bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Air Injection as an IOR Method for the Giant Ekofisk Chalk Field
Authors: Stokka S. , Oesthus A. , Frangeul J.
Published: December 2007

The Ekofisk fractured chalk reservoir located in the North Sea south-west of Norway has been exploited successfully for more than three decades, largely due to injection of sea water. In a study concluded in 2004, air injection was evaluated as a method for additional hydrocarbon recovery beyond the secondary waterflood recovery. Supported by the European Commission through the fifth framework program, the Ekofisk Field owners joined forces with leading European research institutes and a contractor to investigate the potential of air injection as a cost effective IOR method. Through screening studies, extensive laboratory experiments, reservoir simulations, design of processing facilities and project feasibility evaluations, an extensive knowledge base of the air injection process for light oil fractured reservoirs was established.

In the present paper technical results will be presented. Recovery mechanisms related to an air injection process in a fractured light oil reservoir have been studied through laboratory experiments and reservoir modeling. The laboratory experiments verified air injection as a potential IOR method for a light oil fractured chalk field. Laboratory experiments were performed in order to study kinetic properties such as activation energies and ignition temperatures. In addition, diffusion coefficients were estimated through laboratory experiments and verified by numerical simulations. Potential weakening of the chalk due to heat and CO2 was evaluated based on laboratory experiments and geo-mechanical modeling. Combustion tube experiments were conducted in order to study propagation of the combustion front through porous media.

Finally, a field scale air injection feasibility study was performed. The outcome of this study, including an evaluation of potential production benefits and main cost items involved in an air injection project, is presented.
Analyzing Well Performance XII
Authors: McCoy James N.
Published: December 2007

Analyzing well performance is an important step toward increasing profits by improving production techniques. The analysis is made by field tests and examination of well data. The acoustic liquid level instrument offers valuable information since downhole pressures can be determined from the depth to liquid measurement.

Fluid flow in a reservoir is caused by movement of fluid from a high-pressure area to a low-pressure area. Fluid flow into a wellbore occurs when fluids present in the wellbore are removed so that the pressure is decreased in the wellbore. Then, fluid from an area of higher pressure flows into the lower pressure wellbore (Fig. 1).

Fluid flow increases as the differential pressure increases. Vogel1 presents a curve for predicting flow rates based upon the ratio of the wellbore pressure to the reservoir pressure. This curve is shown on the Well Analysis Sheet. Note: approximately 70% of the maximum flow rate will occur when the wellbore pressure is one-half of the reservoir pressure. Also note, 90% of the maximum flow rate will occur when the wellbore pressure is 25% of the reservoir pressure.
Selection and Qualification of Materials for HPHT Wells
Authors: Brownlee J. K. , Flesner K. O. , Riggs K. R. , Miglin B. P.
Published: December 2007

Interest in sour, high-pressure high-temperature (HPHT) wells and in ultra-HPHT wells, i.e. those with bottom hole temperatures greater than about 300° F (150° C) and wellhead pressures greater than about 10,000 psig (690 bar), is increasing worldwide. Due to the desire to monetize reserves more rapidly and due to the aggressiveness of sour, HPHT and ultra-HPHT environments, these wells are likely be completed using large diameter casing and tubing that is manufactured from solid, high-strength corrosion resistant alloys (CRAs). Wellheads will likely be manufactured from high strength low alloy steel that is clad internally with CRAs.

The combination of corrosion resistance and strength offered by solid CRAs and CRA-clad steels has spurred decisions to produce otherwise uneconomic sour, HPHT and ultra-HPHT wells around the world for several decades now. However, current levels of conservatism in materials selection and evaluation and in design of HPHT well equipment is not likely to be sustainable in the future. Thus, this paper provides a review of the knowledge gained from previous HPHT developments with the dual aims of extending the safe and successful development record of the E&P industry related to HPHT wells and improving the cost-effectiveness of future CRA completion designs.

Increasingly aggressive conditions are beginning to expose limitations in current design methodologies for tubing and casing strings, connections, seals, downhole jewelry, and valves. Linear elastic design methodologies are likely to be supplanted by elastic-plastic, fatigue, and fracture mechanics based methodologies in the near future, and this will likely result in a need for detailed data related to CRA materials properties including flow stress, fracture toughness, and low-cycle fatigue resistance, data that is largely nonexistent at present. Therefore, this review also examines the limitations of current CRA test methods and identifies gaps in materials property data that is likely to be required if advanced design methods for critical well equipment are to be successful.

