bluuebunny/crossref_metadata_2025 huggingface dataset:
Demonstration and Teaching of Kick Control Techniques Using Microcomputer Graphics
Authors: Whitman D. L. , Evers J. F.
Published: December 2007

An inexpensive computer program, utilizing the graphical capability of the IBM-PC, has been developed that demonstrates and teaches the control procedures to be used as the result of a gas kick taken during drilling. In order to properly diagnose and control a kick, one must have a complete understanding of what is happening downhole and why. The color simulation that is presented in this paper – which can be run in real-time or accelerated time – aids in this understanding process. The status of the drilling process, as well as the critical surface measurements available, are displayed graphically on the screen before, after, and during the control of the kick. The display shows the gas bubble, its growth as it is circulated out of the hole, locations of all of the different fluids that are involved in the system (drilling mud, kill mud, and gas bubble), and the surface effects that occur during the control procedure.

The program can be run in either a demonstration mode or a control mode. In the demonstration mode, a kick is circulated out by the computer by both the driller's and the wait and weight methods, using the ideal control procedure. An instructor can utilize the demonstration to point out particular points of interest during the process. In the control mode, the operator of the program uses the keyboard to control the process. That is, he or she has direct control of the mud weight to be pumped, choke opening, and pump speed. At the conclusion of a run in either mode, graphs are produced of various pressures as functions of the number of strokes pumped.

In the control mode, the program monitors the correctness of the control scheme and highlights incorrect procedures that would result in either a low bottom hole pressure, causing a secondary kick, or a high pressure at the bottom of the casing, causing a loss of circulation.
Computer Database Program Provides Drilling MUD System Analysis at Rigsite
Authors: Morton E. K.
Published: December 2007

Microcomputers are becoming more prevalent on drilling rigs as a means of monitoring drilling parameters and doing repetitive calculations. Until recently, little, if any software was dictated to drilling mud property analysis that could easily be run on a personal computer on the rig.

A database has been developed that uses an inexpensive commercial software package allowing the user at the rig to input the daily mud properties and treatments. The software package allows the user to design the database to meet any particular situation that he requires. After he has made all of the inputs, all necessary calculations are then performed and a daily drilling mud report can be generated. Along with this package is the ability to instantly produce a graph of any set of properties or calculated values and view this either on the screen or on a printer. Trend lines for a certain property can be established and divergence from this trend line can quickly be noted. Adjustments in mud treatments could then be initiated.

Drilling fluid post well audits and recaps can now be generated as soon as the well is completed as all of the information is stored in the database. In this manner, the mud engineer enters the data at the rig and then this data can be sent to any location by modem or by floppy disk. This alleviates hand written reports that will have to be retyped by a secretary. The information only has to be entered once.

This system has been tested on several field jobs at the present with good results. Also, the program is user friendly and no intensive operator training is required. Input of data is very efficient and can be done in less than 15 minutes. A total drilling mud history for a well can easily be stored on a floppy disk and recalled for any post well analysis or future planning.
Computer Applications in the Planning and Drilling of a 2,000-ft Horizontal Well in Wayne County, West Virginia
Authors: Overbey W. K. , Carden R. S. , Williams J. B.
Published: December 2007

A personal computer with commercially available software was utilized in the planning and drilling of a 2,000 foot horizontal well drilled in the Devonian Shale in Wayne County, West Virginia. Planning procedures, well design and simulations of drilling operations were conducted with the software to identify potential problems and determine the size of rig required for the operation. Drilling progress was monitored with the computer as well as costs of drilling operations. Utilization of the computer was a key factor contributing to the successful drilling operations.
Microcomputer Program Aids for Cyclic Steam Injection Design
Authors: Chu M. H. , Gustafson S. J.
Published: December 2007

A microcomputer program has been developed for use by engineers involved in the design of cyclic steam injection heavy oil processes using a microcomputer. In this program the economic model can be used on either a before or after federal income tax basis. The output data, such as incremental oil production and incremental profit over the unstimulated process, will help engineers evaluate prospective cyclic steam injection projects and make quick investment decisions.
Sand Stability Predictions on a Microcomputer
Authors: Yassin A. A. Md , Peden J.
Published: December 2007

In planning for the production of oil and/or gas from the reservoir that consist of some form of sandstone matrix, consideration must be given as to whether a given well will remain sand-free during its productive life or if failure is to be expected. If failure is forseen, the prediction of the time of failure will allow a timely decision on selecting a suitable sand exclusion technique to be applied hence avoiding costly remedial treatment.

A prediction model was developed on a microcomputer to predict sand stability in a friable sandstone formation from stress-strain analyses around a perforated wellbore. Failure or instability of the formation around the wellbore was studies in terms of a failure initiation (initial failure).

