bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Study and Modeling of Condensation in a Gas Distribution Pipeline
Authors: Adewumi M. A. , Mucharam L. , Watson R. W. , Campbell L. D.
Published: December 2007

This study pertains to a carefully designed non-intrusive field experiment aimed at generating data for gas condensate pipeline. A compositional two-phase hydrodynamic model is used to analyze the system with a view of validating and tuning the model for field applications. The field test was designed as part of an existing gas distribution system to collect data on gas condensation and pressure drop in gas pipeline. The test section is a 6-inch, 52,000-ft long pipe to which natural gas from three different fields is fed simultaneously. Detailed topographic profile of the pipeline is drawn so as to obtain the various inclination and inclination changes along the test section. 120 inclination changes are present in the test section. The spatial distribution of the pressure and liquid holdup are not monitored so as to keep the normal operation of the distribution system as intact as possible. However, pressure and gas flow rates are monitored at some key points along the test section. In addition, periodic pigging provides total liquid accumulation over a 4-month period. Gas Chromatographic analysis provides the composition of the transported natural gas.

A compositional two-fluid steady multiphase hydrodynamic model developed from fundamental fluid dynamics is used to describe the formation and dynamic behavior of the gas/condensate system. The results of production runs demonstrate the predictive capability of the model in terms of the basic engineering design variables for this system. A number of interesting findings concerning the behavior of gas condensate flow are made. The model can be used for both design and operational purposes.
A New Method for Capillary Pressure and Relative Permeability Curve Matching for Gas/Water Flow
Authors: Choho T. , Pelce V. , Fasanino G. , Picard M.
Published: December 2007

Knowledge of gas-water relative permeability and capillary pressure curves is very important for reservoir engineers. A new mathematical procedure is proposed concerning two-phase flow with one compressible phase.

The method consists in the establishment of a criterion evaluating the difference between a historical record of real pressures and modeling pressures. It then automatically determines the optimum capillary pressure and relative gas and water permeability curves that minimize the criterion. The difficulties remain in the numerical criterion estimate and the gradient calculation.

This method was tested for one-dimensional cases and an example of application shows the efficiency of the algorithm. Validations in 2D and 3D are envisaged.
Feature Selection and Extraction for Well Test Interpretation by an Artificial Intelligence Approach
Authors: Stewart G. , Du Kui Fu
Published: December 2007

A technique for the automatic selection and extraction of features from a well test interpretation curve is described which provides a means for transforming a well test signal into a symbolic context; this is regarded as a first step in developing an automated or knowledge-based approach to interpreting transient pressure tests [9]. It uses novel methods paralleling those frequently employed in solving artificial intelligence problems such as vision processing.

The library of recognized features has been chosen by careful observation of a wide variety of well test responses. The criteria of feature selection and extraction are based on the special attributes considered by human experts during the visual diagnosis of an interpretation model and the definition of flow regime. The implementation of feature selection and extraction is carried out by the following steps: Data preprocessingSegmentationGroupingRepresentation relationships between the segmented elements

At the end of this process, a digital signal has been translated into a symbolic string which will be used as a basis for the further analysis e.g. model selection, using knowledge-based methods.
New Methods for the Analysis of Drillstem Test Data
Authors: Peres A. M. M. , Onur M. , Reynolds A. C.
Published: December 2007

This paper presents new procedures for analyzing pressure buildup data obtained from drillstem tests. The new methods apply for cases where the produced fluid does not reach the surface during the flowing period so that, the flow period represents a slug test. The combined effects of variable flow rate, short producing time and changing wellbore storage generally make it difficult to apply conventional analysis methods to DST buildup data. Two new straight-line methods for analyzing buildup data presented in this work account for both the variable rate during the flow period and producing time effects. If the buildup well-bore storage-skin group Csd exp(2s) is small, then shortly after shut-in, a well-defined straight line is obtained for both methods. Using the slope of the straight line obtained by either method, it is shown that the flow capacity (kh), the skin factor (s) and the initial reservoir pressure (pi) can be determined. If the group Csd exp(2s) is large, longer shut-in times are needed before the proper straight line can be obtained. However, for the latter case, it is shown that a multi-rate equivalent time can be constructed so that standard type-curve matching can be performed to obtain estimates of the flow capacity and the skin factor. A field example is presented to illustrate the applications of the proposed methods.
Applications of Cross-Borehole Seismic Tomography To Monitor EOR Displacement Fronts in Heavy-Oil Fields of Kern County, California
Authors: Hutt P. R. , Justice J. H. , Vassiliou A. A. , Cunningham P. S. , Singh S. , Bulau J.
Published: December 2007

Cross-borehole seismic tomography has been applied to assist in the monitoring of an EOR displacement front in a heavy oil field located in Kern County, California. Results from this survey indicate that tomographically processed cross-borehole seismic surveys can image variations in the velocity field of the subsurface. Several factors including the temperature, type, and physical state of the pore filling material strongly affect the velocity field of a reservoir. Cross-borehole velocity profiles, referred to as tomograms, are interpreted to provide insight into the physical changes taking place in the reservoir as an EOR process progresses.