High bottomhole pressures in HPHT wells are likely to result in a need to use large-diameter, heavy-wall tubing strings. Thick, large diameter CRA tubes are generally limited to short lengths, which results in an economic trade off between the increased gas production that can be achieved by using large diameter tubing and greater completion costs that result from more connections and longer completion times. Thus, this paper will also examine size and strength ranges of CRA tubulars that are currently available, and these ranges will be compared with the anticipated needs of HPHT well owners and operators to identify whether critical gaps exist in current CRA manufacturing technology.
North Kern Front Field Steam Drive with Ancillary Materials
Authors: Eson Rodney L. , Fitch Jon P. , Shannon Albert M.
Published: December 2007

Since steam injection became a viable recovery technique nearly three decades ago, the problems of gravity segregation and poor areal and vertical sweep efficiencies have limited recoveries in many heavy oil reservoirs. In many instances the injected steam prematurely breaks through into producing wells creating steam channels. It is believed that overall recoveries of a steam drive can be improved if the steam channeling can be controlled. This paper documents efforts under a Department of Energy cost sharing contract to reduce steam channeling in a conventional steam drive using ancillary materials.

A steam foam solution and a steam foam encapsulated in a polymer gel are being introduced in four steam injection patterns in the North Kern Front Field near Bakersfield, California. The ability of the ancillary materials to improve recovery will be determined through injection profiles, chemical tracer surveys, casing vent gas analysis, core and log data, and residual oil saturation data, as well as through temperature and production data.

It has been shown that in-sitυ steam foams can be used to alter the steam injection profiles to prevent excessive steam channeling. The results of early production data have indicated that as much as 125 B/D of incremental oil is being produced by the four chemical treated patterns.
High Pressure Model Studies of Oil Recovery by Carbon Dioxide
Authors: Doscher Todd M. , El-Arabi Mahguib
Published: December 2007

Linear scaled physical model studies were designed and carried out to study the recovery of crude oil by the injection of carbon dioxide. Viscous and gravity forces and molecular diffusion were explicitly scaled to field conditions. Mechanical dispersion was not scaled, and is exaggerated in the models.

The basic prototype considered in this study is a homogeneous reservor with a permeability of 20 millidarcies and a distance between injector and producer of 462 feet and an equivalent thickness of 28 feet.

Because both the line drive, in contrast to a radial pattern, and the low permeability of the prototype reduce the relative influence of gravity segregation, and the exaggeration of mechanical dispersion in the model reduces the effects of viscous fingering and gravity override; the results of these studies yield optimistic results in comparison with those that may be expected under field operating conditions.

The results reveal that two factors dominate the recovery process: the high mobility of the carbon dioxide, and its solubility in the subject crude oil. The latter in turn appears to be a function of the density of the carbon dioxide.

The effects of pressure, temperature, oil saturation, and slug size on recovery were studied in some detail, and the effect of the composition of the oil to a limited extent. A degree of criticality is observed with respect to the size of the slug on its influence on recovery and the carbon dioxide required to recover a barrel of crude oil. By controlling the slug size, about half of the residual oil can be recovered at ratios of less than 10 MSCF/B whereas continuous injection will recover more of the residual oil but only at ratios in excess of 20 MSCF/B.

No banking of the crude oil is observed and carbon dioxide production occurs rapidly and concomitantly with oil. The complex phase behavior of carbon dioxide, the separation of the heavy fractions and solution of the light fractions in the dense carbon dioxide gas, occurs only after the carbon dioxide has reached a high saturation in the system, and therefore contributes little to the up-front (economic) recovery of residual oil.
Scaling of Flow Parameters for Miscible Gas Flood Simulation Studies
Authors: Breit Vernon S. , Graue Dennis J.
Published: December 2007

This paper outlines the steps involved in determining reasonable flow parameter values for a typical miscible gas flood simulation study using a "mixing-rule" type miscible flood simulator1. In each step we are striving for consistancy between the performance predictions of a coarse grid history matched waterflood model and a miscible gas flood model which usually requires a much finer grid.

A technique is described for calculating the correct imbibition water and oil relative permeability curves to be used in a fine grid study from the set of imbibition relative permeability curves used to obtain a history match of waterflood performance with a coarse grid black oil model. These curves will assure that the fine grid model predicts the same waterflood performance as would be predicted by the history matched model.

Finally, a discussion of the important considerations which must be accounted for in the selection of proper flow parameters to be used in each of the four flow regimes which occur in a typical gas flood: (1) water displacing gas behind the tertiary oil bank, (2) gas miscibly displacing oil at the back of the tertiary oil bank, (3) oil immiscibly displacing water at the leading edge of the oil bank, and (4) water displacing oil in front of the tertiary oil bank.
Tertiary Oil Recovery Economics in Louisiana
Authors: McCarthy Danny W. , Groat Chip , Chen Jan-Ku , Liau Tai-Ho , Weaver Robert E. C. , Aldahir A. S.
Published: December 2007

This paper assembles the relevant economics for the production of tertiary oil in prototype Louisiana situations. The production techniques examined and compared include carbon dioxide flooding, in-situ combustion, steam injection, and micellar/polymer flooding.

A complete cost analysis is constructed for each EOR technique based specifically on reservoir properties with relevance to Louisiana.
Environmental Risks Associated with the Commercialization of Enhanced Oil Recovery
Authors: Riedel Ernest F. , Garrell Martin H. , Kaplan Edward , Sathaye Jayant , Bierman George R.
Published: December 2007

A workshop sponsored by the United States Department of Energy Technology Assessment Division was held during August 1980 to discuss Enhanced Oil Recovery (EOR) production and associated environmental risks. The participants represented industry, government, environmental and private consulting groups.