Application of the model present here in includes the modes of failure around the wellbore, the prediction of the maximum allowable sand free production rate for a give well condition and sensitivity analyses of the factors controlling the production of sand from friable formations.
ISIS: A PC Interface and a Mainframe SQL Data Base
Authors: Snow E. L.
Published: December 2007

An opportunity to reduce surveillance costs and to improve surveillance results was identified within Shell Oil Company's Production Department by implementing a modern production data handling system. The existing data handling system was not being used effectively for production surveillance because it was based on old technology and it was cumbersome to use.

The Interactive Surveillance Information System (ISIS) project was designed to provide operating and engineering staff with access to the mainframe data base without the need to learn sophisticated computer programming skills. ISIS couples an SQL mainframe data base with an interface program which runs on a PC called PCIS--PC Interface to SQL. The primary objective of the project was to develop a data handling system that would make the production surveillance data "more useable."

With ISIS a person can describe the data that he or she wants using a series of menus from PCIS. PCIS translates this description of the data into the necessary SQL code, and sends instructions to the mainframe computer. Once the data is retrieved, it can be printed or plotted or it can be transmitted back to the PC for use in other programs such as a spreadsheet or a local data base.
Multiwell Data Acquisition and Analysis for Permanent Bottomhole Pressure Gauge Installations
Authors: Schmidt H. , Stright D. H. , Forcade K. C.
Published: December 2007

A multiwell data acquisition system has been developed for long-term, continuous monitoring of data from permanently installed downhole instruments. The data collection frequency can be controlled independently with the surface computer system for each well down to a minimum sample time of 1 second. Up to 8 wells can be monitored with the existing system; however, with modifications to the instrument controller, any number of wells could be monitored with one computer system. A database manager is built into the software. This program permits acquisition, storage and retrieval of an unlimited number of pressure data points and enables the operator to select and analyze any portion of the pressure data for any well. The system is applicable to onshore, offshore platform and subsea satellite wells. In addition, the system is compact and portable and can easily be transported to the wellsite for single-well DST and production testing.
Offshore Crude Sweetening by Gas Stripping
Authors: Allen R. F. , Smith S. J. , Walker G. J.
Published: December 2007

On Texaco's Tartan platform in Block 15/16 of the North Sea a crude oil treating facility has been installed to remove H2S from sour zone production and enable export to a sweet product terminal.

Selection and design of the gas stripping process is discussed together with mechanical design, control philosophy, material selection and safety considerations.

The conduct of the project is described and data presented on the performance of the unit and the efficiency of gas stripping.
The Occurrence, Prevention and Treatment of Sulphate Scale in Shell Expro
Authors: Carrell K. D.
Published: December 2007

Shell U.K. Exploration and Production (Shell Expro) operates in the U.K. sector of the North Sea on behalf of Shell/Esso and other joint venturers.

This paper discusses operational problems experienced to date, in Shell Expro's fields, due to the formation of barium and strontium sulphate scales downhole in producing wells. Particular reference is made to the Shell/Esso Brent and Dunlin Fields.
A Continuous Operating Protection System Called Cops
Authors: Chaperon G. , Leuenberger H.
Published: December 2007

The continuous operating protection system called COPS is a diverless solution to achieve the stabilisation and protection of subsea pipelines and cables : the system is based on the use of a continuous fabric formwork mattress which is spread on the sea bed over the pipeline or cable to be protected by a remotely controlled underwater crawler and simultaneously filled with cement grout.

The method has been successfully used in the GULLFAKS field where about 3.6 km of grout mattresses having a cross section of 2 meters by 0.2 meter have been laid.

The performances of the system are presented as well as a trade off comparison with the other stabilisation and protection methods currently used : burying, rock dumping or placement of covers.
The Transparency of Fatigue Cracks To NDT Methods Used for the Inspection of Offshore Structures
Authors: Newton K.
Published: December 2007

This paper presents results from a study of crack transparency to NDT techniques, which has been completed for sponsors of the Harwell Offshore Inspection R and D Service. Different mechanisms which could lead to transparency to the different inspection methods are described, including crack tightness, crack morphology and the bridging of cracks by corrosion or calcareous deposits. Results are presented from experimental measurements with several NDT methods for a range of cracks grown under different conditions. Most techniques available or under development for underwater detection and sizing of cracks are included – magnetic particle inspection, AC potential drop, pulse-echo and time-of-flight diffraction ultrasonics, and eddy current methods, together with some acoustic emission measurements.

It is concluded that for tight air-grown cracks in typical offshore grade steel, large compressive stress can significantly reduce the effectiveness of most techniques. The presence of corrosion products for cracks grown in seawater generally improves performance under compressive load, especially for the electromagnetic techniques. An assessment of the factors affecting the stress distribution at welded node joints on offshore platforms indicates that cracks which are tight at the time of inspection may be uncommon, and those which do occur are likely to be under modest compression. In this case, most NDT methods should be readily applicable. The effects of deposits within more typical open cracks are also investigated.

