bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Analytical Bottomwaterdrive Aquifer Model for Material Balance Analysis
Authors: Yildiz T. , Khosravi A. 
Published: December 2007

Abstract
In this study, we present a new analytical model to predict water influx from finite bottomwaterdrive aquifers (BWDAs). The new model can be used for aquifer representation in reservoir simulators and material balance analysis. The new model is computationally fast. The model has been verified against the results from the Coats and Allard-Chen models. Using the new model, we compare the cumulative water influx from BWD and edgewaterdrive (EWD) aquifers.
In the second part, we couple the new aquifer model with the material balance equation (MBE) and demonstrate its use in reserve estimate. Production data from a bottomwaterdrive (BWD) oil reservoir simulated by Allard and Chen is analyzed. We conducted a McEwen analysis to predict the reserves.
Numerical Modeling of Diffusion in Fractured Media for Gas Injection and Recycling Schemes
Authors: Hoteit H. , Firoozabadi A. 
Published: December 2007

Abstract
Diffusion in fractured reservoirs, unlike in unfractured reservoirs, can affect significantly the efficiency of gas injection in oil reservoirs and recycling in gas condensate reservoirs. The physical diffusion, similar to gravity, results in the change of the path of the injected gas species from the fractures to the matrix, giving rise to late breakthrough. In this work, we present, for the first time, a consistent model to incorporate physical diffusion of multicomponent mixtures for gas injection schemes in fractured reservoirs. The multicomponent diffusion flux is related to multicomponent diffusion coefficients, which are temperature, pressure and composition dependent. These coefficients are calculated from a model based on irreversible thermodynamics. Current simulation models of fractured reservoirs that include diffusion are based on inconsistent models of gas to liquid diffusion at the fracture-matrix interface. We avoid this deficiency by assuming that the gas and liquid phases are in equilibrium at the interface. The concept of crossflow equilibrium (that is, vertical equilibrium) is invoked in our model to avoid the use of transfer functions. In this work, we use the combined discontinuous Galerkin and mixed methods to calculate fluxes accurately and to have low numerical dispersion to study physical diffusion. Four examples are presented. In one of the examples, a field scale study is performed to investigate gas injection in a fractured reservoir away from miscibility pressure and close to miscibility pressure. Results show a significant effect of diffusion on recovery performance away from miscibility pressure. In another example, recycling in a fractured gas condensate reservoir is presented to demonstrate that diffusion has a significant effect on condensate recovery.
Education for the Real World: Equipping Petroleum Engineers To Manage Uncertainty
Authors: Bratvold R. B. , Begg S. H. 
Published: December 2007

Abstract
An accurate assessment of uncertainty is now seen as a necessary starting point from which to make decisions that will create value and/or mitigate loss in value (risk). As such, uncertainty analysis drives the decisions that are made, rather than just being an add-on, or afterthought, piece of "risk analysis". This impacts the way it should be taught - as an integral part of (almost) all technical courses.
Unfortunately, university training in petroleum engineering does not reflect this required focus on uncertainty understanding and management.
In this paper we discuss the current state of uncertainty management in petroleum engineering curricula. We then propose some essential elements that should be a part every petroleum engineer's educational background and discuss ways to implement these elements into the curriculum without reducing the essential understanding that graduates must have for basic petroleum engineering topics.
Numerical Analysis of Radial Flow in a Natural Fracture: Applications in Drilling Performance and Reservoir Characterization
Authors: Lavrov Alexandre , Tronvoll Johan 
Published: December 2007

AbstractA theoretical framework is developed for radial flow of a Newtonian fluid from a single, arbitrarily inclined fracture into a borehole, as it is the case during formation fluid influx in underbalance drilling, or during oil production in naturally-fractured reservoirs. The model should be equally well applicable for the simulation of fluid flow from a borehole into a fracture, as it is the case during mudloss events in overbalance drilling.The fracture is assumed to be rectangular in shape and to obey an empirical exponential deformation law, i.e. hydraulic aperture in function of effective stress.A parametric study is carried out in order to investigate the effect of fracture inclination, fracture dimensions, fracture compressibility, and borehole position, on the flow rate dynamics. The largest in-plane size of the fracture has very little effect on the flow rate at the initial stage of the flow. It does not affect the initial peak in the flow rate versus time curve. It affects, however, substantially the flow rate at later stages, and also the total amount of produced (or lost) fluid. The smallest in-plane size of the fracture considerably affects the initial part of the curve. It also affects the total amount of produced /lost fluid. The initial peak in the flow rate is lower and the duration of the discharge is longer in case of a borehole located at the periphery of the fracture in comparison to the one located in the central part of the same fracture. This holds for different types of fracture orientation and geometry, i.e. horizontal and vertical, isometric and elongated fractures. An increase in the fracture's normal compressibility only slightly affects the height of the initial peak in the fluid flow versus time curve, but has a large effect on the tail of the curve. Higher compressibility also leads to that the cumulative amount of produced /lost fluid is higher.The results also show that the proposed model may be useful in estimating hydrocarbon reserves in place based on drilling data as well as for estimating potential production profiles and recovery factor.
Application of New Technology in the Completion of ERD Wells, Sakhalin-1 Development
Authors: Helmy M. W. , Veselka A. , Benish T. , Yeh C. , Asmann M. , Yeager D. , Martin B. , Barry M. 
Published: December 2007

