bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Ultrasonic and Sonic Bond Tools for Detection of Gas Channels in Cements
Authors: Griffith J. E. , Sabins F. L. , Harness P. E.
Published: December 2007

This paper presents the problems of evaluating the integrity of gas-channeled cement sheaths and with ultrasonic and sonic bond tools utilized extensively in field operations. Findings are based on full-scale models intentionally gas-channeled, logged by standard ultrasonic and sonic bond tools, then exposed for visual inspection. Possible methods to overcome the discovered problems of cement evaluation with bond tools are presented so that alternate methods of determining cement integrity can be used.

Findings presented show that normal cement bond logs will not always detect gas channeling in the cement sheath unless they are created by large gas influx rates which increases the probability for the channels to contact the casing. Laboratory findings verify field examples of logs showing gas-influx cement, but physical inspection indicates distinct gas channels rather than small gas bubble entrainment. The variance method is utilized with averaging impedance values to distinguish between gas channeling and foam cements.

Cement jobs in the industry are typically evaluated with sonic and/or ultrasonic tools to indicate hydraulic isolation. Gas channels in the cement may compromise hydraulic seal if the channel communicates between uneconomical zones and production perforations. This paper provides recommendations to allow evaluation of gas channel cement for a squeeze/no squeeze decision from log responses and physical inspection of the models.
Dynamic Two-Phase Flow Simulator: A Powerful Tool for Blowout and Relief Well Kill Analysis
Authors: Rygg O. B. , Smestad Pål , Wright J. W.
Published: December 2007

A new adaptation of a proven flow simulator is aiding blowout contingency planning. Most important wells require a blowout contingency plan. Part of that plan includes relief well intervention. The flow simulator distinguishes between workable and difficult intervention schemes. It suggests any needed modifications in original well design. And it makes crisis management quicker, cheaper, and more effective. This paper describes the power of using this simulator for both surface and relief well hydraulic kill planning.
Detection of BHA Lateral Resonances While Drilling With Surface Longitudinal and Torsional Sensors
Authors: Paslay P. R. , Jan Yih-Min , Kingman J. E. E. , Macpherson J. D.
Published: December 2007

An analytical model is presented in detail which pre- dicts the oscillatory motions and forces at the top of a drillstring due to forward whirl of the BHA (bottom hole assembly) at a BHA lateral resonance. The geometry and amplitude of the BHA mode shape are used in a scheme which converts the lateral motions to sinusoidally varying axial forces and tangential impulses acting on the BHA. The entire string is then analyzed for wave propagation of the axial forces and torsional impulses. In this manner, the dynamic axial and torsional response at the top of the drillstring can be used to predict BHA forward whirl at each of the BHA lateral resonances. The model has been incorporated in a computer program for practical analyses.
Teaching Teachers about Science and Engineering: An Industry-Sponsored Model
Authors: Barber M. A.
Published: December 2007

An underetanding and appreciation of earth science is essential in today’s technological society. Many of the headlines in the daily newspaper and news magazines deal with earth science issues, yet the schools have poor tools with which to help students understand these complex issues. Business, industry, and government agencies, on the other hand, are well equipped with professional experts and resources which can and should be made available to Hie educational community.

Through a Denver-based industrial model, a series of new curriculum products in earth science education for kindergarten through secondary school is being developed to help prepare young Americans to take on the challenge of maintaining an earth that is in ecological and human equilibrium. The model being used with partners in business, industry, and government agencies in the Denver region can and should be replicated in other parts of the country.
Understanding Gas Markets: An Analysis of Purchase, Transportation, and Sales Mechanisms
Authors: Neal D. B.
Published: December 2007

This paper presents an analysis of the natural gas transportation cost mechanisms used by major pipelines for gas moving on the spot market. The paper also presents an analysis of natural gas upstream (purchase) price and downstream (sales) price mechanisms used by gas marketers in the spot market. It is an attempt to document basic algorithms used for determining the transportation component of gas cost and for establishing natural gas prices at both ends of the pipeline. These issues are explored so market potential can be more easily evaluated and gas transactions can be better understood by non-gas marketers.
Constraints to the Competitiveness of the U.S. Oil Industry in the Global Market
Authors: Gochenour D. T.
Published: December 2007

The American oil industry is shifting the bulk of its new investment overseas in the hopes that there will be greater profits there than in the U.S. This is not likely to be the panacea that senior managers in the oil industry hope it Mill be. This is primarily because the American oil industry is lagging in its competitiveness with the leading industry participants from other countries. In the past twenty years, the dominance of the U.S. oil industry in most fields has been steadily eroded to the point where it no longer has the unquestioned competitive edge. Just the contrary, in many parts of the world, the U.S. oil industry is competitively a Iagger.