The results are used to provide practical guidance on the choice of NDT methods for offshore inspection, in order to minimise the risk of missing or undersizing defects in situations where transparency mechanisms can be significant. Finally, the implications for the choice of samples for validation trials of underwater NDT equipment are discussed.
Simulation of CO2 Huff ‘n’ Puff Using Relative Permeability Hysteresis
Authors: Denoyelle L. C. , Lemonnier P.
Published: December 2007

The CO2 Huff-Puff technique is becoming an attractive technique to stimulate a large variety of wells. This paper presents a new approach to the simulation of this technique, using the concept of relative permeability hysteresis.

A newly developed software was used for the study. It is made of a general purpose compositional simulator system that displays numerous specific features arranged in a modular structure. For increased efficiency, numerical models adapted to given problems, can be automatically generated from this system. In the present study, a model was generated to include among other options the kr, Pc hysteresis and to simulate the Huff–Puff process.

This study is mainly focused on low productivity reservoir for which CO2 stimulation could represent a viable alternative to being shut down.

First the case of a watered out light oil reservoir was investigated. The model was validated by successfully history –matching production data from a typical huff–puff cycle. A performance prediction was performed for additional cycles and parametric runs on amounts of injected CO2 were performed.

Then the case of a heavy oil reservoir with no water production was studied. A successful history match of three consecutive stimulation cycles was obtained. However it was found necessary to introduce a rate of gas dissolution in heavy oil, which is more representative of the physical phenomena.

A performance prediction was conducted for additional cycles; and a number of parametric runs were performed. The results show that for heavy oil, gas injectivity and oil productivity may increase with the number of cycles in an unlimited medium,higher final oil productivity is obtained with short cycles than with long ones,the influence of up to 25% hydrocarbon gas in the CO2 is limited.

Finally it appears that in both types of reservoirs, the relative permeability hysteresis is the main cause for incremental oil production. Oil viscosity plays a major role with the heavy oil only, as would normally be expected.
A New Approach to Multiphase Well Test Analysis
Authors: Al-Khalifah A-J. A. , Aziz K. , Horne R. N.
Published: December 2007

This paper presents a new approach to analyze multiphase well tests. In this approach, multiphase flow is modelled using the diffusivity equation with p2 as the dependent variable. This approach is applied to analyze simulated and literature multiphase tests for a range of PVT properties. Results of this approach are compared to those obtained by the pressure (Perrine's) approach, which is shown to be a special case of the new approach.

Fetkovich's empirical approach for isochronal oil-well testing has been in use since 1973 without theoretical derivation. His approach is derived here using the pseudosteady state solution of the diffusivity equation in terms of p2. The possibility of extending the isochronal testing to three phase systems is also discussed.

This paper derives the pressure-saturation relation, reported by both Muskat and Martin. Assumptions made are also investigated. Martin's total compressibility is derived without assuming negligible pressure and saturation gradients.

Finally, this paper explains the application of a new relative permeability technique, to estimate the absolute permeability of multiphase reservoirs. Two examples to verify this application are also reported.
In-Place Determination of Reservoir Relative Permeability Using Well Test Analysis
Authors: Al-Khalifah A-J. A. , Horne R. N. , Aziz K.
Published: December 2007

This paper describes a new method to estimate two- and three-phase relative permeabilities in-situ, using pressure transient analysis. The technique requires a short drawdown test, consisting of a number of steps of increasing flow rate. The resulting relative permeabilities reflect the properties of the whole drainage area, rather than those of a small laboratory core. The proposed technique is a major improvement over current historical performance methods. These existing methods need data over long periods, yet only cover a range of saturation up to present conditions – all future projections require extrapolation. By contrast, the new method estimates relative permeabilities at sandface saturations, which cover a range of future reservoir conditions. The well test can be repeated at a later stage of depletion to forecast still further into the future.

The proposed technique applies the solutions of multiphase diffusivity equation in terms of the pseudopressure function, m(p). These solutions have already been reported for constant rate tests in solution gas-drive reservoirs. This paper extends the pseudopressure solutions to three-phase systems. Two- and three-phase solutions are then superposed to obtain multiple-rate solutions, the basis for two- and three-phase relative permeability equations. A saturation equation developed originally by Bϕe et al. for solution gas-drive reservoirs, is also extended here to three-phase reservoirs. These pressure-saturation equations can be used to estimate sandface saturations during the test.

Using a commercial black-oil simulator, example well tests were simulated over a 40% range in gas saturation. Both two- and three-phase results show close agreement with input relative permeability curves. In cases where relative permeability is not homogeneous within the drainage area, the resulting estimates of relative permeability curves were very representative of in-situ heterogeneities.

