bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified Gas Porosimeter
Authors: Bousaid Issam
Published: December 2007

Described is a simple glass apparatus for rapidly obtaining gas porosities of porous rocks. The method consists of fast volume measurements of samples at atmospheric and lower pressures. This method applies basically the same principle as Boyle's law, P1V1 = P2V2, however, volume measurements are obtained at atmospheric pressure and lower in one simple operation. The apparatus is easily built from readily available glass components. A diagram of the glass porosimeter is shown in Fig. 1. The porosimeter has five basic components: two 500-cc glass burettes, a glass sample holder, a three-way glass valve, a 1/4-in. glass tube next to a meter stick and a 500-cc glass leveling bulb containing about 200 cc of mercury. The sample holder can be designed to contain samples of any dimensions; in this case, cores of 1 in. diameter X 3.0 in. long are used. The samples initially were placed in a perforated plastic holder that reduced direct handling of the samples and easily allowed their insertion in and removal from the glass sample holder. A relationship was obtained between the volume drop in cc of Hg and the height drop in cm for the right-hand burette. The value of this slope m is shown in Table 1. The method consists of measuring a new gas volume at a pressure below atmospheric. Briefly, the operational procedure consists of two steps for obtaining the grain volume measurements and a third step for obtaining the bulk volume.

- The sample is placed inside the glass sample holder with the lid firmly secured (Fig. 1). Initially, the leveling bulb is brought to Position 1 where the mercury level is adjusted to the zero mark on the right burette.

- The valve to the atmosphere is closed and the leveling bulb is lowered a distance L equal to the room pressure in cm of Hg (read on the meter stick). The new mercury level on the right burette is obtained directly and corresponds to the increase in gas volume in cc at the lower pressure p2. The bulk volume of the sample can be measured from the following step.

- The leveling bulb is adjusted to Position 3 and the valve to the atmosphere is opened gradually, allowing the mercury to rise slowly and submerge the sample up to the reference mark.

The three-way valve is turned slowly to the position connecting the left burette to the right burette. Mercury is drained from the sample holder until the level reaches the zero mark on the right burette. The volume on the left burette v, is obtained directly. Caution must be exercised to prevent any air bubbles from being trapped in the system. All samples are dried

TABLE 1-DESCRIPTION AND OPERATIONOF POROSIMETER

Calibration Data of Porosimeter

Volume of sample holder 79.6 cc Volume of plastic holder 2.6 cc Net volume of sample holder:For grain volume measurements 77.0 ccFor bulk volume measurements 76.2 cc

Average value of slope m in cm of Hg per cc of Hg drop1.137 + 0002

Sample Measurements and Calculations

True volume of aluminum rod = 36.63 cc Volume increase at p2, = 35.5 cc Atmospheric pressure p1 = 75.88 cm Hg

Grain volume of rod = 77.0

P. 335ˆ
Heterogeneities and Geometry of Sedimentary Bodies in a Fluvio-Deltaic Reservoir
Authors: Ravenne C. , Eschard R. , Galli A. , Mathieu Y. , Montadert L. , Rudkiewicz J. -L.
Published: December 2007

This paper gives the initial results of a two- and three-dimensional (2D and 3D) geological study that aimed at describing reservoir heterogeneities. This study serves as a basis for the conditional simulation of the geometry of a fluvio-deltaic reservoir presented in a companion paper. These two studies should solve the difficult problem of interpolating between wells and thereby the problem of forecasting the extension of sedimentary bodies. The research is being carried out by Inst. Français du Pétrole and Center of Geostatistics, Paris School of Mines.

The study was made in the middle Jurassic in Yorkshire, which is very similar to the Brent formation in the North Sea. In the 2D phase, an outcrop consisting of a 1-km [0.6-mile] -long and approximately 30-m [100-ft] -high cliff was described with a photogeological interpretation. The sedimentological representation was carried out by means of several vertical cross sections. In the 3D phase, 36 boreholes were continuously cored and logged behind the cliff over an area of 1 km2 [0.4 sq miles]. The boreholes were about 300 m [985 ft] apart except in one grid where the distance was progressively reduced to 20 m [66 ft]. This phase was designed to follow the evolution of the sedimentary bodies and their physical properties and to compare the correlation that could have been made (1) with fewer boreholes and (2) without the existence of the cliff. These studies provide new tools for understanding and describing the shape and heterogeneities of a reservoir.
Calculation of Bottom-Hole Pressure in Gas Wells
Authors: Aziz Khalid
Published: December 2007

A simple, fact and accurate method for computing flowing and static bottom-hole pressures in gas wells is presented. The method employs any of the well known methods for numerical integration and the Newton-Raphson iteration scheme. The proposed method may he easily programed for digital computers or it may be used for hand calculations. The method is superior to previously proposed methods in accuracy and rate of convergence. Accuracy of the method depends mainly on the type of integration scheme and input data. Several integration schemes are evaluated here for use with this method.