The uncompetitive position of the U.S. companies is due to four chief constraints: the constraints of a transformed, unattractive international investment environment; structural constraints which shape the way the American industry operates; managerial constraints which afflict most companies at the level of individuals; and cultural constraints which are generally true to all American companies. This paper aims to diagnose the causes of the American decline in competitiveness and the scope of the challenges facing the American industry as it goes international.
A Method To Estimate the Value of Well Log Information
Authors: Dunn M. D.
Published: December 2007

The cost of running logs to gather information about a well or reservoir can be a significant portion of an oil company's budget. Although the cost of well logs and surveys are often scrutinized, rarely do engineers or geologists analyze the value of this information.

This paper describes how to compute the value of well logs before they are run by describing the uncertainty of what is already known, and predicting what will be lost as a result of a poor estimate. A probability distribution is drawn about the expected value ("best guess") of the parameter in question (e.g. OWC, porosity), and an opportunity loss is assigned to values that differ from this expected value. An "expected" loss is then computed based on the probability and conditional loss that may be incurred. This expected loss is equivalent to the value of perfect information. The author applies this technique to three examples to show how it is used, and draws general conclusions about the value of well log information.

The paper shows that this relatively simple technique can be used to place a value on well logs to aid the decision making process. The examples show that in fields with little uncertainty, little heterogeneity, and/or low stakes, the value of information is often less than the cost of logs. On the other hand, in very productive fields, or areas where uncertainty is great, the value of information may be high.
A Hybrid Artificial Intelligence Approach in Well Test Interpretation
Authors: Houze O. P. , Allain O. F.
Published: December 2007

In welltest interpretation the model identification was soon foreseen as a possible "Artificial Intelligence" (AI) application. As in most other fields of application of AI, both symbolic and connectionist (neural networks) approaches have been tried. Both have structural and complementary qualities and limitations.

The objective of K.I.W.I., a research project presented in this paper, was to develop an efficient AI module and integrate it in an operational welltest software. This module should identify the shape of even a noisy response, select possible models and estimate parameters with the highest possible success ratio. The only user input would be to select between models suggested by the module. Only a combination of symbolic and connectionist approaches (a hybrid system) could meet these requirements.

After introducing the project specifications and the basic programming tools used in it, this paper presents the different steps of the research and describes how such a hybrid system was developed.
Technical Applications of Design Principles in the Offshore Energy Industry
Authors: Lucas C. M. , Astrup Sandy
Published: December 2007

Attention to exterior and interior design on offshore facilities appears to have been overlooked. Application of design principles focuses on the creation of a balanced working/living cycle, despite extreme surroundings, in order to achieve a safer living space. Benefits of such a cycle include an increase in productivity and a decease in the number of personal injuries ultimately turning an industry loss into a savings.

Existing working/1iving environments on offshore facilities are monotonous and sensorially deprived because of the unvarying and toneless surroundings intensified by harsh climatic conditions, separation from family and friends, and prolonged work schedules. This combination of factors promotes mental fatigue and impaired judgement, causing the most common accidents offshore, trips, slips, and falls. These accidents are traceable to an inability to make quick, proper decisions.

In order to transcend problems inherent in the offshore environment, personnel should be exposed to a variation of color, texture, lighting, and personalization. To implement these correctly requires the investigation of the working/living cycle of offshore life, the four phases being sleep, shift preparation, on shift, and off shift activity. Each phase must be defined and analyzed in terms of efficiency and safety. This analysis must take into account many factors, such as ease of egress, acoustics, thermal control, square footage per space, location of facility, number of personnel, and overall facility function.
Effects of Underbalance and Effective Stress on Perforation Damage in Weak Sandstone: Initial Results
Authors: Behrmann L. A. , Pucknell J. K. , Bishop S. R.
Published: December 2007

Single-shot laboratory flow tests were performed on six Castlegate sandstone cores to determine the effect of perforating a weak sandstone (approximately 1600-psi mean unconfined uniaxial compressive strength). Experiments were performed at two effective stress levels and various underbalances.

The Castlegate was perforated under simulated downhole conditions as described in API RP 43, 5th Edition. Radial flow tests were performed immediately after perforating to establish perforation productivity. These tests gave no information on the distribution of permeability damage; therefore, a radial flow permeameter was used to measure the permeability distribution.