The information collected at the workshop will be used in a DOE research project to identify and evaluate potential environmental, health and safety (E,H&S) concerns associated with the production of petroleum by enhanced oil recovery. This project is part of a continuing DOE program to assure that E,H&S concerns are addressed in a timely and cost-effective manner in energy technology development programs. This paper presents highlights of the workshop proceedings that may be of general interest to other researchers, the oil and gas industry and government agencies. The views presented in general represent a consensus of the workshop, but they do not necessarily represent the opinions of individual workshop participants, the authors, the Department of Energy or the National Laboratories.

A long list of potential environmental concerns were identified in the workshop. Only a few were felt to be potentially important: air quality, liquid waste injection, and worker health and safety considerations. Scenarios for EOR production were also reviewed and critiqued. An accurate production scenario will be required to characterize the magnitude and extent of potential E,H&S concerns from EOR production. Impediments to rapid expansion of EOR, such as lack of reservoir data, technological constraints, and economics and institutional considerations (e.g., windfall profits tax) were discussed. Accurate predictions of future EOR production levels were found to be difficult because of uncertainties in the numerous variables that might have major impacts on these levels. The potentially most significant environmental issue was found to be solid waste disposal and potential problems resulting from enforcement of the new Underground Injection Control Regulations. It was generally concluded that EOR is an environmentally safe form of increased fossil energy.
Well Log Applications in Rock Mechanics
Authors: Sethi Darshan K.
Published: December 2007

In dealing with subsurface engineering problems concerning rock mechanics, the determination of in-situ physical properties of rocks has assumed great importance. In recent years, various techniques have been applied in correlating the log-derived parameters with mechanical behavior of the rocks. These techniques have found applications in the petroleum, mining and construction industries.
Mechanical Behavior of Mesaverde Shale and Sandstone at High Pressure
Authors: Lin Wunan
Published: December 2007

Prediction of the effects of hydraulic fracturing for the stimulation of fluid recovery from low permeability rocks requires a fracture model and certain mechanical properties for input to the calculation codes. For such a study on the Western tight-gas-sands, we report here new rock mechanics measurements taken on Mesaverde shale (source rock) and sandstone (reservoir rock) from about 350-m depth (Colorado) and 1600-m depth (Wyoming). For each sandstone and shale, we have determined:

Tensile strength parallel and perpendicular to bedding, 0.1-MPa pressure. Triaxial stress failure envelope in compression to 300-MPa confining pressure, parallel and perpendicular to bedding, Pressure-volume behavior to 1.2 GPa.

The results for (1) indicate that, in. general, the tensile strength of Wyoming sandstone is about three times that of Colorado sandstone. For both sandstones, the tensile strength is isotropic with respect to bedding. The tensile strength of both shales parallel to bedding is about 30-50% greater than that measured normal to bedding. The shale from Wyoming has a tensile stength about 25-50% greater than that from Colorado.

Strengths and failure modes in compression (2) show that the transition between brittle failure and ductile deformation occurs at a confining pressure of about 0.1 GPa for the Colorado sandstone and, 0.25 GPa for all other rocks tested. No significant anisotropy in compressive strength is observed for these rocks except the Colorado shale. Colorado shale has about 40-50% strength anisotropy with loading perpendicular to bedding stronger than that parallel to bedding. However, the inhomogeneity of this rock may affect the measured strength anisotropy. The relative strengths of these rocks are shown in the following statements. In Colorado, the shale is about 50-70% stronger than the sandstone; in Wyoming, the shale is about 20-30% stronger than the sandstone. The Wyoming sandstone is about 50% stronger than that from Colorado; the Wyoming shale is about 20-30% stronger than that from Colorado.

Pressure-volume (3) loading indicates that - ΔV/V0 at 1.2 GPa for the sandstone from Colorado is about 6-7%; for the other rocks tested, about 3-4%. Bulk compressibility of these rocks as a function of pressure is calculated from the pressure-volume data.
Fracture Optimization in A Tight Gas Play: Muddy "J" Formation, Wattenberg Field, Colorado
Authors: Roberts C. N.
Published: December 2007

Hydraulic fracturing has been performed in the tight gas sand of the Muddy "J" formation in Wattenberg Field since commercial production began in 1971. This study was made to determine the effectiveness of the different stimulation techniques which have evolved in an effort to optimize a procedure for the field. This paper discusses the development and results of this fracture-optimization program for the Wattenberg Field.

Well properties for the analysis were determined from logs, core samples, production data, fracture azimuths, mechanical property logs, and pressure transient data. Fracture treatments were studied by comparing: fluid type and quantity; proppant size, type, concentration, and quantities; and treating rate and pressure. Computer simulation of the induced fracture was correlated with type-curve analysis and actual performance to model the well. Stimulation success was based on economics, well performance, increased reserves, drainage area, and treating fluid efficiency.
Impact of a Disability Management Program (DMP) in a Fortune 100 Petrochemical Company
Authors: Bhojani F. , Tsai S. P. , Donnelly R. P.
Published: December 2007

Background

In an attempt to reduce non-occupational absences at a petrochemical corporation, an in-house disability management program was initiated.

