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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
61 - 80 of 140 results
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A New Analytically Derived Shape Factor for Gas-oil Gravity Drainage Mechanism
More LessMatrix-fracture exchange term is an important parameter in simulation of NFR using double porosity concept. Matrix block located in gas-cap is going to be produced under gravity drainage retarded by capillary force. Hence, oil can be produced as long as gravitational force is greater than capillary force. Interaction of these forces which controls oil production from matrix block may be expressed by a factor named matrix-fracture transfer shape factor. Customarily, this factor has been used as history matching parameter because it isn’t still well understood and formulations used in commercial simulators arenot precise. Therefore, a mathematically derived shape factor reflecting gravity drainage behavior into exchange term using shape factor concept is essential. Traditionally, constant shape factor has been used in most of commercial reservoir simulators. Here, we use analytical modeling to develop a time dependent shape factor for gas-oil gravity drainage mechanism for a single matrix block in gas-cap. Obtained model is verified against several fine-grid numerical simulations as well as two major existing models being used in commercial simulators. Results obtained here will improve understanding of gas-oil gravity drainage in NFR and will find application in more accurate representation of process.
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Cold Production from a Fractured Carbonate Heavy Oil Reservoir in Iran - Case Study
More LessA successful case study on a carbonate heavy/extra-heavy oil field is presented and the techniques and challenges behind the production from highly fractured carbonate Bangestan reservoirs are discussed in this study. The field consists of two fractured carbonate reservoir with about 3.6 billions barrels of initial oil in place of 7.5-18º API heavy/extra heavy oil. The oil viscosity at reservoir temperature (139.3 oF) is around 700-800 cp. The pressure is 927 psi at 1119 mdd but heavy oil does not naturally flow to the surface. Based on field conditions and reservoir characterization, it was decided to implement initially cold production by two experimental methods of lifting with no injection but only swabbing and use of PCP (Progressing Cavity Pumps). simulation showed a good match with the further field data when the cold production scenario was employed. The challenges and techniques employed on field pilot including various techniques of production are summarized and optimized production methods of cheaper lifting procedures of heavy oil to surface is described. Consequently lifting heavy and extra heavy oil to surface using PCP is applicable for this field in stage of cold production prior to any expensive and complicated thermal method implementation in future phases of production.
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Formation of Traveling Liquid Bridges between Matrix Blocks: Modeling and Simulation
More LessIt is widely accepted that under reservoir conditions there exists some degree of block to block interaction that may result in capillary continuity. The formation of liquid bridges causing capillary continuity between blocks will significantly affect ultimate recovery. In this work a mechanistic model with original thought from hydrology for a given steady feeding volumetric flow rate from an upper block (under both gravity and matrix capillary pressure effects) is developed which considers the formation, growth and detachment of pendant liquid droplets perpendicular to the horizontal fracture (assuming to be smooth and parallel walled) between blocks. The length of detached liquid droplet is observed to be weakly related to the flow rate but it increases as the fracture capillary pressure increases. By neglecting the impact of the flow rate, the simple relation is derived for determination of the length of detached pendant droplet which depends on the fracture capillary pressure, liquid density and the gravitational acceleration. Comparison between the horizontal fracture aperture size and the length of detached pendant liquid droplet is then used to evaluate the formation of traveling liquid bridge between upper and lower blocks.
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Sedimentary Control on Early Diagenesis in Shallow-marine Carbonates: Control on Fracturation (Madison Formation)
Authors J. P. Callot, M. Barbier, Y. Hamon and B. VincentThe carbonates of the Madison Formation outcrop in the core of the Laramide fold of Sheep Mountain (Wyoming). The sedimentation is organized in stacked meter-scale fining-up cycles, illustrating a repetitive evolution from (1) a "deep" subtidal environment (mid ramp system), to (2) a subtidal environment subjected to storm reworking, and finally (3) a quiet lagoon environment separated from the open marine setting by migrating oolithic shoals. The diagenetic evolution is controlled by the initial sedimentary facies: (1) mudstones present an intense early dolomitization; (2) oolithic grainstones display isopachous marine calcite cements; (3) mud-supported facies (wacke- to packstones) are poorly impacted by early diagenesis (little early dolomitization of the carbonate mud). The multi-scale characterization of the fracture network reveals a strong control by the coupled depositional pattern and diagenetic imprint.
