bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Fuzzy Logic for Determining Production Allocation in Commingle Production Wells
Authors: Widarsono B. , Atmoko H. , Robinson W. , Yuwono I. P. , Saptono F. , Ridwan Ridwan
Published: January 2008

For oil or gas fields with stratified reservoir layers, detailed production contribution for individual layer is always desired. Unfortunately, in some particular cases, production wells are completed following commingled scheme. This is worsened further if only very few production tests are run for the field. This is the case for the Central Sumatera field with its 95 commingled production wells, among which only a few had undergone production tests and none of them have ever undergone production logging. Problems rise when the occassion came in which detailed production contribution from individual reservoir layer is required for the field's reservoir simulation modeling and production evaluation/prediction.

This paper presents an approach to solve the problem. The approach is basically based on the application of soft computing (Fuzzy Logic) to investigate pattern of relationships between production contribution of layers in commingle wells and rock petrophysical data as well as other relevant geological/engineering data. For the purpose, thirteen wells (key wells) that have production tests are assigned, among which three wells are assigned for checking the validity of the recognised pattern. Using the validated most valid pattern, individual layer's production allocation for other wells are determined with well-log analysis data as the major input.

Result estimates for the candidate wells are better compared to results produced by the conventional method of productivity index (PI) analogy. The resulted variation in water cut and separate oil and water split factors appear to be more realistic from any point of view.
Satisfying Profitability and Non-Flaring Gas Policy in an Emerging Gas Market Context: A Case History
Authors: Boni G. , Castano D. , Dresda S. , Esor E. , Monico C.
Published: January 2008

A zero gas flaring target was established by Nigeria based on the Kyoto Protocol, meanwhile a gas market was emerging in the Country.

This paper deals with a Nigerian onshore multilevel oil field on production for thirty-one years, where the associated produced gas was flared except a part that was re-injected.

An integrated revision study was carried out to investigate the possibility to improve the oil recovery and simultaneously honour the target of not flaring the gas and seize the gas market opportunity.

Several scenarios were studied based on the main alternative concepts to increase the gas injection activity or change the drive mechanism by performing the water injection, with the fixed constraint of not flaring the gas. An upgrade of the existing gas compression unit was required for the gas injection option, whilst a new plant was necessary for the water injection option. The benefit of higher oil recoveries due to gas injection and the advantage of larger gas amounts for the market in the case of water injection were assessed through the economic evaluation.

The highest profitability was achieved in the case of a gas injection increase followed by the conversion of the injectors into gas producers and was the consequence of the gas sale, which largely compensated the shortfall in oil recovery.

The conclusion was that it was possible to satisfy both the zero gas flaring requirement and the economic profitability through the opportunity of the gas market.

A lesson learnt was that the technical results based on the oil recovery alone were not enough to select the optimum development scenario, since the overall economic evaluation played the fundamental role.
Comparison of Well Productivity between Vertical, Horizontal and Hydraulically Fractured Wells in Gas-Condensate Reservoirs
Authors: Hashemi A. , Gringarten A. C.
Published: January 2008

Gas condensate reservoirs usually exhibit complex flow behaviors due to the build-up of condensate banks around the wells when the bottomhole pressure drops below the dew point. The liquid phase accumulation in the near-wellbore region forms a ring that reduces the gas relative permeability. As a result, gas production decreases and the liquid phase which is a significant part of the value of the field remains in the reservoir.

Various solutions have been implemented in order to remediate such a productivity loss. They include drilling horizontal wells instead of vertical wells1-3, hydraulically fracturing vertical wells before or after the development of the condensate bank, and acidizing after the condensate bank has formed4-14.

In this work, we used reservoir simulation to quantify the increase in well productivity from different remediation solutions and assess their effectiveness. The empirical correlations needed to model non-Darcy flow and capillary number effects, which are among the main parameters that control gas condensate well performance, were calibrated with actual well test data.

As should be expected, we found that horizontal wells and hydraulically fractured vertical wells improve well productivity. The degree of productivity enhancement, however, depends on well and reservoir parameters such as horizontal well lengths, permeability anisotropy, fracture length and fracture conductivity. Different simulation models were run above and below the dew point pressure at the same reservoir and flow conditions. The results of our simulations show that horizontal wells enhance productivity significantly below the dew point. Performance improvement with hydraulic fractures, on the other hand, depends on facture length and fracture conductivity.
Recommended Practice for Overbalanced Perforating in Long Horizontal Wells
Authors: Chang F. F. , Mathisen A. M. , Kâgeson-Loe N. , Walton I. C. , Svane G. , Midtbø R. E. , Bakken I. , Rykkje J. , Nedrebø O.
Published: January 2008

Completing offshore horizontal wells often requires killing the wells immediately after perforating before pulling the gun out of the hole and installing the rest of the completion hardware. Perforating practice varies from operator to operator. Some operators prefer to perforate in a clear fluid and spot a kill fluid for well control afterwards. While others perforate directly in a solid containing kill fluid. Both methods are done in overbalance. A two-year extensive research program was carried out to quantify the formation damage caused by these perforating practices.

