bluuebunny/crossref_metadata_2025 huggingface dataset:
Predicting the Pressure Drop in a Cased-Hole Gravel Pack Completion
Authors: Pucknell J. K. , Mason J. N. E.
Published: December 2007

In sand-producing formations, a cased hole gravel pack is usually the preferred completion method. There are various reasons why the alternatives, an open hole gravel pack or a sand consolidation treatment, may not be suitable. However, the productivity of the cased hole gravel pack is much poorer than the alternatives because of high mechanical skins.

Despite the importance of this mechanical skin, the existing pressure drop prediction models are incomplete. Many papers deal with the region of linear flow in the casing/cement tunnels and the flow through the gravel between casing and screen. What happens just outside the casing is rarely mentioned, even though the pressure drops beyond the casing may be significant.

One complication is that perforation tunnels in the formation might either remain intact or they could collapse before gravel packing, creating a void behind the casing.

This paper presents new methods for predicting the pressure drops outside the casing and so allows the construction of a comprehensive model for cased hole gravel pack productivity. A newly-developed finite difference computer simulator was used to produce a general method for intact perforations packed with gravel. For collapsed perforations, an analytical method was developed which is based on the amount of gravel placed behind the casing.
Alwyn North Brent East Panel: Detailed Reservoir Analysis To Improve Reservoir Management and Recovery
Authors: Montmayeur Hugues , Rae S. F. , Coombes T. P.
Published: December 2007

The Brent East reservoir of the Alwyn North Field, with few producer wells and a relatively short production life, represents a challenge for data gathering and reservoir management. Accurate reservoir description had to be obtained rapidly to adjust to unexpected events in order to maximise recovery and prepare enhanced oil recovery programmes.
Real-Time Compression of Logging Data
Authors: Gardner W. R. , Sanstrom W. C.
Published: December 2007

The high telemetry data rates required by state-of-the-art downhole imaging tools have made real-time tool data compression desirable. This increases the effective telemetry data rate and decrease data storage requirements. A variety of lossless and lossy data compression techniques are available for possible logging applications.

Lossless variable-length-coding techniques are applied to different classes of well log data (i.e. dipmeter, density, imaging tools …) to determine the achievable compression ratios and feasibility for real-time processing. Compression ratios of ranging from 1.2:1 to 22:1 are achieved depending on the type of log data.

Lossy image compression techniques developed by the telecommunications industry for the transmission of high definition images over reduced bandwidth channels are adapted to provide real-time compression of imaging logs. The modified image compression algorithms are used to compress log images from a circumferential acoustic scanning tool. Circumferential Acoustic Scanning Tool images compressed by a factor of 20- to-1 were barely distinguishable from the original uncompressed images. Most of the important geologic features are still preserved when the images are compressed at ratios exceeding 80-to-1.
Computation of Test Area of Investigation in Nonradial Geometries
Authors: Ehlig-Economides C. A.
Published: December 2007

Average pressure and permeability values from formation and well tests apply within the area or volume investigated. To integrate these measurements with each other and with other measurements sensitive to permeability and reservoir heterogeneity, it is essential to understand where these values are meaningful. From the practical point of view, the pressure gauge sensitivity is also a consideration.

The conventional approach for a well test is computation of the test radius of investigation. This technique has no application for tests that terminate in a nonradial geometry. Field data that have been published illustrate tests that have terminated in spherical flow (partially completed well), linear or bilinear flow (hydraulically fractured or horizontal well), pseudoradial flow (hydraulically fractured or horizontal well, well near a linear boundary), linear flow (well in elongated reservoir), and pseudosteady state flow. The test radius of investigation concept is equally unworkable for formation tests.

Simple formulas extend the concept of test radius of investigation to nonradial flow geometries. This approach permits meaningful integration of transient test interpretation results (permeability and average pressure estimates, and characterization of inner and outer boundary geometries) in reservoir characterization and in well productivity evaluation.
Current Water-Control Treatment Designs
Authors: Dahl J. A. , Nguyen P. D. , Dalrymple E. D. , Rahimi A. B.
Published: December 2007

Despite significant improvements in completion technology, water production problems associated with encroachment, channeling, and coning still prevail in' many wells. In this paper, different types of water-producing wells are classified corresponding to their onset mechanisms. Various applications of polymers and cements in minimizing water-oil ratio are reviewed. Methods and limitations of current water control processes are evaluated. A general procedure for designing water-control treatments is presented. This paper also addresses difficulties existing in design and performance of water-control treatments. These include (1) lack of an extensive production history and knowledge of prior stimulation of wells requiring treatment, (2) lack of a systematic approach in treatment design, and (3) improper recovery techniques when returning the well to production. Results of wells treated in various fields are evaluated with respect to methods and chemicals used.

