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[en] A large carbonate oil field in Iran is suffering from severe casing collapses and related operational problems in anhydrite, marl and salt sequences of the Gachsaran cap rock formation. To investigate the causes and cures of operational problems, specifically casing collapse, knowing geomechanical properties of anhydrite, marl and salt of this formation is a prerequisite. However, taking cores in this formation is virtually impossible due to high solubility and weakness of the rocks. Moreover, there are insufficient well log data in this formation and the only available running well log is Vp. In this paper, in order to obtain the dynamic parameters of the Gachsaran formation, Vp, Vs and ρb in anhydrite, marl and salt cores, which had been taken from depths up to 300 m, were measured. Moreover, Vp and Vs in salt cores under different triaxial and hydrostatic stress conditions were obtained. The Vp–Vs, (Vp/Vs)–Vp and Vp–ρb relations in anhydrite, marl and salt were investigated. The established relations in these anhydrite samples were verified by the data derived from limited cores which were taken from 3600 m depth. The relations between dynamic properties of salt with lateral and hydrostatic stresses were investigated. In conclusion, Vs, ρb and the ratio of Vp/Vs in anhydrite and marl can be estimated through the established relations and having Vp logs in the Gachsaran formation. As a result, the dynamic properties of these rocks can be calculated in different depths of this evaporitic formation. Furthermore, the dynamic properties of salt rock seem to be constant in various depths and under differing triaxial and hydrostatic stress conditions. (paper)
Journal
Journal of Geophysics and Engineering (Online); ISSN 1742-2140; 
; v. 10(1); [9 p.]
; v. 10(1); [9 p.]
[en] In geothermal exploration, magnetotelluric method (MT) has the capability to resolve conductive body which then can be interpreted as cap rock. A reliable representation of the Earth’s resistivity dimensionality can be achieved by incorporating the direction of geoelectrical strike and geological condition in the geothermal area. In this study, the magnetotelluric method was applied in Tangkuban Parahu volcanic area to reveal the subsurface structure of the area. Due to the uncertainty of MT modelling result, dimensionality analysis (polar diagram) is performed to find out MT data characteristic prior to MT inversion modelling. After that, lineament is mapped based on elevation map to estimate geological strike. Both methods are validated by geological condition in Tangkuban Parahu. The result of polar diagram analysis shows that the direction of geoelectrical strike is dominated NE-SW in mostly frequency and the result of lineament shows similar direction with polar diagram analysis as plotted in rose diagram yields about N45°E. (paper)
Journal
IOP Conference Series: Earth and Environmental Science (Online); ISSN 1755-1315; ; v. 318(1); [4 p.]
; v. 318(1); [4 p.]
[en] The genetic type and accumulation model of the Devonian reservoirs in the Marsel Block remain unclear, despite decades of exploration history. According to the well testing, logging interpretations and sample testing results, the Devonian natural gas reservoir in the Marsel Block has five typical characteristics: (1) It is obvious that the traps contain continuous gas accumulations. Not only the apexes of the structures are enriched in natural gas, but also the slopes and depressions contain gas accumulations. (2) The gas reservoirs are classified as tight reservoirs, but there are also reservoirs with high porosity and permeability in some areas. (3) The general negative or low-pressure in the gas reservoir is obvious, although the pressure in the target layers of some wells is close to normal. (4) The yields of single wells in the Devonian reservoir are quite different: some wells have low yields or are dry, whereas the gas production from high-yield wells has reached 700 000 m3/day. (5) The gas-water relationship is complicated: there is no obvious gas-water interface, but the water-producing layer is generally located at the apexes of structures. Research and analysis have shown that using the model of the conventional gas reservoirs genetic type can only explain the characteristics of parts of the gas reservoir, while the model of accumulation in a deep-basin gas reservoir cannot fully explain the distribution characteristics of the Devonian reservoir. However, the model of accumulation in a stacked complex continuous oil and gas reservoir can reasonably explain the geological and distribution characteristics of the Devonian reservoir. Moreover, the predicted gas distribution along a cross-section of the reservoir is also in agreement with the geological background and tectonic environment of the Marsel Block, therefore, the genetic type of the Devonian natural gas reservoir in the Marsel Block is a stacked complex continuous tight-gas reservoir. Finally, by comprehensively analyzing the source rock, reservoir and cap rocks, as well as the structural characteristics, it is verified that Devonian in the Marsel Block has favorable geological conditions for formation of a superimposed continuous tight gas reservoir.