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Revised Biostratigraphy and Sequence Stratigraphy of the Gadvan, Dariyan and Kazhdumi Formations, SW Iran
Authors F.S.P. van Buchem, D. Baghbani, L. Bulot, M. Caron, F. Gaumet, A. Hosseini, F. Keyvani, R. Schroeder, R. Swennen, V. Vedrenne and B. VincentA regional sequence stratigraphic model is presented for the Barremian to Lower Albian sedimentary systems of southwest Iran. Illustrated with nine seismic scale outcrop sections, and constrained by new biostratigraphic and chemostratigraphic age dating (ammonites, pelagic forams, orbitolinids and carbon and oxygen isotope curves), it proposes a fundamental revision of the geometrical relationships between classically used lithostratigraphic units. The relative influence of both eustatic sea-level fluctuations and regional tectonic control are demonstrated. These new insights have significant implications for both the understanding of the factors controlling sedimentation, as well as the architecture of the mid-Cretaceous petroleum systems in the studied region.
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Microfacies Analysis and Environmental Interpretation of Tertiary Reefs in the Osmaniye-Iskenderun Sub-basins, SE Turkey
By M. IkramThese studies are about the sedimentology and environmental interpretation of middle Miocene reefal carbonates found in the SE Turkey. These rocks comprises hydrocarbon reservoirs in the region. Therefore, detailed sedimentological studies of the outcrops provided a unique opportunity to see the reservoir characters of these rocks.
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Sequence Stratigraphy and Sr Isotope Stratigraphy of the Oligo-Miocene Deposits in the Dezful Embayment (Asmari and Pabdeh Formations, SW Iran) - Implications for Reservoir Characterisation
Authors F.S.P. van Buchem, T. Allan, G.V. Laursen, M. Lotfpour, A. Moallemi, S. Monibi, H. Motiei, N. Pickard, A.R. Tahmasbi, V. Vedrenne and B. VincentA sequence stratigraphic model is proposed for the Oligo-Miocene Asmari and Pabdeh Formations in the Dezful Embayment of South-West Iran. The model is based on both detailed sedimentological observations in outcrops, core and well logs, and an improved high resolution chronostratigraphic framework constrained by Sr-isotope stratigraphy and biostratigraphy. The better understanding of the stratigraphic architecture allows distinguishing four, geographically separated types of Asmari reservoirs.
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The Influence of Obduction on the Late Cretaceous Deposits in the Fars Province-Zagros, Iran
Authors A. Piryaei, J. Reijmer and F. van BuchemDuring the Late Cretaceous the northeastern margin of the Arabian plate (Zagros-Fars Area) is characterized by significant variations in sedimentary facies, sedimentation patterns, accommodation space and by shifting depocentres. A succession of events recording the evolution of the region from a passive to an active margin is documented by the study of eight outcrop sections and one well. This new study uses new age dating (benthic and planktonic foraminifera, nannoplankton and radiolarian biozonations and strontium isotope stratigraphy). Three tectono-sedimentary phases are recognised indicating the evolution from a passive to an active margin: Phase I (Late Albian to Cenomanian, before obduction) comprises three depositional 3rd order sequences comparable to the other parts of the Zagros and Arabian Plate. This interval is composed of shallow-water platform carbonates and intrashelf basins. Phase II (Turonian to Late Campanian, obduction phase) is characterized by major changes in depositional environments and sedimentary facies, due to obduction and foreland basin creation. Phase III (Late Campanian to Maastrichtian, after obduction) shows the development of rudist-dominated carbonates in the NE ,deep basinal facies in the centre of area. In the most-NE no sediments of this age have been recorded suggesting uplift at that time.
