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针对低渗气藏压力稳定时间过长的问题,结合等时试井的思路,对传统的回压试井流程进行改进,以准确评价气井产能。首先采用3~4个递增的工作制度以相同时间连续开井而不要求井底流压达到稳定,再采用一个合理的工作制度延长测试并要求井底流压及产量均达到稳定,最后关井使压力恢复至地层压力。对于改进的回压试井,如果直接套用等时试井的产能计算方法,会过大地估计生产压差而造成计算的产能偏小,因而采用流程转换-流压校正技术,将测试流程转换为等时试井,并运用压力叠加原理推导出井底流压校正方程,以解决该方法的产能计算问题。实例表明,改进的回压试井方法不仅大幅缩短了测试时间、避免了频繁开关井,而且能够保证产能的准确计算。
Aiming at the problem of excess pressure stabilization time in low-permeability gas reservoirs and combining the idea of isochronal well testing, the traditional back-pressure testing process is improved to accurately evaluate gas well productivity. First, using 3 to 4 incremental working systems to continuously open wells at the same time without requiring bottomhole flow pressure to stabilize, and then use a reasonable working system to extend the test and require both bottom hole flow pressure and output to be stable. Finally, Recover to formation pressure. For the improved back-pressure well test, if the productivity calculation method of isochronal well test is applied directly, the production capacity will be overestimated and the calculated capacity will be too small. Therefore, the process conversion-flow pressure calibration technique is adopted to convert the test flow to Isochronous well test, and the use of pressure superposition principle deduced bottom hole flow pressure correction equation to solve the production capacity calculation problem. The examples show that the improved back pressure testing method not only shortens test time, avoids frequent switch wells, but also ensures accurate calculation of production capacity.