Journal
Journal of Earth Science (Internet); ISSN 1867-111X; ; v. 30(5); p. 893-907
; v. 30(5); p. 893-907
[en] Faults, as main pathways for fluids, play a critical role in creating regions of high porosity and permeability, in cutting cap rock and in the migration of hydrocarbons into the reservoir. Therefore, accurate identification of fault zones is very important in maximizing production from petroleum traps. Image processing and modern visualization techniques are provided for better mapping of objects of interest. In this study, the application of fault mapping in the identification of fault zones within the Mishan and Aghajari formations above the Guri base unconformity surface in the eastern part of Persian Gulf is investigated. Seismic single- and multi-trace attribute analyses are employed separately to determine faults in a vertical section, but different kinds of geological objects cannot be identified using individual attributes only. A mapping model is utilized to improve the identification of the faults, giving more accurate results. This method is based on combinations of all individual relevant attributes using a neural network system to create combined attributes, which gives an optimal view of the object of interest. Firstly, a set of relevant attributes were separately calculated on the vertical section. Then, at interpreted positions, some example training locations were manually selected in each fault and non-fault class by an interpreter. A neural network was trained on combinations of the attributes extracted at the example training locations to generate an optimized fault cube. Finally, the results of the fault and nonfault probability cube were estimated, which the neural network applied to the entire data set. The fault probability cube was obtained with higher mapping accuracy and greater contrast, and with fewer disturbances in comparison with individual attributes. The computed results of this study can support better understanding of the data, providing fault zone mapping with reliable results. (paper)
Journal
Journal of Geophysics and Engineering (Online); ISSN 1742-2140; ; v. 10(1); [11 p.]
; v. 10(1); [11 p.]
[en] Highlights: • Four functional elements control the formation of oil and gas reservoirs. • Damage of tectonic movement to petroleum accumulations is analyzed. • The oil and gas prospects of the Sinian-Lower Paleozoic are predicted. -- Abstract: Reliably and conveniently predicting oil and gas prospects and avoiding costly drilling mistakes are the goals pursued by oil explorers and companies. In 2013, the Anyue gas field was discovered in Sichuan Basin, and it was the first discovery of a giant natural gas field in Precambrian strata attracting extensive attention since then. However, the complexity of geology in the Sinian-Lower Paleozoic makes prediction of oil and gas prospects very challenging. Based on the comprehensive review of the Anyue gas field, we identify four functional elements, i.e., a source kitchen (S), paleo-uplift (U), reservoir depositional facies (D), and regional cap rock (C). The combination of these four functional elements in time and space (T- CDUS) controls the Sinian-Lower Paleozoic hydrocarbon accumulation. The probability for hydrocarbon accumulation is determined by a proposed index, Tcdus. As a tectonic movement can damage oil and gas reservoirs formed prior to the movement, a model for calculating the hydrocarbon reservoir preservation probability is also established. The oil and gas prospects in Sinian-Lower Paleozoic are predicted with the combination of the hydrocarbon accumulation and preservation model. 137 wells drilled in the Sichuan Basin show that 88.9% of the successful wells are distributed in the predicted zones.
