bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Generation Directional Survey System Using Continuous Gyrocompassing Techniques
Authors: Scott Anthony C. , Wright John W.
Published: December 2007

This paper describes a radically new wellbore survey system based upon the principle of rate gyrocompass i rig. While the basic concept has been applied for many years in such applications as the initial alignment of inertial platform navigators, it is only recently that repetitive rate gyrocom-passing has been developed in its own right as a means to obtain directional survey data.

The benefits of this approach are that an extremely rugged and reliable sensor can be built into a 1–3/4" o.d. pressure housing as opposed to the 3–5/8" to 10-5/8" pressure housings necessary to contain currently available inertial platform designs. This is of great importance in regards to the versatility of the system to handle all directional survey requirements from orientation to surveys in production tubing.

In addition, the time to acquire a survey will in many cases be significantly reduced by virtue of the high traverse speeds possible and freedom from time dependent gyro drift sampling necessary with directional gyros. Field results to date indicate that positional accuracy is also consistently improved by elimination of systematic errors due to initial gyro alignment, gyro drift and accelerometer bias.
A New Generation 18¾-in.—15,000-psi Subsea Wellhead System
Authors: Baugh Benton F. , Gordon Colin R. , Weiland Glen C.
Published: December 2007

A new generation 18-3/4" 15,000 p.s.i. subsea wellhead system has been specifically designed for deep-water high-pressure use. It features: (1) a breech-block profiled housing to receive a matching seat when only 3 strings are required or a 16" casing hanger for a fourth string, (2) a new seal assembly with 3 metal-to -metal seals in series plus resilient backup, and (3) a single-trip running tool and method which sets the metal-to-metal and resilient seals at a pressure higher than the well pressure to be encountered.

Design criteria were established from "scratch" to focus on actual wellhead requirements unbiased by conventional designs. Breech insert tests, based in many years' previous successful experience with breech-block connectors, involved both scale and full-size prototypes. Major development work on the new metal-to-metal seals involved models, finite-element analysis, and extensive testing.
Infill Drilling for Shale Gas Development: A Field Case Study
Authors: Horton Andrea I. , Mercer James C. , Sawyer Walter K.
Published: December 2007

The U.S. Department of Energy has conducted a reservoir simulation study of a producing Devonian shale reservoir in Meigs Co., Ohio, following an extensive field testing program1 to determine the parameters controlling production from this unconventional gas resource. The purpose of the study was to determine the possible impact of infill drilling in established areas of Eastern gas shales production. A dual porosity reservoir simulator that was developed especially for shale gas formations was used in the study.

The simulation study applied the results of the previous field test program to history match the production from shale gas wells located near the test site in Meigs County, Ohio. A series of 70-year simulations showed that by infill drilling now, 35 years after the completion of the discovery well, cumulative production can be increased by 30 percent or more. Had the closer well spacing been implemented at the earliest possible time, cumulative production over the 70-year period could have been increased by 60 percent or more.
The Prospect And The Significance Of Western Europe's Increased Reliance On Natural Gas
Authors: D'Andrea Lucio
Published: December 2007

Introduction

The purpose of this paper is to review natural gas market developments in Western Europe by briefly examining the history of the region's natural gas market, prospects for indigenous future natural gas production, access to internal and external sources of natural gas, and demand and pricing policies for natural gas. policies for natural gas. Europe's outlook for using natural gas to meet its energy needs changed markedly with the 1972–1973 oil crisis. Before the crisis, natural gas use in Europe had been increasing with the discovery of the Groningen reserves in the Netherlands and those in the North Sea. The relatively low cost and the security of the supply provided sufficient incentives to market the gas for use in the region and to make it available for export within the region. Natural gas was an ideal fuel to replace manufactured gas. After the crisis, Europe recognized the danger of depending on imported oil and looked to other sources of energy to reduce its dependence. In light of the delays and difficulties associated with the development of nuclear energy and the use of coal, natural gas was considered to be a reasonable alternative.

European gas consumption increased rapidly in the 1970s. Although this growth has stabilized in recent years because of the region's ailing economy and the increased price of gas relative to oil, Europe is expected to continue to rely on natural gas for the foreseeable future.
A Wellbore Inertial Navigation System
Authors: Kelsey J. B.
Published: December 2007

A prototype wireline tool which includes a downhole inertial platform and a surface computer to spatially map a well is described. The hardware consists of a single-gimballed inertial platform with accelerometers and gyros to obtain three-axis motion information. The gyroscope and accelerometer outputs are transmitted to a computer at the surface which calculates probe attitude relative to north, east, and vertical. Double integration of the accelerometer data provides the position information. A conventional 7-conductor wireline is used for the system data transmission.

System accuracy is enhanced by advances made in the computer software which processes the data received from the tool. The software uses statistical sampling estimation to obtain optimal estimates of the system errors. Measurement errors are determined by periodically stopping the tool during the logging procedure and observing the indicated velocity measurements. This procedure, known as Kalman filtering, results in increased accuracy of the data. Present mapping systems have an X-Y-Z location accuracy of 100 to 200 feet for a typical well depth of 10,000 feet. Test results show that the new system is accurate to about 1 foot per 1000 feet of well depth. Unlike conventional systems, the inertial navigator does not require any sort of projection of the cable length (which may not be accurately known). Also, this system provides continuous data throughout the wellbore and logging speeds on the order of 10 ft/sec appear possible.

