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Muhammad Khurram Zahoor - One of the best experts on this subject based on the ideXlab platform.
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Prediction and estimation of capillary pressure for wettability and wettability variations within reservoir
Proceedings of Abu Dhabi International Petroleum Exhibition and Conference, 2008Co-Authors: Mohd. Nawi Derahman, Muhammad Khurram ZahoorAbstract:Wettability is defined as a property of a fluid to coat a rock surface, but unfortunately it is not as simple as the name implies. Formation can be oil-wet, water-wet or of mixed wettability. These variations are due to the initial water saturation, composition of oil, salt contents in brine and mineralogy of the formation. Wettability and wettability variations affect the displacement behavior of one fluid by another. This can be demonstrated by a number of experiments, using same core, where the trend of capillary pressure curve changes with reference to changes in saturation. In relation to it, several correlations have been developed to estimate the capillary pressure as a function of saturation based on experiments. In reality different types of wettability can exist in different regions of reservoir and moreover wettability existing at the time of discovery changes with the passage of time as a result of different processes for example, depletion, gas injection. To account for such variations and for proper understanding of displacement behavior within a reservoir a correlation has been developed, which can he used successfully for better reservoir surveillance. With the help of this correlation, if at least one capillary pressure curve is available, it is possible to estimate/predict the capillary pressure under different wettability conditions, which can exist within the reservoir, during different stages of depletion, with the help of which proper history matching, forecasting and hence proper selection of Enhanced Recovery Method is possible, resulting in better decision making and increased profitability.
Carlos Germán - One of the best experts on this subject based on the ideXlab platform.
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Simulation of nitrogen injection as an Enhanced Recovery Method in a tight natural fracture sandstone reservoir with compositional fluids
2019Co-Authors: Herrera Guevara, Carlos GermánAbstract:The construction of a dual porosity/dual permeability reservoir simulation model requires the estimation of the fracture apertures in every grid cell; generally these apertures are generated stochastically in geo-statistical models which generate a limitation in the consistency between the effective fracture permeabilities and fracture porosities measurements and interpretations. This study proposes an effective workflow to overcome the constant aperture assumption generally taken which allows adjusting the apparent aperture for each grid cell by using the matrix permeability, the critically stressed fracture intensity interpretations and the fracture permeability estimated from pressure transient analysis which results in a reliable estimation of shape factors required to estimate the fluid transfer between the matrix and the fracture. Then, using the dual porosity/ dual permeability model it was modeled the nitrogen injection in a gas condensate field. The results shows that: 1) using the Knudsen criteria and capillary pressure measurements it was found that the matrix has a conventional flow even if the permeabilities are very low, 2) the dual porosity/dual permeability model shows a higher oil and gas segregation to the bottom and to the top respectively than the conventional single porosity model due to the high fracture permeabilities, finally 3) it was found that the nitrogen injection shows significant incremental hydrocarbon gas volumes which displacement front can be optimized by adding CO2 into the injection stream.
Martin Krüger - One of the best experts on this subject based on the ideXlab platform.
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Evidence for in situ methanogenic oil degradation in the Dagang oil field
Organic Geochemistry, 2012Co-Authors: Núria Jiménez, Brandon E. L. Morris, Minmin Cai, Friederike Gründger, Jun Yao, Hans H. Richnow, Martin KrügerAbstract:Abstract In situ biotransformation of oil to methane was investigated in a reservoir in Dagang, China using chemical fingerprinting, isotopic analyzes and molecular and biological Methods. The reservoir is highly methanogenic despite chemical indications of advanced oil degradation, such as depletion of n-alkanes, alkylbenzenes and light polycyclic aromatic hydrocarbon (PAH) fractions or changes in the distribution of several alkylated polycyclic aromatic hydrocarbons. The degree of degradation strongly varied between different parts of the reservoir, ranging from severely degraded to nearly undegraded oil compositions. Geochemical data from oil, water and gas samples taken from the reservoir are consistent with in situ biogenic methane production linked to aliphatic and aromatic hydrocarbon degradation. Microcosms were inoculated with production and injection waters in order to characterize these processes in vitro. Subsequent degradation experiments revealed that autochthonous microbiota are capable of producing methane from 13C labelled n-hexadecane or 2-methylnaphthalene and suggest that further methanogenesis may occur from the aromatic and polyaromatic fractions of Dagang reservoir fluids. The microbial communities from produced oil–water samples were composed of high numbers of microorganisms (on the order to 107), including methane producing Archaea within the same order of magnitude. In summary, the investigated sections of the Dagang reservoir may have significant potential for testing the viability of in situ conversion of oil to methane as an Enhanced Recovery Method and biodegradation of the aromatic fractions of the oil may be an important methane source.