Information presented in this paper will provide the completion engineer a broad knowledge of water-control treatment design parameters and chemical applications currently available within the industry.
Influence of Liquid Hydrocarbons on Gas Hydrate Equilibrium
Authors: Becke Peter , Kessel Dagobert , Rahimian Iradj
Published: December 2007

Experimental investigations on hydrate equilibrium conditions in multiphase mixtures incorporating a gas phase, a liquid hydrocarbon (LHC) phase and an excess water phase were performed. Measurements were conducted in a stirred autoclave at pressures up to 12 MPa and a temperature range of 275 to 295 K.

The gas phase consisted of both pure hydrocarbon gases (methane, ethane and propane) and their mixtures. The LHC phase consisted of pure alkanes, cyclo-alkanes, aromatics, their mixtures, and crude oils. In some experiments methanol was added as hydrate inhibitor. The measurements were performed in the hydrate decomposition mode. They aimed at obtaining data for estimating the influence of crude oils on hydrate equilibrium, and at determining their impact on the inhibiting effect of methanol.

For a constant pressure the presence of liquid hydrocarbons leads to decreasing the onset temperature of hydrate decomposition. Generally, their influence on pure gases is insignificant while it is severe on gas mixtures. The equilibrium temperature reduction increases with decreasing molecular weight and with increasing volume of the liquid hydrocarbons. Some cyclo-alkanes were incorporated into the hydrate structure. The inhibition with methanol is not influenced by any of the liquid hydrocarbons; the temperature depression appears to be additive. These findings are interpreted to depend on the preferential solubility of ethane and propane in the oil phase.
Methods and Results of Risk Assessment for Sour Gas Production Systems
Authors: Fischer Franz
Published: December 2007

In view of the toxic effects of hydrogen sulphide sour gas production systems must be carefully installed and safely operated. Investigation and assessment of greatest possible – although rare-accidents, such as a well blowout or a pipeline rupture, are necessary for the determination of safe distances and selection of appropriate measures for the minimization of potential effects. The calculation methods applied as well as the computer models used and the results obtained are described.
A General Solution of Gas/Water Coning Problem for Horizontal Wells
Authors: Guo Boyuh , Molinard J-E. , Lee R. L.
Published: December 2007

Development of horizontal well technology offers a new approach to reducing gas/water coning effect during oil production. However, further improvement of the oil production rate of horizontal wells is still limited by the encroachment of the water cone when bottom water exists. This paper provides reservoir engineers with a general solution of the gas/water coning problem for horizontal wells. The objectives of this investigation include: (1) to determine the location of the stable water/gas cone, (2) to estimate the critical oil production rate, and (3) to find out the optimum placement of the horizontal wellbore so that the maximum critical oil rate can be obtained.

Using conformal mapping method, the location of the stable water/gas cone is determined as a function of oil rate and wellbore location. The critical oil rate is estimated by examining the profile development of the stable cone. It is found that the critical rate is directly proportional to the effective permeability (kh kv), thickness of the oil reservoir, and density contrast between oil and the coning fluid, and inversely proportional to the oil viscosity. The critical oil rate also depends upon the wellbore location in the oil reservoir and takes its maximum value when the horizontal wellbore is placed at about 70 % of reservoir thickness from the unwanted fluid.
Modified Methods for the Determination of Polyacrylic/Phosphinopolycarboxylic Acid and Polyvinylsulphonic Acid Scale Inhibitors in Oilfield Brines
Authors: McTeir M. D. K. , Ravenscroft P. D. , Rudkin Christopher
Published: December 2007

The use of squeeze treatments to deploy scale inhibitors requires accurate determination of inhibitor concentrations in the returned fluids. This information is used, in conjunction with water chemistry and production data, to determine when to re-squeeze a well. In addition, with tightening environmental legislation becoming more probable, the concentration of production chemicals (including scale inhibitors) which are disposed of in produced waters need to be closely monitored. Current analysis techniques, especially for polymers, have proved problematic in field situations. Two spectrophotometric methods have been modified to analyse for polyacrylic acid, polyvinylsulphonic acid and phosphinopolycarboxylic acid scale inhibitors. The improved techniques have been tested in real oilfield brines and are simple, rapid, reliable and sensitive at the low concentrations found in oilfield situations.
Mathematical Model for the Scale-Inhibitor Squeeze Process Based on the Langmuir Adsorption Isotherm
Authors: Shuler P. J.
Published: December 2007

This paper presents a mathematical model for the scale inhibitor squeeze process. This particular model incorporates the Langmuir adsorption isotherm to describe retention/release of the inhibitor with the reservoir rock. This complements a previous, similar squeeze model based instead on the Freundlich adsorption isotherm. The analytical solution for a simplified version of both models requires only minimal computational effort.

Both models calculate the scale inhibitor concentration in the produced brine versus the cumulative produced water volume (and hence the squeeze lifetime). The Langmuir-based model appears to describe inhibitor return data and squeeze lifetime better for reservoirs containing a significant amount of clays and carbonate minerals. The Freundlich-based model better matches field data from cleaner formations such as are found in the North Sea.