Introduction

The basic equation for flow in a vertical pipe and hydrostatic head are well known and are reviewed in a recent manual published by the Oil & Gas Conservation Board of Alberta and in a series of papers published by the author. Only the most general form of these equations used for practical calculations will be presented here. This form of the equations was first proposed by Cullender and Smith. For static bottom-hole calculation we have,

........................................(1)

and for flowing bottom-hole pressure,

........................................(2)

The usual procedure in bottom-hole calculations is to (1 ) assume a value of p, (2) compute the right-hand side of Eq. 1 or 2 depending on the type of calculation being performed (static or flowing) and (3) check to see if the computed value of the integral is equal to the known left-hand side of the equation. If the two sides of the equation are not equal within a certain allowable tolerance, the calculations are repeated with a new estimate of ps. The numerical method used for evaluating the integral is usually either the trapezoidal rule or Simpson's rule.

Proposed Method

A method is proposed here for performing bottom-hole pressure calculations so that a minimum number of iterations is required. The method could be used with any numerical integration scheme. Rewrite Eq. 1 or 2 in the following form,........................................(3)

in this equation, K. y and, hence, 0 take on different values depending on the problem being considered. For the static case,

........................................(4)
Microinduction Sensor for the Oil-Based Mud Dipmeter
Authors: Kleinberg R. L. , Chew W. C. , Chow E. Y. , Clark B. , Griffin D. D.
Published: December 2007

Microinduction sensors are used in the Oil-Based Mud Dipmeter Tool™ to measure formation conductivity through nonconductive mud or mudcake. The sensor consists of small transmitter and receiver coils mounted in a pad. An extensive research effort involving sensor response modeling, laboratory experiments, and signal processing contributed to the development of these new sensors.
Undersea Drilling and Production Sites for Petroleum
Authors: Austin Carl F.
Published: December 2007

Large undersea installations with shirtsleeve environment have existed under the continental shelves for many decades, The technology now exists, using off-the-shelf petroleum and mining equipment, to establish permanent manned installations within the sea floor- that can be used for well drilling and initial petroleum fluid processing. The past and present permanent, in-the-sea-floor mining industry is reviewed and methods now practical for direct access to and from permanent in-the-sea-floor drilling and production sites are outlined. Drill sites beneath the sea floor are free of weather and floating ice hazards, and enable complete access to the wellhead area by technicians and laborers. A present estimate for such an operating site is approximately $50 million.

Introduction

The petroleum industry has become deeply and irrevocably involved in producing gas and oil from the continental shelves. Chief among the problems of offshore drilling today is the hazard presented by the air-water interface, i.e., the damage potential of serious storms and waves, an example of which is the recent destruction of a British petroleum platform, costing 11 lives. To overcome the problems of working at the unstable air-water interface. the present industrial trend is to go to the sea floor. The following statement is appropriate: "The consensus of oil companies is that by 1975, if technology is available, most stationary installations will be on the bottom of the sea, not on the surface."'

In addition to working on the bottom of the sea while keeping the drilling platform on the surface, there is another major potential solution to the problems of offshore drilling. This solution is literally to burrow into the sea floor, using the rock as the construction medium for drilling and production sites in which all activities are carried out in a normal one-atmosphere environment. Fig. 1 illustrates the practicality of this approach. This machine shop bay is part of a mining complex with approximately 7 1/2 sq miles of open, permanent floor space. The individual shop bay is some 500 ft long. The striking aspect is that this existing installation is located beneath 400 ft of water, some 2 1/2 miles off the shore of an island on the eastern coast of Canada. The installation is 1,500 ft below sea level. A series of openings such as the one illustrated, excavated in the sea floor, could obviously contain an extensive petroleum drilling and production installation and very extensive bulk storage and processing installations. This article discusses how the study program called Rock Site, conducted at the U.S. Naval Weapons Center, has led to the conclusion that petroleum production sites, as well as many other industrial operations, can be located within the bedrock beneath the sea floor, using only existing tools and technology.

JPT

P. 1309ˆ
Remaining-Oil Determination Using Nuclear Magnetism Logging
Authors: Freedman R. , Rouault G. F.
Published: December 2007

The determination of the volume of remaining oil in a reservoir is a key ingredient in planning future oil recovery operations. Nuclear Magnetism Logging (NML™) is an openhole wireline logging method that can provide accurate estimates of remaining-oil volumes. The signal processing required to extract these estimates from the logging data and the NML logging procedures used in this application are the subjects of this paper.

The physics of the NML method and the wellsite log-inject-log procedures used for remaining-oil determination is reviewed. The latter procedures include the doping of the mud with magnetite to kill the borehole signal and the injection of paramagnetic ions into regions sensed by the NML measurement to kill the formation-water signal.