As anticipated, the total perforation length in the Castlegate sandstone was greater than in stronger sandstones; however, the shape of the perforations, the amount of debris left inside the perforation tunnel and the effect on productivity due to the level of underbalance were unexpected. Although the number of experiments was limited, the following observations were made: 1)At all conditions the rock around the initial perforation tunnel failed;2)At low effective confining stress, the failed rock was expelled into the "wellbore," creating a large, asymmetric cavity/tunnel;3)At higher effective confining stress, the failed rock remained in the perforation, filling the tunnel;4)Perforation productivity appeared to decrease at higher underbalances; and5)Experimental artifacts may affect measured productivities when testing softer sandstones.
Disposal Tool Technology Extends Gas Well Life and Enhances Profits
Authors: Grubb A. D. , Duvall D. K.
Published: December 2007

The objective of this paper is to present the application of a new saltwater disposal tool, called a Seating Nipple Bypass. This tool has been developed and tested in the Oklahoma Panhandle and Southwest Kansas where gas wells are pumped to remove saltwater from the wellbore and allow gas to flow up the casing tubing annulus. This tool is specifically applicable to gas wells that are not close to a disposal system. The idea of this system allows produced water to be conventionally pumped up a tubing string and gravity fed to a disposal zone below. Water is therefore not handled at the surface which eliminates environmental problems and reduces operating expenses. This paper will address the application of this tool and give case histories of its performance and economic advantages. Use of this system will also allow for increased reserve recovery simply by reducing the disposal expenses and prolonging the economic life of a gas well.
Well Test Systems: Designing for Accuracy
Authors: Tuss B. M. , Kendrick R. A.
Published: December 2007

Conventional well test systems often generate inaccurate results. Separation and measurement problems due to liquid properties are part of the problem. Well production sensitivity to back pressure is another.

Well test accuracy can be improved by upgrading the test system with a liquid transfer pump and an oil/water analyzer. Simultaneous conversion or retrofitting an existing three phase separator to two phase operation will increase liquids capacity five fold.
Dual-Zone, Horizontal Internal Gravel-Pack Completion
Authors: Gilbreath G. W. , Haubert M. A. , Gill S. B.
Published: December 2007

NERCO Oil and Gas, Inc. successfully drilled and gravel packed an extended reach horizontal well from a production platform located in Eugene Island Block 371 to a bottom hole location in offset Eugene Island Block 370 in the Gulf of Mexico in May, 1991. (Refer to Figures 1 and 2).

The well was drilled to a measured depth of 8958 feet and true vertical depth of 3137 feet with a horizontal displacement of 7358 feet. The maximum well deviation was 90.75° with 86° deviation through the completion interval. (Refer to Figures 3 and 4).

The total producing interval length of 725 feet (Refer to Figure 5) was divided into two shorter intervals with an isolation interval for two reasons. First, this would improve the opportunity for successfully gravel packing the shorter intervals. And second, the isolation interval in combination with a shale barrier in the reservoir would allow for an economical plugback of the lower interval should the reservoir prove to have a water drive mechanism.

The initial well test following the completion indicates that the well was successfully gravel packed; however, the platform is currently installing oil handling facilities, and future production will determine the ultimate success of the completion techniques employed on this horizontal well.

This paper will discuss the completion equipment and procedural design criteria and considerations unique to this case study. In addition, operational results and post appraisal analysis of the completion will be described. The methods outlined in this case study may be applied to highly deviated or horizontal gravel packed completions in unconsolidated sandstone formations.
Development of the Suffield Gas Field
Authors: Grant R. A.
Published: December 2007

This paper summarizes the historical development of a major Canadian gas field on federal lands. Using applied technology and a proactive, consultative approach among the producing company and all parties affected by the development, the project has proceeded successfully and over 3200 wells have been drilled, completed and placed on production. The total original recoverable gas reserves within the 1019 square mile Suffield field are estimated to be 1.8 trillion cubic feet and over half have been produced to date. Numerous technical and operational challenges had to be addressed during the course of developing these gas reserves in an area which is dedicated primarily to military training complete with live-fire artillery and tank exercises. To add to the developmental challenges, the Suffield gas field also contains unique wildlife species and environmentally sensitive areas.
Predicting Gas Well Load-Up Using Nodal System Analysis
Authors: Moltz A. K.
Published: December 2007

Predicting the onset of gas well load-up is essential to optimize the performance and maximize reserve recovery from mature pressure-depletion gas reservoirs. The widely used approach of nodal system analysis to evaluate well performance has previously been considered unreliable in predicting the producing rate and reservoir pressure at which load-up occurs. This paper will demonstrate that compositional wellbore fluid modeling is required for applications of nodal analysis on low-pressure gas wells to accurately match performance and reliably predict the occurrence of load-up.
Update of Industry Experience with CO2 Injection
Authors: Hadlow R. E.
Published: December 2007

The main purpose of this paper is to utilize current industry experience to evaluate the performance to date of miscible CO-2 injection projects. Also included is a summary of innovations being implemented by industry to improve recovery from existing CO-2 projects.