Abstract
This paper presents methods for the completion and evaluation of extended-reach-drilling (ERD) wells with greater than 10,000 m measured depth and horizontal completion intervals surpassing 3000 m for the Chayvo Field in the Sakhalin-1 development in Russia. The objectives of the completion strategy are a) maintain a uniform production profile along the wellbore by reducing flow from high permeability zones b) mitigate the potential for sand production and c) maintain zonal isolation between various reservoir facies. A combination of external isolation packers, inflow control nozzles, sand screens, and pre-drilled liner were used. The inflow control nozzles were sized to restrict flow from high permeability zones and maintain a more uniform production profile along the wellbore. Other issues that influenced the final completion design include rock strength, sand particle size, and reservoir deliverability. The design, sizing and placement of the inflow control nozzles, screens, and isolation packers are discussed in detail.
Evaluating the performance of the completion presents unique challenges. A series of production logging and pressure tests were run to reduce uncertainties associated with the estimation of reservoir properties and completion efficiency. These uncertainties were introduced by the presence of the inflow control nozzles and the multi-layer nature of the reservoir. The pressure buildup and production logging data were integrated, and the analysis used to evaluate the effectiveness of the completion technique.
How Minimum Interval Concept Can Improve Bit Performance Evaluation
Authors: Macini P. , Magagni M. , Da Dalt G. , Valente P. 
Published: December 2007

Abstract
The paper analyzes a novel operative procedure of geological and geomechanical subdivisions of the formations, called Minimum Interval (MI). The MI concept, used in combination with other evaluation indexes, can improve consistently the evaluation of bit performances. This research compares three indexes for bit performance evaluation, i.e., cost-per-meter (CM), Specific Energy (SE) and Bit Index (BI), applied to a new type of drilling-bit database, named Formation Drillability Catalog (FDC), organized in order to implement the MI concept. Basically, the FDC is a novel classification of drilled formations conceived and prepared at Eni E&P Division (Italy), aimed to the geomechanical characterization by means of a large number of significant geological and drilling parameters, each one referred to single MI’s. So far, five wells have been identified and tested for bit performance evaluation. The FDC turned out to be functional to BI, since it discloses and organizes lithostratigraphical characters that are not easily detectable or usable from bit records or master logs, allowing for targeted bit performance evaluations. Results of this case study showed that the cross correlation between BI, CM and SE can help to identify the best performer bit for each formation and for each borehole section. The quality of bit performance analyses obtained with BI and SE (through the MI concept) seems more effective than those based on CM, performed on bit records, and can also be used as a valuable tool for drill-bit selection.
Use of Extremely High Time-Resolution Production Data To Characterize Hydraulic Fracture Properties
Authors: Crafton J. W. , Gunderson D. 
Published: December 2007

Abstract
By employing flowback surface rate and pressure data recorded at very high frequency immediately following hydraulic fracture stimulation shutdown, it is possible to obtain estimates of fracture conductivity, fracture length and near-wellbore matrix permeability, as well as confirmation of closure pressure. Because the wellbore and induced hydraulic fracture are liquid filled at very early time, it is possible to observe meaningful signatures in the flowback production data when it is recorded with sufficiently high time resolution, on the order of 20 or more observations per minute. Dissipation of the super-charge is detectable, and the highly elliptical flow dominated by the fracture is clearly evident.
Recognition of these flow regimes makes interpretation of fracture conductivity, effective length and an upper limit estimate of matrix permeability possible. Examples of actual field results are shown in the paper. When compared with published proppant bed conductivities for the expected stress loading, excellent correlation is obtained. The computed effective fracture lengths are somewhat shorter than that expected based on the design. In all cases, the near-fracture matrix permeabilities are higher than observed in later time production histories.
Production Sharing Agreements—An Initiative to Reform
Authors: Wadood S. 
Published: December 2007