A cross-borehole seismic survey is acquired by placing a downhole seismic source system into one wellbore and a downhole seismic receiver system into an adjacent wellbore and recording seismic wavefield information for a series of "shots" from the source to the receiver. The time it takes the wavefront to propagate from the source to the receiver is associated with a raypath. When an adequate number of wavefronts are recorded to properly sample the subsurface profile from source well to receiver well, they may be tomographically processed to provide a velocity profile between the two wellbores.

A tomographic survey acquired in a reservoir undergoing cyclic steaming stimulation resulted in a data set of both compressional and shear wave velocity profiles. These data were combined to produce a Poisson ratio tomogram for one of the two well-to-well surveys. The P-wave, S-wave, and Poisson ratio tomograms are interpreted to demonstrate variations in the type and physical state of the pore filling material of the reservoir. The data may be revealing information with respect to heavy oil saturations as well as highlighting zones of thermally heated reservoir. The interpretations are highly qualitative and require further acoustic core analysis to confirm and quantify the findings.
Drilling Contracting in the Nineties
Authors: De Wardt J. P.
Published: December 2007

The paper will review the construction and content of a new document format which has been selected for use in Shell drilling operations contracting. The review of content will cover a range of items including liabilities, obligations, scope of work, specifications and equipment requirements. The application of the new format to incentive and turnkey drilling operations will be reviewed together with the implications on Operator/Contractor roles in the execution of these types of contract.

The desire to increase operator efficiency is leading a change from supervising the contractor to managing the contract. The implementation of this change will be discussed.

Quality assurance leads to more cost effective operations. The application of QA to drilling operations contracts will be introduced.
Managing Safety
Authors: Stewart D. A. , Young L. P.
Published: December 2007

The objective of this presentation is to highlight the major vehicles of an accident prevention program that allowed the subject company to improve their incident rate by 63 percent over a three year period of time, thereby realizing insurance savings in the million dollar per year range. Included will be a detail of each individual vehicle used in this program and an analysis of their impact. A final result/conclusion will show both the positive impact on employee and customer relations and the profitable impact on the organization.
PDC Bits Using Positive Rake Cutters
Authors: Knowlton R. H.
Published: December 2007

A radical new concept in bit technology has been developed for use in drilling the deep water shales of the Gulf of Mexico and the Mississippi Delta where both milltooth and conventional PDC bits have performed poorly. This new tool utilizes the following technical elements: Large diameter positive rake PDC cutters as the primary cutting elementCurved PDC cutters to stretch the formation to its elastic limits for easy shearingCritical spacing between the cutters to take advantage of rock harmonics and fail the formation in tension.

The applications qualification procedure for the use of this new technology is based upon standard electric logs.
Risk and Economics Evaluation in Drilling Operations
Authors: Willis J. B. , Johnson S. M.
Published: December 2007

A drilling operations time and cost modeling program has been used to perform risk and economic evaluations of drilling plan alternatives. Three major benefits resulted from the use of the modeling program: Speed: major variations can be evaluated quickly allowing far more "what-if s" to be examined.Quality: the comprehensive analysis is superior to previously used methods.Acceptance: because of the quality, conclusions are more readily accepted.

The program uses only normally available well data and time and cost parameters.

Examples include evaluations of directional profile, Top Drive economics, and drilling fluids selection.
Successful Squeezing of Shallow and Low-Pressure Formations
Authors: Grant W. H. , White R. L. , Smith R. C. , Miller A. G.
Published: December 2007

Squeeze cementing technology is available that allows first attempt success In almost any situation. Gone are the days when three, four, and five attempts were necessary. Even a second attempt is rare when this technology is properly applied.

This paper illustrates three areas of squeeze cementing that are generally misunderstood and misapplied: Injection rates are conducted at excessively high rates and pressures and either create or perpetuate damage. Valuable information that could be used to make the right decisions during the squeeze job is lost forever.Proper slurry design is often neglected. Slurries are almost always tested incorrectly if they are tested at all.The slurry is placed downhole at too high a rate because of the fear of cementing up a workstring. This causes excessive formation damage and places the bulk of the slurry so far from the wellbore that It Is of no value to a successful remedial job.

