Study on the Distribution Patterns of Remaining Oil in Thick-Layer Reservoirs with Early-Stage Polymer Flooding Based on Well Pattern Adjustments

To further clarify the distribution law of remaining oil in thick-layer reservoirs with arly-stage polymer flooding under the coupling conditions of well pattern changes and reservoir rhythm, taking Bohai L oilfield as the target, the oil displacement experiments with changing well patterns were carried out on three different rhythm thick layers, namely homogeneous rhythm, positive rhythm and negative rhythm, during the early polymer flooding and water injection processes. The results show that after the well pattern of the negative nine-point well pattern with injection angle wells is changed to the row-column well pattern, the liquid production and oil production of the three different rhythm models increase rapidly, and the recovery rates are improved to varying degrees, indicating that the change of well pattern has a certain effect on expanding the swept volume and tapping the remaining oil. After the well pattern change, the degree of remaining oil enrichment is positive rhythm model > negative rhythm model > homogeneous rhythm model. On the plane, the remaining oil enrichment morphology changes from “similar to a rhombus” to “chessboard” shape, and the remaining oil is mainly enriched between the oil wells. Under different rhythm conditions, the sweep degree, remaining oil distribution range and remaining reserves proportion after changing the well pattern are different. The research results were applied to the adjustment and potential tapping test of Bohai L oilfield. The production of the deployed horizontal well reached 85 m3/d, which can guide the potential tapping of similar oilfields.