气体渗流特征及启动压力规律的研究

A RESEARCH ON GAS FLOW PROPERTY AND STARTING PRESSURE PHENOMENON

实际气藏的生产特征反映出气体渗流与液体一样存在启动压力现象 ,而气体的“滑脱效应”似乎与气体的启动压力现象相矛盾 ,所以极有必要通过试验来研究气体二者现象产生的条件及变化规律。文章利用天然岩心进行了实验室试验 ,探讨和研究了不同压差条件下的气体流量和渗透率变化规律。研究表明 ,气体的滑脱效应是有条件的 ,在更低速条件下 ,气体的渗流具有启动压力现象 ,并建立了室内统计规律 ,即启动压力梯度与岩心的渗透率呈反比。并简单地介绍了利用该规律确定气藏合理井距的计算方法以及该规律在气井稳定试井解释中的实际应用。气体启动压力规律的存在使气井的无阻流量变小、气藏的废弃压力提高 ,造成了气藏采收率的降低。利用气藏启动压力规律可更好地指导气藏的开发设计和动态分析 ,为气藏工程的研究提供了一种新的理论方法和工具 。

The production performance of a gas reservoir idicates that the starting pressure phenomenon occurs in gas flow just as the one occurs in liquid flow and the gas 'slippage effect' seems to be contradictious to its starting pressure, therefore it is very necessary to study the generation condition and change law of the both through testing. The relation between gas flow rate and permeability under different pressure differences was studied and discussed through testing in laboratory by use of the natural cores. In accordance with the research results it is shown that the gas slippage effect was conditioned; under the condition of much lower velocity, the starting pressure phenomenon might be found in gas flow; and a laboratory statistic law was set up, i.e. the starting pressure gradient was inversely proportional to the permeability of core. The calculation method of using such a law to determine the reasonable well spacing of gas reservoir and an application of the law to the interpretation of systematic well testing are simply introduced in the paper. The gas starting pressure phenomenon can cause the open flow capacity of gas well to be decreased , the abandonment pressure of gas reservoir increased and the recovery factor of gas reservoir dropped. The development design and performane analysis of gas reservoir may be well guided by use of the gas starting pressure phenomenon, thus providing a new theoretical method and means for studying gas reservoir engineering, so it is very important to research on the phenomenon.