This paper is the result of field studies in which the injection rate, slurry design, and placement procedures were developed and monitored. Field examples are presented.
Innovative Application of Lift Barge to Mobilize MODU into Shallow Water
Authors: Wolford B. G.
Published: December 2007

Transworld Drilling Company's utilization of auxiliary lift barges to buoy large submersible MODUs extends the shallow-water operating range of these units. These large submersible MODUs offer greater storage and hookload capability than MODUs typically used on shallow-water locations. Two case histories describe the technical and logistical details associated with this innovative application of existing equipment.
Fracture Toughness Criteria for High-Strength Drillpipe
Authors: Szklarz K. E.
Published: December 2007

Higher fracture toughness materials are more resistant to fracture than lower toughness materials under the same loading conditions. This fact is particularly important when considering potential drill pipe failures because there exists no industry standard which specifies fracture toughness for drill pipe. How fracture tough should your pipe be? This question is discussed through a comparison of recent fracture toughness criteria for high strength drill pipe. A Chevron Corp. criterion based on field observations has suggested 40 ft-lbf (54 J) at room temperature from 3/4 size Charpy impacts. Shell Canada Limited has developed fracture toughness criteria based on a fracture mechanics, leak before break concept for a pipe body containing fatigue cracking and on field observations of parted pipe and washouts in pipe. This has allowed the application of a room temperature, 80 J (59 ft-lbf), 3/4 size Charpy criterion in Shell Canada drilling contracts. A single, impact-type criterion has ease of application but flexible, fracture mechanics criteria may allow for better operational use of drill pipe in specific situations. An empirical relationship between fracture and impact properties was determined which allows the use of required toughness curves and leak before break curves based on operating conditions and drill pipe impact properties. Examples are given with respect to tested properties of new, high quality drill pipe and used, failed drill pipe. These show it is possible to obtain drill pipe that will washout before parting but a criterion of 54 J will not guarantee it.
How an Improved Depth Measurement and Smart Processing Can Help the Driller Improve Efficiency
Authors: Unsworth M. I. , Burgess T. M. , Kerbart Y. J.
Published: December 2007

Drilling monitoring systems have been available for many years yet none have ever fully considered the most important active link to drilling safety and performance; The Driller. With this in mind the first computerized drilling monitoring system specified by drillers has been designed and installed by a drilling contractor.

A significantly improved depth measurement has been included in the system. This paper describes how the measurement is made and its applications. The measurement and associated processing have led to automated pipe tally listings; penetration rate resolution of 8" (20 cm) for correlation purposes; and safety improvements due to better drilling break definition and permanent monitoring of the bit or shoe position when tripping pipe or casing. Field experience, examples and case studies from offshore installations are presented to highlight the effectiveness of this driller-controlled system.
Estimating Tooth Wear From Roller Cone Bit Vibration
Authors: Jardine S. I. , Lesage M. L. , McCann D. P.
Published: December 2007

This paper describes the development of processing techniques to extract roller cone bit wear information from near-bit force and acceleration measurements. Laboratory data have been col-lected for bits in a variety of wear states operating in a small atmospheric drilling machine and under the simulated downhole conditions provided by a fullscale drilling test station. This has given information on how bit cone speed increases as the wear process progressively reduces the cone radius. Recent studies are reported and the detailed dynamic features of force mea-surements made on laboratory drilling machines are described. The improved understanding of the nature of the bit signature has led to the development of novel processing techniques for the detection of bit wear from near-bit measurements. A com-parison with results obtained from bit modelling work is also presented.
Air-Drilling, Electromagnetic, MWD System Development
Authors: Harrison W. H. , Mazza R. L. , Rubin L. A. , Yost A. B.
Published: December 2007

Two-way communications, between sensors and other devices at the bottom of, or along, boreholes and the surface, have traditionally been performed by wirelines and stored-data technology. Telemetry (up-link) and command (down-link) func-tions have more recently been performed by use of real-time, mud-based methods.

As more and more horizontal, slant-hori-zontal, arc, and other high-angle bore-holes are drilled (some with air), the need for non-wireline and non-mud-based communications becomes more important because of the difficulty of inserting tools and logs in the absence of a large gravitational force component, and the inability of mud-based systems to operate in air or for that matter in the absence of flow. The oilfield logging industry has developed tubing-conveyed-logging tools, but these too lack the flexibility required, because they still require a wireline. Even with side-entry subs, these tools are too costly or difficult to use in some cases. Air-drilling of directional wellbores is on the rise for a number of reasons, and wireline stee-ring tools and mud-based MWD tools are proving to be less than effective.

In recent years new wireless electromag-netic-based real-time borehole communica-tions techniques have been developed with capabilities for supporting relatively-low data rates (compared with wireline) adequate for some applications. These are in commercial use for Measurement-While-Drilling (MWD) systems. Others are find-ing their way into non-drilling use in connection with oil and gas reservoir evaluation and completion work. While most of the work has been done in larger boreholes, some systems are being built into drill-strings as small as 2.5 inches (6.35 cm) OD. Wireless electromagnetic borehole communications technology holds out hope for providing reliable, two-way, high-data-rate data and command links in wellbores; regardless of hole size and angle, mud or air, flow and no-flow, cased or open-hole.