Similar to the previous model, the Langmuir-based formulation illustrates the importance of the retention/release properties on squeeze lifetime. Parameter studies indicate the total amount of inhibitor injected is the most important design parameter controlling squeeze lifetime.
Scleroglucan Behavior in Flow Through Porous Media: Comparison of Adsorption and In-Situ Rheology With Xanthan
Authors: Huang Y. , Sorbie K. S.
Published: December 2007

Scleroglucan is a nonionic polysaccharide biopolymer which has excellent viscosifying power in a wide variety of reservoir brines, shows high shear resistance and possesses good thermal stability. All of these properties are very important for polymer flooding applications. In order to apply this polymer in the field it is also necessary to develop a good understanding of its transport, retention and in situ (porous medium) theological properties.

This paper follows previous Work on the adsorption and the in situ rheology of xanthan biopolymer. An important aspect of the present work is the comparison of biopolymer characteristics between scleroglucan and xanthan. This comparison highlights some clear differences in the effects of polymer concentration and pH on the in situ rheological behaviour, owing to the different ionic nature of these two polysaccharides. The main new results presented in this paper relate to scleroglucan dynamic adsorption/retention and its effect on the in situ rheological behavior of this biopolymer, both in ballotini glass bead packs and in sand packed porous media. It is found that the general adsorption level is lower and adsorption effect on in situ rheology is negligible for relatively homogeneous, higher permeability ballotini packed porous media. However, the behaviour is very different for lower permeability sand packed porous media where scleroglucan shows very high levels of retention and a clear effect of this retention on polymer in situ rheology. The latter case indicates that there are still concerns on the propagation (filterability) of scleroglucan although these may not be a problem at higher temperatures under field flooding conditions.
Partially Hydrolyzed Polyacrylamide (PHPA) Mud Systems for Gulf of Mexico Deepwater Prospects
Authors: Hale A. H. , Mody F. K.
Published: December 2007

ABSTRACT*

For exploration and development drilling of deepwater prospects in the Gulf of Mexico, operators have primarily utilized a high salt (20 percent w/w), partially hydrolyzed Polyacrylamide (PHPA) mud system. This system has been used for many years as one of the most inhibitive water-based mud systems commercially available to the industry. Observations from both the laboratory and the field indicate that shale is stabilized by the presence of PHPA. In this report, laboratory evidence is presented which investigates possible mechanisms by which PHPA influences cuttings as well as wellbore stability. In addition, results are presented which dictate requirements for maintaining an effective concentration of PHPA for shale stabilization and the impact of thinners on shale stabilization.
Asphaltene Stabilization in Alkyl Solvents Using Oil-Soluble Amphiphiles
Authors: Chang Chia-Lu , Fogler H. S.
Published: December 2007

Asphaltene plugging is a known cause of near well-bore formation damage. The stability of asphaltenes is predominantly controlled by the thermodynamic state of crude oil. Changes of temperature, pressure and compositions of crude oil can result in the precipitaion of asphaltene components. In this study, the stability of asphaltenes in alkane solvents was investigated using a series of alkyl benzene-derived amphiphiles. The results indicate that the effectiveness of amphiphiles on asphaltene stabilization are strongly influenced by their chemical structure, including the polarity of head groups, the length of alkyl tails and the existence of extra polar groups. These results also provide the information about the interactions of asphaltenes and resin molecules in the crude oil. The small-angle X-ray scattering technique was used to investigate the physical structure of asphaltenes in the amphiphile/alkane solutions. The results indicate that solubilized asphaltenes can interact with each other or with amphiphiles to form associated colloids. The phenomena of precipitation and dissolution of asphaltenes in the porous media was investigated using visual micromodel experiments. In a dissolution experiment, the oil-soluble amphiphile/alkane solutions were proved to be capable of removing asphaltene deposits from porous media.
The Effect of Structure on Performance of Maleic Anhydride Copolymers as Flow Improvers of Paraffinic Crude Oil
Authors: Son A. J. , Graugnard R. B. , Chai B. J.
Published: December 2007

The study was conducted to generate a mechanistic understanding of treating problematic paraffinic crude oils so that chemical treatments can be designed easily and applied more universally. Two crude oils, sampled from two continents, with very different wax contents and paraffin distributions were used to observe the influence of chemical structure on performance of various flow modifiers. In the industry, there is no known "universal" flow enhancer, however, a great number of wax-treating chemicals are derivatives of maleic anhydride. The study was focused on this widely used chemistry as the results would immediately benefit the industry. The performance of various esters of copolymers of maleic anhydride was compared using laboratory tests designed to simulate field conditions. A correlation between the wax content, the wax composition, the type of copolymer backbone, pendant groups and ester functionalities was found which can be explained through basic principles of solubility and steric hindrance.
Crude Oil Characterization Using Gas Chromatography and Supercritical Fluid Chromatography
Authors: Stadler M. P. , Deo M. D. , Orr F. M.
Published: December 2007

