Study on the Impacts of Capillary Number and Initial Water Saturation on the Residual Gas Distribution by NMR

Tao Li, Ying Wang, Min Li, Jiahao Ji, Lin Chang and Zheming Wang
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Tao Li: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Ying Wang: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Min Li: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Jiahao Ji: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Lin Chang: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
Zheming Wang: Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MSIN K8-96, Richland, WA 99352, USA

Energies, 2019, vol. 12, issue 14, 1-15

Abstract: The determination of microscopic residual gas distribution is beneficial for exploiting reservoirs to their maximum potential. In this work, both forced and spontaneous imbibition (waterflooding) experiments were performed on a high-pressure displacement experimental setup, which was integrated with nuclear magnetic resonance (NMR) to reveal the impacts of capillary number ( Ca ) and initial water saturation ( S wi ) on the residual gas distribution over four magnitudes of injection rates ( Q = 0.001, 0.01, 0.1 and 1 mL/min), expressed as Ca (log Ca = −8.68, −7.68, −6.68 and −5.68), and three different S wi ( S wi = 0%, 39.34% and 62.98%). The NMR amplitude is dependent on pore volumes while the NMR transverse relaxation time ( T 2 ) spectrum reflects the characteristics of pore size distribution, which is determined based on a mercury injection (MI) experiment. Using this method, the residual gas distribution was quantified by comparing the T 2 spectrum of the sample measured after imbibition with the sample fully saturated by brine before imbibition. The results showed that capillary trapping efficiency increased with increasing S wi , and above 90% of residual gas existed in pores larger than 1 μm in the spontaneous imbibition experiments. The residual gas was trapped in pores by different capillary trapping mechanisms under different Ca , leading to the difference of residual gas distribution. The flow channels were mainly composed of micropores (pore radius, r < 1 μm) and mesopores ( r = 1–10 μm) at log Ca = −8.68 and −7.68, while of mesopores and macropores ( r > 10 μm) at log Ca = −5.68. At both S wi = 0% and 39.34%, residual gas distribution in macropores significantly decreased while that in micropores slightly increased with log Ca increasing to −6.68 and −5.68, respectively.

Keywords: capillary number; initial water saturation; capillary trapping; residual gas distribution; nuclear magnetic resonance (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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