The testing was conducted under downhole conditions in a large-scale laboratory setup, which physically simulates the wellbore and the reservoir, as well as the perforating and production processes. Tests were designed to study the pressure dynamics during perforating; to gain understanding of the effect of the perforating pressure dynamics on fluid loss control and formation damage; to select the most suitable kill fluid; and finally to provide overbalanced perforating design guidelines for production optimization.

The core test results showed that perforating design not only determines the skin damage caused by debris and grain crushing, but also plays a key role in controlling fluid loss, which strongly influences the permeability and productivity of the reservoir. Therefore, proper perforating design not only involves selecting the right shaped charges and gun hardware, but also it needs to take into account the perforating pressure dynamics, fluid formulation, and completion sequence.

In addition to the core flow testing, petrographic studies were performed on the perforated core samples to allow visual observation of the rock alterations caused by perforating and kill fluids.

This paper presents the findings in formation damage mechanisms during overbalanced perforating and kill processes and provides recommended practices in both job design and fluid selection for this type of operation in long horizontal wells.
Learning the Right Lessons—The Key to Delivering a Record ERD Well in the Caspian
Authors: Kidd G. N. , Tukshaitov A. , Najafov F.
Published: January 2008

The Operator has been developing oil reserves from an Early Oil Production (EOP) facility in the Caspian Sea since 1997. Because of the location of the platform, accessing the Northern reserves required the implementation of an ERD drilling program. Four ERD wells have been drilled since 2001. The last well was delivered on time and on budget to a measured depth of 7472m, and a step out of 6,315m making it the longest well drilled in the Caspian basin to date.

This paper summarizes progress that has been made towards delivering successful ERD wells in the difficult Caspian basin. It describes how the basis of design for ERD wells 1 and 2 drew on the lessons from other projects including Wytch Farm, and why that philosophy did not produce the planned results.

The paper will highlight the lessons learned applied to the third well, which was delivered with the majority of the well design objectives satisfied but over budget and with a significant amount of Non Productive Time (NPT). The paper will focus on the planning and execution of the fourth well, detailing how the right lessons, key technologies, key drilling practices, and right resources were applied to deliver the longest ERD well in the Caspian on time and within budget with a total NPT of less than 16%.

The key components of success will be explored in detail. These include implementation of new technologies, including "stress cage", closed end conductor driving, cuttings flow metering, formation pressure LWD tools and"Geosteering" to manage geological uncertainty and allow excellent execution of the plan. The paper will discuss how a systematic, rigorous planning approach was applied. The modeling and simulation techniques critical to success used by the onshore planning team and also employed offshore using real time data for critical decision making will also be described

Finally the process whereby this plan was handed over to the execution team offshore will be explained illustrating the importance of engaging the offshore team in the planning of this type of well. This was linked to the whole team's involvement in the development of the practices and procedures and use of the Technical Limit process on simpler wells before utilising them where there was no room for error.

In conclusion, the paper will show how an integrated, multidisciplinary team can overcome significant technical challenges with the right processes, people, technology and support to deliver a successful well.
Applications of Sequence Stratigraphy and Geological Modeling to Mature Field Development: Khalda Ridge, Western Desert Egypt
Authors: Mahgoub I. S. , Mowafi K. , Hussein H. , Wehr F.
Published: January 2008

A joint study integrating geological and engineering data was undertaken tolocate infill wells and to optimize the injection pattern in Hayat-Yasser, Kenzand Salam fields in the western desert of Egypt. The focus of this work was theCretaceous Bahariya and Abu Roash "G" formations which are sedimentologicallydescribed as estuarine to shallow-marine sandstones deposited in a mixedclastic-carbonate ramp setting.

All major seismic surfaces were remapped using pre-stack time-migrated data.A detailed sequence-stratigraphic framework based on core description andpetrophysical analysis provides the static reservoir framework. These geologicdata are incorporated in a detailed 3D geological model, which forms the basisfor all structural and reservoir mapping.Pressure and production datawere analyzed within this framework, in order to identify potential infill andrecompletion opportunities as well as potential improvements in changingwater-flood pattern from peripheral to internal and to dedicated injection.
Rapid Flash Calculations for Compositional Modeling
Authors: Li Y. , Johns R. T.
Published: January 2008

The computational time for conventional flash calculations increasessignificantly with the number of components making it impractical for use inmany finely-grided compositional simulations.Previous research toincrease flash calculation speed has been limited to those with zero binaryinteraction parameters (BIPs) or approximate methods based on an eigenvalueanalysis of the binary interaction matrix.Practical flash calculations,however, nearly always have some nonzero BIPs.Further, the accuracy andspeed of the eigenvalue methods varies depending on the choice and number ofthe dominant eigenvalues.

