DEVELOPMENT OF AN IN-SITU WATERJETS SYSTEM FOR PERFORATION

为了开发一种利用高压水射流提高天然气产量的原位射孔系统，在压力容器中对氯乙烯套管进行了实验室射孔测试，并测量了冲击压力。根据测试结果，设计了一套原位射孔系统，并对关东南部气田的一口注水井进行了初步的原位测试。主要研究结果总结如下：当环境压力为驱动压力的2 ~ 3%时，射孔面积达到最大值。当隔空距离增大时，无射孔的最大环境压力减小，而在低环境压力下，射孔面积增大。角形喷嘴比传统的直喷嘴更有效。在穿孔区域和最大环境压力下，15个角的喇叭都具有最佳性能。冲击压力的动态分量对环境压力下材料的切削起着决定性和直接的作用。在水射流表现出高性能的条件下，冲击压力功率谱密度有一个峰值，其频率从低环境压力下的几kHz到高环境压力下的约23 kHz不等。动态分量似乎与环境压力下切削材料的有效空化有关。噪声的动态特性与冲击压力的动态特性相似，这使我们能够通过测量压力容器外的噪声来检测切削材料时的动态冲击力。初步现场试验成功进行。根据本研究的结果，采用原位水射流系统对套管进行射孔，大大提高了一口注水井的注入能力。

To develop an in-situ perforation system for increasing natural gas production by using high pressure waterjets, laboratory perforation tests on a vinyl chloride casing pipe and measurements of impact pressure were carried out in a pressure vessel. Based upon the test results, an in-situ perforation system was then designed and preliminary in-situ tests were carried out for an injection well in the South Kanto natural gas field.The main results were summarized as follows :1. The perforated area becomes maximum at an ambient pressure of 2 to 3% of the driving pressure. When the standoff distance is increased, the maximum ambient pressure where no perforation occurred decreases and the perforated area increases at low ambient pressures. Horn nozzles are more effective than a conventional straight nozzle. A horn angle of 15ﾟ performs best both in perforated area and in the maximum ambient pressure.2. Dynamic components of impact pressure play a decisive and direct role in cutting materials under ambient pressure. Under the conditions where waterjets show high performance, the power spectral density of impact pressure has a peak, the frequency of which varies from a few kHz at low ambient pressures to about 23 kHz at high ambient pressures. The dynamic components seems to be related to effective cavitations for cutting materials under ambient pressure. The dynamic characteristic of noises is similar to that of impact pressure, which enables us to detect dynamic impact force during cutting materials by measuring noises outside a pressure vessel.3. Preliminary in-situ tests were conducted successfully. The injectivity of a poor injection well was recovered drastically by perforating the casing pipe with an in-situ waterjets system, which was designed according to the results in this study.