A new NML signal-processing algorithm for determining remaining oil is developed. The algorithm is an improvement over conventional envelope processing in low SNR environments. The algorithm explicitly accounts for the statistical properties of bandwidth-limited Gaussian thermal noise in extracting signal parameters from signal-plus-noise measurements. This is especially important for remaining oil determinations for which accurate estimates of both the fractional bulk volume of remaining oil, Vbro, and the uncertainties in these estimates are required.

The method is applied to residual-oil data from a Shell well. The data consist of repeat waveforms at 44 stations. The FFFs are mostly in the range from 1.0 to 4.0 porosity units (p.u.) and the signal decay times are less than 50 msec. Thus, the data represent an abnormally difficult signal-processing problem as a result of the low SNR's. The results of processing these data are compared with results obtained independently by Shell with their own processing methods, which are widely regarded in the industry as standards. The volumes of residual oil and standard deviations estimated with the new signal-processing method developed in this paper are in excellent agreement with the results of Shell's processing methods.
A Complex Reservoir Characterized By Three-Dimensional Seismic, Geostatistical Reservoir Description, and Sponge-Core Analysis
Authors: Carr L. A. , Benteau R. I. , Corrigan M. P. , Van Doorne G. G.
Published: December 2007

This paper reports the characterization and reservoir description of the Rainbow Keg River "F" pool located in northwestern Alberta, Canada. Significant improvements in reservoir description were made through further delineation of geological structure with a three-dimensional (3D) seismic program, evaluations of residual oil with sponge-core analysis, and a geostatistical reservoir description that uses kriging. Increased accuracy in reservoir analysis was required for the evaluation of the remaining resources under a mature waterflood.

The characterization is examined by matching a cross-sectional reservoir model to production performance, including oil/water-contact (OWC) and gas/oil-contact (GOC) history as well as reservoir-pressure surveys. The result of the program is an increased accuracy in reservoir delineation, improvements to well completion strategy, and a monitor of waterflood performance.
Influence of Clay Distribution on Shaly Sand Conductivity
Authors: de Waal J. A.
Published: December 2007

Membrane-potential measurements were carried out on original and remolded core samples to study the influence of sample crushing on the electrical conductivity of shaly sands. Results show that the distribution of clay minerals has a large influence on their contribution to the electrical conductivity. Consequently, clay conductivities derived from nondestructive membrane-potential measurements are much more accurate than those calculated from conductometric titration measurements.

Membrane-potential measurements were carried out in a new experimental setup that allows the use of unconsolidated and therefore highly permeable samples. In particular, the problem of maintaining a constant salinity contrast over the sample length during the measurement has been solved. With the new equipment, reliable membrane-potential measurements can be made in 20 to 30 minutes per sample.
Relationship Between the Archie Saturation Exponent and Wettability
Authors: Donaldson E. C. , Siddiqui T. K.
Published: December 2007

The calculation of in-situ water saturations from resistivity well logs relies on the saturation exponent of Archie's equation, where n =2 for clean, consolidated, water-wet sandstones. The saturation exponent, however, is a function of the water/oil/rock wettability and was found to range from <2 to 8. The relationship between wettability and the saturation exponent is linear, and the slopes of the lines at low and high temperature are identical for a given sandstone.
General Turbulent Pipe Flow Scale-Up Correlation for Rheologically Complex Fluids
Authors: Lord D.L. , Hulsey B.W. , Melton L.L.
Published: December 2007

A mathematical model d1.20?p/4L = A(8v)s derived from the Blasius equation is proposed to be applicable to turbulent flow through straight cylindrical pipe for time-independent fluids which produce a diameter family of straight parallel lines on a log (d?p/4L) vs log (8v/d) plot or stress-flow diagram. Such a correlation should permit scale-up with data taken from one pipe diameter for Newtonian, inelastic non-Newtonian and viscoelastic fluids, such as dilute polymer fracturing fluids, which produce considerable frictional pressure reductions.

The Newtonian diameter exponent value 1. 20 is shown to be empirically valid for turbulent non-Newtonian flow by application of numerical analysis methods. Multiple regression analysis is applied to a logarithmic linearization of the proposed model. An improved data fit results from further linearization achieved by taking linear terms from a generalized Taylor's series expansion about the multiple regression coefficients.

Extensive experimental data obtained in five pipe diameters with water, sodium carboxymethylcellulose solutions, guar gum solutions, bentonite clay suspensions and calcium carbonate slurries are presented. Except for calcium carbonate slurries, which were investigated rather than time-dependent cement slurries, the fluids studied contain drilling or fracturing fluid additives. The behavior exhibited by these fluids is considered typical of most fluids encountered in drilling, cementing and fracturing operations.

INTRODUCTION

Considerable difficulties have been encountered in predicting turbulent flow pressure drops produced by non-Newtonian fluids flowing through straight cylindrical pipe. Correlations previously presented require extensive experimental data which represent several pipe diameters and a wide flow rate range to estimate the necessary scale-up parameters.1-7 One must implement either elaborate experimental apparatus or spend considerable time and effort to gather the se data. Presented here is a correlation method which should minimize the experimental effort and data analysis normally required by utilizing flow data taken with only one pipe diameter.