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The Asmari Formation Revisited: Changed Stratigraphic Allocation and New Biozonation
Authors G.V. Laursen, S. Monibi, T.L. Allan, N.A.H. Pickard, A. Hosseiney, B. Vincent, Y. Hamon, F.S.P. van Buchem, A. Moallemi and G. DruillionThe essential biostratigraphy of the Asmari Formation was outlined in the early 1950’s and thereby the only published record of the biostratigraphy before the Asmari Formation was formally described in the mid 1960’s. The traditional Iranian biostratigraphy is based on unpublished reports. Unfortunately, these reports were written in a period when the Aquitanian stage was under debate. Recent studies have shown that sediments ascribed to the Miocene “Aquitanian” are in fact Late Oligocene, Chattian in age. This was proved by the application of Sr-isotope stratigraphy to cored sections from 10 Iranian oil fields and 14 outcrop sections, within the framework of a high resolution sequence stratigraphic study down to fourth order cycles (van Buchem et al., in press). For each section, the strontium dates were plotted against the fossil ranges. The strontium ages necessitate a revision of the interpretation of the Chattian-Aquitanian boundary. The Chattian/Aquitanian boundary is marked by a major faunal turnover, with the general extinction of Archaias species and Miogypsinoides complanatus. The previous age interpretation of the early, unpublished zonations necessitates a revision, and the establishment of an updated biozonation. This new zonation and the stratigraphic ranges of selected key-species are presented here.
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Platform to Basin Facies Transition in the Lower Cretaceous Fahliyan Formation: Evidence for the Formation of Garu Intra
Authors M. Khosravi, Y. Lasemi and M. FeiziThe Fahliyan Formation (Berriasian-Valanginian) is an important petroleum reservoir in southwest Iran. Field and microscopic investigation of the Fahliyan Formation in the Izeh Zone, west of Kazroon Fault, resulted in recognition of platform and off platform basinal (calciturbidite and pelagic) facies. Lateral and vertical facies variations of the Fahliyan Formation in the study area indicate deposition in settings related to a carbonate shelf with an east facing shelf margin. Platform facies in the type locality (Fahliyan section) changes towards the northwest in the Eshgar section to chiefly basinal pelagic and calciturbidite facies. In the Eshgar section, mainly calciturbidite facies, sharply overlies the platform facies of the lower part of the Fahliyan Formation suggesting the onset of tectonic activity along the Kazroon Fault system in Early Cretaceous leading to the formation of the north to south trending Garu Intrashelf Basin in southwest Iran
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New Findings on the Dasycladacean Algae from the Fahliyan Formation in the Zagros Basin (SW of Iran)
More LessA very detailed biostratigraphical analysis, sequential interpretation and paleoecological investigations have been carried out based on the Dasycladacean algae and accompanied benthic foraminifera on the Fahliyan Formation in Kuh-e-Khartang and Kuh-e-Gavbast and correlated with Kuh-e-Surmeh, SW of Iran. Vertical variations of lithofacies and cyclic deposits in the shallow water carbonates can be interpreted in terms of sequence stratigraphy. Sequential interpretations reveal at least three 2nd-order and 3rd-order sequences with several parasequence sets throughout the studied successions. The sequences are given in Berrisian – Early Valanginian, Early Valanginian and Hauterivian age. Family Dasycladacea and subfamily Clypeineae are the most frequent and occasionally reported for the first time from the Zagros Basin and/or from the Southern Tethys. The paleoecological and paleobathymetrical investigations indicate that these strata have been deposited in a shallow internal subtidal (protected lagoon) to external subtidal and platform margins with the interval depths of 5 m to 40 m and their salinity ranges from normal marine to super saturated (hypersaline) conditions.
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Evidence for Top Shuaiba Exposure and Incision in Block 5, Offshore Qatar, and Regional Consequences
Authors F. van Buchem, M. Raven, P.H. Larsen, F. Surlyk, H. Steinhardt and M. EmangAn integrated subsurface data set of core, vertical and horizontal wells and seismic has provided evidence for the presence of karstification and quartz sand filled platform incision at the top of the Shuaiba Formation in offshore Qatar. These observations have significant implications for the late Aptian palaeogeography and related understanding of the distribution of late Aptian/early Albian siliciclastics in the region. In addition, it provides a Late Aptian reference curve for the Arabian plate.
