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Shiraz 2009 - 1st EAGE International Petroleum Conference and Exhibition
- Conference date: 04 May 2009 - 09 May 2009
- Location: Shiraz, Iran
- ISBN: 978-90-73781-65-8
- Published: 04 May 2009
121 - 140 of 140 results
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The Impact of Gas Compositions on the Intensity of Positive Coupling Effect in Gas Condensate Reservoirs
Authors A. Gholami, A. Hashemi and S.M. VaziriThe positive coupling effect decreases the condensate saturation as a result of very high flow rates in vicinity of the wellbore. The current work challenges the notion that the positive rate effect does not lead in falling trend of condensate saturation around the wellbore in the case of rich gas composition. According to the results obtained from this parameter case study, four distinct trends would appear in the condensate saturation profile of both lean and rich gas compositions. These quadruplet trends are consistent and their occurrence is mainly related to the considered base capillary number (Ncb) which is likely dependent to the composition of the fluid.
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Numerical Analysis of Geomechanical Aspects of Gas Storage in a Depleted Gas Condensate Reservoir in Iran
Authors S.A. Moosavi, M. Soroush and A. GhazvinianThe study carries out in two steps: first was to determination a scenario for gas storage based on finite difference analysis and the second was preformed to study geomechanical aspects of the scenario. Thus, a wide range of graphs and counters were obtained to study the stress and strain distribution in period of time for present scenario. It has been concerned that the geomechanical analysis of the gas storage field was preformed based on the finite element analysis method as well as the linearly poro-elastic concept. Although the strength gradient source was provided by the pore pressure gradient in the reservoir by pore pressure changes in the period of time, the constant strength source was also provided by gravity. Finally, one of the results is; the largest shear stress was found to be related to the possition where pore pressure vanishes.
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Tight Gas Reservoirs; Opportunities, Characteristics and Challenges
Authors M.S. Shahamat and S. GeramiThe undeniable growing gap between demand and supply, and the advent of technology are making the incentive for development of the unconventional gas resources around the world. One of these unconventional gas resources that recently have attracted the attention of the researchers is the low permeability gas reservoirs, known as tight gas reservoirs. Noting that these reserves are available in enormous quantities all across the world, every and each of them are a project topic by itself and the fact that they retain some specific characteristics and reservoir complexities that are not common in other conventional gas reservoirs necessitate a comprehensive study and analysis of tight gas reservoir characteristics and their well performance. A successful exploitation of these reservoirs requires a basic understanding of the rock original pore structure and properties as well as the processes (like diagenesis) that modify those properties. In this paper, after a brevity about the world wide importance of tight gas reservoirs, a brief explanation of the basic tight gas properties and diagenetic processes affecting porosity and permeability are presented. Moreover some of the problems associated with production from such reservoirs are addressed.
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Laboratory Frontiers in Determining the Packing Style Effect in Carbon Dioxide Hydrates Formation
Authors M. Noroozi and S. Ghahri SaremiMethane production in sequestration process and reducing atmospheric carbon dioxide, a main source of greenhouse gas, has been accentuated recently. An orderly packing style for hydrate will play a fundamental role in hydrate formation rate and efficiency of free water. Surfactant has been reported to help orient hydrocarbon hydrate packing along a metal wall. In this work, it was shown that hydrate packing styles played an important role in carbon dioxide hydrate formation rate. Packing facilitates a high hydrate formation rate and high percentage conversion. Furthermore, in this research, a camera with borescope was used to observe and record the image of carbon dioxide hydrate when it formed with addition of Surfactin, Emulsan, Rhamnolipid, SDS micellar, FS-62/SDS and FSP/SDS into the water solution. We have shown that a full development of the hydrate in the test cell could be obtained with use of FS-62/SDS or FSP/SDS.
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Cold-frac Technology in Tight Gas Reservoirs
Authors M.M. Rafiee, T. Wilsnack, H.D. Voigt and F. HäfnerFor the fracturing processes several frac fluids were presented, described by their properties and behavior in the reservoir formation and the practical experiences in using. Energized fluids such as CO2-foam or commingled CO2 fluids are predominantly used for the optimization of the backflow and the aimed proppant transport. Cold fracturing fluids have strong cooling effect in fracturing process mainly in rock-stress reduction, however these kinds of fluids should be investigate precisely, in terms of thermal stress effect, cleanup process and proppant movement. Cold water fluid has been tested successfully in geothermal reservoirs. This stimulation technique is successful in these fields but not in TGRs. The use of liquid CO2 as a fracturing fluid offers a viable method of stimulation. The successful application of these fluids to a variety of formations in USA was shown. The process has proven be an economical alternative to conventional stimulation fluids. Liquid N2 has also been used in limited cases. From this results it can be concluded, that liquid CO2 seems to be the most efficient frac fluid for future Tight Gas stimulations. The coupling of the cold frac technology with underground CO2 capture and storage (CCS) seems to be a future possibility.