Turbulent flow data (up-stream and dawn-stream pressure and volumetric flow rates) were collected for five pipe diameters through operation of a small pipeline system having an electronic data acquisition and digitizing system.

A mathematical model derived from the Blasius equation was utilized to describe the functional relationship between pressure drop and the two independent variables, diameter and average flow velocity. A correlation, which should produce a valid single-pipe scale-up, resulted from a computer-implemented statistical and numerical data analysis for several time-independent non-Newtonian fluids.
Differences in Fracture Characteristics and Related Production: Mesaverde Formation, Northwestern Colorado
Authors: Lorenz John C. , Finley Sharon J.
Published: December 2007

Reservoirs in the Mesaverde formation in the Piceance Creek basin, northwestern Colorado, consist of naturally fractured, low-permeability sandstones. Permeability along the natural fractures is the primary mechanism of gas production. However, the characteristics of the natural fractures change within the formation at boundaries roughly coincident with changes in depositional environment, as seen in 4,200 ft [1280 m] of core from the U.S. DOE's Multiwell Experiment (MWX) wells. Depositional environment controlled the characteristics of the matrix rock and reservoir heterogeneity as well as the fracture permeability system. Therefore, natural gas production rates from the different zones in the formation can be correlated with the natural fracture characteristics from that zone. The fracture systems consist of unidirectional regional fractures that provide highly anisotropic reservoir permeability trends. Locally, secondary fractures were superimposed on the regional system, and higher production rates resulted. Production rates are low elsewhere, and little well-to-well communication across the fracture trend occurs. Moreover, stimulations of these reservoirs have often been unsuccessful because the hydraulic fractures propagate parallel to the natural fractures.
Water-Injection Profiles in Eola Field Determined by Changes in Thermal- Neutron-Capture Cross Section
Authors: Tesarek P. B. , Heysse D. R.
Published: December 2007

In waterflood operations it is desirable to inject uniformly into the targeted hydrocarbon-bearing sections of a reservoir. Wireline injection profiles have traditionally been used to determine where fluid enters perforations. Profile logs are inadequate, however, where segregation of flow into long, multiple zones is accomplished through a single tubing string and tubing injection mandrels with packers separating the zones. A technique has been proposed and tested successfully for detecting through tubing which intervals are actually being invaded by injection fluids. Logging the cased well with the Thermal Multigate Decay™ (TMD) pulsed-neutron tool while successively injecting fresh water, salt water, and borated salt water delineated invasion through the resultant increase in the thermal- neutron-capture cross section in the flushed intervals. This technique allowed a qualitative foot-by-foot analysis of the injection profile despite the presence of tubing, packers, and flow regulators. It also provided the data needed to improve injection practices and to enhance the recovery of hydrocarbons.
Application of Hand-Held Computers in Gathering Field Data
Authors: Bettis T.A. , Shreve M.A.
Published: December 2007

Recent developments in hand-held computer technology have made feasible the direct daily transfer of field data to a common, easily accessible data base. This low-cost improvement of field-data-reporting procedures benefits field operators, clerical workers, engineering staff, and management by making information available quickly while substantially reducing paperwork.

Introduction

Mitchell Energy Corp. (MEC) implemented a field-data-gathering system in which field personnel enter information into a hand-held computer. Information on 2,350 wells, 134 compressors, and several production facilities previously recorded by hand is collected with a hand-held computer. This information is transferred to a personal computer (PC) and then to the main computer. The main computer manipulates these data to generate daily, weekly, and monthly production reports used throughout the corporation. Daily field reports are received earlier and contain more information than the hand-written reports they replaced. When possible, existing PC's, modems, and communications software available within the company were used. This project was implemented at a capital cost of less than $15,000.

System Concept

Project designers sought a method to enter data into the company's computer system at the first possible entry level: the field. It was desired to use a computer in the field that would be compatible with the existing computer system.

Field management defined the necessary features of the proposed computer. The field computer should be compact and small enough to carry in one hand, leaving the other hand free to enter data. It should be durable enough to withstand the rough conditions of a field environment, and should have enough memory to store all the daily information normally recorded by a lease operator for every well on his route. The unit should be able to store up to 5 days of data for each well to accommodate holiday weekends. Continuous memory would be necessary to maintain the information stored even when the computer was turned off.

For communications purposes, the computer would have to be able to store data in American Standard Code for Information Interchange (ASCII) files and interface with standard data-communications hardware already in use by the company. Keeping cost minimal was desirable, so an "off-the-shelf" computer for which software could be developed in house was preferred.