Methods

An internet-based management tool was used by employees who were required to report all absences on the first day and again on the fourth workday absent. A medical certification form was required for absences of 4 or more working days.

Results

The program resulted in a 10% reduction in total absence days per employee (6.9 to 6.2) in 2003 compared to the previous year, while business units not utilizing the program had an 8% increase (5.5 to 5.9). This disability management program resulted in a more than 4 to 1 return on investment based on direct expenditures and cost savings in terms of reduced absence days, after one year implementation of the program. In addition, the disability management program continues to meet its objective of reducing disability related absenteeism by managing intermediate term absences (i.e. those lasting 4 days to 6 months). The average workdays missed due to illness among refinery workers reduced from 4.6 to 4.4 days per employees between 2002 and 2004.

Conclusions

The in-house disability management program successfully reduced absence duration, increased employee satisfaction and returned on the initial investment.
Status Report on Fracturing of Deep And Low Permeable Formations in West Germany
Authors: Brinkmann Friedrich W.
Published: December 2007

The demand/supply situation in the European gas market led to an extensive effort to develop tight gas reservoirs in West Germany. Geological interpretation including all aspects of petrographical and petrophysical data were taken into account when the stimulation campaign on deep and tight Carboniferous reservoirs was started in 1977.

Thorough analyses on reservoir parameters including mineral contents and substantial compaction effects were used for detailed job design. The Carboniferous reservoirs, characterized by porosities of 8 - 12 %, permeabilities of 10 microdarcies to 1 md*, reservoir depth of more than 4000 m (13120 ft) and net thickness of 20 m (66 ft) can only be produced if MHF treatments of some 500 - 1000 m3 (3150 - 6300 bbl) of fluids and 100 - 200 t (2.2 - 4.4 million lbs) of highstrength proppants are applied. Special provisions have to be made with respect to casing design because salt sections and underpressured sour gas reservoirs have to be penetrated before the wells encounter the tight gas sands. In order to find out optimum job design, various oil base and water base frac fluids and various types of high strength proppants were tested in several MHF stimulation treatments. The success of several jobs was demonstrated by both cased-hole logs and production performance evaluation. The production histories of the stimulated wells and the economic evaluation at various conditions prove that MHF treatments can be justified since there is no other alternative to recover the presently known 20 × 109 m3 (0.7 TCF) of gas reserves in known structures and to produce about 100 × 109 m3 (3.5 TCF) of additional gas reserves which are expected from future exploration activities on Carboniferous in West Germany.

The conclusions which are drawn in this paper refer to 13 stimulation jobs out of 15 which have been executed in Europe, all of them in structures located in West Germany.
Evidence of Permeability Enhancement Through Cyclic Dry Gas Injection
Authors: Branagan Paul , Cotner Gene , Gettman Gregory
Published: December 2007

The phenomenon of deliverability improvement due to the cycling of dry gas in storage reservoirs has been well documented at Colorado Interstate Gas Company's (a subsidiary of The Coastal Corporation) Fort Morgan storage field. Core data from nine original Fort Morgan wells indicated the initial permeability of the Dakota "D" storage reservoir averaged 187 md. After 15 years of cycling gas through the reservoir, the average permeability as determined from pressure buildup is in the one to ten Darcy range. Original open flow potentials averaged about 1 MMcfd, and is considered very conservative.

These indicated permeability and observed productivity improvements were greater than would be expected from the normal core derived relationship between relative permeability to gas and fluid saturation. This empirical experience also observed in other storage fields was the basis for the belief that other phenomena, such as the dehydration of matrix clays and the removal of "skin effects" such as high fluid saturation adjacent to induced fracture surfaces, also contribute to productivity improvement with cyclic dry gas injection.

Based on this experience of improvement in storage fields, Colorado Interstate Gas Company (CIG) and the U.S. Department of Energy (DOE), embarked on a field test to determine if cyclic dry gas injection could improve actual producing wells completed in the tight gas sands of the Dakota Muddy "J" in the Wattenberg field of Colorado. Two wells owned by Machii Ross were made available for use in the project. The project wells, Miller #1 and Sprague #1, located in the western portion of the Wattenberg field, are shown in Figure 1. The initial testing of the experimental wells was designed to provide base data concerning each of the wells, the hydraulic fracture, and the surrounding formation. This testing was then followed by a gas cycling period when the wells would alternately produce gas, have the gas dehydrated and then injected into the other well.
Fluid Loading in Low Permeability Gas Wells in the Cotton Valley Sands of East Texas
Authors: MacDonald Richard M.
Published: December 2007

