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.

SAGD (Steam Assisted Gravity Drainage) is commercially adopted as a main development methods for heavy oil reservoirs and oil sands. Improving recovery rate and heat efficiency of SAGD process is the main pursuit of all researchers. This paper aims to utilize a new additive with carbamide to reduce the steam consumption and lower down the residual oil saturation, hence to improve the recovery efficiency of this method.Study on improving recovery efficiency of SAGD with carbamide in super heavy oil reservoir was carried out. 1-D flooding experiment were carried out at 50°C and 150°C to compare the sweep efficiency between different additives including carbamide, CO2 and alkali. Then simulation were run to evaluate the influence of carbamide to SAGD process. Different additives were compared and influences of different products from carbamide were analyzed in detail.Study reveals that SAGD process can be greatly influenced by carbamide. Carbamide can gradually decompose into ammonia and CO2 in steam chamber. Great solubility of ammonia in water can effectively increase PH value of reservoir liquid and decrease residual oil saturation. The core flooding test results show that the oil displacement efficiency can be improved by 17.7% when 25% mass percent of carbamide was added at 150°C. And at 50°C, NH4OH showed 9% improve of sweep efficiency comparing to water. Solution of CO2 into oil can improve oil water mobility ratio. And in the simulation case the oil saturation in the core part of steam was reduced to 0.12 by ammonia (this value is 0.2 for steam). Distribution of CO2 and ammonia shows that oil drainage maybe start with viscosity reduction with CO2 solution and ends with ammonia flooding in steam chamber. With the result of this paper, the recovery factor of SAGD process can be improved by 15.4% and SOR can be improved by 20% when carbamide was co-injected with steam.