喇萨杏油田特高含水期最低允许流压界限研究

针对喇萨杏油田特高含水期注水开发的特点,将注水系统、油藏系统和采油系统作为一个整体,结合注采平衡原理,给出了给定注水压力条件下最低允许流压的经验公式。应用该公式,结合注水井吸水能力及采油井产液能力的变化规律,可对不同注水压力、不同地层压力保持水平及不同含水率时的最低允许流压进行测算,为油田开发调整和规划编制提供依据。研究表明,最低允许流压随含水率升高而降低的传统认识只是一个特例,其变化规律还与注采能力、油水井数比等有关。对喇萨杏油田SZ开发区来说,为满足特高含水期的提液要求,须通过注采系统调整进一步降低油水井数比,增加注水井注水量。过度降低采油井井底流压将导致地层压力下降,影响最终水驱开发效果。提出的最低允许流压经验公式形式简单,参数易于收集,对特高含水期开发调整政策的制定具有很好的指导意义。

Study of the Lowest BHP during the Extra-high Water Cut Period in Lasaxing Oilfield

As to the development characteristics in extra-high water cut period in Lasaxing Oilfield, the injecting, the reservoir and the producing system are taken into one system to determine the lowest BHP in oil wells. The formula to calculate the lowest BHP in oil well under the given injecting pressure is presented in this paper based on the oil well performance curve and the theory of mass balance. Combing with the variation law of injectivity and productivity in water flooding, the lowest BHP under different injecting and reservoir pressure and different water cut and production-injection well ratio could be easily obtained, thus provides a solid basis for the adjustment of developing strategy and planning. The study shows that the traditional concept that the lowest BHP would decrease as the water cut increases is just a special case, and there are many factors that should be considered, such as injectivity and productivity, production-injection well ratio, etc. As to SZ block in Lasaxing Oilfield, the injecting-producing system should be adjusted to meet the need of enhancing liquid production during the extra-high water cut period. And the measures include lowering of the production-injection well ratio, increasing of the water injection rate. Lowering of the BHP too much would lead to a decreasing in the reservoir pressure and worsen the water flooding effect. The formula presented in this paper has a simple format and the data needed is easy to collect, and it would have significant meaning on the adjustment planning during the extra-high water cut period.