Seismic response to injected gas into reservoir for storage and enhanced oil recovery purposes

Document Type : Research Article

Author

Sahand University of Technology, Tabriz, Iran

Abstract

Natural gas is accumulated in the reservoirs as either separate gas reservoir or the gas cap in an oil reservoir. Besides, gas is also injected into a hydrocarbon reservoir for IOR/EOR or gas storage purposes. Due to the reservoir heterogeneity or fault pattern in reservoir, gas could move to unplanned parts of the reservoir or could even be leaked, which in turn, deviates from the purpose of the gas injection. To overcome this problem and to monitor the fate of injected gas, 4D seismic data has recently been employed by oil and gas companies. 4D seismic, that is indeed, the repeated 3D seismic through the time has been recently revealed to be a successful tool for this purpose. However, there has been reported some challenges about the quantitative estimation of injected gas using 4D seismic data. The source of this challenge is mainly due to the non-linear response of elastic properties of saturated rock versus gas saturation. Once the gas is injected into core plug in the laboratory, the compressional velocity is significantly decreased for a few percents of gas saturation. Nonetheless, for higher gas saturation variation, not a considerable change is observed in compressional velocity. Because of this extremely non-linear behaviour, some researchers have concluded that the quantification of gas response is not possible using seismic data. In this research, it is tried to understand the reservoir scale gas distribution that is found to be different from the laboratory scale. Gas is migrated towards the upper part of the reservoir due to the gravity effect. It is quickly reached at a fixed gas saturation that is around maximum gas saturation (1-Swir). Continuation of gas injection increases gas thickness from top to base of reservoir, while gas saturation is practically fixed. Therefore, unlike the laboratory scale, the only variable on the reservoir scale would be the gas thickness, and not gas saturation. This is the key observation that would assist to understand proper 3D and 4D seismic response to injected gas. Two main 4D seismic attributes are chosen in this paper to understand those responses. The response of time shift and amplitude change were derived analytically and investigated numerically. The variety of reservoir models with different thickness and heterogeneities were made to analyze the seismic response. It can be concluded that for the medium to high-quality reservoirs, seismic response to the injected gas is simply linear; therefore, 4D seismic is still a powerful tool to quantitatively estimate the volume, distribution and migration path of the injected gas. It is proposed to continue this research to understand the seismic response on low quality (permeability and porosity) reservoirs.

Keywords

References

Amini, H., MacBeth, C., and Shams, A., 2011, Calibration of Simulator to Seismic Modelling for Quantitative 4D Seismic Interpretation: 73rd EAGE Conference and Exhibition, Vienna, Austria, DOI: 10.3997/2214-4609.20149409.
Batzle, M. and Wang, Z., 1992, Seismic properties of pore fluids: Geophysics, 57(11), 1396-1408.
Corey, A. T., and Rathjens, C. H., 1956, Effect of stratification on relative permeability: Petroleum Transaction, AIME, 358-360.
Danesh, A., 1998, PVT and phase behaviour of petroleum reservoir fluids: ELSEVEIR Science B. V., Amsterdam, The Netherlands.
Domenico, S. N., 1974, Effect of water saturation on seismic reflectivity of sand reservoirs encased in shale: Geophysics, 39(6), 759-766.
Dumont, M. H., Fayemendy, C., Mari, J. L., and Huguet, F., 2001, Underground gas storage: estimating gas column height and saturation with time lapse seismic: Petroleum Geoscience, 7, 155-162.
Falahat, R., Shams, A., MacBeth, C., 2011, Towards quantitative evaluation of gas injection using time-lapse seismic data: Geophysical Prospecting, 59(2), 310–322.
Falahat, R., 2012, Quantitative Monitoring of Gas Injection, Exsolution and Dissolution Using 4D Seismic: Ph. D. Thesis, Heriot-Watt University.
Falahat, R., Obidegwu, D., Shams, A., and MacBeth, C., 2014, The interpretation of amplitude changes in 4D seismic data arising from gas exsolution and dissolution: Petroleum Geoscience, 20(3), 303-320.
Firoozabadi, A., 1999, Thermodynamics of hydrocarbon reservoirs: McGraw-Hill Book Co., USA.
Gassmann, F., 1951, Ueber die Elastizität poröser medien, Vierteljahrschrift der Naturforschenden Gesellschaft, Zürich, 96, 1-23 (English translation from http://sepwww.stanford.edu/sep/berryman/PS/gassmann.pdf).
Han, D. H., and Batzle, M., 2002, Fizz water and low gas-saturated reservoirs: The Leading Edge, April, 395-398.
Huang, X., Will, R., Khan, M., and Stanley, L., 2001, Integration of time-lapse seismic and production data in a Gulf of Mexico gas field, The Leading Edge, 20, 278-289.
Keelan, D. K., 1976, A Practical Approach to Determination of Imbibition Gas-Water Relative Permeability, Journal of petroleum technology, February, 199-204.
Konishi, C., Azuma, H., Nabuoka, D., Xue, Z., and Watanabe, J., 2008, Estimation of CO saturation considering patchy saturation at Nagaoka: 70th EAGE Conference and Exhibition, Rome, Italy, DOI: 10.3997/2214-4609.20147806.
Lumley, D., Adams, D., Wright, R., Markus, D., and Cole, S., 2008, Seismic monitoring of CO2 geo-sequestration: realistic capabilities and limitations: 78th SEG Annual International Meeting, Expanded Abstracts, 2841-2845.
MacBeth, C., 2004, A classification for the pressure-sensitivity properties of a sandstone rock frame, Geophysics, 69(2), 497-51.
Morgan, J. T., and Gordon, D. T., 1970, Influence of pore geometry on water-oil relative permeability: Journal of Petroleum Technology, October, 1199- 1208.
Morrow, N. R., and Melrose, J. C., 1991, Application of capillary pressure measurements to the determination of connate water saturation. In: Interfacial Phenomena in Petroleum Recovery (ed. N. R. Morrow), 257–287.
Pentland, C. H., Al-Mansoory, S., Iglauer, S., Bijeljic, B., and Blunt, M. J., 2008, Measurements of non-wetting phase trapping in sand packs: SPE Annual Technical Conference and Exhibition, Denver, USA, September, 115697.
Pickup, G. E., and Sorbie, K. S., 1996, The scaleup of two-phase flow in porous media using phase permeability tensors: Society of Petroleum Engineers Journal, December, 369–381.
Sengupta, M., and Mavko, G., 2003, Impact of flow-simulation parameters on saturation scales and seismic velocity: Geophysics, 68(4), 1267-1280.
Tiab, D., and Donaldson, E. C., 2004, Petrophysics, Theory and practice of measuring reservoir rock and fluid transport properties: Golf Professional Publishing, Elsevier, USA.
Timur, A., 1968, An investigation of permeability, porosity and residual water saturation relation for sandstone reservoirs: The Log Analyst, 9(4), 8-15.
Wagner, S., Pennington, W., and MacBeth, C., 2004, Gas Saturation Calculated from Patchy and Homogeneous Models at Foinaven Field, 74th SEG Annual International Meeting, Expanded Abstracts, 1746-1749.
Iranian Journal of Geophysics
Volume 12, Issue 1
July 2018
Pages 107-126

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