This paper presents a new method for significantly increasing the speed offlash calculations for any number of nonzero BIPs.The approach requiresthe solution of up to six reduced parameters regardless of fluid complexity orthe number of components and is based on decomposing the BIPs into twoparameters using a simple quadratic expression.The new approach is exactin that the equilibrium phase compositions for the same BIPs are identical tothose with the conventional flash calculation; no eigenvalue analysis isrequired. Further, the new approach eliminates the Rachford-Riceprocedure and is more robust than the conventional flash calculationprocedure.We demonstrate the new approach for several example fluids, andshow that speed up by a factor of about 3 - 20 is obtained over conventionalflash calculations depending on the number of components.
Exploration Drilling in the Barents Sea; Prevailing Zero Discharge Regime, Challenges and Learning From Recent Exploration Drilling
Authors: Paulsen J. E. , Hoset H. , Rørhuus T. , Larsen V. , Alm D. , Birkeland Ø. , Marker R.
Published: January 2008

The Barents Sea is an environmentally important ecosystem defined as part of the Arctic. The Norwegian environmental regulation is particular strict for this area, a zero discharge regime prevails. This paper describes the challenges of entering the area for exploration drilling. With reference to a recent operation (2005) a presentation of how the challenges were resolved is given. New procedures and new techniques were implemented to achieve compliance with performance expectations. The succeeding experience lead to important learning that has implications for future exploration drilling in such areas.
A Deepwater Monitoring Design and Program to Assess the Environmental Fate and Effects of Paraffin Based Muds and Cuttings off Sarawak and Sabah (Malaysia)
Authors: Ray J. P. , James B. M. , Dorn P. B. , Farmayan W. F. , Hj-Kip S. , Hii K. K. , Rhodes I.
Published: January 2008

Sarawak Shell Berhad and Sabah Shell Petroleum Co Ltd are companies of the Royal Dutch/Shell group of companies operating in Malaysia under a Production Sharing Contract arrangement. Current drilling activities are located offshore the states of Sarawak and Sabah. Due to difficult downhole drilling conditions, the use of synthetic based mud's have become increasingly more important.

In 2005-6, several deepwater locations will be drilled using non-aqueous based drilling fluids. Of key interest is the availability of paraffin base stock from Shell MDS (Malaysia Sdn Bhd.’s plant in Bintulu). Paraffin based systems are currently in use and found to be effective by other operators in the area. Because paraffins do not currently meet all US EPA laboratory test criteria (toxicity and biodegradability), there is a strong interest in collecting actual field data to assess the environmental fate of such discharges. Shell Malaysia is embarking on a unique field study program to assess the fate of the paraffin based mud's and cuttings in water depths ranging from 300-1,500 m and to compare the data to similar studies with internal olefin mud's.

Shell Global Solutions International B.V., with experience in SBM's and deepwater environmental monitoring, had designed an approach to answer the key questions. The primary local contractor on the project is Petronas Research and Scientific Services Sdn. Bhd. (PRSS). Metocean data from the study area is being used, in conjunction with a state of the art drill mud dispersion model to predict the 3-D accumulation of the cuttings and mud on the seafloor. Gas chromatographic techniques (GC-FID) will be used for identifying and quantifying the presence of paraffins in the marine sediments. Ecological risk methodologies are being used to predict potential benthic impacts. Each of four drilling locations will be sampled post drilling and one year later. This will provide important insight into the weathering rates of paraffins in sediments.

The study design, methods to be employed, and preliminary modeling and ecorisk evaluations are presented and discussed in the paper.
New API Practices for Isolating Potential Flow Zones During Drilling and Cementing Operations
Authors: Bannerman M. , Calvert J. , Griffin T. , Levine J. , McCarroll J. , Postler D. , Radford A. , Sweatman R.
Published: January 2008

This paper summarizes the progress by government and industry representatives of the API Work Group on Annular Flow Prevention and Remediation in studying the causes and prevention of deepwater shallow water flows (SWF) and annular flow incidents in other wells resulting in loss of well control linked to the well-cementing process. An overview is provided on two new API recommended practice publications (RP-65 Parts 1 and 2) that describe preventive and controlling measures for SWF in deepwater wells and for any flow zone in almost any type of well. This includes key well planning, drilling, and cementing practices designed to help ensure isolation of potential flow zones. The paper also mentions plans to prepare Part 3 of RP-65 on prevention and remediation of sustained annular casing pressure during production.

This paper introduces and promotes the use of best practices associated with prevention of annular flow incidents. It will also help inform the industry on pending regulations that may require the use of RP-65 in preparing Applications for Permits to Drill (APD) and in drilling and cementing operations in areas regulated by the MMS (Minerals Management Service) of the U.S. Department of the Interior.
Development and Implementation of a High Strength "Mild Sour Service" Casing Grade Steel for the Kristin HPHT Field
Authors: Nice P. I. , Øksenvåg S. , Eiane D. J. , Ueda M. , Loulergue D.
Published: January 2008

The Kristin Field is a high pressure high temperature gas condensate field located in the Haltenbanken area on the Norwegian Continental Shelf.

