低渗透油藏生产井关井测压时间的计算与应用

Calculating method of shut-in time for pressure survey in production wells in low permeability oil reservoirs and its application

低渗透油藏的生产井压裂后,在单井试油试采过程中,压力恢复测试关井时间不同,其中有些井压力恢复曲线不能出现边界反应段,渗流不能反映地层中真实流动特征。针对这种情况,基于长庆绥靖油田塞39井区长2低渗透油藏大量试井和实际生产资料,利用现代试井解释理论,研究合理关井时间的界限及其计算方法。结果表明,当油井关井测压时间达到3倍地层径向流开始出现的时间后,利用此时的压力数据解释地层参数和地层压力,其结果的误差小于5%,同时能较准确地判断边界类型。计算的理论曲线和霍纳法解释值非常接近,对于塞39井区,若预先知道某生产井地层有效渗透率值,可从理论曲线查出压力恢复试井的关井时间,否则,建议按照该井区地层有效渗透率(大约在6mD左右),将不稳定试井测试时间控制在25d以上为宜。

The reasonable time limit of shut-in wells and its computational method for fractured wells in low permeability reservoirs were studied by the modern well test interpretation in Chang 2 low permeability oil pool of Sai 39 block in Suijing of Changqing Oilfield. The results show that when the time of shut-in pressure survey triples the occurrence time of radial flow, the error of well-testing results about the formation parameters and formation pressure gained by pressure data at this moment is smaller than 5%. The border types can be diagnosed. The theoretical curve is similar to the Horner method interpretation value. For Sai 39 block~ if effective permeability is given, ~hut-in time for pressure ~urvey can be obtained by the theoretical curve. Otherwise, according to the effective permeability in this block （about 6mD）, it is proposed that the measuring time of transient well testing be controlled for more than 25 days.