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Oil Formation Volume Factor Correlation For Middle East Crude Oils
Authors B. Moradi, E. Malekzadrh and R. KharratOil Formation Volume Factor (OFVF) is an important reservoir fluid property. Ideally, OFVF is determined experimentally in the laboratory; However, this value is not always available and correlations are consequently used to determine it. At this work, first the published OFVF are reviewed and then a new correlation is developed to estimate OFVF of crude oils in Middle East. This correlation is applicable for crude oils of API ranging between 19 to 49. The comparison of this new correlation with other published ones shows that it is much more accurate then the other ones. The absolute average deviation error (percent) of the new correlation is about 1.13%.
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New Mathematical Correlation for Diffusivity Coefficient and Geostatistical Relation of Asmari Reservoir
Authors A. Qazvini Firouz and A. MortezapourDiffusivity coefficient shows fluid ability flowing through porous media respect to wellbore storage coefficient. It can be used to identify reservoir characterizations which its value can be obtained from welltest analysis. A new mathematical correlation between productivity index (PI) and Diffusivity coefficient has been obtained which applying it and PI, value of diffusivity constant and consequently permeability of area around wells and other reservoir zones can be achieved without doing welltest. It is very useful especially when we haven’t enough welltest data. We found a unique equation for the Asmari reservoir of Iranian fields using available data for three fields and extending the result for the whole reservoir. Finally we applied geostatistical method to represent distribution pattern of K and PI for different parts of reservoirs to find different sectors of reservoir with higher or lower PI and K to detect the best locations for drilling new wells with higher PI, which is another dominant point of this paper.
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An Uncertainty Catalog for Oil and Gas Decision Making
Authors B. Jafarizadeh and R.B. BratvoldAll decision-making in the oil and gas industry is in the face of uncertainty. From reservoirs’ volume, well placement and concept choice, to facilities design and oil price, there is always a need to deal with uncertainty. An efficient way to study uncertainties in valuation and decision-making is to classify them into two major groups; public uncertainties, those that can be hedged using market instruments, and technical uncertainties, that are project-specific and have no relation to market movements. Commodity prices, such as oil and gas prices, are public uncertainties and by definition cannot be diversified away in a project. The prices not only have a large impact on the value of a hydrocarbon project but will also affect the important decisions during the course of a petroleum venture. There are several price processes available to model commodity prices; however the most relevant stochastic price process for valuing oil and gar projects is the two-factor model presented by Schwartz and Smith. Technical uncertainties are also present in every project. Not only these uncertainties must be quantified but we must also include a suitable a learning process in order to update the relevant probabilities in a consistent manner.
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Uncertainty and Risk Analysis to History Match and Optimize the Development Plan of a Naturally Fractured Oil Reservoir
Authors S. J. Fathi, N. Alizadeh and S.A. ZiaeeThe application of statistical methods such as response surface methodology and experimental design theory enable us to effectively deal with the uncertainties in the reservoir simulation. The method was successfully applied to the field case. First, sensitivity analysis was performed from the simulation results, which ranks the influence of the uncertain parameters regarding any simulation data, like the cumulative oil production. The method also provides the possible interactions between the parameters. Second, the most influential uncertain parameters from the previous step were considered as history matching parameters to match the simulated data with the observed data. Then the experimental design approach was used, with a fewer number of parameters, to perform a risk analysis. The result is an accurate and predictive quantification of the studied response (cumulative oil production) as a function of uncertain parameters. This function is then used to compute distribution of the studied response from some probability distributions of the uncertain parameters, using the Monte-Carlo sampling technique. The results from sensitivity and risk analysis showed that the cumulative oil production strongly depends on well locations. The Pareto Plots indicated that there exists an optimal set of well locations for each matched model.
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Integration of Fuzzy Kohonen Clustering Networks (FKCNs) with Neural Networks for Well Log Properties Estimation
Authors H. Jamali, N. Keshavarz F.K, G.H. Montazeri, S.M. Behrouz and M.R. KamaliIn this paper we propose a Fuzzy Kohonen Clustering network (FKCN) to estimate the porosity log from seismic attributes in an oil field in south-west of Iran. There are two main reasons why we have used Kohonen self organizing map which is an online method. First, in Geophysics generally we are dealing with a large volume of data which can deteriorate the performances of Neural Networks. Since this technique, unlike off line methods, gets data one by one, it helps Neural Networks to work properly by reducing mathematical complexity. Second, this method allows our model to be adapted as new wells are drilled. Here we have applied this clustering technique to obtain a more accurate result to classify seismic data. Results indicate that, integrating FKCN with neural network can be a strong predictor of reservoir characteristics through its application on seismic data. Performance exploration of neural networks with or without appliance of such technique has been studied comparatively. The outcome of applying this method on conventional neural network such as PNN or RBF proposes a considerable improvement in porosity log estimation compared to the same neural networks when no such technique is performed.