Fluid buildup in the wellbore has long been recognized as a detriment to flow from gas wells. This is particularly true for wells completed in formations with low permeability, where hydraulic fracture stimulation is a prerequisite to commercial production. In natural flow, the gas velocity governs whether the fluid produced into the wellbore will be conveyed to the surface or allowed to fall back on the formation. It is therefore of extreme importance that a method for predicting the minimum or critical velocity be established. Prediction methods previously documented in literature have proven inaccurate for the flow conditions encountered in Cotton Valley wells in the East Texas area. A modified calculation procedure, based on actual flow data, for the determination of fluid loading of said wells is presented. To sustain natural flow it is imperative the gas velocity be above the calculated critical value. A number of methods are available for increasing the gas velocity. The effects of tubing size and wellhead pressure as they pertain to gas velocity are presented.
Prop Transport in a Large Vertical Model
Authors: Sievert John A. , Wahl Harry A. , Clark Peter E. , Harkin Michael W.
Published: December 2007

A large vertical-slot model without fluid loss was used to evaluate the roles of fluid type, fluid viscosity, prop concentration and flow rate on prop transport and pack growth. Individual particle trajectories as well as overall pack growth were measured.

With non-Newtonian fluids, changes in either prop concentration or gel concentration (viscosity) produced significant changes in pack growth. By contrast, a 0.03-Pa·s (30-cp) Newtonian fluid system allowed the prop to settle so rapidly that no influence due to the variables of interest could be detected. A 0.06-Pa·s (60-cp) Newtonian system showed a flow rate effect when the prop concentration was held constant.

Observations made during the experiments indicate that some forces present in the gelled system were absent from the Newtonian system. Measured pack growth rates do not agree with those calculated by substituting measured particle fall rates into existing mathematical models. This is true for both Newtonian and non-Newtonian fluids. Much work remains to be done before prop transport and deposition in vertical slots is adequately understood.
Embedment of High Strength Proppant into Low-Permeability Reservoir Rock
Authors: Volk Leonard J. , Raible Clarence J. , Carroll Herbert B. , Spears Judy S.
Published: December 2007

Embedment of sintered bauxite into Berea, sandstone core, and shale core at closure pressures up to 10,000 psi (69 MPa) is reported. Several variables influencing fracture closure are examined: closure pressure, proppant size and size distribution, proppant concentration (up to a monolayer), formation hardness and surface roughness. Comparison is made with sand proppant. Empirical equations are derived to describe embedment into sandstones and shale for non-crushing proppants such as sintered bauxite.
New Proppants for Deep Gas Well Stimulation
Authors: Cutler Raymond A. , Jones Arfon H. , Swanson Stephen R. , Carroll Herbert B.
Published: December 2007

Existing high strength proppants have desirable strength characteristics for propping deep hydraulic fractures, but also have high specific gravities and high cost when compared to sand. A low specific gravity proppant would reduce costs and improve fracture control.

Theoretical stress and strength analyses suggest that porous and hollow ceramics offer an alternative to dense proppants. Fracture conductivity as a function of closure pressure was experimentally determined for several materials. Good correlation of experimental results with theory was observed for solid and porous proppants.

Fabrication methods for the production of inexpensive lightweight proppants are discussed. Spray drying into a fluidized bed appears to be a viable method for producing both porous and hollow proppants. Characterization of spray dried proppants is discussed as well as materials which may be effective lightweight proppants. Areas of emphasis for future research are discussed.
Recovery of Heat and Carbon Dioxide from Compressor Station Exhaust Gas
Authors: Fang Cheng-Shen , Garber James Daniel , Farshad Fred F. , Broadhurst Robert C.
Published: December 2007

Gas compressor flue gas has sufficient heat content that heat recovery is practical. Steam and electrical power can be generated in this manner which reduces the utility cost of removing carbon dioxide from the flue gas.

A survey of various methods of removing carbon dioxide from flue gas has shown that monoethanolamine (MEA) is the best chemical absorbent at the low pressures available for this process.

A system has been designed to compress, dehydrate, and transport carbon dioxide to the receiving oil reservoir which could be 10 or 100 miles away from the available source.
Pressure and Temperature Dependent Properties of the Rock-Fluid Systems in Petroleum and Geothermal Formations
Authors: Ehlig-Economides Christine A. , Economides Michael J.
Published: December 2007

A number of experimental studies have focused on the properties of the porous medium and the fluids contained therein at elevated pressures and temperatures. Rock properties which appear to be affected by the pressure and temperature levels include permeability, porosity, and compressibility. Single phase fluid properties of interest include viscosity, density, compressibility, and vapor pressure. Fundamental properties which govern the behavior of multiple phases include surface tension and wettability. Finally, two properties which are used to represent multiple fluid phase behavior in the porous medium are capillary pressure and relative permeability.

Methods exist for measuring rock properties for various rock types, bulk properties of single phase fluids, and the properties of multiple contacting phases as functions of pressure and temperatures. Capillary pressure curves and relative permeability data are then determined for reservoir conditions using additional experimental measurements and calculations based on the measured rock and fluid properties. However, certain experimental results suggest that the fluid and rock properties may be affected by the particular rock-fluid combination.