The carbon number distributions of 26 stock tank oils were determined by simulated distillation using gas chromatography and supercritical fluid chromatography using high-pressure CO2 as the carrier fluid. Carbon number distributions determined by the two methods were equivalent within normal experimental scatter. Comparison of the fraction of each crude oil eluted in the GC and SFC analyses indicates that for most oils, a significantly larger fraction of the oil elutes in an SFC analysis. In fact, essentially 100% of the hydrocarbons present in light oils elute from the column. In such cases, the internal standard analysis can be eliminated from SIMDIS without loss of accuracy. Another advantage of SIMDIS by SFC is that there is no danger of hydrocarbon decomposition at high temperature.
The Influence of Crude-Oil Composition on Mineral Adsorption and Wettability Alteration
Authors: Wolcott J. M. , Groves Frank , Lee Hyo-Guk
Published: December 2007

Berea sandstone cores were contacted with six different crude oils to determine the effects of oil composition on mineral adsorption and wettability alteration. The crude oils employed in the study encompassed a wide range of chemical and physical properties. Three different types of Berea sandstone cores were contacted with each crude: dry, untreated cores; cores that contained an initial brine saturation prior to contact with oil; and cores that were treated with potassium hydroxide (KOH) for clay stabilization and contained an initial brine saturation prior to contact with oil. The Amott method was used to evaluate wettability alteration. Thin-sections, total organic carbon (TOC), and Rock-Eval analyses were performed to assess the extent and nature of adsorbed organics.

Positive correlations were noted between wettability alteration and oil resin and asphaltene content, and between the extent of adsorption and oil resin and base content. The extent of adsorption was also found to be inversely related to the oil saturate content. There was little correlation between extent of adsorption and wettability alteration.
Effect of Nonproduced Fluids on Produced Water Treatment Equipment Efficiency
Authors: Bansal K. M.
Published: December 2007

With increasingly stringent environmental limitations on the disposal of treated produced water in offshore operations, it has become even more important to gain a better understanding of the process upsets which contribute to poor disposal water quality. One such process upset is caused by the handling of the non-produced fluids (fluids resulting from well stimulation or remedial operations and from miscellaneous processes such as deck drainage) in water treatment equipment (e.g. flotation cells, hydrocyclones etc.). This paper discusses the results of the field tests with various chemicals, normally present in non-produced fluids, on the performance of a bench model flotation cell. These results are not limited to flotation cells but are also applicable to other water treating equipment such as hydrocyclones. An approach to minimize the impact of the non-produced fluids on produced water treatment equipment efficiency is presented in the paper.
Filter-Cake Formation of Fracturing Fluids
Authors: Prud’homme R. K. , Wang J. K.
Published: December 2007

The buildup of a polymer filter cake on the fracture face during hydraulic fracturing results in a decrease in the rate that water leaks off into the formation. The ability to predict this fluid loss is crucial to correctly design pumping schedules and to predict fracture geometry. It is also critical for the interpretation of the pressure and flow rate logs during fracture treatment. Laboratory tests of dynamic fluid loss are time consuming, and it is not possible to simulate in the laboratory the filter cake characteristics that occur far from the well bore. We have begun a fundamental study of filter cake formation that considers the micro-scale processes that govern cake formation. Filter cake formation is determined by the polymer concentration dependence of the permeability, osmotic pressure, and yield stress in the filter cake --all of which can be independently measured. This model will predict the polymer concentration profile in the filter cake, filter cake thickness, and fluid leakoff as a function of pressure drop across the filter cake. To verify this model we have developed a single fiber fluorescence probe to directly measure the polymer concentration in situ during filter cake deposition. Measurements of the concentration profile are presented for dilute HPG (hydroxypropyl guar) solutions and for 0.48 wt% (40 lb/Mgal) solutions.
Crosslinking of Hydroxypropyl Guar with Metal Ions
Authors: Clark P. E. , Balakrishnan M. , Sundram L.
Published: December 2007

Crosslinking of guar and hydroxypropyl guar (HPG) with metal ions is used extensively in the oilfield to increase the viscosity and thermal stability of solutions made from these polymers. Guar and HPG molecules have cis-hydroxyl groups that can react with metal ions or metal ion agglomerates to form crosslinks between polymer molecules. Crosslinking results in a viscous, gel-like solution that is difficult to characterize rheologically.