This paper traces the development of wireless electromagnetic borehole commu-nications technology, and describes the state-of-the-art in oilfield and non-oilfield applications. Development of, and field results from, a recently-com-pleted air-drilling model are presented.
Analysis of Gas Influxes in Oil-Based Muds in the Gullfaks Field
Authors: Rommetveit R. , Olsen T. L. , Sorheim J. O.
Published: December 2007

Several gas-influx events have occurred during drilling with oil-based mud on the Gullfaks field. These have usually started when hard chalk stringers were penetrated, and abnormal pressurized gas bearing zones were drilled into. These zones are often of low productivity and volume.

Based on all available data from the influxes in wells I and II, the events have been analyzed. The analysis has helped to explain the development of the influx events, and also the control phases have been evaluated.
A Computer Model for Kicks in Water- and Oil-Based Muds
Authors: White D. B. , Walton I. C.
Published: December 2007

A computer model of kicks in oil- and water-based muds has been developed as part of a contract from the UK Department of Energy. This work followed a study by the safety directorate of gas kicks taken while drilling deep, high pressure wells. The study highlighted the need for comprehensive mathematical modelling of kicks in oil-based muds incorporating the effects of gas solubility.

A ‘research’ model developed jointly by Schlumberger Cambridge (SCR) and BP International, includes both oil- and water-based muds, pressure transient effects, the density and dispersion of gas-cut mud and new models for the migration of free gas. This paper describes the philosophy behind the code structure, the solution techniques and modes of operation.The capabilities of the simulator are summarised, the coding considerations discussed and com-parisons between kicks in oil- and water-based muds are illustrated. Some details of the validation of the code against field and experimental data are given.

The code structure is designed for maximum portability and is highly modular, allowing ease of maintenance and upgrade. The full mass and momentum equations are solved in a core algorithm using an implicit finite difference scheme. An equation of state developed by BP is used to describe the density of gas-cut drilling mud at conditions of up to 15,000 psi and 350 deg F. The temperature dependence of the drilling mud rheology and the rise velocity of gas bubbles in non-Newtonian fluids are described by new experimental work from SCR.
The Design, Fabrication, and Utilization of a Leg Support Structure for Drydocking and Repairing the Spud Cans on a 300-ft Water Depth Jackup
Authors: Graham D. J.
Published: December 2007

The "Diamond M Nugget", a Levingston Class 111 jack-up, had been operating for the past 12 years in the Straits of Magellan off the coast of Chile. Bottom soil conditions in this area were found to be very hard with numerous large rocks or boulders just beneath the surface. Underwater in Lieu Of Drydocking examinations which were carried out to meet the U.S. Coast Guard and the American Bureau of Shipping requirements revealed that the hard sea floor had caused indentations and cracking in the bottom shell plating of the rig's footings. After monitoring the progression of the can damage for the past ten (10) years, the regulatory agencies and Diamond M's Engineering staff recommended that provisions for drydocking the rig and repairing the damaged spud cans be made.

Many alternatives were investigated for drydocking the rig. Facilities that could lift the rig out of the water were not geographically close enough to be considered economically feasible. Transportation of barges or other equipment to the Straits of Magellan also would have been too costly. With these limitations in mind it was decided to design and fabricate a LEG SUPPORT STRUCTURE which could be floated out to a predetermined location and positioned underneath the jacked up rig. The rig would then jack down, pushing the structure to the sea floor. The structure would then be wedged between the sea floor and the rig's bottom, providing the support necessary to raise one leg out of the water until its spud can had sufficient clearance to effect repairs.

The 327 ton LEG SUPPORT STRUCTURE was successfully designed, fabricated, and utilized in repairing all three damaged spud cans on the "NUGGET". This project proved to be a practical and economical solution to drydocking and repairing a large jack up drilling rig in a remote location where conventional facilities are not available.
Performance Testing of Jars
Authors: Kyllingstad A. , Halsey G. W.
Published: December 2007

This paper presents results from a test programme on jars and jar accelerators. More than twenty jars in the range of 6.25" OD to 8" OD have been tested in a horizontal jarring rig built especially for this investigation. The test program comprises both single tool tests and full jarring tests where the jars are tested together with accelerators. In the single tool tests, the jars are extended and closed slowly to provide data on release forces, friction forces, jar strokes and delay times for hydraulic jars. In the full jarring tests the jars have been tested dynamically under realistic conditions. In these tests the dynamic friction is measured at realistic telescopic speeds and the strength of the jar is checked. The tests have revealed significant differences in the performance of various jars. In particular, dynamic friction forces vary widely between tools. The test results and their applications to downhole jarring are discussed.
Gravel-Sizing Criteria for Sand Control and Productivity Optimization
Authors: Leone J. A. , Mana M. L. , Parmley J. B.
Published: December 2007

Field experience has demonstrated that gravel sized at 5-6 times the mean formation grain size usually results in adequate sand control. However, the use of larger gravels could provide greater well productivity since the pressure drop through gravel-filled perforations is often significant. Larger gravels are especially attractive in those cases where both fracture stimulation and gravel packing are required. This study was undertaken to determine an optimum proppant/gravel that will provide maximum proppant permeability and effective sand control in a friable sandstone reservoir.