In this paper, experimental results from several major studies and the interpretations offered are examined in detail. Since the interpretation for one set of results have frequently been inconsistent with results of related experiments, a unified theory is sought.
Dynamic Modelling of Produced Water Reinjection in Depleted Naturally Fractured Gas Fields
Authors: Weijermans P. -J. , Warren G.
Published: December 2007

NAM in the Netherlands is currently conducting studies to redevelop the Schoonebeek oil field, onshore in the Netherlands. Steam flooding is the envisaged process.

Large volumes of produced water from this field are to be re-injected in regional depleted Zechstein fractured carbonate gas fields. Estimates of injection rates and volumes are required for reservoir selection and pumping requirements.

This paper demonstrates a methodology which permits injection rate and volume predictions to be made in a simple spreadsheet model based on historical measured gas production rates and volumes. The paper describes how to convert an analytical gas productivity index solution for dual-porosity systems to a water injectivity index. The conversion was validated using rigorous dual-porosity simulations and sensitised to a broad range of matrix and fracture properties. It was found that injectivity in the fractured Zechstein carbonate is constrained by the effective permeability of the fracture system and is relatively insensitive to matrix permeability and fracture spacing. This behavior was verified by calculation of a dual-porosity pseudo skin factor. Partially fractured models also demonstrate that some matrix pore space which was capable of producing gas, cannot be effectively accessed by injected water volumes.

The converted water injectivity index combined with other nonlinear repressurisation, relative permeability and water viscosity effects were combined with surface pump curve and wellbore head/friction calculations to construct a spreadsheet capable of predicting long term injectivity on an individual well basis. A large number of wells were screened and optimized using this practical tool.

This methodology can be readily applied to other water disposal projects targeting depleted, naturally fractured or matrix only gas fields.
A Stable Numerical Model for Vertically Fractured Gas Reservoir Incorporating Stress Sensitivity
Authors: Chen Shing-Ming , Evers John F.
Published: December 2007

The transient pressure behavior of a vertically fractured reservoir has been solved successfully based on numerical solutions.1,2 These solutions enhance the understanding of early time portion during the drawdown or the build-up test conducted in a vertically fractured reservoir. To completely understand the performance of a gas reservoir, solutions for later time are also necessary. However, stability considerations always complicate the design of the model. The main objective of this work is to develop a numerical model which could be stable for all times.

The model is formulated for a fracture of limited and radial extent completely penetrating the producing formation vertically. The model equations are transformed using conformal mapping. Appropriate stability criteria are developed and the resulting finite difference equations are solved using the Iterative ADIP method. The boundary conditions are handled using a special numerical approach resulting in stable solutions for all times. Another feature of the developed procedure is the ability to handle finite fracture conductivity and stress sensitivity.
Platform Design/Construction — Overview
Authors: Dunn F. P.
Published: December 2007

I would like to start my discussion by giving you a brief history of offshore platform development since its beginning in 1947 in the Gulf of Mexico. I will then discuss the important preliminary steps which must be undertaken before a decision is made to develop an offshore field after a discovery has been made. I refer specifically to such items as the establishment of environmental criteria, water depth, foundation conditions, number of wells required, number of drilling rigs, production equipment needed, etc. The many different types of structures will then be reviewed, along with reasons for choosing one type over another for a specific discovery. Deep water (> 1000′) development will be discussed, with an emphasis on the special problems associated, and the structures anticipated for such development. I will then discuss briefly the improvements needed in our technology as we go into deeper water and give my opinion as to where we can be in the next ten years, given the opportunity.

Though some drilling had taken place in offshore waters from timber trestles and in inland waters and marshlands before World War II, the first steel platform on which drilling took place was installed in 1947 in the Gulf of Mexico in about 20 feet of water. Through the 50′s, offshore development was concentrated in water depths less than 200′. During the 1960′s, development began in the southern North Sea area in about 100′ of water, a much more hostile environment than the Gulf of Mexico. During this time also, ice-resistant structures were successfully installed in 100′ of water in Alaska.

The 400′ water depth, considered to be a barrier for a while because of anticipated problems with dynamic response, about which the industry knew very little before the early 70′s, was exceeded in the mid 70′s. By 1981, five structures had been successfully installed in water depths exceeding 600′ in the Gulf of Mexico, the deepest of which is in 1025 feet (Figure 1). Several huge platforms have been installed in greater than 500′ of water in the North Sea, and Brazil is presently developing fields with platforms in excess of 400′. The Far East will soon have two platforms in over 400′ of water--one offshore Japan and one offshore Australia.
Optimization methods applied for sustainable management of water-scarce basins
Authors: Cetinkaya Cem P. , Fistikoglu Okan , Harmancioglu Nilgun B. , Fedra Kurt
Published: December 2007