Pilot Project

A hand-held computer satisfying the outlined criteria was found for which field-data-gathering software was developed. A pilot project was initiated involving three lease operators, each using his own hand-held computer to gather data on 42 tertiary recovery wells, 12 primary wells, and a production facility. A 4-month pilot period was successfully completed. Results were such that expansion of the hand-held-computer data-gathering system to the entire North Texas Region was authorized.
A Nonintrusive Flowmetering Method for Two-Phase Intermittent Flow in Horizontal Pipes
Authors: Kouba Gene E. , Shoham Ovadla , Brill James P.
Published: December 2007

An experimental and theoretical investigation of horizontal two-phase slug flow was performed to develop a nonintrusive method of measuring the in-situ gas and liquid flow rates. The key measurements were the instantaneous liquid holdups at two positions along the pipe. A new drift model was developed to predict the liquid velocity in the slug from the measured slug translational velocity. Both liquid and gas flow rates were predicted within an accuracy of ±10% of range.
Linear and Radial Flow Targets for Characterizing Downhole Flow in Perforations
Authors: Deo M. , Tarlq S. M. , Halleck P. M.
Published: December 2007

Two types of sandstone targets are commonly used to test flow efficiency of shaped-charge jet perforations: "linear" targets, in which flow enters only the unperforated end of the cylindrical sample, and "radial" targets, in which flow enters through the end and sides of the sample. To determine which of these targets best represents downhole conditions, the flow distribution along the length of a perforation has been studied by three-dimensional (3D) finite-element analyses. Linear and radial laboratory targets have been compared with downhole perforations under varying conditions. For ideal perforations, the low-shot-density (LSD) case is adequately represented by the radial target, while the high-shot-density (HSD) case falls between the two targets. With realistic crushed and damaged zones, the HSD case closely matches the linear target, and the LSD case falls between the two targets.
A Study of Horizontal-Wellbore Failure
Authors: Hsiao C.
Published: December 2007

A theoretical model of horizontal-wellbore failure has been developed based on maximum-normal-stress theory (for tensile fracturing) and Drucker-Prager failure theory (for compressive failure) under openhole conditions. This model may be used to help determine the permissible borehole operating-pressure range, providing a convenient scheme for selecting borehole pressure to minimize the risk of borehole failure during drilling and production.
Fracturing of a Deviated Well
Authors: Yew C. H. , Li Y.
Published: December 2007

The fracturing of a deviated well and the deviation of a hydraulically induced fracture plane were analyzed by applying three-dimensional (3D) elasticity theory. It was demonstrated that, under the influence of the off-plane shear-stress components, the fracture lines on the well surface were inclined at an angle with respect to the direction of the well axis and that the plane initiated from these fracture lines deviates from the plane formed by these initial fracture lines.
Computed Tomography for Rock-Property Determination and Fluid-Flow Visualization
Authors: Withjack E. M.
Published: December 2007

This paper discusses the development and application of X-ray computed tomography (CT) for the determination of rock properties and the study of miscible displacements in laboratory cores. Saturation (relative permeability) and porosity measurements by CT scanning are described, and the results are compared to those of conventional methods. Results of corefloods with miscible fluids show the influence of rock heterogeneities (bedding planes) and mobility ratio on volumetric sweepout. The corefloods also illustrate a new display technique that combines a series of two-dimensional (2D) CT slices into three-dimensional (3D) perspective views.
Ultrasonic Saturation Mapping in Porous Media
Authors: Soucémarianadin A. , Bourlion M. , Lenormand R.
Published: December 2007

The theory of acoustic propagation in porous media was described by Biot in 1956, but the experimental acoustic technique for measuring two-phase profile saturations along a sample is much more recent. We present an extension of this method for two-dimensional (2D) mapping and comparisons with gamma ray attenuations and visualizations in a transparent cell. The method is based on the difference between the sound velocities in the various liquids saturating the porous medium. The signal is generated by a pulse generator, and the time delay between transmission and reception is measured with a timer/counter. The saturation mappings are obtained by an automated displacement of an array of 32 sensors along the sample followed by computer reconstruction. To check the capabilities of the setup, we performed miscible and immiscible displacements in a three-dimensional planar cell (nonnegligible influence of height). The fluid boundaries are followed simultaneously by visualization and by ultrasonic measurements. We show that this technique not only locates the flood front in the stable case but also reconstructs the exact structure and motion of viscous fingers associated with unfavorable-viscosity-ratio displacements. Unlike X-ray shadowgraphs, quantitative fluid saturation data can also be obtained.
Influence of Electrical Surface Charges on the Wetting Properties of Crude Oils
Authors: Buckley J. S. , Takamura K. , Morrow N. R.
Published: December 2007

Reservoir wettability is important to oil recovery by waterflooding and many other oil recovery processes. The difficulties associated with determination of in-situ wettability, together with uncertainties about application of laboratory observations to field conditions, necessitate a more basic understanding of factors that control wettability. We previously reported that the adhesion of crude oil to a solid surface could be related to wettability alteration. In this work, conditions under which oil adheres to a particular solid surface are demonstrated for several crude oils. For a given oil, pH and ionic strength were varied to obtain a mapping of conditions under which adhesion occurs. Results were satisfactorily explained by double-layer calculations in combination with the ionizable surface group model. Lack of adhesion signifies the presence of a stable water film that results from double-layer repulsion between the crude oil and the solid surface.
Relative Permeabilities at Simulated Reservoir Conditions
Authors: Donaldson Erle C. , Clvan Faruk , Alam M. Waqi Ul
Published: December 2007