Experience to date has shown that on balance, CO-2 injection projects have performed better than anticipated and offer a significant opportunity for improving ultimate recovery from existing reserves.
Interwell Heterogeneity Representation and its Effect on Steamflood Performance
Authors: Kumar Mridul
Published: December 2007

Interwell heterogeneous reservoir properties for a California heavy oil field were obtained using geostatistical techniques. Fine-grid, cross-sectional and three-dimensional steamflood simulations were then conducted to evaluate how small-scale heterogeneities and methods to represent them affect predicted performance (steam breakthrough time and oil recovery). Actual log-derived properties (which were first calibrated against core measurements) were used.

Results show that oil recoveries during intermediate times (0.6 to 1.2 pore volume cold water equivalent steam injection) differ by 15-25% when small-scale heterogeneities are included (using kriged or conditional simulation) compared with when uniform properties are used. The difference in predicted recoveries between the kriged and conditional simulations were smaller (generally less than 10%). Inclusion of small-scale heterogeneities resulted in higher recovery and delayed steam breakthrough compared to the uniform permeability case when permeability variations were uncorrelated between the injector and producer. On the other hand, it resulted in lower recovery and earlier breakthrough when permeability variations were large and correlatable. Three-dimensional (3-D) heterogeneous flow simulation results show that oil recoveries using kriged geological models are generally higher than those from conditional models. Predicted recovery using the 3-D model has a shape similar to and compares reasonably with field data.
Promoting Subsurface Pump Efficiency and Developing Working Conditions of Mechanical Oil Production System by Means of Real-Time Numerical Control Technology
Authors: Li Yugeng , Zhu Shaozeng
Published: December 2007

Both the stroke length and the stroke per minute of the conventional pumping unit remain constant under the given working conditions. Therefore, it is impossible that the working conditions of the surface pumping unit and the subsurface pump are all in a state of the optimum match. The subsequent results are low efficiency of subsurface pump, large impact load, high energy consumption, and low production rate.

A new-type N/C pumping unit is under development. The following new technologies are used: —Microcomputer controlling the operation procedure of pumping unit by means of the numerical control technology.—AC frequency conversion and speed regulation technology.—High power and low electricity consumption motor in which the rotor is made of rare earth metal.—Framework for long stroke pumping unit and precision mechanical driving system.

The sample pumping unit is 6m in stroke length. In fact, it is easy to refit into the N/C pumping unit with 10m or longer stroke length. The new type pumping unit is both adjustable at will in the stroke length and stepless variable in the stroke per minute.

A cycle movement of the N/C pumping unit consists of the following four processes which are shown by curves: —"S shape" acceleration process at the beginning.—Uniform speed ascending process.—"Reversal S shape" counter direction acceleration process.—Uniform speed descending procees.

During the whole cycle movement, the computer continuously measures and analyses the holebottom conditions and regulates the movement parameters of the pumping unit, thus enabling necessarily the well to obtain the optimum oil production result.
The World Conservation Strategy As It Affects The Energy And Petroleum Industries
Authors: Holdgate Martin W.
Published: December 2007

The important thing about this Conference is that it is to be practical: to improve the performance of the energy, and especially the petroleum and gas industries, in che fields of health, safety and environment.

The purpose of this paper is to describe the World Conservation Strategy as it affects these industries - and, in particular, sets specific targets for then to address. The following sections: (a)explain what the World Conservation Strategy is, and what it says;(b)examine its message for industry in more detail;(c)proceed to a narrower consideration of the energy and petroleum industries; and(d)discuss practical issues that should feature in the dialogue between the industry, government and environmental scientists.
Horizontal Well Gravel Compaction Simulator Tests With Rotary Vibration in a Water Packing System
Authors: Solum J. R.
Published: December 2007

Horizontal well tests for gravel packing completions have been run for the last 10 months. This simulator was designed to create above ground, the same events and conditions that occur beyond the curve in horizontal and near-horizontal bore holes. The mock-up, forty four feet in length, consists of 18 feet in clear lucite tubing in three equal sections, connected alternately to 4 sections of 8-5/8″ casing. Located on each casing section are two 12″ by 1/2″ I.D. lucite tubes, one vertical and one horizontally mounted, with stainless steel needle valves for leak-off testing measurements. A 5″ slotted liner runs inside the full length of the simulator, and two rotary compactor vibration tools are placed inside the liner for evaluation of die vibraton factor.
Optimization of the Drilling Performance in the 6-in. Section of Development Wells in the Paris Basin, France
Authors: Besson Alain , Pontneau Bernard , Leseultre André
Published: December 2007

The 6" PDC bits application of development wells in the Paris Basin (France) has been carried out for a long time. A long directional 6" section of about 1600 meters composed of chalk, sand, shales, hard limestones, with dolomite and anhydrite stringers is currently drilled. In spite of the good results already obtained, several problems were still remaining, the major one was a hard stringer that could not be drilled by PDC bits and was forcing the operator to pull out or to destroy the PDC bit, beside that, nozzle plugging was very frequent.