Lei Qin - One of the best experts on this subject based on the ideXlab platform.
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Pore variation of three different metamorphic coals by multiple freezing-thawing cycles of liquid CO2 injection for coalbed methane Recovery
Fuel, 2017Co-Authors: Cheng Zhai, Shimin Liu, Lei QinAbstract:Abstract Liquid CO 2 (LCO 2 ) Enhanced coalbed methane Recovery had been studied in laboratory experiments and field applications, supporting many improvements and achievements. Previous studies primarily investigated the gas bursting, flooding effect and adsorption effect; however, the freezing-thawing phenomenon (drikold formation and gasification) that commonly occurs during the LCO 2 injection process was insufficiently studied. The freezing-thawing phenomenon might enhance the pore volume and change the permeability evolution of the coalbed; thus, cyclical LCO 2 injection was proposed to exploit the phenomenon, and the influence of multiple freezing-thawing cycles on the coal pores was investigated in this paper. Nuclear magnetic resonance (NMR) and infrared thermal imagery (ITI) were used to monitor the pore variation and surface temperature distribution, respectively. Low temperatures could make the saturated water in the pores freeze and undergo a 9% volume increase. The three coals used in this experiment displayed different crack intensities and forms with ITI. After cyclical LCO 2 injection, the NMR amplitude increased, and the T 2 range was widened under a saturation condition, while the cores under a centrifuge state had lower amplitudes and a narrower T 2 range; this difference indicated that the pore structure could be altered by multiple freezing-thawing cycles of LCO 2 . The more freezing-thawing cycles the cores experienced, the greater the change in pore structure was. The total porosity φ t and effective porosity φ e increased while the residual porosity φ r and T 2cutoff values decreased with more freezing-thawing cycles. However, the variations with coal rank were observed; with higher coal ranking, φ t and φ e increased less, and the φ r and T 2cutoff values decreased less, which suggests that lower ranking coals could be most easily affected by the LCO 2 Enhanced Recovery Method and have the most improved pore connectivity. Moreover, the enhancement ratio of φ t and φ e increased for all three coals tested, which could be fit with quadratic functions with fit coefficients greater than 0.99. The increasing relative ratio D e / t of anthracite was fit with a linear function, while the lignite and bitumite were fit with quadratic functions. These functions all indicate that the multiple freezing-thawing cycles of LCO 2 injection had a positive impact on the enhancement efficiency of pore porosity. Finally, a potential field application of cyclical LCO 2 injection was also discussed to improve the fracturing effect.
Mojtaba Ghaedi - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Recovery From Naturally Fractured Gas Reservoirs With Seismic Vibrations
Journal of Energy Resources Technology, 2020Co-Authors: Khadijeh Zare, Hojjat Mahiyar, Mojtaba GhaediAbstract:Abstract Water level rising in fracture networks of a naturally fractured gas reservoir is extremely challenging and can significantly decrease the ultimate Recovery due to reservoir heterogeneity. Although capillary drainage and gravity force can enhance the displacement of gas Recovery from matrix to fracture, these forces may not be so effective in mobilizing a large amount of trapped gas through the matrix. So called, the use of seismic wave can be suggested as a low cost and environmentally friendly Enhanced Method compared with the other conventional Enhanced Methods. This article is aimed to examine the ability of seismic vibration in generating an efficient driving force for moving the remaining gas into the fracture which, to the best of the author’s knowledge, has not been reported so far. To this end, an in-house numerical simulator has been developed to investigate this Enhanced Recovery Method and also to evaluate the effect of wave characteristics as well as rock properties on the ultimate Recovery. The governing equations are solved numerically using finite difference approach and the accuracy of these equations was compared with a commercial simulator for verification. The results are very encouraging and show substantial gas Recovery enhancement by applying seismic waves. Our investigation also shows that this stimulation Method is more efficient at lower frequencies and also in higher permeable matrix and fractures.