Journal
[en] Geological storage of CO2 as an effective way of reducing CO2 output to the atmosphere receives growing attention worldwide. To evaluate the feasibility of this technique in the Xingou oil field of Jianghan Basin in China, 2D and 3D models of CO2 geological storage were established using TOUGH2 software. Results showed that CO2 gas can be stored in the deepest reservoir through continuous injection over 50 years, and will remain effectively confined within the space under the second cap-rock during its diffusion over 500 years. Compared with 2D models, 3D models showed that the diffusion process of CO2 gas in the reservoir will create a mushroom-shaped zone of influence. (authors)
Journal
Procedia Earth and Planetary Science; ISSN 1878-5220; ; v. 7; p. 669-672
; v. 7; p. 669-672
[en] Dawsonite-bearing carbonate veins are abundant in a compact mud-stone layer of the lower part of the Izumi Group, SW Japan. The mode of occurrence of the veins probably indicates fracturing and mineral sealing associated with upwelling of CO2-rich fluid evolved in the reservoir beneath. The carbonate veins studied here can be a natural support to fracturing and healing of mud-stone cap-rock in the CO2 geological storage. (authors)
Journal
Procedia Earth and Planetary Science; ISSN 1878-5220; ; v. 7; p. 636-639
; v. 7; p. 636-639
[en] This paper described a procedures for history matching surface movements resulting from the warm-up phases of a steam assisted gravity drainage (SAGD) project in Saskatchewan. Surface movements were measured using tilt meters that covered the area influenced by the steam injection processes. A thermal reservoir model was then coupled to a geo-mechanical model in order to calculate the surface movements. Surface heave was computed by matching a minimum curvature surface to the tilt vectors. Surface heave data were extracted in order to facilitate comparisons between observed and simulated heave. Injection constraints were defined from measured injection rates in order to match pressure histories. The study showed that the coupled model accurately interpreted monitoring data. Seismic signatures indicated strike slip and potential overthrust fault slippage or casing failures. Uplift was largest at the heel of the well. Results were explained by reservoir heterogeneities. Surface heave was accurately measured using the tiltmeters. Micro-seismic data were used to constrain failure mechanisms and provide information needed to identify conformance and potential cap rock breaches. It was concluded that the model can be used effectively to optimize injection conformance and recovery. 10 refs., 4 tabs., 28 figs
Source
Society of Petroleum Engineers, Richardson, TX (United States); Petroleum Society of CIM, Calgary, AB (Canada); Canadian Heavy Oil Association, Calgary, AB (Canada). Funding organisation: Schlumberger Canada Ltd., Calgary, AB (Canada); Equinox Engineering Ltd., Calgary, AB (Canada); CAN-K Group of Companies Inc., Edmonton, AB (Canada); Total E and P Canada Ltd., Calgary, AB (Canada); PGS, Houston, TX (United States); Kudu Industries Inc., Calgary, AB (Canada); GRB Engineering, Calgary, AB (Canada); PALL Fuels and Chemicals, Portsmouth (United Kingdom); Serpa Petroleum Consulting Ltd., Calgary, AB (Canada); [1500 p.]; ISBN 978-1-55563-199-4; ; Oct 2008; p. 1-20; ITOHOS 2008 : The 2008 SPE/PS/CHOA International Thermal Operations and Heavy Oil Symposium : Heavy Oil : Integrating the Pieces; Calgary, AB (Canada); 20-23 Oct 2008; Available from the Society of Petroleum Engineers, 222 Palisades Creek Drive, Richardson, Texas, 75080-2040, USA
; Oct 2008; p. 1-20; ITOHOS 2008 : The 2008 SPE/PS/CHOA International Thermal Operations and Heavy Oil Symposium : Heavy Oil : Integrating the Pieces; Calgary, AB (Canada); 20-23 Oct 2008; Available from the Society of Petroleum Engineers, 222 Palisades Creek Drive, Richardson, Texas, 75080-2040, USA
[en] An andesite rock sample was taken from potential geothermal area on Lili-Sepporaki, west Sulawesi. The sample is an impermeable cap rock with a high silica mineral at alteration zone around a manifestation. Its Three-dimensional rock structure was analyzed to see its deformation due to temperature change. Change of temperature from 24˚C to 100˚C, 150˚C, 200˚C, and 250˚C was applied to the sample. Subsequent to each change of temperature, the sample was scanned using a micro-Computed Tomography Scan (μ-CT Scan). From the scanning process, a sub-volume 300 pixels were reconstructed, and its 3D pore and mineral structure were characterized. It is found that porosity {φ (T)}, specific surface area {SsA (T)} decrease polynomial for pore structure and increase polynomial as temperature increases. This result show that as temperature increases the volume of mineral is bigger make the pore volume smaller. The Fractal dimension for pore structure (2.65 ± 0.02) and for mineral structure (2.89 ± 0.015). (paper)
Journal
Journal of Physics. Conference Series (Online); ISSN 1742-6596; ; v. 1280(2); [8 p.]
; v. 1280(2); [8 p.]
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