海上轻质油藏水驱渗流阻力特征研究

轻质油藏注水井常存在井口压力不断升高的现象，酸化、微压裂等常规措施并不能有效降低井口压力。为进一步探究注入压力过高的原因，以流管模型为基础，依据水电相似原理，开展井间渗流阻力变化规律研究。结合达西定律推导了渗流阻力表达式：渗流阻力与储层形状和总流度有关。而非活塞驱替过程的总流度变化通常分为两种：单调增加（中、高黏），先减小后增加（低黏）。原油黏度较小时，总流度会呈现减小的趋势，渗流阻力随之增加，导致注入压力升高，此时表现在注水井井口压力不断升高，即发生了“伪堵塞”，严重制约油田注水。通过对渤海南部区域不同油田注采井间渗流阻力的计算，得到了能够反应渗流阻力变化规律的无因次阻力系数图版，图版展示了“伪堵塞”可能发生的含水阶段，能够有效指导注水井的治理。结合KL油田群的治理实践，当注水井发生“伪堵塞”时，可采取以下措施：（1）对高破裂压力、低裂缝发育的油藏，实施提压增注；（2）对低破裂压力、高断裂程度的油藏，采取层内生气调驱；（3）对超低原油黏度、埋藏深的油藏，可考虑气驱开发；（3）对多层合采开发油藏，应优先解决纵向水驱矛盾。

Percolation Resistance Characteristics of Water Drive in Offshore Light Oil Reservoirs

In the water injection wells of light oil reservoirs,the wellhead pressure is constantly rising.Conventional measures such as acidification and microfracture cannot effectively reduce wellhead pressure.To explore the causes of injection pressure increases further,the law of variation in percolation resistance among wells is studied based on the flow tube and the principle of hydropower similarity.An expression of percolation resistance is derived by applying Darcy′s Law.Percolation resistance is related to the shape of the reservoir and the total fluidity.The total fluidity change of the non-piston displacement process is usually divided into two types:monotonous increase(medium and high viscosity)and initial reduction followed by a slight increase(low stickiness).When the viscosity of crude oil is low,the total fluidity decreases,and the percolation resistance increases,resulting in increased injection pressure.In such circumstances,the wellhead pressure of the water injection well is increasing,and“pseudo-blocking”occurs,which substantially restricts the water injection.Through calculating the percolation resistance between injection and production wells in different oilfields of the southern Bohai Sea,a graph of the dimensionless resistance coefficient that reflects the law of variation in percolation resistance is obtained.The graph depicts the possible waterbearing stage of pseudo-blocking,which can effectively guide the management of the injection well.Combining this analysis with the treatment practice of the KL oilfield group,the following measures can be taken when pseudo-blocking occurs in the injection well:(1)Increase pressure and water injection for high fracture pressure and low fracture reservoirs.(2)Control the profile and oil displacement for low fracture pressure and high fracture reservoirs.(3)Develop gas drive systems for ultra-low crude oil viscosity and deeply buried reservoirs.(4)Give the vertical water drive contradiction priority for multilayer comingled mining development reservoirs.