Conventional gravel sizing procedures are based on laboratory studies performed with clean river sands substituted for actual formation materials. In this study, experiments were performed in flow cells using formation core plugs and carcass material. Brine, oil, and gaseous carbon dioxide were injected through the formation material at rates representative of the maximum expected in the nearwellbore region. Gravel permeability and the movement of formation material into and through the gravel pack were then evaluated as a function of gravel size and size distribution, formation mineralogy, degree of formation consolidation, type of flow (single- or multi-phase, steady or pulsed), and experiment duration.

The results indicate that effective sand control is obtained in this formation with larger than expected gravels (ratio of mean gravel diameter to mean formation diameter = 16:1.) Much higher well productivity can be obtained with the experimentally determined optimum proppant/gravel as compared to that attainable with a gravel/proppant sized using a conventional 5 to 1 gravel to formation ratio. The mechanisms which give rise to effective sand control with such large gravels were determined and are discussed. The method of experimentally determining the optimum gravel size for any formation is described and shown to be simple and fast to perform. The approach can be used with any formation requiring sand control. In many cases the optimum gravel size obtained by this method will be consistent with that predicted by conventional procedures; however, much greater well productivity is possible when the laboratory method indicates that larger gravels can be used.
Phase Behavior Properties of CO2/Heavy Oil Mixtures for EOR Applications
Authors: Sayegh S. G. , Sarbar M.
Published: December 2007

The objective of this study is to measure the phase behavior and physical properties of a Canadian heavy crude oil (11°API) saturated with carbon dioxide as a function of pressure and temperature. These data are used to evaluate the feasibility of using carbon dioxide as a pretreatment for steam floods or as a steam additive.

Experimental measurements were carried out at 69.8°F (21°C), the reservoir temperature, and at 284°F (140°C). The saturation pressures were between 400 psi (2.8 MPa) and 1,500 psi (10.3 MPa). At each pressure level the solubility of CO2 in the oil, the density, and the viscosity of the saturated mixture were measured.

The results showed an increase in the solubility of CO2 in the oil with increasing pressure and decreasing temperature, while the densities of the mixtures did not change to a large extent with changing compositions. The most dramatic effect observed was the decrease in viscosity with CO2 dissolution in the oil: A 53–fold reduction occured at 69.8°F (21°C) and a 2–fold reduction at 284°F (140°C).

SARA analyses of various samples were carried out. It was found that at 69.8°F (21°C) some redistribution of asphaltenes and resins occurred at pressures above the liquifaction pressure of CO2 (850 psi or 5.9 MPa).

These results indicate that, from a phase behavior point of view, enhanced oil recovery by CO2 injection in the heavy oil reservoir is feasible, and that viscosity reduction would play a major role in improving productivity at lower temperatures. The asphaltenes/resins balance should be taken into account when selecting the injection pressure.
Injection Profile Control in a Multizone Los Angeles Basin Waterflood
Authors: Dayvault G. P.
Published: December 2007

Following is a review of 51 waterflood injection well workovers designed to improve vertical sweep efficiency in the Inglewood field, California, from 1984 through 1988. A cost comparison is made for five types of workovers based on improvement in injection profile for two years after the workover. Damage mechanisms known to occur in these injection wells are: 1) bacterial slime; 2) iron sulfides; 3) calcium carbonate scale; 4) migrating clays and formation fines; 4) drilling fluid damage; and 5) formation crushing during jet perforating.

An index was developed to characterize a well's injection profile with a single value, allowing objective comparison of injection profiles before and after workovers and comparing profiles between different wells. The index was developed after reviewing actual data from about 200 temperature-spinner-tracer (TST) surveys. The index is equal to the total feet of perforated sandstone taking water injection, modified to account for uniform or nonuniform vertical distribution. The index is independent of total completion interval, allowing comparison of wells with differing net pay.