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Possible Mechanisms in MIOR Processes
Authors M. Shabani Afrapoli, C. Crescente, O. Torsaeter and S. OstvarAbstract: Microbial Improved Oil Recovery, MIOR, consists in increasing the population of bacteria with beneficial properties for mobilizing additional oil in the reservoir, and thereby generating improved oil recovery (IOR). Determining which mechanisms allow bacteria to increase oil recovery and how these mechanisms occur and interact is the key to understanding, predicting and planning MIOR projects successfully. The authors have carried out experimental works with Rhodococcus sp. 094 and the main objective of the works was to get a better insight into the complex mechanisms allowing this bacterium species to increase oil recovery. This includes investigations of interfacial tension reduction, wettability changes due to the bacteria solution, glass micromodel flow tests and core flood experiments. From the results, it is possible to propose a theory of how Rhodococcus sp. 094 improves the oil recovery. The theory suggests which type of bacteria is most active and thereby gives IFT reduction, wettability alteration to both oil- and water-wet systems and gives favorable changes in the flow pattern.
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Micromodel Studies of Bioplugging Efficiency in Heterogeneous Porous Media by Means of Mixed Culture of Microorganisms
Authors M.S. Karambeigi, M. Schaffie, M.H. Fazaelipoor and M. SaadatOn of the most important problems of water-flow control and water flooding is heterogeneity of porous media. This problem causes water to canalize through high permeable zones and low permeable zones remain intact A possible method for decreasing this unwanted phenomenon is bioplugging of high permeable zones. In this study the efficiency of microbial treatment for improvement of water flooding of Persian gulf in a heterogeneous micromodel with 2 layers of low and high permeable zones was visualized using 2 sets of experiments. The first one was water flooding and the other was microbial treatment with a mixed culture of microorganisms that followed by water flooding. Results of visualization and image analysis studies showed that water canalizing through high permeable layer in the first experiment decreased considerably via bioplugging of this layer and the oil recovery enhanced considerably.
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The Comparison of Effects of Immiscible Injection of Natural/Nitrogen Gases on Asphaltene Precipitation Process
Authors R Rostami Ravari, A. Hajizadeh and M. AmaniAsphaltene and wax deposition in the course of production of many Iranian reservoirs has become a serious problem. In order to investigate the effect of injecting rich and dry natural gases and also nitrogen, on the asphaltene precipitation process a comprehensive research study was launched. Three phase equilibrium calculation of NGHIEM and his co-workers is used. In the method pure asphaltene in the oil is considered as solid and the heavy part of the oil is split as precipitating and non- precipitating. The provided model is able to describe the phase behavior of reservoir oil encountered with a compositional disturbance caused by injecting light fluids into the reservoir during the production period. In this work, first, the natural depletion model of each case is constructed and then the changes of behavior by injecting rich and dry natural gases and also high nitrogen content gas is investigated. Also the change in onset of asphaltene precipitation for different injections is shown. The achieved results show that the nitrogen gas has more moderate effect on precipitation process compared to more vigorous effect of dry and rich gases.
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Fractal Analysis of Surface Roughness Induced by Asphaltene Deposits: Effect of Surface Topography on Wettability Altera
Authors EHSAN Nikooee, J. Sayyad Amin, S. Ayatollahi, A. Alamdari, H. Jahromi and M. EscrochiAsphaltene precipitation is known as one of the side effects of gas injection in the depleted oil reservoirs. In this study surface topography alteration during high pressure precipitation process on different substrates (mica and glass) was studied. Fractal analysis of the surface images was performed which led to the calculation of fractal dimensions (D). The difference statistics method was used to calculate fractal dimensions. To obtain the images of asphaltene deposits on the surface, in micro scale size, a high pressure cell was designed. The condition for asphaltene precipitation in a solution of Asphaltene/Toluene/ Heptane was maintained by changing the pressure of the cell. Results showed that by increasing of pressure, the mica and glass surfaces tend to be altered to the oil wet conditions because of the increase in fractal dimension which is the representative of surface roughness. It was also observed that fractal dimension of asphaltene-deposited glass surface is more than the one for asphaltene-deposited mica surface at the end of experiment. Since number of nucleation- growth sites on mica surface are much more than those of glass surface thus asphaltene growth on mica surface is much more noticeable which can fill micro-asperities.