The hardware and software associated with this mapping system are described and the recent field test results are reported.
Stickiness Factor—A New Way of Looking at Stuck Pipe
Authors: Love T. E.
Published: December 2007

The stickiness factor is an empirically derived number strongly related to the chances of freeing stuck pipe in a well. The number is defined by the following equation: (1)Stickiness Factor =(∡ + 10°)(OH + 5000')(MW2)×(2 + FL)(BHA+800')1×1011

where: ∡ is the maximum angle in the open hole (degrees); OH is the amount of open hole (feet); MW is the mud weight (lb/gal); FL is the API-fluid loss (cc/30 min); and BHA is the bottom-hole-assembly length (feet).

The relationship between the stickiness factor and the historic chances of freeing stuck pipe is illustrated by the chance curve of Figure 1. Basically, the stickiness factor should be kept below 2.5 wherever practical. Since stuck pipe costs are largely dependent on the ability to free stuck pipe and avoid sidetracking a well, it follows that reduced stickiness factors should result in reduced stuck pipe costs. The stickiness factor is commonly lowered by reducing the API-fluid loss of the mud, reducing the bottom-hole-assembly length, or setting casing.

The stickiness factor is based on a study of Gulf of Mexico wells drilled by Exxon Company, USA. Therefore, it will not necessarily apply well in other areas. The factor does. not predict when pipe will stick, but simply predicts the chance of freeing pipe that has already been stuck.

The stickiness factor will also help evaluate various spotting fluids and fishing techniques since it indicates the relative difficulty (chance of success) of a soaking or fishing job.

Finally, a reduced stickiness factor should reduce the chances of sticking pipe.
How and When to Run a PDC Bit in the Upper Texas Gulf Coast—An Operator's Viewpoint
Authors: Cress L. A.
Published: December 2007

PDC bits have become a recognized part of new technology in the oilfield. But, the coming of age of this type bit has necessarily required a considerable amount of field test results to be able to make an economic performance analysis. The problem, is knowing when good data is being analyzied and how to make an engineering recommendation to use a PDC bit.
A Review of the Environmental Acceptability and the Toxicity of Diesel Oil Substitutes in Drilling Fluid Systems
Authors: Thoresen K. M. , Hinds A. A.
Published: December 2007

The passage of the National Environmental Policy Act (NEPA) in 1969 and heightened concern for the environment has led to increased government regulation, especially in environmentally sensitive areas such as the Georges Bank, The Flower Gardens, and offshore California. At the same time oil exploration and drilling in these areas have been increasing. The discharge of diesel oils and cuttings containing diesel oil from offshore drilling platforms is a major concern since diesel oil is known to be toxic to marine life. Current regulations prohibit the discharge of oil based muds and unwashed cuttings from drill rigs.

The primary bases for determining the environmental acceptability of an oil, are the regional, national, and international water quality criteria for discharges.

Any potential substitutes for diesel oil must be acceptable to the operator as well as the regulating agencies. A comparison of the composition, chemical and physical characteristics, and toxicity of various animal, vegetable, and petroleum oils suggests that white mineral oil (a highly refined petroleum oil) is a potential substitute for diesel oil in drilling fluid systems.

Diesel oil and white mineral oils are compared in a review of toxicity, and environmental impact studies including persistence, degradation, and bioaccumulation data. The paraffinic, cycloparaffinic, aromatic and polynuclear composition of diesel oil and white mineral oils are examined. The aromatic hydrocarbon content and certain polynuclear aromatic compounds appear to be the main source of toxicity in hydrocarbon based oils. The relatively low toxicity of white mineral oil is attributed to the absence of high concentrations of these polynuclear aromatics.

Case studies show that white mineral oil performs well in drilling muds. The discharge of cuttings (containing absorbed white mineral oil) has been sanctioned by some EEC countries. The development and use of non-toxic oils in drilling fluid systems raises prospects for the direct disposal of drilled cuttings and spent muds offshore, resulting in lower mud maintenance and disposal costs for the operator.
Drilling Improvements Using Power Swivels
Authors: Zinkgraf H. L. , Hammett D. S , Boyadjieff George
Published: December 2007

This paper presents the technical advances made in the use of power swivels in replacing the rotary table. The equipment, drilling techniques and accelerated drilling time are reported. Specifically, special features of the use of a power swivel are also presented, i.e., drill up, remote pipe stabs, safety, operating cost reduction, drilling down 90 ft. stands. The object of this report is to acquaint people with the recent advances in the use of the power swivel.
Chargers for Better Piston Pump Performance
Authors: Collier S. L. , Jefferies R. K.
Published: December 2007