Abstract
Production Sharing agreements are the predominant type of contractual arrangement, governing the relation between governments and foreign oil companies throughout the exploration and development phase. PSA were first introduced in Indonesia in 1966 and since then varied in some elements but witnessed no major development.
The paper/presentation will argue that in the current context of sustained oil prices, need of increasing production, depletion of reservoirs, and the remaining reserves, Governments and Foreign Oil companies need to revisit some of the basic elements of the PSAs in order to address the above context adequately.
The rigidness of the current structure of PSA does not allow government and E&P companies to adapt their strategies throughout the development phase. To overcome some of the disadvantages of PSAs, governments can introduce dynamic variables such as: Dynamic profit share linked to Crude prices.Flexible Cost Recovery systemsIncentive system based on key performance indicators
Application of new materials and parts for ESP units running in wells of abnormal operating conditions
Authors: Grebenyuk Alexander N. 
Published: December 2007

Abstract
Analysis of OAO "NNP" wells for 2004 showed that total number of premature failures made 618 and compised 167caused by cable faults, 371 caused by ESP faults, 43 through fault of downhole pump and hydraulic protection, and 37 due to tubing failures.
The main part of failures falls to ESP units. That is why quality of materials used in ESP operating parts should be of top priority. The main causes of ESP failures across OAO "NNP" are the following: aggressive environment (corrosion) – 13%, mechanical impurities – 43%, scales – 25%, proppant washout – 11%, tubing leaks – 11%, poor inflow – 1%.
The main factors aggravating the ESP work are salt deposits on the operating parts and their corrosion. Salt deposits and corrosion result in flow characteristics deterioration, vibration amplification, what consequentially shortens failure free operation time of ESP units. The average failure free operation time of these wells made 95 days due to scales and 103 days due to corrosion.
Salt deposit and corrosion causes
High watercut level (exceeding 80%) significantly intensifies the aggressive environment impact and corrosion process.
Having analyzed composition of salts and deposit formation process we can specify 3 root causes of salt deposits in ESP parts.
The first one is based on the definite reservoir fluid properties – watercut level exceeding 80%, presence of dissolved and undissolved minerals as wells as aggressive environment.
The second cause is of operational nature and may be entailed by: change of thermobaric conditions in a well or in ESP, leading to precipitation of some compounds of the first group. So, shift of the work zone to the left side of the flow dynamic properties (i.e. when the pump is forced to decrease the flow rate) leads to rising of the flowing fluid temperature and enhancement of cavitation processes, what subsequently leads to precipitation of CaCO3 (calcium carbonate), in particular;Mixing of formation fluid with injected water of different composition in the process of water injection for formation pressure maintenance may result in creation of salt-forming compounds and aggressive environment.
The third cause is design of ESP which may lead to: formation of vortex and stall zones;corrosion of working parts surfaces which leads to damage of smooth surfaces where salt deposits can easily form then;Besides, salt deposits may be resulted from influence of electrostatic forces (initiation of galvanic couples).
Applications of Artificial Neural Networks and Dipole Sonic Anisotropy in Low-Porosity, Naturally Fractured, Complex Lithology Formations in the Southern Land Region of México
Authors: Bueno E. O. J. , Pérez I. C. , Escamilla G. , Mesa H. , Ponce B. , Graham R. , Kessler C. , Murillo J. 
Published: December 2007

Abstract
The Antonio J. Bermudez basin in Southern Mexico is a low porosity massive Jurassic and Cretaceous carbonate reservoir that is extensively faulted and fractured due to post depositional salt intrusions. The natural fractures create many drilling challenges and obstacles. Underbalanced drilling with foam fluid systems has been used to minimize mud losses in these fracture systems. The underbalance drilling, and drilling with casing greatly improves well construction, but these drilling techniques also create many formation evaluation challenges. For example, open hole sonic logs require a liquid filled borehole. Also, formation resistivity is such that lateral logs would be the preferred resistivity device, but they require a conductive borehole fluid.
Artificial Neural Network (ANN) methods have traditionally been used for reconstruction of petrophysical data due to tool pulls and poor borehole conditions. Drilling obstacles, in this field, sometimes prohibit the running of conventional open hole logs. Thus, an ANN technique has been developed that uses cased hole pulsed neutron log (PNL) data to synthetically generate a conventional, open hole, triple combo log. These logs are used for well-to-well correlations and for petrophysical evaluation. Still, due to the synthetic smoothing of an ANN result based on casing formation evaluation data (i.e., PNL), detection of natural fractures remains problematic using ANN-based synthetic density data. On the other hand, cased hole dipole sonic anisotropy analysis is routinely used successfully to identify natural fracture systems and far field stress orientation for geomechanical applications. Intervals to be perforated are selected by combining through-casing sonic information with petrophysical analysis of synthetic open hole logs.
Data and production results from several wells will be presented and discussed in the paper.
A New Model to Describe Particle Movement and Deposition in Porous Media
Authors: Kalantari-Dahaghi A. , Moghadasi J. , Gholami V. 
Published: December 2007