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2-D Kirchhoff Prestack Time Migration of Seismic Synthetic Records by MATLAB
Authors P. Hadian and A. JavaherianIn this paper, a MATLAB software is presented that synthesizes 2-D shot records with up to four flat reflectors with different velocities and then migrate them using kirchhoff prestack time migration method. Migration algorithm needs two matrices as inputs which they are shot records and the velocity model. Shot records are either synthesized from the data entered in the graphic interface or received as an input file. Prestack Kirchhoff time migration is applied via software written with MATLAB. A GUI (Graphical User Interface) was designed to work with codes for convenience of operator. Same model was migrated with the industrial software. Results were compared and proved good agreement between them.
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Geostatistical Simulation of Petrophysical Parameter (Porosity) in Gachsaran Oil Field by SGS Method
Authors S. Behzadi, M. Shaban and A. PouladiGachsaran oil field is located approximately in south-west part of Iran. The main reservoir of this field is Asmary formation. Petrophysical parameter which has been used in this study was porosity related to 21 wells. The average porosity reported as 9 percent. Before simulation of petrophysical parameters, some basic statistical analysis had been worked out. Directional variogram, anisotropy ellipsoid was determined and then by using SGS, 100 realizations of porosity were generated.
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Using a Genetic Algorithm in Constructing Ensemble Combinations of Neural Networks to Estimate Reservoir Rock Porosity
More LessArtificial neural networks (ANNs) can be used for reservoir characterization. Ensemble combination of ANNs, which is a type of committee machine having parallel structure, are used for reservoir characterization and may lead to better results compared to single ANNs. In this research, ensemble combinations of single ANNs were used to estimate Kangan gas reservoir rock porosity in Southern Pars hydrocarbon field, in Iran. Well logging data, related to Kangan formation, were given as the input of the networks whiles the porosity data were considered as the output. Back propagation method was used for training single networks having different structures. Then, 7 networks, which had the best results, i.e. contained minimum mean square error (MSE) in the test step, were selected. A genetic algorithm was used to obtain the coefficients of the ensemble combinations of the selected single networks. Thus, we obtained optimal linear combinations of the networks, in which maximum reductions in MSE of the test step compared to the best single networks were achieved. The best ensemble combination, compared to the best single neural network, reduced MSE in the training and test steps 14.4% and 12.5%, respectively.
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Feasibility Study of Produced Water Re-Injection in Sirri Oil Field in Iran
Authors S. Ashoori, M. Zahedzadeh, R. Masoudi, M. Saboormaleki, S. Abbasian and E. RoayaeiThe current drive within the Persian Gulf to reduce the environmental burden of chemicals and oil discharge to the environment has focused attention on challenge of produced water re-injection and has introduced new challenges for compatibility of sea, produced and formation waters. This paper investigates the feasibility of produced water re-injection and water managment in an Iranian offshore oil field named Siri. Sirri oil field located in south Iran’s border producing from a common formation between Iran and United Arab Emirates, which is under seawater injection since 1983. Recently, produced water re-injection has been considering in order to abolish environmental threat and improve the oil recovery. The major active damaging mechanisms during waterflooding could be Solid invasion, Mineral scale deposition and Corrosion. In this study, the first two mechanisms have been investigated. Several atmospheric and core flood tests, were performed to investigate the mentioned damages and the results were compared with the field outcomes. A special core holder has been designed and constructed by the research group for the better results. According to the achievements, appropriate ratio of produced water to the seawater, the right filter size and suitable chemical treatment are proposed to avoid such damages in Siri.
