鄂尔多斯盆地东部气井压裂液氮伴注比例优化研究

The Optimization Research about Liquid Nitrogen Injection Ratio of Gas Well Fracturing in the Eastern Ordos Basin

提高返排液效率,减少压裂液对地层的伤害,是压裂技术面临的重要课题。通过对鄂尔多斯盆地气井排液现状分析,结合管柱结构,开展井筒持续排液条件研究。当井深2 500 m时,必须满足井底液柱压力≤15.68 MPa,或平均气液混相密度≤0.61 g/cm^3。建立液氮比例运算模型,计算得出当液氮伴注比例≥6%时,井筒可实现自主持续排液。现场试验表明,调整液氮伴注比例后,一次喷通率提高69%,返排率提高19%,试气产量也随液氮比例呈现较好正相关性。

The task of improving flowback efficiency,decreasing the formation damage caused by fracturing liquid had already become a vital question for the fracturing technology. Through the analysis about the present situation of Ordos Basin gas well drainage. In combination with pipe string structure,the wellbore continuous flowback conditions was researched. When the well depth was 2 500 m,the bottom-hole pressure must be above15. 68 MPa or the average density of miscible gas and liquid was lower than 0. 61 g/cm3. And then,liquid nitrogen proportion computation model was established,when liquid nitrogen with a proportion of 6% or more,shaft can realize continuous flowback. Field tests showed that the increase in liquid nitrogen with injection ratio,a directly spray unobstructed rate increased by 69%,flowback rate increased by 19%,at the same time,the gas production presented better correlation with liquid nitrogen ratio.