In this study, data generated with a cone and plate rheometer equipped with a special flow-through test fixture is used to demonstrate how the reaction rate and order change with shear rate. These data are used to develop a model for the reaction that explains not only the observations made in this laboratory, but also the observations made in a number of other research studies. In general, the reaction is fast at low shear rates and almost stops at high shear rates. Reaction rates and orders are a function of shear rate and the reaction product is also shear rate sensitive. Experimental evidence points to a shift from inter- to intramolecular reactions at high shear rates.
Laboratory Acidization of an Eolian Sandstone at 380°F
Authors: Wehunt C. D. , Van Arsdale Howard , Warner J. L. , Ali S. A.
Published: December 2007

Formation damage was simulated by injecting completion fluid into cores and conditioning at 380°F (193°C) overnight. Low hydrofluoric (HF) acid concentrations from 0.05- to 0.1% blended with 10% acetic (HAc) effectively removed the damage. Some other acid systems we tested also worked well. Acidizing did not reduce the measured compressive strengths of the cores; however, microscopic analyses showed layers within the cores may have been seriously weakened.
Divalent Ion-Resistant Polymer Gels for High-Temperature Applications: Syneresis Inhibiting Additives
Authors: Albonico Paola , Lockhart T. P.
Published: December 2007

This paper introduces a new strategy for improving the high temperature stability of acrylamide polymer solutions and gels in aqueous solutions containing the divalent cations Ca2+ and Mg2+. Specifically, certain low molecular weight compounds capable of complexing with the divalent cations are shown to reduce significantly their negative impact on the solubility of acrylamide polymers and on the stability of crosslinked acrylamide polymer gels with regard to syneresis. Where the inhibitor-divalent ion complexes formed are soluble, it should be possible to propagate their polymer or gelant solutions through matrix rock; where insoluble divalent ion-inhibitor complexes are formed, these inhibitors may still be compatible with gel placement in fractured reservoirs or in the immediate vicinity of the wellbore. The results obtained offer the possibility to extend the upper temperature limit for the use of polyacrylamides and acrylamide copolymers in brines in both polymer flooding and polymer gel treatments.

Related studies show that pH is a key factor influencing the solubility of acrylamide polymers in the presence of divalent cations. This fundamental variable has been overlooked in earlier studies correlating PAAm solubility with the degree of polymer hydrolysis, divalent cation concentration, and temperature.
Weak Gel Formulations for Selective Control of Water Production in High-Permeability and High-Temperature Production Wells
Authors: Kohler Norbert , Rahbari Ramine , Han Ming , Zaitoun Alain
Published: December 2007

Two gelling systems involving a thermally stable biopolymer-namely, polysaccharide G- and two different crosslinkers-namely, X-linker A and X-linker B- have been tested in the lab for water control applications. The methodology involved tube tests to check the phase diagrams, kinetics and stability of the gel under various temperature, salinity and pH conditions. The gel formed with X-linker B was shown to be much more stable and easier to control than the gel formed with X-linker A. With the X-linker B / Polysaccharide G system, at neutral pH, the kinetics of gelation was extremely slow at room temperature, but quicker above 70°C. Such a system can thus be mixed in surface facilities without any risk of premature gelling and behaves like a single polymer solution during the injection phase. In high-permeability cores, the weak gel formed with X-iinker B / Polysaccharide G was shown to induce a drop in the relative permeability to water an order of magnitude greater than the single polymer, while maintaining very good permeability to oil.
Quantifying the Impact of Geological Uncertainty on Reservoir Performing Forecasts
Authors: Ballin P. R. , Aziz Khalid , Journel A. G. , Zuccolo Luca
Published: December 2007

This study addresses the problem of transferring uncertainty in the geological model through the flow simulation model (the comprehensive simulator – CS) up to the reservoir production forecasts. The uncertainty in the geological model is characterized by the differences between many equally probable reservoir descriptions that honor available data and that are generated by geostatistical stochastic simulation. The uncertainty in the production forecasts can be characterized by the variability or spread in the responses derived from the flow simulation, or more precisely by the probability distribution of response variables, such as cumulative oil production, oil recovery, breakthrough time, cumulative water-oil ratio, etc.

A new methodology to perform this transfer of uncertainty is summarized. Each reservoir description is first ranked using a fast simulator (FS) rather than the comprehensive flow simulator (CS). A few selected descriptions are then processed through the CS to generate an approximate probability distribution of the reservoir production response.