Today's economy requires that greater attention be given to improve performance of drilling equipment. Understanding the operation of the piston (slush) pump and the associated mud system is vital to improving operations. Improved operation of the piston pump is achieved by providing a mud supply which insures proper filling of the piston pump on each stroke. Testing in a high pressure mud pump research laboratory provided the substantiation of the analytical design approach presented in this paper.
A Proven Elastomer Compound for Extremely Hostile Geothermal and Oilfield Environments
Authors: Hirasuna A. R. , Friese G. J. , Stephens C. A.
Published: December 2007

Since 1979 the Y267 EPDM elastomer has been independently tested by other organizations in a variety of field and laboratory applications. The following are some examples. The same &267 EPDM O-rings worked with no leaks as logging tool seals for multiple trips to 4600M (15k ft.) at 320C (608F) BHST. A packer element performed flawlessly for five months in a 204C (400F) continuous steam injection well and was retrieved at the end of the test in an as-new condition. A high-pressure Y267 EPDM packer test was performed with complete success at 232C (450F) for a 7.5 day test in sour crude with differential pressures to 138 MPa (20 ksi) and the seal condition was only very slightly changed by the test. Comprehensive compatibility testing of 34 compounds from 15 companies in geothermal brine, isobutane, and oil at 191C-266C (375-510F) showed that the Y267 EPDM was best of the 34 in all three fluids.

Over 15 laboratory and over 20 field case histories of Y267 EPDM such as the above examples are reported. All strongly establish that Y267 EPDM is at the cutting edge of technology.
Status Of Thermal Recovery
Authors: Howard J.V.
Published: December 2007

Thermal recovery of oil has received a large increase in interest in the past year. Steam and hot-water flooding, forward combustion and cyclical steam injection are considered. A brief review of forward combustion and the techniques used to predict its performance are discussed. The predictive techniques for hot-water and steam floods are discussed. A discussion of cyclical steam injection is made, and the lack of a predictive technique in the literature is stressed. Some of the basic considerations in predicting the performance of cyclical steam injection are presented. Conclusions are reached that reasonable methods exist for the prediction of forward combustion, hot-water and steam flooding and that none exists in the literature for steam stimulation.
Areal Sweep Efficiency Increases By Scheduled Changes Of Injection-Producing Patterns
Authors: Oakes Dave T. , Bunch W.H.
Published: December 2007

Results and procedures are presented which demonstrate a novel means Of changing the injection and producing pattern (rotation) to increase substantially the areal sweep efficiency and recovery during pattern water flooding. Two types of laboratory tests were made. One series was made On sand-packed areal models utilizing oil and water solutions with an oil-water viscosity ratio of approximately 1. A second series of tests was made on Hele-Shaw (fluid mapper) models utilizing glycerol solutions to represent both oil and water with mobility ratios of 1, 3.5 and 9.2.

Based on the sand-packed model studies, it is concluded that by injecting into the center well a volume of water equal to approximately 50% of the volume normally required for breakthrough, then rotating the injection into a diagonal opposite well, the areal sweep efficiency at breakthrough and at a water-oil ratio of 90:1 is increased 5–8% as compared to conventional five-spot flooding. This would mean an increase in oil recovery of about 6–9%.

From the fluid mapper studies it is concluded that:

at a mobility ratio of 1, the areal sweep efficiency is increased by approximately 10% by a scheduled rotation that does not entail shutting in the center well, but maintains a given injection ratio (1:5.9) between the center and offset diagonal wells, at a mobility ratio of 1, the areal sweep efficiency of an inverted nine-spot rotated to a five-spot is also increased by approximately 10%; the areal sweep efficiency at adverse mobility ratio is reduced due to viscous fingering. However, an increase in sweep efficiency over conventional five-spot flooding continues to be observed on the rotated tests.
High Efficiency Fracturing Fluids for High Temperature Reservoirs
Authors: Baumgartner S. A. , Parker C. D. , Williams D. A. , Woodroof R. A.
Published: December 2007

Reservoirs with bottomhole temperatures in excess of 250°F are commonly encountered in the ever-expanding search for hydrocarbons. Successful completion of these wells often requires the use of Massive Hydraulic Fracturing (MHF) treatments.

The fracturing fluids used in MHF treatments are frequently subjected to excessive shear and prolonged exposure at high bottomhole temperatures. Early fracturing fluids proved unsuitable for these MHF treatments due to a rapid loss of viscosity at high temperatures. As a result, narrow fracture widths, excessive fluid loss and poor proppant transport occurred. Cool-down pads, increased polymer concentrations and delayed polymer hydration systems were employed in an attempt to improve the MHF treatment success ratio.

A laboratory investigation was undertaken to develop a more efficient high temperature fracturing fluid. Rotational and pipe viscometers were used to evaluate thermal and shear stabilities at reservoir conditions. Fluid loss testing measured the control of fluid leakoff to the formation. Fluid breakout testing ensured a controlled loss of viscosity and rapid cleanup. As a result of this study, a more efficient high temperature fracturing fluid was developed.