The well design and operation challenges during the drilling and completion phases, as well as the long term production phase, of the Kristin wells required the need for a "mild sour service" production casing grade capable of handling large differential pressures and high axial loads. To meet the requirements, the initial selection was a large OD, heavy weight C-110 grade casing. However, the overall casing weight, the annular flow area during cementing and the compression capabilities of the available connections called for a material grade with specified minimum yield strength of 125 ksi (862MPa). This grade would allow for a down scaling of the casing dimensions and the use of qualified premium connections suitable for the Kristin conditions.

The recent development of a 125ksi (862MPa) high strength low alloy (HSLA) steel casing grade for "mild sour service" applications has permitted this specific design requirement to the Kristin production casing OD to be met.

This steels metallurgical design included reducing the dislocation density and controlling carbide morphology to enhance the sulphide stress cracking (SSC) resistance. It was found that vanadium containing steels, produced lower dislocation densities than vanadium-free steels, at same strength levels, because vanadium containing steels were tempered at a higher temperature than vanadium-free steels. The higher temperature tempering enhanced the SSC resistance, as a result of the uniform and spheroidized M3C distribution and decrease in dislocation density. A decrease in chromium (Cr) content, which had little effect on temper softening resistance, was beneficial for preventing M23C6 (M=Fe, Cr, Mo) formation. The 0.5Cr-0.7Mo-0.1V steel without M23C6 carbide had higher SSC resistance than the 1Cr-0.7Mo-0.1V steel.

This paper will describe this specific well design challenge provided by the Kristin field production wells and how this was resolved by the introduction of this new HSLA steel grade. Then explain the detailed metallurgical design development needed to provide improved SSC resistance that was required for the "mild" sour service conditions found in the Kristin reservoir fluids.
Unlocking the Value in West Sak Heavy Oil
Authors: Targac G. W. , Redman R. S. , Davis E. R. , Rennie S. B. , McKeever S. O. , Chambers B. C.
Published: January 2008

West Sak is a heavy oil accumulation within the Kuparuk River Unit on the North Slope of Alaska. It is a Cretaceous, shallow marine sandstone. It contains 7–9 billion barrels of oil in place with an oil gravity that ranges from 10–22 degrees API. Initial oil production began in 1997 at approximately 3,000 BOPD and has increased to over 16,000 BOPD in March 2005. Development plans are in place to achieve a rate of over 40,000 BOPD by 2007.

This paper describes the evolving development plan for the West Sak field, with emphasis on the technical advances that have resulted in large-scale commercial development. Early West Sak development consisted of stimulated vertical wells on a 40-acre waterflood pattern with typical production rates of 150-250 BOPD. Utilizing the evolution in horizontal and multi-lateral drilling technology, the development plan has progressed to extended reach multi-lateral injectors and producers with horizontal and undulating slotted liner completions is excess of 8000 feet per lateral. Peak rates of over 5000 BOPD and sustained rates of over 1500 BOPD have been achieved. With the higher reservoir throughput rates, the distance between wells has increased, reducing well count and improving the development cost per barrel.

Significant changes have also been made to the completion design and production strategy. These include changing from sand exclusion to sand management, adding intervention capabilities with multi-lateral completion equipment, optimizing the drill-in-fluid, and adding a backup gas lift system to the standard electrical submersible pump (ESP) completions.

Finally, the enhanced recovery process has evolved from waterflood to a viscosity reducing water-alternating-gas (VRWAG) process, improving expected recovery by 2-3 percent of OOIP.

Application of new technology and optimized development decisions have reduced development cost by approximately 25% in terms of $/BOE and unlocked value in a major resource.
Diffusion and Dispersion in the Simulation of Vapex Process
Authors: Das S.
Published: January 2008

The solvent based recovery process "Vapex" has a great potential for the recovery of heavy oil and bitumen resources, due to the low energy intensity and reduced GHG emission associated with the process. The process has been extensively investigated in the laboratory models and through numerical simulation studies. This has indicated the technical viability of the process as an alternative to thermal recovery processes, viz. SAGD. In the last few years several proprietary pilot has been developed to establish the commercial viability of this concept.

The most important uncertainty about this process is the rate of mixing of solvent molecules with high viscosity hydrocarbons. Due to low molecular diffusivity the theoretical predictions of extraction rates are significantly lower than the SAGD process. However, the results of physical model experimental carried out by this author showed a considerably higher mass transfer rate at the solvent bitumen interface. The process, whether in the laboratory model or in the reservoir porous media, takes place in a microscopic level. An experimental evidence of this phenomenon will be presented in the paper.