The index is used to evaluate cost effectiveness of the workovers and to estimate vertical sweep efficiency of the waterflood.
Long-Term Production Response of Sequential HF Acid and Conventional HF Acid in the NCL Field
Authors: Marino A. W. , Underwood P. J.
Published: December 2007

Long-term production response to matrix acidizing has been analyzed in the Stevens Sand in the North Coles Levee field in the San Joaquin Valley. Twenty-nine acid jobs on production wells, using either sequential hydrofluoric acid (SHF) or regular hydrofluoric acid (HF), have been performed over the last 15 years. SHF treatments were considerably more effective than regular HF treatments over the entire period of response to the stimulations.
An Innovative Method To Determine Low- and High-Pressure Steam Properties
Authors: Alcocer C. F. , Onuba L.
Published: December 2007

Oil recovery by the use of steam injection techniques involves the evaluation of steam properties at varying temperature, pressure properties at varying temperature, pressure and volume. This evaluation is necessary in order to determine heat losses and the varying nature of steam quality at the surface lines, wellbore and within the reservoir during the steam Injection process. process. Several authors have developed correlations for pressures below 500 psi and yet others in most recent publication have developed in some instances, several sets of correlations for the steam properties as a function of pressures between 500 psi to 2500 psi. pressures between 500 psi to 2500 psi. This work presents an innovative mathematical model that predicts the properties of the steam as a function of pressure from as low as 1 psi to as high as 3200 psi as obtainable in revised steam tables (laboratory data).

The computer model presented here is about 99.98% accurate and was developed based on numerical analysis techniques, in combination with the use of an advanced statistical package available at USL Computer System. package available at USL Computer System. The powers to which the pressure was raised was obtained and suitable designed for this task. The model uses an equation developed especially for this computer program written in Fortran 77.

It Is now possible to determine the value of steam properties as a function of pressure for any practical range of pressures. The values obtained from the correlation closely match the experimental values given in professional steam tables. professional steam tables. In general the results generated by this new correlation are far better than any other correlations that have been published at present. present. P. 602
Application of Saturation Pressure Profiles to Detect Oil Vaporization in CO2-Oil Systems
Authors: Beladi M. K. , Ghalambor A. , Alcocer C. F.
Published: December 2007

Crude oil vaporization using carbon dioxide (CO2) is known to have application in oil recovery for highly fractured formations and heterogeneous reservoirs where the major oil content is contained in the non-fractured porosity or isolated oil patches with little associated permeability. Oil vaporization is also the triggering element for formation of miscible front which displaces the oil in CO2 enhanced oil recovery process.

The objective of this experiment was to establish a saturation profile and examine the Pressure-Volume relationship of crude oil in the presence of different CO2 concentrations. The saturation pressure with its Carbon Dioxide concentration is believed to be the required condition necessary for initiating the oil vaporization.

To achieve the above objective a series of experiments were performed to show the oil swelling behavior and obtain the saturation pressure profile and pressure at which vaporization takes place.

The pressure-volume profile of the swelling tests showed that an increase in CO2 concentrations will increase the saturation pressure and cause a dampening on the pressure-volume curve. It also showed that the saturation pressure of the mixture increases according to exponential increase in CO2 concentration.

This study in swelling of crude oil by CO2 will provide an insight into the oil property and behavior as the vaporization takes place, and will provide the explanation on how the misibility is triggered. It will also provide the minimum CO2 requirement to achieve vaporization.
A Regulatory Approach to Horizontal Drainholes
Authors: Richter T. H. , Bright B. R.
Published: December 2007

In response to the increasing number of horizontal drainholes being drilled in Texas, the Railroad Commission of Texas developed guidelines for issuing drilling permits for these wells. While these guidelines do serve the purpose of outlining permitting procedures, they do not address such issues as between well spacing requirements, acreage and allocation assignments and the definition of a horizontal drainhole for regulatory purposes. A general statewide rule is being formulated by the Commission to address these issues. The proposed rule should offer some flexibility to encourage the use of this relatively costly and complex technology while honoring the Commission's legislative mandate to prevent waste and protect correlative rights.
Electricity Cost Reductions in the Oil Field
Authors: Balch G. R.
Published: December 2007

Oil producers must reduce electrical costs in order to remain competitive. Established reservoirs are maturing, and new fields are becoming more remote. As a result, oil production is increasingly more expensive to obtain; however, higher operation and maintenance costs are not being supported by higher product prices. The challenge faced by today's oil producers is to reduce production costs while at the same time they are also being called upon to produce oil from maturing and remote fields.

This paper outlines a successful electrical cost reduction program developed by Exxon Company, U.S.A. Electrical cost reduction is an obvious goal of any cost control program since it typically is the largest single operating cost component of a particular field. In large fields, even minor reductions can result in significant savings.

