Performance of Near-Miscible Gas and SWAG Injection in a Mixed-Wet Core

Performance of Near-Miscible Gas and SWAG Injection in a Mixed-Wet Core

M. Sohrabi, D.H. Tehrani and M. Al-Abri
Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, Scotland

This paper was prepared for presentation at the International Symposium of the
Society of Core Analysts held in Calgary, Canada, 10-12 September, 2007

Abstract:
Oil recovery from mature waterflood can be enhanced by combined injection of water and gas in an alternating (WAG) or simultaneous (SWAG) scheme. However, less experience has been gained on the performance of WAG and SWAG in mixed-wet systems with low gas-oil IFT. We present results of a series of high-pressure displacement tests in a mixed-wet sandstone core.

We demonstrate that In near-miscible continuous gas injection, unlike immiscible gas injection, the oil recovery continues at a significant rate after the main gas breakthrough and nearly total oil recovery can be achieved. The results of near-miscible SWAG injection experiments that we have performed with different SWAG (gas/water volumetric) ratios are also presented and discussed. Comparison of oil recovery by water injection, continuous gas injection and SWAG injection shows that oil recovery due to SWAG is the highest, in this mixed-wet core.

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About the Society of Core Analysts

Objectives
The name of this organization is the Society of Core Analysts (SCA) and was founded in 1986. This organization is a Chapter-at-Large of The Society of Petrophysicists and Well Log Analysts (SPWLA) and is established with two objectives:

To promote the aims, purposes, and membership of the SPWLA which is a non-profit scientific organization.
To serve the interests of all persons who use or obtain reservoir evaluation information from rock and core samples.

As a guide for fulfilment of the first objective, this Chapter stands responsible to, and subject to, the rules and regulations of the SPWLA.

As a means toward the second objective this Chapter will sponsor technical speakers, projects, and presentation of papers dealing with formation evaluation. This Chapter will hold membership open to all core analysts, log analysts, geologists, geophysicists engineers, service company personnel and all others interested in the study of rocks and their interstitial fluids. This Chapter will also actively encourage membership and participation in the activities of the SPWLA.

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