疏松砂岩气藏自流注气井射孔工艺研究

Artesian Well Perforating Technology Research in Weakly Consolidated Sand Formation Reservoir

由于目标气田产能有较大下降趋势,为稳定气区产能,进一步提高高烃区块的采出程度,采取将Ⅲ上气组高含CO_2的气体通过水平井井筒注入到压力衰竭的高烃Ⅱ下主力气组,采用射孔方式打开上层压力已衰竭的套管封固的Ⅱ下气组。而自流注气水平井段长,疏松砂岩气藏射孔过程中容易造成沉砂、卡枪,且该区块无射孔经验可以借鉴。因此建立了水平井射孔完井出砂临界压差模型,分析射孔井的出砂临界压差,对比定方位射孔与常规射孔出砂压差,确定了射孔时合理的射孔方向,对定向射孔时的出砂量进行了预测。对比研究了负压射孔、平衡压力射孔、正压射孔时,不同射孔方式井筒内压力变化对该井的出砂影响,最终制定了满足该自流注气井射孔工艺安全的射孔方案。该疏松砂岩气藏射孔工艺优选理论,对现场具有指导意义。

Since productivity of target gas field declined prominently,we injected high CO_2-containing gas of Ⅲupper into high hydrocarbon gas of pressure-depleted Ⅲlower through artificial migration in order to form stable productivity and further increase recovery efficiency. Casing cemented Ⅱlower formation was opened by perforating where the upper pressure was depleted. However,in accordance with long horizontal interval of artesian well,perforating are more likely to cause sand setting and buried gun. In addition,no perforating experience can be used in the block. Therefore,for sand production prediction in the horizontal well with casing perforation completion,we established critical pressure differential model,analyzed critical drawdown pressure. Also,we discussed the feasibility of oriented perforation compared with conventional perforation. Finally the perforating direction and sand production prediction were determined. In the paper,we show that the different influence on sand production and gas injection rate between negative pressure perforating and balanced pressure perforating as well as positive-pressure perforating,and finally established perforating process optimization theory and developed perforation scheme for the requirement of the safety instrument system in artesian well perforation.