EN HANCED OIL RECOVERY OF AN IRANIAN CARBONATE RESERVOIR BY MISCIBLE NITROGEN INJECTION

In this work Nitrogen is selected to inject to an under-saturated Asmari carbonate reservoir in southwest of Iran because there was a reservoir in this area which contains huge Nitrogen and can be used for injection in this oilfield. The main purpose of this study is to improve recovery by miscible Nitrogen Injection at reservoir pressure. PR (1978) EOS model was tuned for reservoir fluids to use for Nitrogen injection simulation. Initially 10 core samples are prepared and their porosity and permeability are measured in laboratory. Then 3 cores with the highest permeability values are selected for experiments. The MMC ofnitrogen and the reservoir oil was determined by swelling test results, Ternary diagrams and simulations. The MMP of nitrogen and reservoir oil was determined in laboratory and simulation 5638 and 6000 psi by the Slim-tube test. As the reservoir pressure was 5000 psi , so Nitrogen and the first stage gas were combined in a defined ratio for application of injecting in the Slim-tube and cores to reach miscibility at 5000 psi .Theultimate recovery for the MMP and MMC tests in Slim-tube was 98 and 92 percent respectively, besides in core tests the ultimate recoveries in MMP and MMC tests was 88 and 85 percent respectively. So mixture of first stage gas and Nitrogen (9 to 1) injection is the best mixture to increase ultimate recovery at least to 85 percent.

Keywords:

MMP , MMC , EOR , Nitrogen Injection