Transferring this microscopic phenomenon into a macroscopic simulation model presents a serious challenge. Artificially higher diffusion or dispersion coefficients are used to match the experimental data. Even with that both the production rate and the solvent saturation profile can not be matched simultaneously. For example the higher dispersion coefficient results in deep penetration of the solvent, resulting in a diffusion zone, thicker than the experimentally determined value. Lower dispersion coefficient results in a lower production rate. Some of these simulation results are presented in this paper. A recent development in the simulation model, Dynamic Grid Refinement, improves the simulation match by allowing the use of smaller grid blocks at the diffusion boundary layer.
Novel Reservoir-Simulation Methods Enable Direct Optimization of Expansion Decisions in Giant Heavy-Oil Field
Authors: Osterloh W. T. , Menard W. P.
Published: January 2008

Giant, geologically complex heavy oil fields can take decades to develop, so development decisions made early in the life of the field can have long-range implications. Decision and risk analysis (D&RA) is often used to make decisions that will maximize risk-adjusted economic benefit. Unfortunately in large heavy oil fields, D&RA can be very challenging due to the large number of variables and the endless number of development and expansion scenarios to analyze. The time needed to complete a D&RA can become prohibitive when full-field reservoir simulation is the main tool for forecasting primary production and well count, with one simulation taking many hours or days to complete.

This paper describes two new simulation tools developed to overcome these challenges: 1) a method for populating a model with hundreds-to-thousands of horizontal wells, and 2) a method to quickly and directly optimize expansion decisions.

A semi-automated spreadsheet-and-simulation method was developed to quickly place and select hundreds-to-thousands of hypothetical/future horizontal wells in a multi-million grid-block model. Because the method automatically accounted for all model static properties and their effects on dynamic production response, the hypothetical wells had productivity characteristics very similar to actual drilled wells placed in the model.

A multi-variant non-linear interpolation method was developed that enabled full-field forecasts – for any combination of acreage allocation, well count, drilling order, and expansion rate constraint – to be calculated in less than 5 seconds, compared to about 20 hours for traditional simulation. Extensive validation work showed that well count and production curves from the spreadsheet virtually overlaid those obtained using traditional simulation of the particular expansion scenario. Such close agreement was possible because the basis of the spreadsheet forecast was utilization of traditional simulation forecasts from a handful of relevant cases.

A key breakthrough beyond just fast forecasting was the coupling of the following three components inside the same spreadsheet: the fast forecasting method, calculation of an economic indicator/objective function (NPV), and commercial optimization tools. This linkage made possible, perhaps for the first time (at least at this scale), realization of direct optimization of any development scenario in a matter of minutes to a few hours, depending on the number of variables being optimized.
Experimental Study on Cuttings Transport With Foam Under Simulated Horizontal Downhole Conditions
Authors: Chen Z. , Ahmed R. M. , Miska S. Z. , Takach N. E. , Yu M. , Pickell M. B. , Hallman J.
Published: January 2008

The use of drilling foams is increasing because foams exhibit properties that are desirable in many drilling operations. A good knowledge of cuttings transport efficiency under downhole conditions is essential for safe and economical foam drilling. Previous cuttings transport studies with foam are limited to low pressure and ambient temperature conditions. No experimental study has been conducted under downhole (i.e., elevated pressure and temperature) conditions. This paper presents an experimental study of cuttings transport with foam in a horizontal annulus under simulated downhole conditions.

Experiments were conducted to determine the effects of polymer additives, foam quality, flow velocity, temperature, and pressure on foam cuttings transport. Experiments were carried out at elevated pressures (100 to 400 psi) and temperature (80 to 170°F) conditions in a unique full-scale flow loop with a 73-ft long test section (5.76×3.5 in. concentric annulus). A field-tested commercial foam system consisting of surfactant (1% v/v) and hydroxylethylcellulose polymer (HEC) was used in the experiments. Three different polymer concentrations (0.0, 0.25, and 0.5% v/v) were tested. Foam quality was varied from 70 to 90%.

During a test, cuttings were injected continuously to the flow loop until a steady state condition was established in the test section. In-situ cuttings volumetric concentration (i.e., the ratio of the volume of cuttings in the suspension and the cuttings bed to the volume of the annulus) in the test section was determined using nuclear densitometers, load cell measurements, and by weighing cuttings flushed out of the flow loop. Test parameters recorded during the experiments were: liquid and gas injection rates, cuttings weight in injection and removal towers, mixture density, friction pressure loss, and pressure and temperature in the annulus.

Two flow patterns, stationary cuttings bed, and fully suspended flow, were observed during the cuttings transport tests. The flow pattern depends on polymer concentration, foam quality, and annular velocity. Annular flow velocity, foam quality, and polymer concentration all affect cuttings transport efficiency and frictional pressure loss. This paper will help to better design foam drilling and cleanup operations.
New Shape Factor for Vertically Fractured Well Produced at Constant Pressure
Authors: Haryanto E.
Published: January 2008

The Dietz shape factor is one of the key parameter for predicting production performance of oil and gas wells. Except for vertical well, the libraries of shape factor are currently available only for a well producing at a constant rate. This condition however is unlikely to occur in the reality as compared to condition under a constant pressure.