The proposed technique offers a means to estimate two- and three-phase relative permeabilities at in-situ reservoir conditions, accounting for heterogeneities, wettability and fluid composition. It also seems to be the most appropriate way to obtain estimates for subsequent reservoir engineering analysis.
Systematic Design and Analysis of Step-Rate Tests to Determine Formation Parting Pressure
Authors: Singh P. K. , Agarwal R. G. , Krase L. D.
Published: December 2007

Step rate testing (SRT) has been used for several years to determine the formation or fracture parting pressure (FPP). Unfortunately, little is available in the literature regarding SRT design and analysis. Further, the available guidelines are inadequate and may lead to questionable values of the FPP.

A systematic investigation of several significant factors affecting SRT design and analysis is presented. The analysis of SRT data influenced by wellbore storage and changing wellbore storage is investigated. The proper application of multirate analysis methods to SRT data is outlined. A new method is proposed for determining parting pressure from SRT data on fractured wells. Field examples are included. This work should significantly enhance our ability to successfully design and analyze the step rate tests.
Fracture Identification and Productivity Predictions in a Carbonate Reef Complex
Authors: Dennis B. , Standen E. , Georgi D. T. , Callow G. O.
Published: December 2007

In order to optimise well completions and production in naturally fractured reservoirs and to predict the effectiveness of enhanced oil recovery schemes, it is important to locate and describe the in-situ fractures. A combination of log measurements and core data were employed to locate and orient the fractures and assess their overall contribution to reservoir performance in a Devonian reef complex. These techniques include the imaging of the wellbore with the Formation MicroScanner Log (FMS)* and the Borehole Televiewer (BHTV). The image data were compared to detailed core analysis, where available, and were used to determine the length, orientation and probability of fractures as a function of porosity. The Array-Sonic* tool was also run to help identify fractured zones using full waveform data and to quantify producibility from Stoneley wave data in comparison to flowmeter production logs.

From the comparison of the images with core, the utility of the FMS and BHTV Logs were established in identifying fractures and fracture sets as well as detenriining the orientation and vertical extent of the fractures. In addition, the response of FMS images to different porosity types was confirmed by core data. Comparison of the Array-Sonic data and the flowmeter production log data established the usefulness of the Stoneley wave attenuation as a means of identifying permeable zones.

The study results permit better definition of tool response to porosity types and fractures, and reveals the influence of fractures on the overall production of the reef complex. These results have implications on the initial and secondary production techniques of this and other carbonate reservoirs.
Exact Solution of Double-Porosity, Double-Permeability Systems Including Wellbore Storage and Skin Effect
Authors: Liu X. , Chen Z. , Jiang L.
Published: December 2007

The mathematical model describing flow of slightly compressible fluid through a double-porosity and double-permeability medium is solved rigorously with consideration of wellbore storage and skin effect. The exact solutions obtained for a well producing at a constant rate from a radial drainage area with no-flow or constant-pressure outer boundary condition are expressed in terms of ordinary Bessel functions. The numerical computation of these solutions is made and the behavior of the systems is studied as a function of various reservoir parameters. The limitations of the Warren and Root model are also examined.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
An Engineering Perspective of the Promulgation and Application of West Virginia's New Rules and Regulations for the Oil and Gas Industry
Authors: Johnston J. H. , Streit T. M.
Published: December 2007

The West Virginia Legislature created the West Virginia Department of Energy in April, 1985, by amending Chapter 22 of the West Virginia Code. This "Energy Act" empowered the Division of Oil and Gas of the Department of Energy to be responsible for all matters pertaining to the extraction of oil and gas resources. Previously, the oil and gas industry had been regulated by several state agencies and the creation of this Department made possible what was termed "one-stop shopping". This concept allows an operator to receive all required permits from one agency and effectively consolidates the regulation of the industry under one agency.

New rules and regulations that correspond to the "Energy Act" were necessary to effectively administer the duties mandated by law. New regulations governing hazardous waste, solid waste, water discharge permits, and underground injection were required in addition to modification of the Department of Mines regulations dealing with oil and gas such as casing and reclamation. Eight series of Rules and Regulations were adopted by the 1987 Legislature to fulfill the requirements created by passage of the "Energy Act".

This paper describes: 1) How the Rules came to be written and how they passed through various hearings and committees prior to being enacted, 2) what purpose they have in the overall scheme of "one-stop shopping", and 3) the application of the rules and regulations in practice and what effect they have on a typical West Virginia operation.
Dimensionless IPR Curves for Predicting Gas Well Performance
Authors: Chase R. W.
Published: December 2007

Dimensionless IPR curves for predicting the current and future performance of both unfractured gas wells, and fractured gas wells with positive, negative, or zero skin factors are presented in this paper. An example is presented in which the current and future performance of a gas well is forecasted and compared to the results obtained from a modified isochronal test.