液体胶塞在低压易漏失含硫气井修井中的应用——以Z-7井为例

Application of gel plug in workover of low pressure and prone leakage sulfur gas well :A case study of Z-7 well

关键词:  液体胶塞  修井  压井  低压  易漏失  含硫气井

Key words:  liguid gel plug  workover  well killing  low pressure  prone leakage  sulfur gas well

摘要:

针对低压易漏失含硫气井修井过程中压井液易漏失、含硫气气窜带来的压井难题,以Z-7井为例,分析了这类井的压井难点,重点阐述了以高含量植物胶为稠化剂,通过可控交联手段形成的液体胶塞在该类气井修井过程中安全压井的适应性。现场应用效果表明:清水、清水+除硫剂的压井方式对于低压易漏失含硫气井适应性差,气窜带来的安全风险高,液体胶塞暂堵压井是可行的；正注液体胶塞9 m³,反注液体胶塞14 m³后,封堵压力分别达48.5 MPa、11.5 MPa,现场解决了“上窜下漏”问题；因含硫气体对于液体胶塞的破胶作用明显,大幅缩短了压井的有效期,添加可降解纤维能提高液体胶塞的封堵性能。 

Abstract:

In view of the well killing problems caused by killing fluid losing and sulfur gas channeling during workover of low pressure and prone leakage sulfur gas wells, taking Z-7 well as an example, the difficulties of well killing in this kind of wells are analyzed in this paper. With high concentration vegetable gum as thickening agent, the adaptability of gel plug formed by controllable crosslinking reaction in the safe well killing process during workover is emphasized. The field application results show that:the well killing mode of clear water, clear water plus sulfur removal agent have poor adaptability for low pressure and prone leakage sulfur gas wells. The safety risk is high which caused by gas channeling. It is feasible to use the cementation between gel plug and pipe string and the friction resistance to block the low pressure and easy to lose sour gas well. The sealing pressure reached, 48.5 MPa and 11.5 MPa respectively after 9 m³ of positive injection liquid plug and 14 m³ of reverse injection liquid plug, which solved the problem of “upward channeling and lower leakage” in the field. The sulfur gas has obvious breaking effect on gel plug, which greatly shortens the effective period of well killing. The pressure bearing capacity of gel plug can be greatly enhanced by adding degradable fiber.