This paper presents laboratory data comparing the thermal stability, shear stability and fluid loss control of the High Temperature Gel (HTG) with those of a conventional titanate crosslinked gel. Field case histories are presented to demonstrate the efficiency with which HTG has been used to successfully stimulate wells with bottomhole temperatures in excess of 250°F.
Gas Well Operation With Liquid Production
Authors: Lea J. F. , Tighe R. E.
Published: December 2007

Prediction of liquid loading in gas wells is discussed in terms of intersecting tubing or system performance curves with IPR curves and by using a more simplified critical velocity relationship. Different methods of liquid removal are discussed including such methods as intermittent lift, plunger lift, use of foam, gas lift, and rod, jet, and electric submersible pumps. Advantages, disadvantages, and techniques for design and application of the methods of liquid removal are discussed.
Geologic and Engineering Analysis of Blanket-Geometry Tight Gas Sandstones
Authors: Finley R. J. , O'Shea P. A.
Published: December 2007

A comparative survey of over 30 blanket-geometry tight gas sandstones in 16 sedimentary basins was prepared for the Gas Research Institute. For each stratigraphic unit a uniform set of information was obtained on general attributes, economic factors, geologic parameters of the basin and the formation, reservoir engineering data, and operating conditions. Each tight gas reservoir was considered within a sedimentary framework of associated lithogenetic facies that make up a depositional system. In contrast to lenticular sandstones, which are primarily fluvial deposits, blanket-geometry tight gas sandstones were deposited as deltaic, barrier strandplain, and shelf systems. The reservoir geometry resulting from the deposition of blanket sandstones is expected to mitigate selected reservoir engineering problems associated with tight gas sand development. Results of this survey are being utilized in a more detailed study, now underway, which will ultimately lead to the selection of two prospective field test areas, possibly consisting of individual stratigraphic units, geologic basins, or depositional systems.
Predicting Turbidite-Contourite Reservoir Intervals in Tight Gas Sands: A Case Study From the Mancos B Sandstone
Authors: Witherbee L. J. , Godfrey R. D. , Dimelow T. E.
Published: December 2007

The Mancos B Zone is a classical tight gas formation, considered an attractive exploration target along the Douglas Creek Arch due to its widespread distribution. The unpredictable success of such wells led to a regional study investigating the environment of deposition, the nature of the porosity, and the relationship between lithology and log response in the Mancos B. Potential reservoir intervals can be differentiated successfully from non-reservoir intervals by integrating the results of detailed lithologic and wireline log analysis.
A Coordinated Seismic Study of the Multi-Well Experiment Site
Authors: Searls C. A. , Lee M. W. , Miller J. J. , Albright J. N. , Fried Jonathan , Applegate J. K.
Published: December 2007

A series of seismic studies were performed at the Department of Energy Multi-Well Experiment site to delineate the character of the beds within the Mesaverde group in western Colorado. The experiment consisted of a three-dimensional seismic survey of the area, a vertical seismic profile of the two wells and a cross borehole survey covering zones of special interest. The combined analysis of these data and well log and core information was used to relate the seismic records to the geology of the area.
Liquid CO2 for the Stimulation of Low-Permeability Reservoirs
Authors: King S. R.
Published: December 2007

The effects of residual fluid in the stimulation of low permeability reservoirs has long been a problem. The use of conventional fracturing fluids (water or oil) in tight reservoirs, especially those considered to be dry gas sands, generally results in the loss of 50-75% of the fracturing fluid. Total recovery of the conventional fracturing fluid is usually never accomplished as the fluid becomes immobile at irreducible saturation. The use of liquid carbon dioxide (CO2) as a fracturing fluid was developed to combat the problems of fluid imbibition that are encountered with conventional fluids. The liquid CO2 fracturing system is essentially a non-damaging system that reverts to a gaseous state at static formation conditions. The CO2 is then returned to the surface under controlled rates as a gas. The result being a more rapid cleanup and evaluation of the well following the treatment.
Development of a Fully Three-Dimensional Simulator for Analysis and Design of Hydraulic Fracturing
Authors: Cleary M. P. , Kavvadas Michael , Lam K. Y.
Published: December 2007

This paper describes our formulation and numerical implementation of the framework for a full three-dimensional hydraulic fracturing simulator (3DHFRAC). Solid rock deformation is described by efficient singular integral equation techniques and fluid flow in the fracture is captured by effective viarational/finite-element methods. The choice of (local vs. global) interpolation techniques allows the same mesh to be used for both processes, and major mesh regeneration costs are greatly reduced. The computationally prohibitive problem of fluid flow near and propagation of the fracture perimeter is rendered tractable by means of a leading-edge concept, which draws on existing experience with simpler models. Testing of the model components is demonstrated by solving some crack-opening and fluid flow problems with existing solutions; then the overall model is verified with reference to our simpler models, for circular, CGD and P3DH-type fracture geometries. Further, the containment role of barriers to fracture growth specifically confining stress variations between reservoir and adjacent strata is demonstrated; the more general potential of the model to describe the role of the many other mechanisms is emphasized, thus allowing calibration of simpler models or even direct use for treatment design.
The Application of a New Second-Generation High-Strength Proppant in Tight Gas Reservoirs
Authors: Callanan M. J. , Cipolla C. L. , Lewis P. E.
Published: December 2007

An analysis is made to illustrate the effectiveness of a new second generation high strength low density proppant as compared to that of sintered bauxite and Ottawa sand in a variety of applications. This is accomplished through the use of a reservoir simulator and a fracture design program. Gas producing formations are simulated which exhibit permeabilities between 0.001 md and 0.1 md and closure stresses up to 9500 psi. In these simulations the second generation proppant and sintered bauxite yield essentially identical production histories. However, the second generation proppant shows far superior performance to Ottawa sand in all applications. Also shown are cases revealing that tail-ins with the second generation proppant can yield a higher return on investment than pumping all high strength proppant.