Relative permeability was determined at conditions from ambient to those simulating a depth of 1200 m [3,940 ft] from laboratory displacement data. The data were analyzed with the semianalytical interpretation method of Civan and Donaldson, which includes capillary pressure. The unsteady-state displacement method requires that the data be collected at high flow rates to diminish the influence of capillary end effects. including capillary pressure removes this constraint but results in a more complex mathematical model.

The results show the capillary end effects and the error introduced by not including them in the calculation of relative permeability. When capillary pressure was ignored in our model, it reproduced the literature values. Relative permeability measurements at elevated temperature show the characteristic temperature effect of higher oil relative permeability and lower residual oil saturation (ROS). These effects result from a change of wettability to a more water-wet condition at the higher temperatures.

The equipment used for relative permeability measurement can easily be constructed; in fact, some commercial designs can be used without modification. The results represent data at reservoir conditions; the data are taken on cores that are recompressed, eliminating the adverse influence of microfractures and changes of pore-size distribution frequently present in field cores run at ambient conditions. The displacement data are not restricted to high-flow-rate experimental conditions; removal of this restriction allows the analysis of low-permeability cores when flow rates are necessarily low.
Boundary and Crossfflow Behavior During Displacement in Nodai Systems
Authors: Lambeth Nell , Dawe Richard A.
Published: December 2007

Conducting fault boundaries are common features in reservoirs, but realistic modeling of flow through such systems is difficult because the flow is grossly distorted, particularly at the nodes of the permeability contrasts. Standard finite-difference simulators use an uneconomical number of gridblocks and still do not represent the correct physical features. Nevertheless, the realistic simulation of faulted systems is essential for practical waterflood planning and consideration of EOR schemes. This paper presents an extension of a curvilinear grid technique to model the complex crossflow processes that occur in heterogeneous systems where nodes and boundaries are well defined. To test our methods, we performed experiments in a model nodal system and obtained displacement and streamline profiles for unit and nonunit mobility ratios for a permeability contrast of 2.5 and viscosity ratio range of 0.3 to 3.0. Grids were constructed by the numerical solution of a system of generating equations and incorporated into existing simulators. We show that the number of gridblocks required to model the systems effectively may be substantially reduced. This work demonstrates that there is scope for modifying grid generation for current simulators and incorporates more of the physical reality of the displacement processes in heterogeneities with nodes, such as faulted systems.
A General Formulation for Simulating Physical Dispersion and a New Nine-Point Scheme
Authors: Shiralkar Gautam S. , Stephenson Robert E.
Published: December 2007

This paper presents a general numerical formulation for simulating physical dispersion that avoids the convergence and grid-orientation problems associated with numerical dispersion. The formulation is applicable to a wide range of problems, including enhanced gasdrives with phase discontinuities. A new nine-point scheme is also presented, along with general rules for any nine-point scheme to obey Darcy's law. Converged solutions are obtained for displacements at adverse mobility ratios of 5, 000 with no grid-orientation effects.
Gas Gravity Drainage in Fractured Reservoirs Through New Dual-Continuum Approach
Authors: Festøy S. , Van Golf-Racht T. D.
Published: December 2007

Present theory assumes that a capillary holdup zone of oil remains in all single matrix blocks in fractured reservoirs producing by gas gravity drainage. Model simulations applying a dual-continuum approach in a conventional reservoir simulator showed that, even with a low degree of continuity through the matrix between the blocks, the oil from the capillary holdup zone in each block is produced. The expected oil production rate and recovery is much higher than predicted by the present theory.
Realistic Sand-Production Prediction: Numerical Approach
Authors: Morita N. , Whitfill D. L. , Massie I. , Knudsen T. W.
Published: December 2007

This paper provides an analysis of perforation-tunnel stability through a set of three-dimensional (3D) transient fluid-flow and geomechanical finite-element codes. The results are quantitatively accurate and can be applied to field design completion problems. The paper clarifies the causes of sand problems occurring in a field and suggests techniques to minimize the problems.
Parametric Study of Sand-Production Prediction: Analytical Approach
Authors: Morita N. , Whitfill D. L. , Fedde O. P. , Lovik T. H.
Published: December 2007

An unconventional perforation-tunnel stability analysis is conducted in this work by separating the role of two independent factors on sand production: well pressure and local pressure gradient around a cavity. Such a separation clarifies most of the phenomena observed during sand production in oil fields. Simple analytical solutions for poroelastoplastic materials allowed repeated calculations for a parameter sensitivity study. The results obtained should be used qualitatively because of some degree of simplification.
Sensitivity Analysis of Two-Phase Reservoir History Matching
Authors: Watson A. T.
Published: December 2007

