Abstract

Fengcheng Oilfield, an ultra heavy oil reservoir (viscosity of the gas-free crude oil is 151000mPa · s at 50°C), is controlled by lithology structure and sheltered by faults. The oil bearing area and OOIP of this reservoir are 6.0 km2 and 1190.21 × 104t, respectively. The depth of the oil formation is from 170 to 210m, and the net pay of the oil layer is from 25 to 40.7m.

Because of the ultra-high viscosity of the crude oil, steam huff and puff with horizontal well was employed to improve the recovery of Fengcheng Oilfield. For many years, this technology has been the main and key Enhanced Oil Recovery (EOR) technique for this Oilfield. However, as the formation energy depletes and oil saturation decreases in the near-wellbore area in the later stage of the production, water cut increases tremendously in every soaking cycle, oil-gas ratio decreases and the development effectiveness is seriously inhibited. In order to improve the performance of the steam huff and puff in heavy oil reservoir, flue gas and flue gas foam assisted steam huff and puff with horizontal well was applied for the super heavy oil reservoir, which can improve the sweeping efficiency of the steam in the near-wellbore area.

In this work, the viscosity for the flue gas-crude oil systems was measured, and the results show that t the crude oil viscosity is reduced for the dissolution of flue gas with the formation energy improved. The injected flue-gas foam can improve the performance of the mobility of the steam. Additionally, numerical simulation was employed to optimize the injection volume of flue-gas and flue-gas foam. The simulation results indicate that the optimum injection schedule is as follows: 0.5 pore volume flue-gas foam was injected firstly to control the conformance, and then 0.3 pore volume flue-gas and steam were alteratively injected. Such results are vital for the design of a flue Gas and foam assisted steam injection project in similar oil fields.

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