Improved oil recovery (IOR) has been attracting renewed interest amongst many operators in Trinidad in recent times. High oil prices and government incentives have increased number of studies and pilot projects in secondary and tertiary recovery processes. Whilst IOR selection is driven by rock and fluid conditions, historically most operators still gave preference to infill and outstep drilling campaigns for that last hope of primary oil. Reviews conducted on Trinidad’s past projects indicated mixed economic success of IOR projects with thermal flood projects being most successful.

Nitrogen injection has never been extensively analyzed or implemented in Trinidad and now more than before is the most opportune period to establish its place amongst the other injection mediums. This paper reviews the history and use of nitrogen injection around the globe, focuses on application to Trinidad’s fields and analyses the reservoir/geologic parameter impact on recovery through reservoir simulation. Numerical simulation was performed on blocks within an onshore mature field and recovery results showed promising project potential. Simulation was also carried out on synthetic models which mimicked the various structural dips and porosity-permeability relationships that Trinidad’s southern onshore acreage posses. The findings herein, based on immiscible injection dynamics, explains the mechanism of nitrogen injection for Trinidad’s shallow onshore reservoirs.

The overall results suggest that nitrogen injection is a real alternative and much more practical and economic than previously envisioned by investors. The technology of modern day reservoir simulation has made analysis fast and efficient using structural, stratigraphic and reservoir properties that reflects the subsurface in Trinidad. The encouraging results of this study means nitrogen injection for enhancing oil recovery can now be seriously considered by mature acreage operators who wish to lengthen the economic life span of their fields.

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