This new methodology is applied with a coarse grid as the FS model to a two-phase, three-dimensional field scale problem with five producing wells, 8×106 STm3 original oil in place, and a very large and active aquifer. The impact of uncertainty in absolute permeability and porosity on the field cumulative oil production is considered over 7.8 years of production. Good results are achieved with a 85% to 93% reduction in the computer time over the use of the CS alone. The favorable results achieved show that extension of the proposed approach to other types of problems is worthwhile.
Parallel Nested Factorization Algorithms
Authors: Maksimov M. M. , Galushko V. V. , Kutcherov A. B. , Surguchev L. M. , Bratvold R. B.
Published: December 2007

This paper presents a new technique for solving the linear equations arising in reservoir simulation using multiple processors in parallel. The parallel algorithms for the Nested Factorization method are developed and implemented on a network cluster of highperformance IBM RISC System/6000 workstations as well as on a network of transputers. It is demonstrated on different 3-D data sets varying from 10,000 to 750,000 grid cells that a very high efficiency is achieved on MIMD, local memory, parallel platforms.
Implementation of an Adaptive Implicit Method
Authors: Young L. C. , Russell T. F.
Published: December 2007

This paper describes an Adaptive Implicit Method (AIM) for reservoir simulation. The method is based on an extension of the generalized compositional solution procedure. In addition to the creation of a robust method, we have tried to minimize the overhead associated with the method, so that our implementation is almost as fast as an IMPES (implicit-pressure-explicit-saturation) method when few implicit blocks are needed. Several test problems demonstrate important aspects of the switching logic and the tradeoffs between large highly implicit time steps and smaller time steps with less implicitness. We find that in most cases the greatest efficiency occurs when only a small number of blocks (less than 5 percent) are treated implicitly. In many cases the most efficient method is IMPES with time steps selected using the numerical stability calculations of AIM, Smaller time steps lead not only to higher efficiency, but also to solutions with less numerical dispersion. In general. AIM appears to benefit compositional problems more frequently than black oil problems.
The Productivity Index of an Inclined Well in Finite-Difference Reservoir Simulation
Authors: Lee S. H. , Milliken W. J.
Published: December 2007

In finite difference reservoir simulation, a well is generally treated as a point source or sink. As a result, a well productivity index must be specified to relate the difference between wellblock pressure and wellbore pressure to the production rate. However, analytical formulas for productivity indices are known only for a vertical or horizontal well in a homogeneous formation. In this paper, the method of reflections and slender body theory are shown to provide a means to obtain accurate measures of the productivity index in complex reservoir formations.

Using slender body theory, we have derived an asymptotic solution of single-phase flow around an inclined well that is applied here to the determination of the productivity index. The method of reflections can account for the presence of layer boundaries through the application of image solutions. In combination, these techniques permit the calculation of the productivity index in anisotropic formations with layer boundaries. A comparison of the results with numerical solutions verifies their accuracy. The previous formulas sire shown to be recovered as a special case.

Several examples are presented. The effect of layer boundaries on the productivity index is shown in both two and three dimensions. We consider both permeable and impermeable layers. We also investigate the productivity index of an inclined well in a layered anisotropic formation.
The Prediction of Waterflood Performance in Mixed-Wet Systems from Pore-Scale Modelling and Simulation
Authors: McDougall S. R. , Sorbie K. S.
Published: December 2007

The wettability characteristics of a porous medium play a major role in a diverse range of measurements including: capillary pressure data, relative ^rmeability curves, electrical conductivity, waterflred recovery efficiency and residual oil saturation. This study descritos the development and implementation of a pore-scale simulator capable of modelling multiphase flow in porous media of nonuniform wettability. By explicitly incorçxrating pore wettability effects into a steady-state mtoel, it has toen ^ssible to explain many experimental observations from a microscopic standpoint.

Results are presented which show how a (the fracrion of pores which are assigned oil-wet characteristics) affects resulting capillary pressure and relative Jtermeability curves. Simulated capillary pressure data demonstrate that some standard wettability tests (such as Amott-Harvey and free imbibirion) may give spurious results when the sample is fractionally-wet in nature. The corresponding relative pemeability curves have been used to calculate waterflood displacement efficiencies for a range of wettability conditions, and recovery, is shown to to maximum when the oil-wet pore fraction approaclies 0.5.

Furthermore, a novel test is promised which could to used to determine the wettability of both fractionally-wet and mixed-wet jxrrous media. To date, no such satisfactory test exists.
Fully Implicit Simulation on the Connection Machine
Authors: Dupuy Alain , Killough J. E.
Published: December 2007

A fully-implicit, black-oil, reservoir simulator has been successfully ported to the Connection Machine massively parallel computer. Several problems with up to sixty-four thousand cells were simulated on a 4K processor Connection Machine 2 with performance similar to that of a large-scale, shared-memory, supercomputer. Scaled performance on a 64K processor CM-2 exceeded 1 GFLOP. Key to the parallelization of the model was the development of a fully-implicit linear equation solver based on the constrained pressure residual technique of Wallis1. Implementation of the solver involved the use of both multigrid-like and conjugate residual acceleration techniques. The effect of implicit well equations on the solver performance was investigated. Degradation of solver performance with problem and time step size was also investigated. Finally, the effect of communication overhead on model performance was evaluated for several cases.
A New High-Performance Linear Solution Method for Large-Scale Reservoir Simulation
Authors: Wallis J. R.
Published: December 2007

