Title: Scaling analysis of capillary transition zones

Authors: Ting Sun; Christopher D. White; Yuanyuan Shuai

Addresses: Offshore Oil and Gas Research Center, China University of Petroleum, Beijing, China ' Tulane Unversity, New Orleans, USA ' Shell Oil Company, Houston, USA

Abstract: Unsaturated flow in aquifers commonly includes a transition zone reflecting the balances among viscous, gravity, and capillary forces. Saturation varies within this zone, affecting properties of interest, including effective permeability and acoustic velocities. Moreover, in systems with a rising or falling water table, the shape and length of the transition zone varies. In this study, capillary transition zone is studied through reservoir simulation and scaling analysis is used to investigate how the length of capillary transition zones changes during production. Two new dimensionless numbers - capillary time and capillary length are first introduced. Thirty models with different grain sizes have been run. The length of capillary transition zone is calculated through reservoir simulation and results are summarised using capillary time, capillary length, and gravity number. It is concluded that the capillary length are the same when capillary times and gravity numbers are the same in different models. [Received: May 16, 2016; Accepted: October 20, 2016]

Keywords: capillary transition zone; water-air system; saturation boundaries; scaling analysis.

DOI: 10.1504/IJOGCT.2018.093958

International Journal of Oil, Gas and Coal Technology, 2018 Vol.19 No.1, pp.22 - 34

Received: 16 May 2016
Accepted: 20 Oct 2016
Published online: 10 Aug 2018 *

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