Determination of method for developing upward (downward) layers of ClassⅡoil reservoirs in Lasaxing Oilfield

The primary upward development of Class Ⅱ oil reservoirs in the Daqing Oilfield will terminate completely, and the secondary upward (downward) development is challenged by the choice of drilling new wells or using the existing well pattern. In order to determine the upward (downward) development mode of ClassⅡoil reservoirs in different blocks, this paper presented a systematic economic evaluation model with the eastern Duandong Block in North 1 Area as an example. This model regards the layers in initial interval and the upward layers as one development system. A cumulative oil production limit chart of the layers in initial interval in two modes was established at different oil prices, and the production limit of the layers in initial interval was determined respectively for drilling new wells or using the existing well pattern. With the economic limit water cut model and the prediction model combining arc tangent water cut and waterflooding rules, the interim cumulative oil production of the block from the time of designed upward development to the time of economic limit water cut was obtained. Based on the economic limit chart, the upward (downward) development mode for the block was defined. The study results suggest that the existing well pattern should be used for upward (downward) development in eastern Duandong block when the oil price is 40/bbl, whereas new wells should be drilled when the oil price is 70/bbl.