaCO3 scale modeling. Most practical field applications of the CaCO3 scale modeling efforts were ignored.
In this present paper, we elaborate on the same mechanisms of CaCO3 scale formation in a typical oil field emphasizing some of the more practical aspects of this scale modeling for field operators. None of the theoretical but only some very practical aspects of this scale formation are stressed in this present paper. The outcome of some scale model runs is used to show some practical field applications of any serious model efforts. An attempt is made to show some field problems related to this common type of oil field scale and how a proper modeling can overcome some of these problems. A series of different produced fluids are used in fifteen (15) examples (representing 15 different wells) to illustrate the complexity and intricacy of various CaCO3 scale formations in a hypothetical oil field.
This paper is a logical follow-up of a recently issued SPE paper [1] and is mainly written for a practicing petroleum engineer who is concerned mainly with practical field operations. Therefore, all of the pertinent thermodynamics and other basic physical and chemical correlations are kept at a bare-bone minimum. Instead, we are stressing the more practical aspects of fighting CaCO3 scale in a "typical" oil field based on some model considerations and some actual calculations. Any theoretical and any serious computational considerations are deemphasized.
Downhole Measurement on Pumping Oil Wells
Authors: Albert G. D. , Purcupile J. C. , Chacin J. C. 
Published: December 2007

ABSTRACT
For the past 60 years, the dynagraph has been useful in measuring well performance and diagnosing trouble conditions downhole. More recently, surface dynagraph data, with other well-specific parameters, has served as input to mathematical models for predicting downhole behavior. Various computer programs exist to perform this task, and none have previously been verified empirically. In fact, no downhole force measurements have been made since 1942, by Lamberger and Langer (see Ref. 1).
An apparatus was developed, as a master's thesis project, to make these measurements. The device is a microcomputer-based data acquisition system that is wholly contained in a five-foot section of standard tubing. It was designed and built to mount in series with the sucker rod string, directly above the pump, and to sample and store real-time data of load, displacement, pressure, and temperature for analysis at the surface. This paper describes the unit, some of its development, and the results of the successful August 1986 field test, executed at over one mile of depth.
Application of a Full-Scale Compositional Reservoir Simulation Package on a Microcomputer
Authors: Brooks R. J. , Jepson P. J. 
Published: December 2007

ABSTRACT
Advantage has been taken recently of the memory management scheme of a state-of-the-art compositional reservoir simulator to instal the complete program package on an IBM-compatible PC.
Although obviously limited from a time and space consideration in its scope for full scale field simulations, the main simulator can handle grids containing 500 blocks with 10 components on a PC with 640k RAM and associated hard disc capabilities.
Two possible applications for the use of such a package on micro-computers are discussed :
The generation of PVT data for compositional simulation The simulator has several different options for calculating fluid properties ranging from simple black oil representation, through special 3-component correlations, right up to a choice of Equation of State (EOS). Sensitivity studies as part of the decision process in defining a grid with a view to eliminating numerical dispersion and grid orientation effects Particularly applicable to the simulation of miscible displacement processes in a five-spot pattern, Koval1 dispersion theory has been successfully applied to radial diverging and converging flow. Using a biradial mesh with various grid block sizes, results are compared to show the effectiveness of this approach.