宝浪低渗油层注水压力变化规律及特征

Regularity and Characteristics of Injection Pressure for Low Permeability Reservoir in Baolang Oilfield

针对低渗透油藏特殊的渗流规律,在宝浪油田油层温度(90℃)和压力(23 MPa)下,通过岩心驱替实验研究低渗透储层(≤23×10-3μm2)的启动压力梯度及注水压力变化规律。结果表明,启动压力与启动压力梯度均随岩心渗透率的升高而降低,可分为急剧下降区、下降区和基本平衡区。在0.176×10-3～0.23×10-3μm2内,随渗透率的增加,启动压力梯度由10.77 MPa/m迅速降至5.64 MPa/m。启动压力梯度过高,注水困难。随岩心渗透率的增大,注水压力梯度与油层突破压力梯度降低,可分为平缓下降区、急剧下降区、基本平衡区,而突破压力点对应的含水率逐渐增大至100%。注水开发时,岩心含水率很快达到90%,而注水压力梯度随注入量的增加而增大,这与一般储层注水时注水压力梯度在高含水阶段稳定或下降不同。降压增注是高效开发宝浪油田的重要方法。

The regularity of threshold pressure gradient and water injection pressure were investigated on low-permeability reservoir（≤23×10-3 μm2） through core flooding experiment in Baolang oilfield with reservoir temperature 90℃ and pressure 23 MPa.The results showed that the threshold pressure and threshold pressure gradient decreased with increasing permeability which might be divided into 3 regions,such as the sudden letdown region,letdown region and basic balanced region.The threshold pressure gradient decreased rapidly from 10.77 MPa/m to 5.64 MPa/m with increasing permeability which was of 0.176×10-3—0.23×10-3 μm2.The irrigation became difficult when the threshold pressure gradient was very high.The injection pressure gradient and breakthrough pressure gradient reduced with increasing permeability which might be divided into 3 regions,such as the gentle letdown region,sudden letdown region and basic balanced region.At the same time,water cut that breakthrough pressure point corresponding increased gradually to 100%.The core water cut achieved 90% very quickly in flooding,while injection pressure gradient increased with increasing injection volume.It was different from general reservoir irrigation which injection pressure gradient was stable or decline at high water cut stage.The water injection well stimulation was the important and highly effective method to develop Baolang oilfield.