An engineering study was performed and the analysis of the problems encountered led to the choice of new PDC bit body profile with new cutting structure and nozzles design. These choices were improved by means of hydraulic tests run in laboratory and specific methods of cutters positioning.
Collapse Pressure of Oval Coiled Tubing
Authors: Newman K. R.
Published: December 2007

Coiled Tubing (CT) is sometimes used in applications where the pressure outside the CT may be higher than the pressure inside the CT. These applications include operations in high pressure wells1 and reverse circulation operations where a fluid is pumped down the annulus and returns are taken up through the CT. If the difference between the internal and external pressures becomes too large, the CT will collapse. CT collapse could lead to serious well control problems.

During its life CT becomes oval due to bending around the reel and over the gooseneck. This ovality reduces the collapse pressure of the tubing. The pressure and tension limits for CT were analyzed in reference 2. The need for further work to understand the affect of ovality on the collapse pressure of CT was mentioned and is the purpose of this paper.

First an analysis was made to develop an analytical method for calculating the collapse pressure of an oval tube. Then testing was performed to validate this method.
Practical Considerations of Horizontal Well Fracturing in the "Danish Chalk"
Authors: Owens K. A. , Pitts M. J. , Klampferer H. J. , Krueger S. B.
Published: December 2007

Placement of a propped hydraulic fracture in a horizontal well is dependent on several parameters. These parameters include topics such as reservoir conditions, drilling practices, and completion techniques. This paper outlines some of the practical considerations that must be accounted for during the placement of proppant in a horizontal well. In describing a propped fracture treatment on an offshore horizontal well, the paper discusses treatment design considerations and verifies the operational and logistical improvements which can be made by utilizing a state-of-the-art stimulation vessel.
Oil Shale As A Potential Source Of Liquid Fuels
Authors: Katell Sidney
Published: December 2007

Oil shale is a potential source of liquid fuels, and the vast known reserves in the West have served as an impetus for utilizing this reserve. The economics of a system using oil shale in the production of liquid products is examined in this paper. Included production of liquid products is examined in this paper. Included are mining, retorting, and refining to produce the salable product. Capital cost, operating cost, and a financial analysis are detailed.

Introduction

Oil shale deposits are available in many parts of the world and at one time were one of the major sources of petroleum-like products in several localities. The Scottish deposits were utilized on a commercial scale starting in the 1850's and were still being utilized until about 1964. In this country the Eastern shales associated with coal were used as a source of both oil and gas prior to the Drake well discovery. Between 1916 and 1920 there was a flurry of activity in the Western oil shale fields when there was some feeling that crude oil production was lagging behind an increase in consumption. Imports were available, chiefly from Mexico, but were not sufficient to make up the deficit. The discovery of the oilfields in Oklahoma, California, and Arkansas in the early 1920's, accompanied by the recession in that period, almost completely obviated the experimental effort in Colorado.

The oil shale resources of Colorado, Utah, and Wyoming occur in over 11 million acres and it has been estimated that 1.8 trillion barrels are available (having a grade of at least 10 gallons per ton) under the classification of "known reserves." Recently, interest in these reserves has been reactivated, largely because of the anticipated need to broaden the resource base to supplement conventional crude petroleum. This need to fill the gap between energy supply and demand petroleum. This need to fill the gap between energy supply and demand is anticipated before 1980, by both government and industry.
Study of Mechanisms for Naturally Occurring Radioactive Materials and Souring in Gas Production Facilities in the Antrim Shale of the Michigan Basin
Authors: Ortiz Isaias , Anthony R. V. , Oddo J. E. , Pope D. H. , Frank J. R. , Becker D. M.
Published: December 2007

Naturally occurring radioactive materials (NORM) and souring have been observed in certain gas production facilities associated with wells producing from the Antrim shale in northern Michigan. The results of a study managed by the Gas Research Institute have shown that only 1 of 99 wells surveyed had detectable radioactivity while the separators had considerable radioactivity. Only four wells had high sulfate levels. Most of the other wells had low to moderate amounts of barium. The data suggest that barium sulfate scaling (with co-precipitation of NORM) does not occur until produced waters containing sulfate are co-mingled with waters containing barium. Above ground this occurs principally in the common piping, separators and tanks. High sulfate wells were not correlated with wells having evidence of corrosion nor with activities of acid producing bacteria. High sulfate levels were found in wells along the steeply folded and possibly faulted flanks of anticlinal structures. These wells also had aerobic bacteria. It can be inferred from these observations that sulfate may be associated with waters migrating into Antrim wells from underlying formations (e.g., Traverse where anhydrite (CaSO4) layers may lie close to the Antrim) possibly through faults, natural fractures or up wellbores drilled to the deeper formations. The role(s) of the aerobic bacteria are presently unclear. Their presence may, however, support the water migration model. More work is needed to confirm or deny these models.

