Injection of non-condensable gas into steam chamber during SAGD (Steam Assisted Gravity Drainage) process is a widely adopted method to improve the efficiency of heavy oil recovery. In Liaohe oilfield, China, a non-condensable gas injection pilot test was initiated since 2011.
This paper describes the operation history of the first N2-SAGD pilot test in China and gives an integrated evaluation based on the field data and history matching results for the first time. The effects of N2 injection was discussed by comparing the production dynamics before and after N2 injection. The steam chamber development process was analyzed on the basis of accurate history matching of production dynamics.
The production dynamic analysis shows that the result of the pilot test was very promising. After N2 was injected, the oil steam ratio increased by 80% with the oil production being enhanced by 20%. Also the water-cut decreased gradually. The results of analysis of steam chamber development indicates that, upon N2 injection, the vertical growth rate of steam chamber is decreased by 30~40%, whereas steam chamber volume expansion rate is increased by 7 times. At the same time the steam chamber grows more steadily and more lateral-preferentially. With N2 injection the life-cycle of SAGD process can be prolonged by 6 years with improved recovery.
The results of this paper show that non-condensable gas injection is an effective method in adjusting the development of steam chamber and improving the efficiency of the whole recovery process. Also this paper could serve as an enlightenment for the exploitation of similar heavy oilfields in China.