The simulations reveal the importance of non-Darcy flow and conductivity damage considerations in proppant selection. It is shown that these two factors have much less of an effect on the performance of the second generation proppant than on that of sand. With all of this considered the second generation proppant should prove to have a substantial economic advantage over both sintered bauxite and sand in a variety of applications.
Reservoir Simulation of the Falher Conventional/Low Permeability System: Corrected to Insitu Conditions
Authors: Dawe B. A.
Published: December 2007

Indentification of the recovery mechanism for the more permeable conglomerate/low permeability sand system in the Falher formation in Alberta, Canada was accomplished by reservoir simulation of single wells. Reservoir properties of porosity, permeability, and water saturation were corrected to insitu conditions.

Results show that vertical percolation of gas from the low permeability sand into the conglomerate is generally not the rate limiting factor due to the large areal contact between the two intervals. Gas recovery from low permeability sands is controlled by very low permeability high water saturation zones* These zones become effective barriers in the ten nano-darcy range.
Production Data Reporting and How it Aids Surveillance in Thermal Recovery Fields
Authors: Dever R. E. , Womack F. A.
Published: December 2007

Modern surveillance requirements in large thermal recovery oil fields overwhelm manual efforts at collection, retrieval, and reporting of operations and production data. The introduction of a customized data base management and reporting system for this purpose can benefit Operations and Engineering through 1) increased production from timelier awareness of field operating conditions, 2) reduced operating expenses, 3) better steam utilization, and 4) significant manpower productivity increases.
Unitizing and Waterflooding the California Yowlumne Oil Field
Authors: Burzlaff A. A.
Published: December 2007

The Yowlumne field, located at the southern end of the San Joaquin Valley of California, is one of the largest new onshore oilfields discovered in California in the past twenty years. The field, at an average depth of 12,200, has produced over 42 million barrels of oil since its discovery in 1974.

In May, 1982, a portion of the Yowlumne field was unitized and called Yowlumne Unit "B". Nine operators and about 160 royalty owners cooperated to form this unit. A two phase unitization formula based on 1) remaining primary and 2) initial hydrocarbon pore volume was used to form Unit "B". A secondary waterflood project is being implemented which is estimated will increase oil recovery by some 25 million barrels.
Softening of Oilfield Produced Water by Ion Exchange for Alkaline Flooding and Steamflooding
Authors: Reyes R. B.
Published: December 2007

Oilfield "produced" waters usually contain high hardness, and high dissolved solids along with some alkalinity. The problem of disposing of these waters and the need for huge volumes of water for alkaline water flooding and steam generation for steam floods, necessitate the softening and reinjection of softened produced water. Water for alkaline and steam flooding needs to be softened to almost zero hardness to prevent plugging during injection and to prevent scaling on boiler tubes.

Softening of high TDS and high hardness waters requires a very selective resin with high operating capacity such as a weak carboxylic acid-type ion exchange resin. Conventional softening with strong acid resins would not work under these conditions.

This paper discusses the different processes in softening oilfield produced water. Data obtained in softening varieties of produced waters from different oilfields in California will be presented. Performance characteristics of weak cation exchange resins and their chemical regenerant requirements will also be discussed.
An Analysis of Stimulation Treatments of the Randolph Sand in the Semitropic Field, Kern County, California
Authors: Mitchell M. D. , Chamberlain C. R.
Published: December 2007

The Semitropic field is located approximately ten miles west of Wasco in the San Joaquin Valley of California. The original productive zones in the field were the Mya and the Mulinia gas sands occuring at depths of 2,200′ to 4,400′. In the last six years, the Randolph Oil Sand at 7,800′ has been actively developed and is now the major productive interval. Recently, several of the Randolph wells have been stimulated with hydraulic fracturing treatments. A majority of these wells have shown productive increases of varying degrees depending upon field location, job volume and proppant size. This paper will discuss the geologic production history of the Randolph Zone, completion techniques, reservoir characteristics and stimulation design and treatments.
EOR Prospect Evaluation Using Field Manufactured Polymer
Authors: Milton H. W. , Argabright P. A. , Gogarty W. B.
Published: December 2007