Substantial savings can be obtained in the utility company costs. This paper explains why utilities charge the way they do, and it shows what to look for when evaluating electric bill reduction possibilities.
The Development of a Marginal Clearfork Waterflood Prospect
Authors: Hunter C. D. , Kilgo W. M. , Hickman T. S.
Published: December 2007

The effect of depressed oil and gas prices on investors' confidence has been reflected by the low activity levels in the Permian Basin as elsewhere. Yet, even during the 1986-87 period viable projects were available to the industrious and imaginative.One example is the Wentz (Clearfork) Field where a small independent operator recognized potential in what appeared to be a very marginal waterflood prospect. Through data gathering and engineering, the potential was documented to the point that investor funding became available.A cooperative waterflood plan was agreed to with the field's other operator. The project was installed with an emphasis on practicality, cost savings and attention to details. After a year of injection, production response is exceeding expectations.
Mixing System for Fracturing Slurries
Authors: Reidenbach V. G. , Phillippi M. L.
Published: December 2007

Fracturing operations in Texas and other locations have been improved by (1) mixing fracturing slurries under microprocessor control, (2) applying new baffle and agitator design concepts, and (3) using new methods for achieving rapid material wetting. With these new methods, high sand concentration slurries can be mixed in high-viscosity gels, at low or high rates. A ramped pumping schedule can be used to help achieve greater fracture length since pumping stoppage caused by "sandout" can be delayed or prevented.

This paper presents the design and description of the mixing system that makes possible the above-mentioned improvements. and presents case histories of field applications. Proppant schedules and job data are also presented.
Techniques for Temporary Stabilization of Formations
Authors: Himes R. E. , Parker M. A. , Simon D. E.
Published: December 2007

Application of a class of organic molecules provides highly effective temporary formation stabilization while well completion and stimulation fluids are in contact with the formation. These molecules are more effective than commonly used inorganic stabilizers (salts) and can be used in much lower concentrations. As liquids, the method of application results in more efficient utilization and reduces the potential for negative environmental impact.

Literature is plentiful on the subject of temporary formation stabilization by applying inorganic cation to treating fluids to maintain a neutral net surface charge on clay surfaces. In the past, this has been done by the use of salts, such as potassium chloride. Unfortunately, inorganic cations with the necessary properties to stabilize formations as effectively as the aforementioned organic compounds are rare and impractical for large volume applications. A large-scale study of stabilization qualities of a number of these compounds was undertaken to obtain definitive performance data.

Subject paper reviews clay Stabilization theory and chemical theories on which research was based, describes research performed, and presents temporary formation stabilizers for use in well completions and stimulation operations. Results of field application of these organic formation stabilizers and benefits to improved fracturing efficiency and environmental impact will also be presented.
Viscous Fingering, Gravity Segregation, and Reservoir Heterogeneity in Miscible Displacements in Vertical Cross Sections
Authors: Araktingi U. G. , Orr F. M.
Published: December 2007

Combined effects of gravity segregation, viscous fingering and reservoir heterogeneity are examined in particle-tracking simulations of flow in vertical cross sections. Differences in model formulation from previous descriptions are reviewed briefly. The accuracy of the simulation representation of the physical flow mechanisms is tested. For homogeneous cross sections, simulator calculations are presented that illustrate the transition from flow in a single gravity-dominated tongue at low viscous to gravity ratio (Ngr) to flow dominated by viscous fingering at high values of Ngr. Quantitative accuracy of the simulator is tested against the experimental results of Pozzi and Blackwell. Simulation results agree with experimental results over wide ranges of mobility ratio, viscous to gravity ratio, and aspect ratio. Additional simulations also agree well with Stalkup's correlation of breakthrough recovery as a function of mobility ratio and Ngr.

The validated simulator is then used to augment Stalkup's correlation with results for additional mobility ratios. In addition, plots are presented of recovery after breakthrough as a function of Ngr for several mobility ratios. The results confirm that in homogeneous porous media, better displacement performance is observed at high viscous to gravity ratio for any mobility ratio. For heterogeneous porous media, however, that conclusion must be qualified. Example simulation results show that for injection of light solvent into a layered reservoir with high permeability low in the reservoir, better displacement efficiency is observed at intermediate values of Ngr than at high or low values. If the high permeability is at the top of the reservoir, high Ngr is still preferred.
Three-Phase Relative Permeability of Water-Wet Berea
Authors: Oak M. J.
Published: December 2007

Two-phase and three-phase relative permeabilities of water-wet Berea sandstone have been studied exper-imentally. Eight cases of saturation history have been investigated. About 1800 data have been collected using the steady-state method: about half of them for two-phase flow and the other half for three-phase flow. The experimental results are compared with predictions by Stone's methods.

Stone's predictions of three-phase oil relative permeability are unsatisfactory. The experimental data do not support the assumption that two-phase relative permeability data can be used to predict three-phase relative permeability with a similar saturation history. The data suggest that displacement of trapped oil by gas is an important factor affecting three-phase oil permeability. It is also suggested that there exists a critical oil phase saturation to initiate three-phase flow from water-oil two-phase flow, which can be different from that in the two-phase flow. The prediction methods fail to account for these factors.
Study of the Mechanisms of Carbon Dioxide Flooding and Applications to More Efficient EOR Projects
Authors: Haynes S. , Alston R. B.
Published: December 2007

The mechanisms of carbon dioxide flooding at pressures below the minimum miscibility pressure (MMP) were studied using a numerical model of a slim tube to determine a means of increasing the efficiency of such floods. Results of these studies indicate that, in multiple contact flooding (MCF), the gas phase at the liquid-gas front approaches a constant composition denoting a bank of solvent approaching conditions of miscibility, but not achieving it because of the quantity of methane, nitrogen, and other light gases that overwhelms it. The ethane plus components (C2+) composed approximately five percent of the reservoir gas phase. This constant compositional gas phase formed early in the flood and persisted throughout the flood until eventual gas breakthrough.