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Feasibility Study of Non-hydrocarbon Gases Generation During Water Flooding in Darquin Oil Field
Authors A.R. Rabbani and E. DehyadegariReservoir souring is a serious problem that appears normally when seawater is injected into sweet reservoir during secondary recovery programs. The presence of sulfides in produced oil creates various problems for the petroleum industry due to their toxicity.Owing to the fact that the main cause of non-hydrocarbon gas generation is the existence of anaerobic bacteria such as sulfate reducing bacteria (SRB), the main aim in this process has been set to investigating samples pertinent to microbial aggregations of Darquin oil reservoirs for delineating sulfate reduction potential of consumed factors. In addition, temperature effect on microbial process of sulfate reduction and nutrition needed by bacteria is studied in order to be able to anticipate amount of growth of bacteria and non-hydrocarbon gas generation in alternate temperatures. The effect of biocide and base nitrate on anaerobic bacteria growth and different kinds of non-hydrocarbon gas generation has already been discussed. Because of biocide and base nitrate compounds existence in Karoon River, which occasionally results from activities of industrial units, so after mixing with water produced from reservoir, the generation of H2S was anticipated, however the reverse was observed.
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The Optimized Dispersivity Coefficient for a Miscible Displacement Process
Authors MEISAM Kamalipour, M. Jamialahmadi and A. ShahrabadiMiscibility is controlled by physical dispersion during miscible processes. It comprises of two parameters: diffusion and mechanical dispersion.2 Unfortunately, this parameter is usually ignored during simulating the miscible processes which would be considered as an enormous source of error. Testing different dispersivities on a synthetic model shows the existence of three regions at which each component of physical dispersion controls the miscible displacement in porous media. For dispersivities between 0.73m to 0.83m the miscible process is controlled by physical dispersion mechanism while dispersivities lower than 0.73m specifies a region controlled by diffusion. The third region is the region for dispersivities greater than 0.83m and the main parameter affecting the miscible process in this region is mechanical dispersion. This study also shows that if the miscible process designed to be in transition zone, the highest amount of recovery would be achieved.
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Prediction of Wax Precipitation Temperatures in Petroleum Reservoirs upon Methane Injection
Authors T. Derakhshan and A. ShariatiWax precipitation from crude oil is a major problem faced by the petroleum industry during the depletion phase from reservoirs. Reservoir oil in contact with gas tends to get enriched in very heavy fractions that may precipitate as wax under some operational conditions. In order to alleviate the problem, it is necessary to have a model that can predict the conditions under which precipitation occurs. To simulate continuous contact of the injection gas and reservoir oil, forward and backward multiple contacts are considered in this work,. The equilibrated composition of the oil samples and the injected gas is computed by material balance and flash calculations. A modified multisolid-wax model is used to study the effect of mixture composition on wax-appearance temperature. The vapor and liquid phases are described using the Peng-Robinson equation of state. It is shown that the composition variation of the oil upon methane injection has very significant effects on the wax-appearance temperature.
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Experimental Study of Asphaltene Adsorption on Reservoir Rock Minerals
Authors R. Matoorian, M. Malaieri and M. RanjbarThe main objective of this study was improving basic perception of physicochemical crude oil’s asphaltene properties in liquid and solid surfaces (asphaltene/mineral interactions). Using asphaltene obtained from Maroun crude oil and different reservoir rock minerals, static adsorption tests were performed. The amount of adsorbed asphaltene was calculated from mass balance after determining the equilibrium concentration by UV/VIS method (288 nm). Adsorption isotherms of asphaltene on Quartz, Kaoline, Calcite and Feldspar were analyzed and compared.
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Effect of Slugs Arrangement Injection During Chemical Flooding in Vuggy Rocks
Authors SH. Ayatollahi, N. Bahar, M. Shiea, M. Gholipoor, M. Nabipour and M. AoudiaFifty percent of the world’s oil in place is in dolomite reservoirs. A significant part of this oil is in highly heterogeneous, fractured and vuggy rocks. A set of core flooding tests using the surfactant and polymer is utilized to check the oil recovery efficiency from vuggy rocks containing light oil, the same as an oil reservoir located in the south of Iran. Polymer injection prior to surfactant flooding is tested and verified through this laboratory investigation.
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Experimental Study of Sulfonated Polyacrylamide/Chromium Triacetate Hydrogels for Water Shutoff in the Ahwaz-Asmari Reservoir Conditions
Among the methods available to reduce water production, injecting a gelling system composed of a polymer and a crosslinker has been widely used. In this work a new hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate. The effects of co-polymer and crosslinker concentration and ionic strength were investigated by dynamic shear method (rheometer). Study of the viscoelastic behavior using dynamic rheometery showed that the limiting storage modulus of the hydrogels increased with increasing co-polymer and crosslinker concentration but its increasing effect from 1:5 to 1:2 crosslinker/co-polymer weight proportions on increasing elastic modulus is negligible. The effect of aging on G'/G" proportion showed that crosslinking rate decreases with increasing time. Water permeability for third water injection was about 1.8, while relative permeability was about 52 for second oil injection. Thus these gels indicated DPR (Disproportionate Permeability Reduction) and they are suitable candidates for water shutoff conformance.
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