Prospect evaluation starts with laboratory studies of various enhanced oil recovery (EOR) processes. Results of EOR floods in waterflooded cores are given for caustic, dilute surfactant, mi cellar solution flooding, and polymer augmented waterflooding. In this work, partially hydrolyzed polyacrylamide (PHPA) was used as the mobility control agent. A pilot scale PHPA manufacturing plant, built in the field, supplied polymer for both lab and field testing. Results are presented from a polymer injectivity test at a water injection well. The injection well completion and surface facilities used in the test are described. Water to polymer injectivity is compared as a function of polymer concentration. Pressure data are used to establish the effect of polymer on solution mobility in the reservoir. Computer modeling was also used to match the lab and field results and to predict field oil recoveries for making economic calculations. Economic studies are the final step in the prospect evaluation procedures. Economic results using the same example field project for two different EOR methods are presented.
Evaluation of a Direct Contact Downhole Steam Generator in a Field Environment—Final Results
Authors: Marshall B. W. , Moreno J. B. , Muir J. F.
Published: December 2007

A test program to demonstrate the operation of downhole steam generators (DSG) in an oil field environment was conducted in the Wilmington Field at Long Beach, CA. Two DSG design variations were used. One burned diesel fuel in air and was placed downhole; the other burned diesel in oxygen and was located on the surface. Gas communication was established with all wells in the production patterns. Relative rates of movement of nitrogen, CO2 and CO were inferred and the wells were monitored for any production changes. Operating lifetimes of both prototype units were limited by the corrosion of various system components. Metallurgical analyses of degraded components of the generator and support systems have been completed.
Use of a Mobile Diving Support Vessel, Offshore California
Authors: Carroll J. P.
Published: December 2007

The Blue Dolphin is a converted workboat with a one-atmosphere manipulator bell diving system. It provides diving support for Chevron's offshore drilling program. This support includes underwater inspection, repair and salvage.
Porosity and Permeability of Mesaverde Sandstone Core from the U.S. DOE Multiwell Experiment, Garfield County, Colorado
Authors: Randolph P. L.
Published: December 2007

As received water saturation was measured and several dry core analyses were performed on 32 Mesa Verde sandstone core samples from depths between 1496 m (4910 ft) and 2475 m (8118 ft) in Garfield County, Colorado. Eight of the higher permeability samples were then selected for determination of the effect of fractional water saturation upon permeability.

The samples were from 13 sandstone intervals covering four depositional environments (fluvial, coastal, paludal and marine). The dry core analyses measured porosity, Klinkenberg permeability, Klinkenberg slope, and pore volume compressibility at net stress representative of the midpoint of reservoir drawdown. In addition, pressure was measured using a conventional mercury injection porosimeter.

Klinkenberg permeabilities for the samples dried to constant weight at 60°C and 45% relative humidity at 1 atmosphere pressure averaged 1.9 μ darcy at net stress representative of the midpoint of reservoir drawdown. Porosities under these same stress conditions varied between extremes of 4.4 and 11.4% with an average of 7.2 %.

The decline in permeability to gas with increasing fractional water saturation was found to be surprisingly sharp. For net confining stress representative of the midpoint of reservoir drawdown, water saturations required to reduce relative permeability to 0.01 were in the range of 40% to 55% with an average of 46%. Of the 8 samples, only two exhibited Klinkenberg permeability in excess of 0.1μ darcy for water content equal to the as received" value.

Measurement of the variation in permeability to gas as functions of net stress and water content revealed a dramatic difference between fluvial samples with high pore volume compressibility and paludal samples with lower pore volume compressibility.
Viscosity of Surfactant-Polymer Solutions
Authors: Hornof Vladimir , Neale G. H. , Chaaraoui Ali
Published: December 2007

Viscosity effects occurring in aqueous solutions containing a combination of surfactants, polymers and salts are of considerable interest in enhanced oil recovery operations. High molecular weight polymers, which are normally employed to improve sweep efficiency, lose much of their viscosity because of mechanical degradation and other adverse conditions in the reservoir. The mixing of the surfactant slug with the polymer slug in micellar flooding may lead to phase instability and low recovery efficiency.

The formation of surfactant-polymer aggregates on the other hand, might have a positive effect on recovery. Such association complexes do not lose their viscosity permanently due to shear as they are quickly rebuilt upon cessation of shear forces. The present work shows that significant viscosity increases can be obtained by combining a petroleum sulfonate surfactant with a low molecular weight polyethylene oxide. For example, an addition of Carbowax®−20M to 4% Petrostep®−420 at 1.5% NaCl salinity first results in a viscosity increase with a maximum at about 0.2% of polymer. After this, the viscosity drops sharply reaching a minimum at 0.5% of polymer. Beyond this point, the viscosity begins to rise again at a rate which is somewhat higher than that observed for the polymer solution alone. The behavior observed with Carbowax®−6000 was similar although the increase in viscosity was smaller. No discernible effects were observed with Carbowax®−600. The magnitude of the viscosity increase observed at 0.2% of polymer was found to be strongly dependent on salinity.
Characterization of Hydrocarbon-Su rfactant Systems by Alcohol-Brine Titration and Hydrocarbon Displacement Experiments
Authors: Terry R. E. , Robinson J. C. , Mandel R. S.
Published: December 2007

Shah1 and Shah, et al2 presented a correlation of a property of the pseudo-ternary (isopropanol, brine, and a constant ratio of surfactant to hydrocarbon) phase diagram with the equivalent alkane carbon number (EACN) of the hydrocarbon phase. The work suggested a new approach to characterize hydrocarbon-surfactant systems. Their work was performed on pure alkanes and mixtures of pure alkanes.