This paper aims to present the information-based technologies used for water management in a test basin within the scope of the EU-sponsored SMART and OPTIMA projects. The study uses a dynamic simulation model with its associated databases and a water resources planning and optimization system, established through a web-based client–server implementation to support distributed use and easy access for multi-criteria optimization and decision support. The results clearly illustrate how a consistent and well-integrated set of advanced but practical Decision Support System (DSS) tools can be used for efficient “optimal” water management strategies and policies of use, designed for a participatory public decision-making process.
Local water independency ratio (LWIR) as an index to define the sustainability of major cities in Asia
Authors: Han M. , Kim S.
Published: December 2007

This paper defines the Local Water Independency Ratio (LWR) as a new parameter for evaluating a city' s safety and sustainability in terms of water supply. The present LWR values of major Asian cities Seoul, Tokyo, Osaka, Beijing and Shanghai are compared. In order to increase the LWIR, non-structural alternatives and structural alternatives are suggested with regard to prioritize the ranking and the most suitable methods for these cities.
Treatment of acidic water from Bekok River using open limestone channel
Authors: Aris A. , Mokhtar N. , Muslim R. , Ujang Z. , A-Majid Z.
Published: December 2007

Bekok River is one of the raw water resources for Batu Pahat treatment plants which supply treated water for domestic, institutional, commercial and industrial use. Due to soil characteristics and agricultural activities in the catchment area, pH of lower than 5.5 is common to the river, particularly in the stretch where the water intake point is located. However, at times, Bekok River registered low pH of less than 3.5 and hence caused problems to the treatment plants. The cost to neutralise the water increased and treatment scheduling became more complicated. A preliminary laboratory scale study has been conducted to determine the viability of using an open limestone channel as an in-situ pH treatment in the river. Two sets of experiments using synthetic and actual raw waters with various sizes and amount of limestone were carried out. Results indicate the viability of the process. Depending on the initial pH and acidity of the raw water, the pH can rise to 6.0 within 30 minutes of contact time. The amount and size of limestone was found to play an important role in minimising the contact time.
Caspase‐3 targets pro‐interleukin‐1β (IL‐1β) to restrict inflammation
Authors: Kim Seon Sook , Seo Su Ryeon
Published: March 2024

The interleukin (IL)‐1 family of cytokines plays a pivotal role in immune responses. Among the members of IL‐1 family, IL‐1β is synthesized as an inactive precursor (pro‐IL‐1β) and becomes active upon cleavage, which is typically facilitated by inflammasomes through caspase‐1. In our research, we explored the potential role of caspase‐3 in the cleavage of pro‐IL‐1β and found that caspase‐3 cleaves pro‐IL‐1β, specifically at Asp26. Moreover, we found that in the absence of caspase‐3 cleavage, the release of active IL‐1β via the inflammasome is increased. Our study introduces pro‐IL‐1β as a new substrate for caspase‐3 and suggests that caspase‐3‐mediated cleavage has the potential to suppress IL‐1β‐mediated inflammatory responses.
Multifunctional Coatings on Mg‐Based Metallic Biomaterials and Implants
Authors: Li Qilong , Kong Hui , Zhang Nannan
Published: March 2024

Multifunctional materials are propitious materials with numerous functionalities that make them an ideal option for implants and biomedical applications that should simultaneously fulfill various requirements, including satisfactory mechanical strength, biocompatibility, antibacterial property, hydrophilicity, etc. Magnesium, as a metallic biomaterial, fulfills the required mechanical properties, but unfortunately, in some ways alone, it cannot provide the required biological properties. For instance, magnesium alloys suffer from poor corrosion resistance and high biodegradability, which should be carefully controlled. On the other hand, multifunctional materials alone are not able to provide the required properties in biomedical applications because the vast majority of them do not have the necessary strength and stability. Therefore, the use of magnesium together with multifunctional or composite coatings will be a very advantageous choice for meeting the needs of implants and biomedical materials. The current study focuses on the introduction and utilization of various multifunctional coatings and composites on Mg‐based alloys for biomedical applications. Numerous organic and inorganic materials could be utilized as composites or multifunctional materials. In this regard, numerous types of coating and composite materials, their production technologies, mechanisms, resultant properties, and the involved parameters are thoroughly discussed to provide a comprehensive guide for those interested in this field.
Observing High‐Cycle Fatigue Damage in Freestanding Gold Thin Films with Bulge Testing and Intermittent Transmission Electron Microscopy Imaging
Authors: Krapf Anna , Merle Benoit , Gebhart David D. , Reiter Marco , Lassnig Alice , Göken Mathias , Cordill Megan J. , Gammer Christoph
Published: March 2024