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Comparison Between Natural and DFN Models in Water-flooding Numerical Simulations
Authors M. Belayneh and S.K. Matthaithis method is error prone due to post-burial processes. Mineralised fractures (vein) attributes are good candidates as analogues for open fracture formed under in-situ conditions and to establish the relationship between length versus aperture and help to reveal the conditions at the time of their formation. Vein attributes were used to condition stochastic generation of fractures using the Discrete Fracture Network (DFN) code, FracMan. Comparison of water breakthrough time and oil saturation at breakthrough were then determined by applying constant pressure gradient for each realisation to simulate water-flooding numerical simulation using the combined finite element – finite volume method (FEM – FVM). Stochastic realisations were compared with the actual system. The results indicate that, depending on the variability of the above attributes, fluid flow in fractured rocks vary from pervasive where the fractures play subordinate role to a highly localised flow where most of the flow occurs through single or connected network.
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Challenges of Modelling Naturally Fractured Reservoirs: IOR/EOR Studies
More LessCharacterization of naturally fractured reservoirs is complicated. The reservoir model of such reservoirs must represent both fracture and matrix systems and interaction between the two. It is important to choose correct dual continuum model parameters to build the most representative of a fractured reservoir. In this study, we try to improve our understanding of interaction between matrix and fracture and how this can be captured by dual porosity/permeability model. We look at a homogeneous, a simple heterogeneous and a detailed pore-type based heterogeneous model. Fracture act as boundary conditions. First, interaction of forces during various depletion scenarios is studied. Then, oil recovery by gas/water injection is simulated in the fine scale. Dual continium models corresponding to the fine scale models have been built and it has been tried to achieve a good match between fine scale and dual continuum model, by adjusting dual continium model parameters. Observations from this study highlight the importance of capturing the fine scale heterogeneity in fractured reservoir modeling. Furthermore, the ability of reproducing fine scale results, by final simulation model will depend upon selected upscaling/coarsening methodology and how parameters of the coarse scale model are generated/tuned.
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Evaluation of Different Flooding Scenarios as Enhanced Oil Recovery Method in a Fractured Reservoir: A Case Study
Authors B. Moradi and A. ShahvaranfardBecause of technological complexity and financial requirements to initiate a gas flooding project, a thorough evaluation before it is performed would be necessary. In this paper reservoir modeling approach was used to evaluate different flooding processes (miscible and immiscible) in a fractured oil reservoir. This study included: 1) equation of state (EOS) modeling of experimental PVT data, 2) determining MMP for different gas compositions using an slimtube model and studying the effect of grid number on results (numerical dispersion), 3) studying the effect of completion pattern and injection rate on recovery performance, and 4) comparing recovery performance in different flooding scenarios(CO2, N2, methane, enriched methane and water injection)
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Simulation Study of Conventional Fire Flooding (CFF) in Fractured Combustion Cells: A Promising Tool along Experiment
Authors R. Kharrat, S. M. Fatemi and C. GhotbiThe Conventional Fire Flooding (CFF) process application feasibility on fractured carbonated reservoirs remained questionable. In this paper first combustion parameters and reaction kinetics of a naturally fractured low permeability carbonated heavy oil reservoir in Iran called Kuh-E-Mond applied to simulation study. After that, simulator has been validated with Kuh-E-Mond combustion tube experiment. Recovery mechanism in single block matrix is different from one in conventional model since oxygen first flows into the fractures and then diffuses from all sides into the matrix. Combustion of the oil in the fractures produces some water ahead of fracture combustion front which prohibits oxygen from early breakthrough through fractures into production well. Water imbibes to the matrix and causes matrix oil drainage to the producer. This oxygen diffusion/water imbibition based recovery mechanism is slower in production rates compare to conventional model recovery mechanism, and causes lower produced oil quality since less oxygen is available for matrix. Further, sensitivity analysis on air injection rate, formation thickness, injection well depth of perforation, horizontal fractures and also effect of water alternating air process on fracture model results have been studied.
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