The solution of nonsymmetric linear systerns associated with a large three dimensional grid is frequently the most computationally expensive part of the reservoir simulation process. A new highly efficient iterative technique has been developed which significantly improves simulator performance particulary on vector computers such as the Cray Y-MP. The new preconditioning MVP combines power-ful approximation techniques used in preconditionings such as ILU(O)1, MILU(0)2, Nested Factorization3, INV4 and RS/ILU(0)5 with new ideas to develop a hybrid preconditioning very amenable to vectorization yet is very robust. The method has applicability to three dimensional grids using the conventional 7-point IMPES or implicit finite difference formulations and efficiently treats logically vertical faults and pinchouts. The method also reduces work and storage requirements by using a reduced system iteration.
Cost Control and Risk Mitigation of Major Projects
Authors: Caddy D. G.
Published: December 2007

In this paper and presentation, the four major types of estimates will be discussed, i.e., capacity factored, equipment factored, semi-detailed and detailed. Key relationships between particular portions of estimates will be discussed such as the relationship between direct field labor and indirect field costs.

Having set the basis for developing a project's cost through estimating, the paper will then list and discuss the fifteen key steps which must be followed to control the costs of a project.

Next, the subject of allowances and contingency will be discussed and defined and the differences between the two will be highlighted.

Having established exactly what contingency is, the subject of risk analysis through RANGE estimating will be discussed. The methods used to establish a precise contingency and probability of an over/under run will be discussed.

Finally, the paper will discuss the methods by which a project manager, owner or contractor can mitigate risks; that is to eliminate, transfer or minimize their effect.
Jerneh Gas Project Challenges and Implementation Performance
Authors: Perreau M. E.
Published: December 2007

The Jerneh gas project is part of Peninsular Malaysia's Gas Utililization Project, a mammoth undertaking to provide gas from the offshore fields off Malaysia's East Coast, to power stations and other industrial users throughout Peninsular Malaysia and Singapore. Prior to 1992, the only customers of the offshore Peninsular Malaysia gas were a local power station, and a steel mill in Terengganu, linked to the "Phase I" pipeline system shown in the map of Fig. 1. The Bekok platform is Esso Production Malaysia Ine (EPMI)'s gas collection platform for existing associated gas fields. The Duyong and Sotong platforms are gas production/compression platforms operated by PETRONAS (the Malaysian national oil company).

In late 1991, the onshore pipeline system was extended by PETRONAS to cover the west and south coasts of Peninsular Malaysia and Singapore depicted in the map (Fig. 1) as the "Phase II" system. With the completion of the Jerneh platform and offshore trunklines, Jerneh became the primary source of supply to an increased number of customers in the wider Phase II gas network. Jerneh is estimated to have three TCF of non-associated gas. Phase I customers were utilizing about 120 MSCFD and the demand is expected to initially step-up to 400 MSCFD in 1992 and progressively increase thereafter.

This paper provides an overview of the USS400M Jerneh project for which detailed design commenced in 1989 and was commissioned in 1992. The paper describes the technical challenges, project execution, safety record and actions to achieve the fast track schedule for this project.
Aluminum Chemistry Provides Increased Shale Stability With Environmental Acceptability
Authors: Clark D. E. , Benaissa Saddok
Published: December 2007

Previous laboratory and field evidence have proved that complexed aluminum compounds can be utilized in water-based drilling fluids to increase shale stability. This environmentally-sound chemistry has never been used to its utmost potential, primarily because the previous aluminum complex required pre-solubilization and pH neutralization. The low aluminum concentration resulted in high dilution volumes with associated increased drilling fluids cost, while taxing the surface mixing equipment on the drilling rig.

A newly invented approach simplifies the use of aluminum chemistry in drilling fluids. This new chemistry is the result of laboratory investigations that confirmed the inhibition characteristics on Wyoming bentonite. Further laboratory work proved the effectiveness of this chemistry on numerous shales of varying mineralogy. Field evidence in several areas of the world has reconfirmed that this aluminum chemistry can, cost effectively, be used to reduce the hydration rate of troublesome shales, stabilize well-bores, and reduce drilling problems. This chemistry has proved to have application when drilling troublesome shales with freshwater systems on land, seawater systems offshore, and high chloride systems in deepwater operations.