As hydraulic fracturing plays a major role in well stimulation to increase production, there is a need to develop Dietz shape factor for hydraulical vertical fracture well producing at a constant bottom hole pressure.

In this paper, by using reservoir simulation, the new shape factors are developed for closed rectangular reservoir, with single vertical fracture well, at infinite and finite fracture conductivity, under a constant bottom hole pressure. The new shape factors should replace Dietz shape factors for vertical hydraulic fracture well producing at a constant rate, particularly when evaluating the production performance of a vertical fracture well at a constant bottom hole pressure with finite fracture conductivity.
Fabrication of Synthetic Reservoir Rock Core and Application to NMR Logging
Authors: Ronan L.
Published: January 2008

The Petroleum industry for decades has relied on the acquisition and correct interpretation of reservoir logs to provide important reservoir information used to determine the "payzone" of the reservoir. One such logging tool is based on the principles of Nuclear Magnetic Resonance (NMR), the alignment of hydrogen proton spins with an applied magnetic field and the subsequent proton relaxation observed when the external magnetic force is removed. This technique has become a useful non destructive and seemingly matrix independent method for determining pore size distribution in fluid filled pores. However, the presence of paramagnetic material such as iron or manganese within reservoir rock, particularly sandstones, increases the proton relaxation rate and as a result the pore size distribution appears smaller and subsequent permeability calculations will be erroneous.

The significance of this paramagnetic material and its effect on surface relaxation is the essence of this study. There were two series of synthetic core samples created, one with a varying paramagnetic concentration and constant grain size and the other with a varying grain size and constant paramagnetic concentration. NMR experiments were conducted using these core samples to study the surface relaxivity effect

The NMR analysis of the synthetic core samples has shown a strong correlation to NMR theory.
An Integrated Method for Modeling Fluid Saturation Profiles and Characterising Geological Environments Using a Modified FZI Approach: Australian Fields Case Study
Authors: Biniwale S.
Published: January 2008

Laboratory derived capillary pressure data can be seen as an important tool for the purpose of establishing water saturation- height relationships as a function of rock type, forming the basis for a number of petroleum engineering and geoscience estimates. A modified ‘FZI-λ’ method, capable of giving better estimates of fluid distribution for Australian reservoirs, is proposed. The new methodology is particularly well suited for interpolating among different lithologies and diverse rock types as evident from a comparison with other methods reported in the literature, using a case study of the Griffin area fields.

Reconciliation of capillary pressure data with core and log data can be advantageous for better reservoir description. In this work, the Carman-Kozeny (C-K) equation based Hydraulic Flow Zone Unit (HU or FZU) methodology has been found ideal in characterizing geologic depositional environments and modelling fluid saturation profiles. For this purpose, the concept of ‘Global Characteristic Envelopes’ (GCEs) has been introduced, to analyse geological and petrophysical characteristics and for the integration and correlation among the wells. Capillary pressure data, based on such FZU and depositional grouping, may be further used for modeling saturation profiles over the uncored intervals and allows meaningful averages to be assigned for geocellular modeling and reservoir simulation.
Permeability Prediction Using Artificial Neural Network (ANN): A Case Study of Uinta Basin
Authors: Singh S.
Published: January 2008

The purpose of this paper is to develop a methodology to predict the permeability for wells in the same field using conventional logs (Gamma Ray, Neutron logs and Density log). This methodology involves the application of Error Back Propagation Neural Network. The advantages of this learning algorithm is that, an error in the final output gets back propagated and gradually updates the weight and hence leads to the best network structure.

Present study was made using published literature on Uinta Basin, southwest Utah field (available on Utah Geological Survey's (UGS) website). It has an areal extent of 14900 km2. In this, study data from 13 wells was taken. Data from seven cored wells in the field was used for training, and subsequently prediction and verification was done on core permeability for remaining six wells.

The result of this study shows that ANN generated permeability is consistent with core analysis result. This study was done using MATLAB® 6.1’s ANN Toolbox.
Compressible Streamlines and Three-Phase History Matching
Authors: Cheng Hao , Oyerinde Dayo , Datta-Gupta Akhil , Milliken William
Published: January 2008

Reconciling high-resolution geologic models to field production history is still by far the most time-consuming aspect of the workflow for both geoscientists and engineers. Recently, streamline-based assisted and automatic history-matching techniques have shown great potential in this regard, and several field applications have demonstrated the feasibility of the approach. However, most of these applications have been limited to two-phase water/oil flow under incompressible or slightly compressible conditions.