Souring was not positively correlated with high sulfate wells, but was positively correlated with sulfate reducing bacteria levels. Possible mechanisms for souring are: sour wells are fractured (naturally or by completion) into portions of the deeper formations which contain sour gas but not sulfate or that much of the migrated sulfate is converted to sulfide either by microbial activities in the wellbores, or reactions with organic material in the black shales.
The Development of a Novel Scale Inhibitor for Severe Water Chemistries
Authors: Sweeney F. M. , Cooper S. D.
Published: December 2007

For several recently developed oil fields conventional scale inhibitor chemistry has been found to be ineffective in controlling/preventing scale formation. The failure of these scale inhibitors has been due to several factors; most notably a combination of high barium and calcium ion levels with low bottomhole pH and high reservoir temperatures. BP operates one such field, the Miller reservoir. The development of a suitable scale inhibitor for Miller was considered essential to enable the field to be produced effectively without the use of more sophisticated and costly facilities, such as reverse osmosis units for seawater treatment prior to injection.

The development of more effective scale inhibitors was progressed by identifying a relationship between inhibitor performance and molecular structure. From this relationship, several inhibitors were developed which showed significant improvement over commercially available products when evaluated in the laboratory. The best inhibitor, PO-85, has now been produced under licence by a major chemical manufacturer, and is ready for deployment on Miller.
Formate Brines: Novel Drilling and Completion Fluids for Demanding Environments
Authors: Downs J. D.
Published: December 2007

After more than 30 years of development and refinement, the technology for formulating halide-based brines for drilling and completion-fluid duty is relatively mature. Nevertheless, the halide brines still exhibit certain performance deficiencies that can significantly limit their utility.

Laboratory tests indicate that a series of organic brine systems based on the alkali metal salts of formic acid have a promising range of properties that are superior to those of the halide brines in nearly all respects. The outstanding features of the formate salts are: –They can provide high-density brines that are non-hazardous and appear to be compatible with oilfield hardware.–They are environmentally responsible and readily biodegradable.–As powerful anti-oxidants, they can protect viscosifiers and fluid-loss polymers against thermal degradation up to temperatures of at least 150°C–They are compatible with formation waters containing sulphates and carbonates.

It is anticipated that formate brines will soon find application as high-performance drilling and completion fluids in a number of demanding operational environments where conventional fluids have difficulties in meeting the required performance specifications.
Optimization of Oil-Base Mud Chemistry for Cementing
Authors: Harder C. A. , Carpenter R. B. , Freeman E. R. , Brookey T. E. , Gandy R. G.
Published: December 2007

Oil base muds (OBM) and their formulation can have a pronounced impact on cement performance in wellbores. This occurs when cement and OBM become mixed during normal well cementing operations. Increased mud contamination can ultimately compromise cement integrity. To minimize these mixing effects, the ability to improve compatibility of the mud system becomes paramount to completion success. The OBM base oil and the type and concentration of emulsifier can be especially crucial.

The most common type of OBM primary emulsifier is a fatty acid which reacts with calcium hydroxide to form a calcium soap. A partially water soluble emulsifier (an alkanolamide) is used as a secondary emulsifier in most OBMs because it keeps the emulsion stable even if the calcium source is depleted, but it is rarely used as a primary emulsifier. When employed as a primary emulsifier, the alkanolamide has shown the ability to reduce the effects of OBM contamination on cement. In a correlative work similar benefits have also been realized by mixing a water soluble surfactant with cement.

Proper design and management of an OBM system provides better cement performance. Although using an alkanolamide as the primary emulsifier costs slightly more than using a fatty acid, reducing the impact of OBM/cement contamination can more than offset the increased cost.
Colloidal Structure of Asphaltene Solutions and Heavy-Oil Fractions Studied by Small-Angle Neutron and X-Ray Scattering
Authors: Espinat D. , Ravey J. C.
Published: December 2007

Asphaltene and heavy oil colloidal structure were studied by small angle X-ray and neutron scattering (SAXS – SANS). Different suspensions were analysed: *asphaltene after n-heptane precipitation; effect of different good solvents on the asphaltene macrostructure, effect of n-heptane on the state of molecular aggregation, temperature effect.*resins, after fractionation, in solution in toluene, and effect of the addition of a small amount of n-heptane,*in order to precise the effect of resins on asphaltenes in solution, we studied mixtures of the two kinds of molecules,*Safanya vacuum residuum (VR), we foccussed our attention on the effect of temperature.

