非水化地层微量出水后气体钻井最小注气量理论研究

Theoretical Study of Minimum Gas Influx in Gas Drilling after Water Production from Unhydrated Formation

气体钻井过程中,当钻遇水层时,地层出水容易造成岩屑聚并,影响井眼净化效果,严重时会导致施工无法正常进行,因此地层出水是限制气体钻井应用范围的最大障碍之一。当地层微量出水时,可采用增大气体注入量的方法继续钻进,而计算增加多少气体注入量是关键。前人只研究了地层大量出水条件下,地层出水量与注气量的关系。为此,在前人研究的基础上,对气体钻井过程中地层微量出水时的携岩基本规律和有关理论进行了研究,并对气体钻井过程中最小气体注入量模型进行了分析和修正,从而推导出了确定地层微量出水时气体钻井所需最小注气量的计算公式,以方便现场计算地层微量出水时所需的最小注气量,指导气体钻井安全顺利进行,以达到提高钻井速度、节约钻井成本的目的。

In gas drilling,cuttings will accumulate due to formation water production when water layer is drilled. Borehole purification effect will be affected seriously and drilling work cannot be carried out, so formation water production restrains the application of gas drilling. When formation water production is small,increasing the amount of gas injection should be used in order to continue drilling. The key point is how to calculate gas injection volume. The relationship between formation water production and gas injection was already studied with large formation water production. Based on previous work,cutting transport and associated theory is investigated when formation water production is small. The model of minimum gas injection is analyzed and modified. The required minimal gas injection is derived when small formation wa ter production is confirmed. This could ensure gas drilling safely and smoothly with the aim of increasing drilling speed and saving drilling cost.