## LSU Historical Dissertations and Theses

1997

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Joanne M. Wolcott

#### Abstract

Cyclic gas injection processes have been primarily restricted to the use of pure CO$\sb2$ or CO$\sb2$ that has been slightly contaminated with reservoir gases. However, it is difficult to employ CO$\sb2$ in certain circumstances due to transport, economic, or corrosion problems. This study presents the results of laboratory investigations of the cyclic gas injection process using methane, nitrogen and combinations of these gases with CO$\sb2$. Cyclic gas injections were performed at immiscible conditions in consolidated sandstone cores that contained waterflood residual oil under analogous conditions to previous cyclic CO$\sb2$ injections for comparative purposes. Pure methane recovered approximately the same amount of waterflood residual oil as CO$\sb2$, whereas pure nitrogen recovered about half that amount. Certain CO$\rm\sb2/N\sb2$ and CO$\rm\sb2/CH\sb4$ combinations yielded outstanding results, recovering 2-3 times the waterflood residual oil produced by CO$\sb2$ alone. Maximum recovery was obtained with combinations containing 10-25% CO$\sb2$. Produced data showed that methane and nitrogen were considerably less mobile than CO$\sb2$. Oil recovery was attributed to a combination of CO$\sb2$'s favorable phase behavior effects and the flow profile modification effects of the inert gas.

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