We have shown that asphaltene are flat aggregates whose size and molecular weight mainly depend on the solvent and the temperature. As temperature increases, we noticed a decrease of the molecular weight; then asphaltenes follow an aggregation equilibrium. The n-heptane addition induces an increase of the molecular weight.

The resins behavior is singular; SANS experiments showed that resins suspensions are heterogeneous, exhibiting concentration fluctuations. As temperature increases, the system becomes more homogeneous.

We observed a decrease of the asphaltene molecular weight when we added a small amount of resins.

Scattering spectra of VR dilutions in toluene are quite similar to those of pure resins in the same solvent and at comparable concentrations. Pure VR exhibits a very strong scattering at small Q-values which suggest important density fluctuations in the medium. As temperature increases, the scattering decreases due to more homogeneous system.
Wax Deposition Mechanism Under High-Pressure and in Presence of Light Hydrocarbons
Authors: Hamouda A. A. , Viken B. K.
Published: December 2007

When a waxy crude oil is cooled, i.e. in a submarine pipeline, the crude oil temperature reaches the ambient temperature. At temperatures below die cloud point/wax appearance point (WAP), paraffins start to crystallize.

The wax precipitated from oil mixtures primarily consists of C18 to C36 (paraffin waxes) or C20 to C60 (microcrystalline waxes), both made up of aligned paraffinic and naphtenic molecules(1)). Paraffin waxes are also called macrocrystalline(2).

The wax may be deposited in pipelines at higher temperatures than those measured in the laboratory where the pipeline wall roughness and/or presence of nucleation sites, such as solids, corrosion products etc., play great role for depositing wax from undersaturated fluids.
A Study of In Situ Combustion in a Segregated System
Authors: Khelil Chakib
Published: December 2007

Khelil, Chakib, Member AIME, D.R. McCord and Associates, Inc.

Some or the field pilot studies made to date have indicated that forward combustion proceeds in a segregated manner in oil proceeds in a segregated manner in oil reservoirs and that surfaces at which combustion is occurring develop both parallel and perpendicular to the general direction of air injection.

Although mathematical studies or combustion in a segregated system have been made, no experiments involving such a system have ever been attempted.

The objectives of this investigation are to study experimentally the factors affecting oxygen consumption and oil recovery in a segregated system and to provide a better mathematical means than those now available for estimating the distribution of temperature, oxygen and fuel throughout the reservoir. The mathematic model is also useful in studying the effects of some factors not examined experimentally.

Nine combustion tube runs were made wherein all of the factors involved in the process were studied. The objectives of this study were then fulfilled by correlating the data obtained from material balance by means of a multiple regression analysis program.

The results obtained showed that burning in a segregated system is characterized by the fingering of the coke zone, the formation of secondary surfaces of combustion, low pressure gradients, and migration of oil into the gas cap. There is more even oxygen consumption at low than at high flux and pressure. Oxygen consumption increases as flux, pressure, clay content, water saturation and oil gravity increases. The recovery of initial oil in place also increases as crude oil gravity place also increases as crude oil gravity increases. It is also noted that recoveries in this type of system are substantially the same as those in similar vertical tube runs but differ in the time of oil breakthrough.

The mathematical model has been developed to simulate burning in a segregated reservoir. The models presented by previous authors are shown to represent particular cases of this model.

The mathematical study shows that a more rapid burning in the horizontal direction is caused by one or several of the three following factors:heat losses to the surroundings from the oil zone,an increase in gas cap thickness, anda decrease in air flow rate through the oil zone.

It is also found that a decrease in gas cap porosity leads to lower heat transport through the gas cap and consequently to slower burning in the horizontal direction.
Advanced Asphaltene and Paraffin Control Technology
Authors: Bernadiner M. G.
Published: December 2007

Asphaltenes and paraffins deposit in the wellbore zone, tubing, downhole pumping equipment, pipelines, and in surface equipment, and, also, cause a high viscous stable water-in-oil emulsion inside the tubing and surface equipment, dramatically decreasing well productivity. Modern asphaltene and paraffin control technologies and demulsification methods usually do not correspond and even may contradict each other, resulting a high cost and ineffectiveness of oil production. The advanced way to utilize the technological methods in the most efficient manner is creating a common technology to put on line several asphaltene and paraffin problems.