Reducing the number of unknown reservoir properties (through a method like zonation) is generally recognized to be necessary to obtain accurate estimates from history matching; however, no reliable guidelines exist on how this can best be accomplished. Toward this end, we use a one-dimensional, incompressible, two-phase reservoir model to examine some of the fundamental issues in the estimation of spatially variable permeability and porosity from pressure data. Analytical expressions are developed that relate spatial variations in property values to perturbations in the measured pressure drop. Permeability and porosity are retained as functions so that the developed expressions are functional derivative sensitivity coefficients. Examination of these functions reveals the importance of the saturation distribution in regard to information about reservoir properties represented by pressure data. We determine that the rock properties ahead of the flood front cannot be determined from pressure data. Consequently, having more than a single zone for regions that have not undergone two-phase flow would be unwarranted on the basis of pressure data. Behind the flood front, the sensitivity of the pressure drop to variations in permeability and porosity, for M ≤ 1, declines with time. Consequently, the reliability of forecasts may actually improve with time. Based on measures relating the relative variability of porosity and permeability functions, the contribution of permeability variations to pressure perturbations exceeds that of the porosity by more than a factor of five when M ≤ 1. Thus, the representation of porosity with fewer zones than permeability is appropriate.
Thermal Recovery of Bitumen at Wolf Lake
Authors: Hallam R. J. , Hajdo L. E. , Donnelly J. K. , Baron P. R.
Published: December 2007

For more than 20 years, BP Resources Canada Ltd. has faced the technical and economic challenges of oil-sands exploitation in the development of the Cold Lake oil sands of east-central Alberta. In 1985, the Wolf Lake 1 project began commercial bitumen production (7,000 to 8,300 B/D [1100 to 1300 m3/d]), with cyclic steam stimulation used to exploit the Clearwater formation. Construction of a 12,600-B/D [2000-m3/d] expansion started in 1987. Also in 1987, production started from a 22-well satellite that exploits the Lower Grand Rapids formation, a channel sand overlying the Clearwater formation. To develop this and other potentially commercial technology, four experimental projects were conducted: two steamfloods, a cyclic steam and combustion pilot in the Clearwater formation, and a single-well test in the Lower Grand Rapids formation.

Experimentation to develop combustion as a follow-up process to cyclic steam with air lasted from 1979 to 1984 and with oxygen from 1983 to 1988. One of the Wolf Lake 1 satellites will be converted to combustion to obtain further operating experience.

While operating experience has been obtained, numerical models have also been developed and used to improve the cyclic-steam operating strategy. These models, along with the formation properties and project histories, are described. Also, principles of the injection and production operations used in the combustion pilot are covered, and some solutions are offered on how these procedures overcame or avoided problems typically associated with combustion operations.
Study of Continuously Mixed Crosslinked Fracturing Fluids With a Recirculating Flow-Loop Viscometer
Authors: Harris C. Phillip , Harms M. Weldon , Norman Lewis
Published: December 2007

Continuously mixed gel fracturing fluids were successfully prepared with polymer slurries of guar, derivatized guar, and derivatized cellulose. The rheological behavior of the continuously mixed fluids was measured on a recirculating flow-loop viscometer over a temperature range of 80 to 300°F [27 to 149°C].

Rapid and complete base-gel hydration required proper pH control and high mixing energy. Oil-based polymer slurries allowed rapid hydration rates sufficient to achieve performance from a crosslinked fluid prepared during a completely continuous operation. Water-based polymer slurries required a short holding period for complete hydration.

Delayed-crosslink-gel viscosity was influenced by shear rate and the degree of base-gel hydration. Chemical factors influencing viscosity development included base-gel concentration, crosslinking-agent concentration, fluid pH, and ionic strength. Hydration time and pH requirements may differ for specific polymer/crosslinker pairs.
Significance of Regulatory Constraints on the operation of Packerless Waste Injection Wells
Authors: Kamath Krishna I. , Harmon Gary D. , Anzzolin Roger A.
Published: December 2007

U.S. federal regulations for groundwater protection require all hazardous-waste disposal wells to be constructed so that casing leaks can be reliably monitored. Wells constructed with static-fluid seals instead of packers are incapable of meeting this requirement and are therefore not in compliance with the regulations.

Introduction

Though fluids (liquids) have been injected into the subsurface to recover minerals and to dispose of oilfield brine in the U.S. for many years, deep-well disposal has been an approved means of industrial waste management for only a few decades. This method now accounts for the subsurface disposal of increasingly large volumes of industrial liquid waste. If not property controlled, the injected waste could threaten the safety of our drinking water supplies.

