Research on Determination of the Action Radius of Nitrogen Huff and Puff in Low-Permeability Reservoirs
Because of starting pressure gradient and invalid injection-production network, low-permeability trapped reservoir shows low oil recovery degree. Field applications manifest that nitrogen huff and puff can effectively improve the recovery of the low-permeability trapped reservoir. But the ambiguous knowledge of action radius in oilfield leads to imbalance in nitrogen gas application. Based on those problems, this research provides a method to determine the action radius of nitrogen huff and puff in low-permeability trapped reservoirs. Firstly measuring the starting pressure, gradient of oil-nitrogen gas two-phase flow in target core; then using numerical software to model and match the production history of the reservoir, to get the relationship between pressure and time on each position. Finally, through data integration, we can get the relationship between pressure gradient and time on each position. If the formation pressure gradient of the position is equal to the starting pressure gradient, then the position is the action radius of N2 huff and puff in low-permeability trapped reservoirs. The result shows that this method can predict the action radius of N2 and get the relationship between the action radius and the time. It provides a good basis to determine the well placement and optimum nitrogen consumption for the next move.
KeywordsLow-permeability trapped reservoir N2 huff and puff Starting pressure gradient Action radius
The authors sincerely thank others in Foam Fluid Research Centre in China University of Petroleum (East China) helping with the experimental research.
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