Multi-combination exploiting technique of ultra-heavy oil reservoirs with deep and thin layers in Shengli Oilfield

There isnʹt any mature technique to develop ultra-heavy oil reservoirs in the Shengli Oilfield because of large oil viscosity, deep and thin layer, high rate of resin and asphaltene. The multi-combination exploiting technique is developed which combines the techniques of under-pressure foam flow-back, efficient oil-soluble viscosity reducer, CO2 immiscible and steam huff and puff. The following experiments were conducted about the recovery mechanism of the technique: (1) measuring foam viscosity, sands suspension property and sands washing capacity; (2) comparing the capacities of viscosity breaking and emulsion breaking of oil-soluble viscosity reducer with the conventional viscosity reducer; (3) measuring emulsion breaking of CO2. The experimental results show: Foam has the advantages of greater viscosity, remarkable capacities of suspending and washing sands; the combination viscosity reducer has greater advantage on viscosity breaking over xylene. The emulsion breaking capacity of the combination viscosity reducer and CO2 is excellent, and the higher the W/O emulsion, the greater the capacity of emulsion breaking. Field tests show that the multi-combination exploiting technique is good in improving production of ultra-heavy oil reservoirs.