Abstract
Formation damage resulting from invasion of solid suspensions have been studied by several investigators and some modeling approaches have also been reported in the literature, most notably the application of effective medium theory and percolation theory in two and three-dimensional capillary networks.
This paper presents a new model, which is based on mass balance transfer function of particles flowing through the porous media. The linear forms of the model are described as well as the radial forms. Although the differential equations derived are similar to the general form of diffusion-convection equations, the marked difference is the suitability of the model, for being applied for variation of parameters, such as particle concentration in the fluid, injection rate, density of solid particles, against the depth and time of invasion. This transfer function is solved by MATLAB program (Version 5.3.2) and SIMULINK software. The results of the simulation run agree reasonably well with the experimental damage data obtained in laboratory.
Implementation of a Total System Production Optimization Model in a Complex Gas-Lifted Offshore Operation
Authors: Nadar M. S. , Schneider T. S. , Jackson K. L. , McKie C. J. N. , Hamid J. 
Published: December 2007

Abstract
A total system production optimization model has been implemented in a complex gas-lifted offshore operation, resulting in production gains and operating cost reductions. Whereas previous optimization models considered only the wells and production gathering network, the new model is able to consider the combined performance of the total system, including downhole well configurations, the complex production gathering and lift-gas distribution pipeline networks, separators, compressors and pumps. The model is applicable to most gas-lifted fields, and will be particularly beneficial when applied to those with complex production systems, and where compressors are a constraint on total system performance.
The output from the optimization model principally comprises recommended values for individual well gas lift injection rates, separator pressures, compressor discharge pressures and compressor utilization. Field results are presented in the paper to demonstrate how implementing the optimizer's recommendations in the field resulted in economic benefits through increased production and reduced operating costs. Also described is how the model allows field operations engineers to re-optimize field control parameters on a more frequent basis and with less manpower than previously.
The successful implementation of a complex model with such a broad scope is as dependent upon the implementation process as it is upon the technology. Therefore, in addition to describing the details of the model itself, this paper will cover the issues that arose during the implementation and how they were resolved. These include the level of manpower and support required, project organization and execution, and the processes required to sustain the benefits after the initial optimization gains have been realized.
Research of Surfactants Effect on Methane Hydrate Formation
Authors: Bin Dou , Guosheng Jiang , Xiang Wu , Fenglin Tang 
Published: December 2007

Abstract
This paper deals with the effects of a surfactant additive on the formation of methane hydrate in water system with and without sodium dodecyl sulfate (SDS). The results manifested that the presence of SDS could not only accelerate the hydrate formation process, but also increase the partition coefficient of methane between hydrate and vapor drastically. The paper then describes our experimental observations of the hydrate formation from methane, to show how the hydrate formation behaviors are affected by the additives of chamber partially filled with a quiescent pool of water (pure water or an aqueous SDS solution) to compensate for the gas consumption due to the hydrate formation, thereby maintaining a constant pressure inside the chamber. The results revealed that the addition of SDS not only on the liquid-pool surface but also on the chamber walls above the level of the pool surface, leaving the bulk of the liquid pool free from hydrate crystals. An excessive addition of SDS beyond the solubility was found to cause a decrease in the rate of hydrate formation but an increase in the final level of the water-to-hydrate conversion.
A New Method for Accurate and Practical Upscaling in Highly Heterogeneous Reservoir Models
Authors: Zhang Pinggang , Pickup Gillian , Christie Mike 
Published: December 2007

Abstract
Geologists often generate highly heterogeneous descriptions of reservoirs, containing complex structures which are likely to give rise to very tortuous flow paths. However, these models contain too many grid cells for multiphase flow simulation and the number of cells must be reduced by upscaling for reservoir simulation. Conventional upscaling methods often have difficulty in the representation of tortuous flow paths, mainly due to the inappropriate assumptions concerning the boundary conditions. An accurate and practical upscaling method, which is able to preserve the flow behaviour caused by highly heterogeneous fine scale geological features, is therefore required.
In this paper, the problems encountered in routinely used upscaling approaches are outlined, and a more accurate and practical way of performing upscaling is proposed. The new upscaling method, Well Drive Upscaling (WDU), employs the actual reservoir boundary conditions. The main advantage of this method is that the dominant flow paths can be preserved, and thus the geological knowledge can be assimilated appropriately. The new method has firstly been applied to a synthetic model with a tortuous channel, and is shown to have significant improvement over the traditional approach. The sensitivity study on the scale up factor using a bench mark model shows the advantage of the method with various scale up factors. The method was then applied to a model of a field in the central North Sea, which involves three phase flow. In the cases studied, the WDU method produced a comparable result to the dynamic Pore Volume Weighted approach which involves running the fine grid simulation and computing appropriate relative permeabilities and inter-block transmissibilities. The new method makes the upscaling process both practical and accurate and ensures that field predictions can be made more confidently with greater geological realism.