In the past, subsurface waste disposal was generally regulated by state programs, which varied widely in technical detail. The need for uniform standards for groundwater protection has been obvious for some time. In recognition of this need, the U.S. Congress enacted the Safe Drinking Water Act in 1974 and the Hazardous and Solid Waste Amendments (HSWA) in 1984. The Underground Injection Control (UIC) regulations, which are a part of the HSWA, set minimum standards for the siting, construction, and operation of injection wells in the U.S. The U.S. Environmental Protection Agency (EPA) administers this program directly or through the states to meet the Congressional mandate.

UIC regulations require all injection wells to be constructed with tubing set in packers. This feature allows the well operator to use the tubing/casing annulus for monitoring well casing leaks that could endanger the safety of adjacent underground sources of drinking water (USDW's). As of 1984, only 80% of all hazardous-waste disposal (Class I) wells in the U.S. were completed with packers. The regulations permit the operation of packerless wells only if the operator can demonstrate that the mechanical integrity of these wells can be reliably monitored at a level comparable with that of the well with packer. The most common type of the packerless well currently approved by the EPA features a "static-fluid seal" in the annulus-i.e., annulus filled with a mineral oil, in place of the packer, which totally isolates the annulus from the injected waste.

This paper examines the extent that the packerless well with the static- fluid seal is comparable with a conventional well with packer in providing reliable protection to groundwater. Considerations of theory and available operating-well data from the Great Lakes region facilities suggest that packerless wells do not meet applicable requirements and therefore do not comply with UIC regulations.
Pressure-Buildup Test Analysis— Variable-Rate Case: A New Approach
Authors: Blasingame T. A. , Lee W. J.
Published: December 2007

This paper presents a new method of estimating a constant-rate analog for a variable-rate flow period followed by a pressure-buildup test. The time and rate in the analog are used to generate a conventional Horner plot for the buildup test. The approximation is derived rigorously from the Horner buildup and variable-rate superposition equations. The major advantage of this method over other proposals is that it not only forces the production volumes to be equal (material-balance constraint) but also forces the pressures at a particular time to be equal.

Our approximate method has been verified for several variable-rate schemes with a finite-difference numerical simulator. The effect of wellbore storage was studied at both surface and sandface rates. The effects of a short shut-in time and a shut-in time equal to the duration of the production period were also investigated. The results of the new method seldom varied more than 5% from the results obtained with rigorous superposition.

The new method is not intended to replace superposition, but rather to give the best possible constant-rate analog. This method enhances our ability to use the conventional (constant-rate) Horner theory to generate accurate results. Also, our new method requires a single superposition calculation rather than a superposition calculation for each data point, as in the case of the superposition plot.
Novel Approach to Sensitivity Analysis
Authors: Genrich J.F. , Sommer F.S.
Published: December 2007

An entropy function is introduced to quantify the uncertainty in reservoir engineering parameters that are represented as random variables and described by probability distributons. When combined with a given algorithm and a Monte Carlo simulation routine, the concept can be used to estimate the degree of certainty required in input variables to yield a given certainty of the output parameters. The method is illustrated with a simplified model for water-alternating gas (WAG) miscible flooding. Two ranking schemes for five input variables are established and compared. The rankings provide an assessment of the overall model response with respect to a base case as related to average value and to degree of certainty of each input variable.

Introduction

Many reservoir engineering studies rely on data that contain some known or unknown error. Measurements are not always available, and key parameters are often estimated by other means. To account for this uncertainty, quantities can be described by probability distributions. Any parameter dud depends on one or more of these quantities has a probability distribution that is a function of the input probability distributions. Uncertainties often accumulate, leading to variances of output parameters that are unacceptably high.

If the overall uncertainty of input variables is reduced, output variances will be lowered. The commitment of manpower and financial resources necessary to achieve this reduction, however, can be substantial. It is important, therefore, to estimate a priori the amount of reduction in uncertainty required for each input parameter to obtain a given increase in output certainty currently used sensitivity analyses do not yield this information.

Combining an entropy function with a Monte Carlo simulation approach yields a new method that provides these estimates.

S Value

The notion of entropy, originally introduced in its differential form as S= /T in thermodynamics, has been successfully applied in other fields as a measure of randomness or disorder. In statistical physics, if quantilies the closeness of a system to equilibrium and plays a central role in describing the thermodynamic properties of ideal gases. In communication theory, it specifies the average amount of information transmitted per symbol. It is used in ergodic theory as a characterization of partitions and measure-preserving transformations. In terms of the underlying measure space, is defined similarly for all three cases.
Extension of the Generalized Dykstra-Parsons Technique to Polymer Flooding in Stratified Porous Media
Authors: Mahfoudhi Jalel E. , Enick Robert M.
Published: December 2007

This paper presents an analytical solution for oil recovery from a stratified reservoir during a polymer flood. Although the model used in the derivation does not incorporate several of the mechanisms and characteristics of an actual polymer-flooding displacement process, the analytical solution provides some interesting information concerning the effects of slug sizes, gelling, and permeability reduction. Computational costs are very small for the program.*