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72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010
- Conference date: 14 Jun 2010 - 17 Jun 2010
- Location: Barcelona, Spain
- ISBN: 978-90-73781-86-3
- Published: 14 June 2010
781 - 797 of 797 results
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Influence of Cementation Factor on Water Saturation in Carbonates of Main Dolomite in North-West Poland
Authors P. Krakowska and M. NiepsujDetermination of hydrocarbon saturation in carbonates is challenge for the geophysical interpretation. Cementation factor is one of the main coefficients in petrophysics which strongly affect water saturation. Its wrong determination causes serious error in water saturation value. In the paper water saturation was determined using two equations: Borai and Shell formula. By using computed water saturation and fluid substitution method theoretical velocities of P-waves and S-waves (also P-wave/S-wave velocity ratio) were calculated. Diversity in P- wave and S-wave velocity is a source information about lithology. In reservoir rocks Vp/Vs ratio may also work as a confirmation of gas saturation.
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Application of Artificial Neural Networks to the Evaluation of Formation Permeability
By P. KurnikANNs enable the recognition of relations between input and output data and the prediction of permeability. The network was created using Statistica and MATLAB Neural Network Toolbox. Permeability, one of the most important reservoir parameters of rocks, defines ability to transmit fluids in porous space of rock formation. Permeability is affected by structure and texture (shape, size, and degree of sorting and cementation), porosity, shaliness and carbonate volume. There is no general formula for permeability calculation on the basis of factors influencing fluid flow in porous rocks. ANNs enable the prediction of permeability.
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Influence of N2/CO2 Injection to the Wettability Behavior of the Coal-water-gas System
Authors N. Shojaikaveh, E.S.J. Rudolph and S.N. AshrafizadehGeological sequestration of carbon dioxide (CO2) is one of the viable methods to reduce the CO2 emission and to stabilize the concentration of greenhouse gases in the atmosphere. Carbon dioxide (CO2) or flue gas (N2/ CO2) injection into coal layers serves the dual purpose to enhance coal bed methane production (ECBM) and to store CO2. Because of the important rule of coal wettability in ECBM efficiency, we have undertaken an experimental study to investigate the wetting properties of different coal types by means of contact angle measurements in a modified pendant drop cell at in-situ conditions.
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Development of Reservoir Characterization Techniques and Production Models for Exploiting Naturally Fractured Reservoirs
Authors I. Oraki Kohshour, B. Habibnia and K. DalvandFor many years,geoscientists and engineers have undertaken research to characterize naturally fractured reservoirs. Geoscientists have focused on understanding the process of fracturing and the subsequent measurement and description of fracture characteristics. Engineers have concentrated on the fluid flow behavior in the fracture-porous media system and the development of models to predict the hydrocarbon production from these complex systems.This research attempts to integrate these two complementary views to develop a quantitative reservoir characterization methodology and flow performance model for naturally fractured reservoirs.The research has focused on estimating naturally fractured reservoir properties from seismic data, predicting fracture characteristics from well logs, and developing a naturally fractured reservoir simulator.It is important to develop techniques that can be applied to estimate the important parameters in predicting the performance of naturally fractured reservoirs.This project proposes a method to relate seismic properties to the elastic compliance and permeability of the reservoir based upon a sugar cube model. In addition, methods are presented to use conventional well logs to estimate localized fracture information for reservoir characterization purposes. This is an important step in developing exploitation strategies for optimizing the recovery from naturally fractured reservoir systems.
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Could CO2 Storage Site Performance Be Compromised by Palaeo-Gas Migration Conduits in the Overburden?
Authors G. D. Nicoll, M. Naylor, A. J. Cavanagh, S. Geiger and R. S. HaszeldineFormations below the North Sea are proposed as a major repository for anthropogenic CO2 to mitigate climate change. Two such sites are already operational offshore Norway. Large areas of the North Sea are known to have leaked natural gas over geological time, so are these areas suitable for CO2 storage, given that geological heterogeneities and natural gas palaeo-migration pathways could serve to compromise CO2 storage sites in the longer term? We have identified similar features at the Utsira CO2 storage site offshore Norway, thus we use this site as a case study to investigate whether CO2 leakage is possible and if so under what conditions. We evaluate the main uncertainties affecting this storage site and present a risking methodology and screening tool that could be used to assess future storage sites and minimise the risk of compromise due to inappropriate site location.
