COMPARATIVE ANALYSIS OF GAS CONDENSATE RECOVERY BY CARBONDIOXIDE HUFF-N-PUFF; CARBONDIOXIDE ALTERNATING NITROGEN AND NITROGEN INJECTION: A SIMULATION STUDY

Condensates are liquid hydrocarbons that dropout of the gas during gas production and accumulate around the wellbore when the reservoir pressure drops below the dew point pressure. A phenomenon referred to as condensate banking. The continuous accumulation of condensates, block the pore spaces around the wellbore leading to decrease in gas productivity. Conventional methods to produce gas condensates are to maintain the reservoir pressure above the dew point pressure by water and/or dry gas injection. These methods, often results to late response to water and dry gas injection and low achievable drawdown pressure. In this study a new gas condensate development technique (CO2 alternating N2 injection) was modelled and simulated, and the performance was compared to other developmental techniques. PVTi preprocessor was used to model reservoir fluid. ECLIPSE compositional simulator was used to simulate five enhanced gas and condensate recovery scenarios for a heterogenous reservoir system using CO2 and N2 gas for a period of 9 years. CO2 huff-n-puff, CO2 cyclic injection, CO2 and, N2 continuous injection and the Gas Alternating Gas (CO2 and N2) were simulated. Parametric studies on injection rate, production rate, cyclic time and injection fluid composition investigated. PVTi modelling indicates that the reservoir is a lean gas condensate reservoir with a maximum liquid loading of 6.32%. N2 and CO2 continuous injection produced 3.83% and 3.81 % respectively of incremental oil. The cyclic and GAG resulted in a 2.9% and 1.85 % increment in oil volume produced respectively. CO2 huff-n-puff achieved highest oil recovery with a 6.1% oil increment. It was observed that the huff-n-puff produced the least volume of gas. Increasing the production and injection rates showed an increase in the volume of oil and gas produced. The results also showed that the highest influencing parameter for improve gas productivity is the production rate while that for improved oil productivity is the injection rate