The work reported in this paper extends the correlation to pure and mixtures of pure alkylcyclohexanes and alkylbenzenes and to mixtures of these types with each other and with alkanes. The correlation was found to hold for the systems studied.

In another phase of the research, an attempt was made to compare the behavior of pure alkanes and mixtures of pure alkanes in displacement experiments in sandpacks. The hydrocarbon saturated sandpacks were flooded to residual saturation with a brine flood. The sandpacks were then flooded with a surfactant system to displace the residual oil. The results indicate that, for the EACN values studied, the mixtures and pure components behave similarly in displacement experiments.
Adsorption of Sulfonate on Kaolinite and Alumina in the Presence of Gypsum
Authors: Somasundaran P. , Ananthapadmanabhan K. P. , Viswanathan K. V.
Published: December 2007

Loss of surfactants by adsorption and precipitation that can occur during enhanced oil recovery by micellar flooding is a complex phenomenon dependent not only on solution properties such as pH and salinity, but also on the presence of even minor mineral constituents such as gypsum and limestone. In this paper, the results on adsorption of isomerically pure decyl-benzenesulfonate on gypsum, kaolinite and alumina are presented. Sulfonate abstraction by kaolinite and alumina in the presence of trace amounts of gypsum is also determined.

Adsorption of sulfonates varied significantly from mineral to mineral. Gypsum exhibited a sharp increase in adsorption above 4-6×10−5 kmol/m3 of residual sulfonate. Tests using the supernatant of gypsum showed sulfonate precipitation by the dissolved mineral species to be a major factor responsible for the high uptake.

A thermodynamic analysis of the solubility and stability characteristics of gypsum and anhydrite is presented. The sharp rise in abstraction has been shown to correspond to the onset of sulfonate precipitation. Presence of trace amounts of gypsum either with alumina or kaolinite is found to markedly increase the sulfonate uptake by these minerals. It is shown that in kaolinite-gypsum and alumina-gypsum mixtures, the total abstraction at high sulfonate levels is due to adsorption on alumina and kaolinite and precipitation caused by gypsum.
Chemical Separation and Structural Identification of EOR-Active Compounds in Water-Soluble Petroleum Sulfonate
Authors: Rajan K. S. , Chettur Govindan , Kamath K. I.
Published: December 2007

Earlier research by Kamath et al1 has indicated that the ability of certain water-soluble petroleum sulfonates for successfully recovering tertiary oil from water-flooded Berea sandstone cores can be traced to the presence in them of certain specific but yet-unidentified minor components. This paper summarizes the results of a closely integrated interdisciplinary research consisting of physicochemical and EOR-activity studies directed toward isolating the active components from a commercial petroleum sulfonate (Witco's Pyronate-40) and identifying their chemical structure. Following a pre-extraction with n-hexane and isopropyl alcohol, samples of Pyronate-40 in the acid, sodium salt and methyl ester forms were fractionated chromatographically on a silica gel (Florisil) column using gradient elution, initially with 100% acetonitrile and incrementally adding methanol to a final composition of 100% methanol. The EOR-activities of the chromatographic fractions were determined by means of core flood tests using Berea Sandstone core, 1-1/2" diameter × 8" long, and a small slug of the sodium sulfonates in 2% brine at pH ∼10.10 mg samples of the most EOR-active fractions gave an oil recovery of 0.8-1.6 ml which correspond to 4.4 to 2.2 lb respectively of the sulfonate for producing one barrel of tertiary oil. The EOR-active fractions were subjected to further resolutions by means of Flash chromatography using octadecylsilanized (ODS) silica gel column followed by reversed phase High Performance Liquid Chromatography (HPLC). GC/Mass Spectral examination of the EOR-active fraction (which corresponded to 2% of the starting sample of Pyronate-40) has indicated the presence of a number of components amongst which the identifiable ones corresponded structurally to the synthetic alkylaryl sulfonates such as, 5-(4-ethylbenzene-3-sulfonic acid)-dodecane. A critical discussion is presented on the chromatogrpahic resolution of such a complex mixture to a point where structural identification of EOR-active fraction could be meaningfully undertaken.
Chemistry of Precipitation and Scale Formation in Geological Systems
Authors: Katsanis E. P. , Krumrine P. H. , Falcone J. S.
Published: December 2007

