Carbon Dioxide Flooding Feasibility of Well Groups in Ultra-deep High Temperature, High Pressure and High Salt Reservoirs - An Example from the Donghe 6 Block of Tarim Oilfield

The Donghe 6 block in Tarim oilfield has the problems of ultra-deep, high temperature, high pressure, high salinity, low permeability, strong water sensitivity, low oil production, low water cut and low recovery rate of recoverable reserves relying on natural energy depletion. Based on the brief introduction of the geological characteristics of the block, the basic situation of the single well and the review of the old wells in the Donghe 6 well group were analyzed, with the emphasis on the nitrogen injection test. Combined with the actual situation of Donghe 6 well group, the feasibility of CO2 flooding in ultra-deep, high temperature, high pressure and high salt reservoir group was demonstrated by continuously injecting supercritical carbon dioxide into the high part of the structure to give full play to the gravity assisted flooding effect of injected gas. The demonstration results show that the Donghe 6 well group adopts the continuous gas drive mode of one injection and two production of pure carbon dioxide, with a cumulative injection of 16000 tons of liquid carbon dioxide, and a predicted cumulative oil production of 26800 tons in five years, with a stage increase of 4.9% in recovery, and considerable economic benefits. This achievement can be popularized and applied to carbon dioxide flooding in other similar reservoirs.