Bulge testing is a potent technique for measuring the mechanical properties of freestanding thin films, but in situ imaging is only possible in limited experimental configurations. This poses a serious limitation for unraveling nanoscale failure mechanisms, such as the deformation mechanisms induced by cyclic loading in freestanding gold thin films of 150 nm thickness. Herein, a new experimental workflow combining standalone bulge cyclic testing with intermittent high‐resolution imaging by transmission electron microscopy (TEM) at specific positions of interest is introduced. The observed low dislocation activity in planar areas of the thin films is consistent with the slow strain accumulation during high‐cycle fatigue testing. In contrast, notches in the films lead to localized plasticity with sustained dislocation activity, but also grain growth and subgrain formation. At a more advanced stage, cracks proceed along grain boundaries, with crack bridging seemingly slowing down their propagation. The presented setup can be used with a number of TEM‐based characterization techniques and has the potential to reveal cyclic deformation mechanisms in several thin‐film systems.
Debridement Strategy by Pre‐Bending Passivation for Flexible All‐Inorganic Perovskite Solar Cells Beyond 70 000 Bending Cycles
Authors: Liu Huijing , Xu Jia , Han Huifang , Zhao Chenxu , Fu Yao , Lang Kun , Zou Pengchen , Pan Xu , Gao Xingyu , Zhao Kui , Yao Jianxi
Published: March 2024

The mechanical durability and efficiency of all‐inorganic flexible perovskite solar cells (f‐PSCs) still require enhancement for practical applications. In this study, a creative debridement strategy to improve the mechanical durability and photovoltaic performance of all‐inorganic f‐PSCs by pre‐bending the flexible perovskite film and then depositing the passivation agent 2‐mercaptopyridine is proposed. The pre‐bending process induced the generation of microcracks in the perovskite film surface, and 2‐mercaptopyridine can more effectively penetrate the interior of the film through the microcracks, thereby further passivating deep surface defects. These microcracks and defects can be perfectly repaired by 2‐mercaptopyridine. Bidentate coordination sites of S and N in 2‐mercaptopyridine show stronger binding energy with surface defects. The debridement strategy effectively enhanced the crystallization of the film surface and markedly inhibited crack propagation during the film's bending process. The optimized device achieves a champion power conversion efficiency (PCE) of 14.74%. The pre‐bent and passivated all‐inorganic f‐PSC shows 104% of its initial PCE after 15 000 bending cycles at a curvature radius of 3 mm. Remarkably, even after undergoing 70 000 bending cycles at a curvature radius of 5 mm, pre‐bent, and passivated f‐PSC can retain over 93% of its initial PCE, exhibiting excellent mechanical durability.
Tailoring Tribological Characteristics in Titanium Alloys by Laser Surface Texturing and 2D Ti3C2Tx MXene Nanocoating
Authors: Zhang Qicheng , Li Yong , Liang Fei , Zhang Haoran , Wang Bin , Li Xiaopeng , Lin Zifeng , Lin Yan , Chen Xiang
Published: March 2024

The inferior tribological properties of titanium (Ti) and its alloys, due to their limited work hardening capability and the mechanical instability of their oxide scale, pose substantive challenges in practical applications. Surface texturing and the application of 2D material coatings are acknowledged as efficacious strategies for enhancing these properties. Nevertheless, the rapid loss of effectiveness when employing these methods in isolation highlights a significant limitation. Herein, a 50‐nm‐thick MXene nanocoating is deposited onto groove‐textured pure Ti surface, effectuating a reduction in the coefficient of friction (COF) from ≈0.57 to 0.17, thereby substantially mitigating wear on the Ti substrate. The grooved surface architecture plays a vital role in storing MXenes and facilitating lubricant replenishment through the stirring effect of frictional stress during subsequent friction process. Further, the continuous decomposition and reorganization of MXene coating results in the formation of a robust tribofilm that resists oxidation and plastic deformation in the subsurface layer, markedly enhancing the friction and wear resistance. These findings are crucial for improving tribological performance in Ti and its alloys and provide a straightforward yet effective strategy for tailoring their tribological properties by integrating LST with 2D material nanocoating.
Retina‐Inspired Nanofluidic Membranes for Underwater Visual Imaging Based on Active Ion Transport
Authors: Wang Lili , Zhang Yuhui , Chen Yupeng , Jiang Lei
Published: March 2024

Through evolution, biological organisms have developed ways to sense light using ion channels, which holds several advantages, such as energy efficiency and water resistance, over humanmade optoelectronic devices. Herein, a retina‐inspired nanofluidic system is presented with a Janus heterogeneous membrane (J‐HM), which can achieve underwater visual imaging through light‐driven active ion transport. The J‐HMs are obtained through sequentially assembled WS2, and a kind of metal–organic framework nanosheets via the reaction between 2,3,6,7,10,11‐hexahydroxytriphenylene hydrate (HHTP) and Cu2+ (Cu‐HHTP). Due to the formed intramembrane electric field caused by the efficient charge separation under illumination, a photovoltaic driving force is generated for active ion transport from Cu‐HHTP to WS2. Furthermore, the unidirectionally active ion transport can be enhanced by self‐diffusion under a concentration gradient. The J‐HM with a single‐pixel design shows a nearly linear response with light intensity and has enough resolution for basic object recognition as well as a long‐term memory after data processing using a defined pixelated matrix, which can pave an avenue for designing more intelligent sensing systems.