Although the chemistry of scale formation and inhibition downhole and in surface equipment for oilfield and geothermal applications continues to be studied extensively, the mechanism by which it occurs has not been given sufficient attention. In this paper, the chemistry of precipitation and scale formation in geological systems is discussed in terms of precipitation (solubility) domains for the sodium silicate system alone and in the presence of salt and hardness ions. The regions which delineate the conditions under which precipitates form are very sensitive to time, hydrogen ion and salt concentrations, and hardness ions present. Calcium and magnesium ions at concentration levels of only 100 ppm each change the shape and position of the silicate domains by several pH units and several orders of magnitude in the concentration of SiO2 needed for precipitation to occur. In an alkaline flood there are a number of mechanisms contributing to the presence or absence of various ions in solution whose composition is constantly changing as it moves through the formation. Ions can go into solution by several mechanisms, including the dissolution of and ion exchange with clays and other minerals. A theoretical model has been developed which takes into account the ion exchange reactions of Ca+2/Na+ and Na+/H+ that can occur in strata formations during an alkaline flood. These reactions can deplete the alkaline slug and change its composition and pH value to levels where precipitation and scale formation occur.
Areal Sweep Efficiency Determination in Steam-Drive Projects Utilizing Chemical Tracers
Authors: Cooke R. W.
Published: December 2007

Ever since continuous steam injection (steam drive) became a viable recovery technique nearly three decades ago, attempts have been made to accurately determine areal sweep efficiencies. Until recently, the ability to determine the areal movement of steam was limited to radioactive techniques. By using common chemical tracer materials containing nitrate, bromide, iodine, or thiocyanate ions, the need for specialized radioactive materials and handling equipment is eliminated. This paper documents the efforts to use safe, inexpensive and readily detectable chemical tracer materials to determine the areal steam distribution in steam drive patterns.

The work described herein was part of the work conducted under a DOE cost sharing contract in conjunction with Stanford University Petroleum Research Institute; Chemical Oil Recovery Company of Bakersfield, California; and Petro Lewis Corporation of Denver, Colorado.
Improvement in Sweep Efficiencies in Thermal Oil-Recovery Projects Through the Application of In-Situ Foams
Authors: Eson R. L.
Published: December 2007

Even though steam drive is the most successful of all EOR processes, accounting for nearly 74% of all of the United States’ EOR production, it is not without its problems. Gravity segregation (steam override) and poor areal and vertical sweep efficiencies have limited recoveries in many heavy oil reservoirs since the first thermal projects were initiated in the 1960's. In many instances the injected steam prematurely breaks through into producing wells creating steam channels. It has been shown3, 7, 8, 9, 10 that in-situ steam foams have proven effective at reducing the mobility in these steam channels and diverting the injected steam into alternate flow paths, thus improving the sweep efficiency of the steam drive process.

This paper looks at the sweep efficiency improvement in three separate injection patterns utilizing in-situ steam foams. In each pattern, a slight variation in the application technique and material utilized is experienced. To determine the effectiveness of these three different approaches, radioactive injection profiles, production and the cost per incremental bbl of oil produced will be compared.
Paraffin Deposition and Rheological Evaluation of High Wax Content Altamont Crude Oils
Authors: Matlach W. J. , Newberry M. E.
Published: December 2007

The Altamont area in Utah produces one of the highest wax content crudes anywhere in the world. These high pour point and hard to handle crude oils are an even tougher problem because of their location in a geographical area subject to very low ambient temperatures. Millions of dollars are spent each year heating these crudes in order to expedite their production and transportation. Crude oil samples from the area have been tested using a variety of techniques. Paraffin deposition, viscosity, cloud point, pour point, yield values, wax extraction and GLC tests have been conducted in order to characterize the crude oil samples. The effects of various chemical additives were then analyzed using the same tests. The effective paraffin inhibitors not only reduced the quantity of wax deposited, but dramatic shifts in molecular weight range and configuration were also apparent. GLC data indicates that effective chemical structures all reduced the quantity of C40-50 molecu1-ar weight waxes contained in the resulting paraffin deposits.
A Six-Year Simulated-History Match of The Piper Field
Authors: King P , Robinson T , Abdullah A A , Waldren D , Brindle D , Dake L P
Published: December 2007

This paper describes the techniques applied and the results achieved in matching the six years of production and pressure history of the Piper field. Although Piper is an excellent oilfield it is nevertheless a difficult one to model using numerical simulation techniques. There are complex fluid-flow patterns across non-sealing faults between the offset sand sequences, together with a variable degree of vertical communication across the main reservoir unit. With six years of field data to match, the task was a large one and the question is raised – that, even though a satisfactory history-match was achieved, to what extent can it be regarded as unique?
Field Examples of Production-Logging Problems in Large-Diameter Deviated Wells with Biphasic Flow and their Implications on Reservoir Management
Authors: Scrimgeour J A , King P A , Kelman J F
Published: December 2007

This paper discusses field examples of production-logging problems in large-diameter, deviated wells, with bi-phasic flow. Two distinct flow regimes that tend to make flow-profile evaluation somewhat problematic have been identified. The paper gives examples of both flow regimes and details of how the existence of these particular phenomena can be predicted. The paper discusses the problems that these phenomena can cause in reservoir management and gives a brief discussion of the flow-loop research project that has been initiated at Robert Gordon's Institute of Technology in Aberdeen. The project is designed to simulate the complex flow regimes that exist in large-diameter deviated holes and, by means of the visual and mechanical aspects of the loop to aid in developing tools or interpretation techniques to help overcome the problem.