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Fracture Characterizations from Well Testing Data Using Artificial Neural Networks
Authors R. Eslamloueyan, B. Vaferi and S. AyatollahiDual porosity model refers to those reservoirs which have two different media. The interporosity flow coefficient (λ), and storativity ratio (ω). Well testing analysis is used to estimate reservoir parameters that are used in the reservoirs description. Pressure derivative plots corresponding to different value of λ and ω, are dissimilar. Derivative plots are used to design a model based on ANN to estimate λ and ω. In this study the capability of Artificial Neural Network to estimate λ and ω from well testing data has been investigated. Well testing data for dual porosity reservoir have been generated and converted to derivative plots. The best configuration of ANN has been selected by a trial and error procedure through applying different training algorithms and changing the number of neurons in the hidden layer. Using this procedure, a two-layer ANN model has been found as an efficient tool to estimate ω and λ. The trained ANN has been validated using the test data not been used in the training data set. The results have shown that the ANN is capable of estimating λ and ω using derivative plot obtained from the reservoir simulation as well as the information obtained from the literatures.
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A Poroperm Function To Evaluate the Dynamic Pore Connectivity of Porous Media
Authors M. I. Al-Mossawy and B. DemiralThe pore connectivity affecting the permeability can be called the dynamic pore connectivity, to distinguish it from the average pore connectivity determined by the technique of digital image processing. Digital image processing of the porous media can not evaluate numerically the dynamic pore connectivity. Neithalath et al. (2006) have derived a factor from Kozeny-Carman equation to characterize the enhanced porosity concrete according to the relationship between the porosity and permeability, called the hydraulic connectivity factor (ßH). This factor included conductivity factor, specific surface area of pores, and pore shapes factor. In order to find new relationships between the porosity and permeability, a different model has been used in the present study. A capillary-bundle model was developed to represent the porous media and to derive two relationships between the porosity and permeability. Either of these relationships can be used to characterize the porous media according to their dynamic pore connectivity. One of these relationships had been modified to a function called poroperm (Pp) to be with the same units of permeability. Applying Pp and ßH to characterize seven sandstone cores yielded an excellent matching.
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Reconciling Well-test and Production Data in Mapping Permeability-thickness Trends
By A. PetrovDuring a field development process, one of the parameters used to decide the in fill well locations is permeability-thickness (kh) map. This map can provide us with overall trends in the conductivity of the formation as well as information about optimizing water flood patterns. One difficulty typically observed in generating kh maps is a prominent display of "bull's eyes". The values of kh can change dramatically from well to well, which causes problems in interpolation of these values. Sometimes, because of large discrepancies, the overall patterns are hard to discern and well planning is more difficult. In the proposed work, we developed a procedure for capturing the trends in kh maps by removing the bull's eyes. The kh values are determined by two methods: use the production data and using simplified procedure, determine the value of kh or evaluate well test data and determine the kh values. The procedure was validated by applying it to a large oil field located in Siberia with successful application of in-fill well program.
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Diffusion-to-telegraph Equation Conversion to Analyze Pressure Transient Behavior
Authors A. Moaddel Haghighi and Y. FallahzadehFor many years, pressure propagation in porous media has been the main tool of oil and gas reservoir characterization. Almost all available related petroleum literature states that Instantaneous-Action-at-a-Distance (IAD) is a natural part of diffusion process and it's a "particular behavior of the linear diffusion equation which indicates an infinitesimal change in pressure everywhere in the reservoir following a disturbance at the wellbore". For the first time in the filed of well testing,we have converted a Diffusion equation to its equivalent Telegraph equation. Initial conditions are reconstructed from those of diffusion equation. Here, through a simulation study, we examine the early time behavior of a 1D diffusion equation and its reconstructed conjugate telegraph equation to study the possible discrepancies these two equations may have. This can light up the way to more rigorous study of pressure transient analysis in well testing for better reservoir characterization. The simulation we have conducted is the first try to examine effect of finite speed of pressure propagation in telegraph equation in comparison to the infinite speed of disturbance propagation in diffusion equation which for many years has been a matter of controversy among petroleum engineers.