The current paper discusses an optimal stimulation method recovering the mentioned above problems by using just one treatment. The method consists of a periodical application of detergent designed to remove the deposit and simultaneously to destroy the water-in-oil emulsion. In addition, the detergent adsorbing on the equipment surface prevents further asphaltene and paraffin deposition.
The Efficacy of Formaldehyde for the Control of Biogenic Sulfide Production in Porous Media
Authors: Kriel B. G. , Crews A. B. , Burger E. D. , Vanderwende E. , Hitzman D. O.
Published: December 2007

The souring of reservoirs by microbial activity has become a major concern to the oil and gas industry. In the present study, core flood experiments were used to evaluate the efficacy of periodic formaldehyde injection for the control of in situ biogenic reservoir souring. In these floods two reservoir environments were simulated: the near-injection well, and the deep-formation. Formaldehyde treatments were demonsrated to control souring in both enviroments; if the formaldehyde can be transported through the reservoir, in situ biogenic souring should be mitigated.
Two Tracer Test Method for Quantification of Residual Oil in Fractured Porous Media
Authors: Grigorievich B. P. , Archer J. S.
Published: December 2007

The method for identification of residual oil from the data of flow of two tracers with different solubility in oil is developed for fractured-porous reservoirs.

The solubility of tracer in the immobile phase (oil, retrograde condensate) leads the lag of the tracer front propagation behind the displacement front. The ratio of the tracer front velocity and the velocity of total flux is determined by the saturation of immobile phase. It allows us to determine the saturation of the residual hydrocarbon phase from the data of flow of two tracers with the different magnitude of the constant of tracer distribution between the water (gas) and oil (condensate).

A new equations for flow of two tracers in fractured-porous media are derived. Both diffusive and convective mechanisms of the tracer mass transfer between blocks and fractures are taken into account. The hydraulic interaction between fluxes in cracks and in matrix is described as well. Problem of one-dimensional flow leads to the linear system of hyperbolic equations. Analytical solution for ID problem of injection of water (gas) with the two tracers is obtained. Results of theoretical prediction of tracers wave propagation are in a good agreement with the data of laboratory experiments.

Exact explicit formulae for propagation of the concentration wave of two tracers allows us to solve an inverse problem. Method for improved characterization of fractured-porous media from data of two tracers concentrations on the exit of reservoir is developed. Measurement of the first tracer concentration allows us to determine the following properties of fractured-porous media: fractional flow function (fraction of the flux via fractures in the total flux); fraction of porous space of cracks in the total space of fractured-porous media; coefficient of mass transfer between fractures and matrix. Information about the concentration of the second tracer permits us to determine the saturation of the immobile phase separately in fractures and in blocks.
Ion Exchange Between Hydrogen and Homoionic Brines Related to Permeability Reduction
Authors: Souto Esperanza , Bazin Brigitte , Sardin Michel
Published: December 2007

Formation damage due to clay migration may be observed when the injected brine replaces the connate water during operations such as waterflooding, chemical flooding including alkaline, surfactant and polymer processes.

This work deals with the effects of physico-chemical changes induced by brine replacement on the permeability behavior of consolidated argillaceous sandstones.

The experimental investigation is made up of: –core flow experiments in clayey sandstones. Effluent pH and ionic concentration are measured at the outlet of the porous medium and permeability variations are simultaneously monitored when the injected salinity is abruptly decreased.–batch coagulation tests giving both critical salt concentration and pH in a salinity-pH diagram.

Brines are prepared with sodium and potassium salts.

A physico-chemical flow model is also developped based on cationic exchange with the proton when the salinity decreases. The model allows: –the interpretation of the experimental observations (pH and concentration)–the knowledge of the transition compositions–the effect of the major parameters like the clay content through the cation exchange capacity.

The model gives pH and salinity profiles. The comparison of these values with the salinity-pH diagram critical ones leads to the prediction of the effect of the fluid composition on the damage process.
Remedial Treatment for Polymeric Damage Removal Provides Improved Well Productivity
Authors: Tjon-Joe-Pin Robert , Brannon H. D. , Rickards A. R.
Published: December 2007

Recent advances in biotechnology have led to the identification and isolation of polymer-specific enzymes. This new technology has been incorporated in the development of improved damage removal systems. The polymer specific reactivity of the new systems provides environmentally safe polymer degradation without causing damage to the formation or tubular goods.

Polymer specific systems have been developed for removal of damage caused by polymers such as cellulose, guar, and starch. The treatments can be applied over a wide range of downhole conditions to polymeric damage resulting from fracturing, gravel packing, or workover operations.

Fracture conductivity and core flow evaluations have shown that multi-fold improvements in permeability are achieved with the new systems. Damaged wells treated with the new systems have experienced up to three-fold improvement in well productivity. A detailed study and analysis of laboratory and field data are presented.