Abstract:

Gas injection is an effective way to increase oil recovery in low permeability reservoir,especially in ultra-low permeability reservoir.But if the sizes of gas injection slug are different,the effects of enhanced oil recovery are also different.The authors of this paper study the influence of three sizes of gas injection slug for enhanced oil recovery on Shanshan low permeability reservoir.There are associated gas flooding after water flooding,0.3HCPV associated gas is injected after water flooding then water flooding adopted again and 0.6HCPV associated gas injected after water flooding then water flooding adopted again respectively.The results show that the breakthrough time is earlier in the second step than in the first and third steps,however the breakthrough time in the first and third steps are similar,the GOR under the first condition is much higher than that under the second and third conditions,and the GOR under the condition of re-injected 0.6HCPV associated gas after water flooding is higher than that under the condition only re-injected 0.3HCPV associated gas injection after water flooding;the displacement efficiency are 6.41% and 13.61% respectively under the second and third conditions.The oil recovery ratio of continuous associated gas injection after water flooding increase by 0.79% on the basis of re-injected 0.6HCPV associated gas after water flooding.But the increase is only modest,so the 0.6HCPV injection is the appropriate amount.

Key words: Shanshan low permeability oil reservoir, gas injection slug, enhanced oil recovery, associated gas displacement