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An Experimental Study to Minimize Capillary End Effect During Flooding in Porous Media
By M. AhmedCapillary end effect arises from saturation discontinuity existing at the outlet face of the porous medium during a flow test. This phenomenon results in a saturation gradient in the flow system. This results in errors in the calculated relative permeability of the porous media. Accurate relative permeability measurements are essential for many applications. It was observed that the length of the rock affects the measured values. At the end of this study, the optimum length of rock and the flow conditions for our application to minimize the capillary end effect was identified.
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The Use of VSP and Well Data To Design De-multiple Techniques
More LessIn this project, VSP and well log data are used to assess multiple activity on 3D land seismic data. Synthetic VSP data were created using well log data. Observations from these synthetic data are used to determine whether well log data are sufficient to understand the multiple wave field or VSP data are required; whether the multiples identified from the borehole can be used to design de-multiple filters and what is the optimum multiple attenuation technique to use.
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3-D Seismic Ray Tracing on Irregular Tetrahedral Grid
Authors D. M. Molodtsov and Y. V. RoslovWe apply shortest-path method of seismic ray tracing to irregular tetrahedral grid, which is useful for modelling highly heterogeneous media with complex geometry of interfaces. To combine low computational complexity with satisfactory accuracy we introduce specially organized interpolation of traveltimes on the second-order grid. The algorithm is extended on multiple arrivals. Performance of the algorithm is studied in numerical experiments.
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Outcrop-seismic-core Plugs Correlation in a UAE Cretaceous Carbonate
Authors A. H. El Husseiny, S. A. Al Mesaabi, S. Vega and M. AliIn this study, we investigate potential correlation between rock properties and seismic to better understand factors that affect seismic response in UAE Cretaceous carbonates. We correlate geological and geophysical parameters at three different scales: outcrop, seismic and core plugs. We acquired a 2D seismic line on the top of an outcrop. From the same outcrop we examined 17 core plugs. We found that acoustic velocities decrease with increase in fracture density. This result was supported by the outcomes of the outcrop-seismic correlation where changes in fracture density were found to be the main cause of reflection events in these carbonates.
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The Hough Transform for Seismic Profile Interpretation
More LessWe use Hough transform for seismic interpretation, by detecting parameterized shapers through mapping from the image space into the parameter space. We apply the Hough transform for the parabola detection in the real seismic data. Before the transform we use an erosion operator to delete the non-useful information and keep the useful information as much as possible. The result shows a good match between the original image with the detected image.
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Gravimetric Monitoring of the Base of the Mosque Kul Sharif
By A. AbdullinThe research task was determination of facilities of gravimetric method in research of the influence of groundwater on the base of the mosque Kul Sharif. The survey using several gravimeters was carried out, error estimate of measurements was done, and all the obtained data was analyzed. The conclusion is that research of the groundwater influence on the basement of the mosque can be carried out using gravimeters of Scintrex type, which provide high precision. It’s reasonable to carry out research over a longer period of time and take the necessary steps for strengthening the foundation.
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First Time Arrivals Tomography
By N. BelayouniThe tomography consists on detecting the variation of the accoustic waves velocity in the formation in the near subsurface. Within this work, we established a new algorithm of first time arrivals tomography that considers the advances in the IT domain and meets the expectations of geologists and geophysicists in term of ease of parametrization. The work is divided essentially in three parts. We began by resolving the direct problem which consists in calculating the first arrivals time for a given source and velocity model by dicretizing the eikonal equation on a Cartesian grill. Then, we resolved the inverse problem which consists in determining the velocity model which best fits observed times on surface by the method of adjoint state. Finally we added the a priori information in the Least Squares cost function to refine the inversion results.
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New Development for Model Selection Criteria in Reservoir History Matching
Authors M. M. Rafiee and F. HaefnerHistory matching, which is to find a suitable model, such that the simulator correctly predicts the future production, is absolutely needed for a real reservoir simulation. From mathematical point of view the selected model should be minimized in terms of objective function -OF- (necessary condition for model selection) and also the condition of parameter uniqueness (sufficient condition for model selection) must be fulfilled in a successful reservoir history match. Although the value of minimized OF in normal practice get smaller with increasing the number of parameters, the comparison of OF values does not show the unique solution. In this work we developed Penalized Objective Function (POF) strategy based on penalization concept of OF and principle of parsimony, to avoid over-parameterization to find out most probable unique solution for reservoir history matching. The new strategy (POF) has been implemented successfully on field case and could be applied generally for different deterministic model concerning the reservoir engineering decision.
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