This approach for drilling fluid chemistry provides an environmentally sound replacement for current additives. It demonstrates increased shale stability without the addition of potassium or chloride ions. The resulting reduction in clay hydration eliminates the need for chrome lignosulfonate additions, especially in polymer-based drilling fluids.
A New Technique To Predict Multilayered Reservoir Characteristics Using Pulse Testing Data
Authors: Osman M. E. , Mohammed S. A. E.
Published: December 2007

In this study, a mathematical model was developed to present pulse and interference testing for multilayered reservoirs. It was found that apparaent storativity calculated from pulse testing data is always less than or equal to the actual storativity of the reservoir and that apparaent transmissibility is always greater than or equal to the actual transmissibility. For short cycle intervals, the fractional production rate from a particular layer is not proportional to it's tranmsissi-bility fraction. The effect of storativity variation on fractional production rate is negligible. Wellbore damage; affects both apparent transmissibility and storativity. Less accurate estimation of reservoir characteristics is obtained using pulse-test data as the contrast in reservoir properties increases and vice versa. A new approach is suggested to use data of single well test and pulse test to estimate properties of individual layers. The approach is demonstrated by a three-layer numerical example.
Reservoir Characterization: Efficient Random-Walk Methods for Upscaling and Image Selection
Authors: McCarthy J. F.
Published: December 2007

In recent years, with the increased availability of powerful computers, there has been much emphasis placed on improving the characterization of heterogeneities in reservoirs for simulation purposes. Software packages are becoming available which enable geologists and engineers to combine their field knowledge with the sophisticated techniques of geostatistics to generate stochastic simulations of the geological and petrophysical reservoir data. These simulations produce a (theoretically infinite) number of possible "realizations" of the reservoir, honouring the available data points and having the same histogram and spatial variability as the data. Fluid flow simulations appropriate to the recovery project being evaluated can be performed on an array of possible realizations to give a range of possible outcomes for important quantities such as the oil recovery factor. The object of the procedure is to facilitate a quantification of the uncertainties caused by the lack of detailed knowledge of the reservoir heterogeneity.

This paper addresses two difficulties associated with the above procedure — those of "image selection" and "upscaling". The stochastic simulations of the reservoir geology are usually performed on fine-scale grids to incorporate all the lithological data available from logs, cores and seismic. Before performing fluid flow simulations it is necessary to choose a few possible realizations representing the "best", "worst" and "average" cases. This is the problem of image selection. It is also necessary to use averaging procedures for the petrophysical parameters in order to scale the grid to a size accessible to reservoir simulations. This is the problem of upscaling. It is particularly difficult to devise efficient upscaling procedures for permeability because it is a transport parameter.

It will be shown how random walk methods provide an efficient and accurate alternative to costly fine-scale finite difference computations for upscaling and image selection in reservoir characterization. Simulations are performed on a variety of different realizations of the permeability distribution, generated by geostatistical, fractal and boolean methods, including the difficult case of sandstone/shale reservoirs. Both 2d and 3d examples are presented. Comparisons are made with finite difference simulations and with a variety of approximate methods suggested in the literature.
Development of New Modified Black Oil Correlations for Malaysian Crudes
Authors: Omar M. I. , Todd A. C.
Published: December 2007

In reservoir engineering calculations, reservoir fluid property data are one of the important input data sets. These data can be obtained either by conducting a laboratory study on reservoir fluids or estimated from empirical correlations. Although laboratory results give better accuracy where controlled reservoir conditions can be imposed, the results are heavily dependent on the validity of the reservoir fluid samples, especially when the reservoir has depleted below the bubble point pressure. In situation where the experimental data cannot be obtained or there is a need to cross check the laboratory results, empirically derived PVT correlations can be used to estimate the physical reservoir fluid properties. Since no black oil correlations have been developed for Malaysian crudes and none of the existing correlations give good estimates of fluid property for Malaysian crudes, this paper describes the development of suitable black oil correlations which give results more accurate than any correlations available in the literature.

A total of 93 PVT data taken from various Malaysian offshore oil-fields was used in the study. The PVT data consist of oil gravity range from 26.6 "API to 53.2 "API and bubble point pressures of 790 psig to 3851 psig. The crudes are essentially free of hydrogen sulphide with low nitrogen content (maximum of 1.15 per cent).

Using both non linear and linear regression analyses, new black oil correlations (of bubble point pressure and bubble point oil formation volume factor) were established for Malaysian crudes. These new correlations were developed based on Standing's existing equations. The most sensitive coefficient in the Standing correlations was determined and expressed as a linear function of other independent variable PVT parameters. The accuracy of the new correlations was determined by conducting statistical and graphical error analysis.

The results show that the new correlations give better accuracy in estimating reservoir fluid properties of Malaysian crudes than other known correlations available in the literature. The new correlations give low values of absolute average percent relative error, standard deviation with correlation coefficient values close to an ideal value of 1.0.
Development Planning in a Mature Oil Field
Authors: Pang S. S. M. , Faehrmann P. A.
Published: December 2007

The implementation of a plan for a 3-rig revisit campaign in a mature field, needs not only a sound multi-disciplinary field review as a basis, but also very detailed day-to-day actual well planning during the drilling phase. This is due to the need for constant evaluation of the impact of incoming well data on the yet to be drilled wells. Samarang Revisit Campaign II provides an Illustration on how a closely coordinated effort achieves the aim of maximising reserves in the most economic fashion. This effort is discussed in the context of a Joint Venture & Production Sharing Contract (PSC) environment.