We propose an approach to history matching three-phase flow using a novel compressible streamline formulation and streamline-derived analytic sensitivities. First, we use a generalized streamline model to account for compressible flow by introducing an "effective density" of total fluids along streamlines. This density term rigorously captures changes in fluid volumes with pressure and is easily traced along streamlines. A density-dependent source term in the saturation equation further accounts for the pressure effects during saturation calculations along streamlines. Our approach preserves the 1D nature of the saturation equation and all the associated advantages of the streamline approach with only minor modifications to existing streamline models. Second, we analytically compute parameter sensitivities that define the relationship between the reservoir properties and the production response, viz. water-cut and gas/oil ratio (GOR). These sensitivities are an integral part of history matching, and streamline models permit efficient computation of these sensitivities through a single flow simulation. Finally, for history matching, we use a generalized travel-time inversion that has been shown to be robust because of its quasilinear properties and converges in only a few iterations. The approach is very fast and avoids much of the subjective judgment and time-consuming trial-and-error inherent in manual history matching.

We demonstrate the power and utility of our approach using both synthetic and field-scale examples. The synthetic case is used to validate our method. It entails the joint integration of water cut and gas/oil ratios (GORs) from a nine-spot pattern in reconstructing a reference permeability field. The field-scale example is a modified version of the ninth SPE comparative study and consists of 25 producers, 1 injector, and aquifer influx. Starting with a prior geologic model, we integrate water-cut and GOR history by the generalized travel-time inversion. Our approach is very fast and preserves the geologic continuity.
An Output Controllability Problem for Semilinear Distributed Hyperbolic Systems
Authors: Zerrik E , Larhrissi R , Bourray H
Published: January 2008

An Output Controllability Problem for Semilinear Distributed Hyperbolic Systems

The paper aims at extending the notion of regional controllability developed for linear systems to the semilinear hyperbolic case. We begin with an asymptotically linear system and the approach is based on an extension of the Hilbert uniqueness method and Schauder's fixed point theorem. The analytical case is then tackled using generalized inverse techniques and converted to a fixed point problem leading to an algorithm which is successfully implemented numerically and illustrated with examples.
Optimal Approximation, Simulation and Analog Realization of the Fundamental Fractional Order Transfer Function
Authors: Djouambi Abdelbaki , Charef Abdelfatah , Besançon Alina
Published: January 2008

Optimal Approximation, Simulation and Analog Realization of the Fundamental Fractional Order Transfer Function

This paper provides an optimal approximation of the fundamental linear fractional order transfer function using a distribution of the relaxation time function. Simple methods, useful in systems and control theories, which can be used to approximate the irrational transfer function of a class of fractional systems for a given frequency band by a rational function are presented. The optimal parameters of the approximated model are obtained by minimizing simultaneously the gain and the phase error between the irrational transfer function and its rational approximation. A simple analog circuit which can serve as a fundamental analog fractional system is obtained. Illustrative examples are presented to show the quality and usefulness of the approximation method.
The Choice of the Forms of Lyapunov Functions for a Positive 2D Roesser Model
Authors: Kaczorek Tadeusz
Published: January 2008

The Choice of the Forms of Lyapunov Functions for a Positive 2D Roesser Model

The appropriate choice of the forms of Lyapunov functions for a positive 2D Roesser model is addressed. It is shown that for the positive 2D Roesser model: (i) a linear form of the state vector can be chosen as a Lyapunov function, (ii) there exists a strictly positive diagonal matrixPsuch that the matrixATPA - Pis negative definite. The theoretical deliberations will be illustrated by numerical examples.
Redundancy Relations for Fault Diagnosis in Nonlinear Uncertain Systems
Authors: Shumsky Alexey
Published: January 2008

Redundancy Relations for Fault Diagnosis in Nonlinear Uncertain Systems

The problem of fault detection and isolation in nonlinear uncertain systems is studied within the scope of the analytical redundancy concept. The problem solution involves checking the redundancy relations existing among measured system inputs and outputs. A novel method is proposed for constructing redundancy relations based on system models described by differential equations whose right-hand sides are polynomials. The method involves a nonlinear transformation of the initial system model into a strict feedback form. Algebraic and geometric tools are used for this transformation. The features of the method are made particular for uncertain systems with a linear structure.
Object Library of Algorithms for Dynamic Optimization Problems: Benchmarking SQP and Nonlinear Interior Point Methods
Authors: Błaszczyk Jacek , Karbowski Andrzej , Malinowski Krzysztof
Published: January 2008

Object Library of Algorithms for Dynamic Optimization Problems: Benchmarking SQP and Nonlinear Interior Point Methods