A simulated low-temperature flash of the reservoir gas phase produced a solvent that contained more than 75 percent ethane and propane. Slugs of this solvent were used to produce miscible displacements with CO2 gas at pressures 40 percent below the MMP. These findings were confirmed in further studies using fluids from several other reservoirs.
The Effect of Microscopic Heterogeneity on CO2-Foam Mobility: Part 2-Mechanistic Foam Simulation
Authors: Chang S. H. , Owusu L. A. , French S. B. , Kovarik F. S.
Published: December 2007

CO2-foam flow mechanistic studies (Part 1 in JPT1) continue to be concerned with (1) the visualization of high-pressure gas/oil/surfactant solution flow through glass micromodels which helps determine the principal oil recovery mechanisms at the pore level during CO2-foam displacement at reservoir conditions. (2) high-pressure, foam coreflood displacements to generate new physical correlations which can be used in field studies, and (3) the development of a generalized, mechanistic foam flood simulator.

Flow visualization experiments have been run to compare the performance of in-situ-generated foam displacements with water-alternate-gas displacements. Also, displacements comparing pregenerated and in-situ-generated foam have been performed. For heterogeneous models in the presence of crude oil, increasing flow rates resulted in improved sweep efficiencies for both pregenerated foam and in-situ generated (simultaneous injection) foam strategies. For WAG displacements, increasing flow rates decreased recovery. WAG displacements demonstrated, on average, the poorest sweep efficiencies. For the layered (communicating zone) model, it was observed that static or leave behind lamellae were not as effective in zone blockage and fluid diversion as a dense foam in the presence of oil.

A new foam coreflood apparatus was constructed and is being used to investigate CO2/foam systems. Coreflood experiments were run with (1) simultaneous injection of CO2 and brine, and (2) simultaneous injection of CO2 and surfactant solution into Berea sandstone. The cores were initially saturated with brine. Pressure drop and effluent volumes were matched with the new foam-flow model, thus fixing physical correlation free parameters. A new correlation has been proposed for the relationship between gas mobility and gas fraction, interstitial gas velocity, surfactant concentration, and oil saturation.

The two-dimensional, mechanistic, foam-flow-in-porous-media model is presented. Here, foam is generated by the following mechanisms: snap-off or lamella division, and leave-behind, all of which are included in the simulation. In addition, foam coalescence and trapping processes are incorporated in the simulator. The model can represent many of the mechanisms associated with high-permeability zone blockage, fluid diversion, and increased trapped oil recovery.
Foams for Effective Gas Blockage in the Presence of Crude Oil
Authors: Hanssen J. E. , Dalland M.
Published: December 2007

A study of foams for possible application in a new process with a potential for improving production from thin oil rims by formation of effective barriers against gas coning is reported. A total of 48 foaming agents for aqueous and non-aqueous systems have been evaluated using a gas-blockage test, as well as bulk foam stability tests and measurements of relevant surfactant properties. All experiments were performed in contact with sea water and crude oil at elevated temperature. In the gas-blockage test, foam is generated in 2-m long, 8.5-µm2 bead packs by constant-pressure displacement of a surfactant solution by gas at residual oil saturation. Stabilized gas rates through the foam-filled glass-bead pack are subsequently measured as a function of stepwise increasing pressure gradients. Only 4 foams were found capable of reducing gas permeability to the order of 0.1 µm2 or lower, at pressure gradients of 1 to 5 bar/m. These four products were found to be effective also in long-term tests at a constant pressure gradient of 1.5 bar/m. A number of foams known to be efficient gas-blocking agents in oil-free media were non-blocking in presence of residual oil. Bulk stability could not predict the gas-blocking ability for the foams studied. Further, no correlation was found between foam gas-blocking ability and the interfacial tensions, spreading conditions, oil saturation, foam quality, surfactant oil solubilization, or relative wetting abilities of surfactants measured. The four successful products found are fluorinated surfactants, from three different manufacturers, and were effective at 0.5 to 1 wt% concentration. Several fluorinated surfactants failed the gas-blockage test. Possible relations between observed gas-blockage performance and other properties are discussed. The phenomena involved appear to be complex and no clear relation between surfactant properties and foam performance has been found. Speculation is offered on what may be the controlling factors for foam gas-blockage efficiency.