The main purpose of this paper is to describe the design, implementation and possibilities of our object-oriented library of algorithms for dynamic optimization problems. We briefly present library classes for the formulation and manipulation of dynamic optimization problems, and give a general survey of solver classes for unconstrained and constrained optimization. We also demonstrate methods of derivative evaluation that we used, in particular automatic differentiation. Further, we briefly formulate and characterize the class of problems solved by our optimization classes. The solution of dynamic optimization problems with general constraints is performed by transformation into structured large-scale nonlinear programming problems and applying methods for nonlinear optimization. Two main algorithms of solvers for constrained dynamic optimization are presented in detail: the sequential quadratic programming (SQP) exploring the multistage structure of the dynamic optimization problem during the solution of a sequence of quadratic subproblems, and the nonlinear interior-point method implemented in a general-purpose large-scale optimizer IPOPT. At the end, we include a typical numerical example of the application of the constrained solvers to a large-scale discrete-time optimal control problem and we use the performance profiles methodology to compare the efficiency and robustness of different solvers or different options of the same solver. In conclusions, we summarize our experience gathered during the library development.
Real-Valued GCS Classifier System
Authors: Cielecki Łukasz , Unold Olgierd
Published: January 2008

Real-Valued GCS Classifier System

Learning Classifier Systems (LCSs) have gained increasing interest in the genetic and evolutionary computation literature. Many real-world problems are not conveniently expressed using the ternary representation typically used by LCSs and for such problems an interval-based representation is preferable. A new model of LCSs is introduced to classify realvalued data. The approach applies the continous-valued context-free grammar-based system GCS. In order to handle data effectively, the terminal rules were replaced by the so-called environment probing rules. The rGCS model was tested on the checkerboard problem.
Evolving Racial Identity and the Consolidation of Men's Authority in Early Twentieth-Century Quebec
Authors: Vacante Jeffery
Published: January 2008

This article explores the evolution of ‘racial’ identity in Quebec and the ways in which it was intertwined with considerations about manhood. It suggests that growing concerns about manhood in an urban and industrial environment, coupled with the suspicion that women were turning their backs on motherhood, led some French-Canadian men to redefine their racial identity in ways that would bolster their masculine and patriarchal authority. So long as blood was said to be central to French-Canadian racial identity, women, in their roles as child-bearers, and thus physical reproducers of the race, could expect to exert at least a symbolic influence over the direction of the race. But as traditional gender roles appeared to come under attack in the 1920s and 1930s, some men grew increasingly uncomfortable with the ‘revenge of the cradle’ ideology that tied men's political and economic influence to women's ability to produce as many children as possible. Anxious about becoming too dependent on women's bodies and armed with international developments in race theory, French-Canadian men began to downplay the role that biology played in one's racial identity and to promote a cultural definition of racial belonging. In this way, men diminished women's role in racial regeneration, and in the process regained control over their economic, political, and ‘racial’ destinies.
Asymmetric Synthesis of Polyfunctionalized Mono‐, Bi‐, and Tricyclic Carbon Frameworks via Organocatalytic Domino Reactions
Authors: Enders Dieter , Hüttl Matthias R. M. , Raabe Gerhard , Bats Jan W.
Published: January 2008

An asymmetric organocatalytic multi‐component domino reaction is used as a key process for the stereoselective synthesis of polysubstituted mono‐ and bicyclic cyclohexene‐carbaldehydes. Furthermore, the extension of the domino reaction and further synthetic transformations of the cascade products were investigated. The combination of the three‐step cascade with an intramolecular Diels–Alder reaction opens up an entry to tricyclic decahydroacenaphthylene and decahydrophenalene skeletons, which are valuable characteristic carbon cores of natural products.
Association study of the 15q11‐q13 maternal expression domain in Japanese autistic patients
Authors: Kato Chieko , Tochigi Mamoru , Ohashi Jun , Koishi Shinko , Kawakubo Yuki , Yamamoto Kenji , Matsumoto Hideo , Hashimoto Ohiko , Kim Soo‐Yung , Watanabe Keiichiro , Kano Yukiko , Nanba Eiji , Kato Nobumasa , Sasaki Tsukasa
Published: January 2008

Chromosome 15q11‐q13 has been a focus of genetic studies of autism susceptibility, because cytogenetic abnormalities are frequently observed in this region in autistic patients. An imprinted, maternally expressed gene within the region may have a role in autistic symptomatology. In the present study, we investigated the association between autism and the maternal expression domain (MED) in the region, containing the UBE3A and ATP10C genes, and the upstream imprinting center (IC), which mediates coordinate control of imprinted expression throughout the region. We analyzed 41 single nucleotide polymorphisms (SNPs) in 166 patients with autism and 416 controls from a Japanese population. As a result, a statistically significant difference after correction for multiple testing was observed between the patients and controls in the genotypic distribution of SNP rs7164989 (SNP8 in this study) located in SNRPN, whose promoter corresponds to the IC (P = 0.018, corrected for multiple testing). In the analysis of a four‐marker haplotype located in ATP10C, a statistically significant difference after correction for multiple testing was observed in the frequency of one haplotype between male patients and controls (permutation P = 0.033, corrected for multiple testing). Thus, the present study may suggest the association between autism and the MED or the upstream IC in chromosome 15q11‐q13 in the Japanese population. © 2008 Wiley‐Liss, Inc.