摘要
文章着重研究了由于施工液体的温度过低而引起的地层冷伤害对气井增产措施的影响。实验选用了鄂尔多斯盆地的气藏岩心,在恒压和45℃、30℃、25℃、15℃、5℃下进行了水测渗透率实验,发现随着温度的降低,岩心的渗透率也随之降低;岩心的原始渗透率越低,其降低程度越大,尤其是在5℃左右,渗透率降低到最低。当温度由5℃恢复至45℃时,岩心的渗透率不能恢复至原来的值。由此可见,当气层受到冷伤害后其伤害程度有部分是不可逆的,气层不能恢复至原始状态。在同样的实验条件下,进行了压裂液的返排实验。在低温状态下,压裂液的返排效果很差。由此推断在低温状态下,由于突然的冷刺激导致岩心的孔隙结构发生变化,原来张开的微裂缝闭合,使其渗透率大幅度降低;加之低温条件下压裂液的破胶能力差,导致其返排能力变差。两者共同作用的结果必然会导致增产措施失败或不能发挥其作用效果。该结果对冬季施工提供了极其有益的资料。
The influence of formation cold damage caused by the ultralow temperature of working fluid on gas well stimulation is studied in the paper. Through testing the water permeabilities of the gas reservoir cores collected from E' returnabilityerduosi Basin at a constant pressure and different temperatures as 45, 30, 25, 15 and 5°C, it was found that the core permeability reduced along with the decrease in temperature; the lower the primary permeability of the core, the larger the loss of the core permeability;the loss of the core permeability was the largest at about 5°C; and the primary permeability of the core couldu't be reinstated when the temperature returned form 5°C to 45°C. For this reason, the partial cold damage of gas reservoir is irreversible, in other words, the virgin state of the gas reservoir can't be reinstated. Then a returning experiment of fracturing fluid was carried out under the same experimental conditions. The returning effectiveness of fracturing fluid was poor at low temperature. It was deduced that the core permeability reduced greatly owing to the open microfractures' close-up caused by the change in pore structure in the core because of a sudden cold stimulus; and the poor returnability of fracturing fluid was caused by its low cementation-broken ability at low temperature. Therefore the failure of well stimulation is inevitable,or its ideal result can't be achieved, by the action of the both. Such a conclusion is useful for carrying out stimulation in winter.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2004年第10期54-55,共2页
Natural Gas Industry
基金
中国石油长庆油田分公司重点攻关项目
关键词
渗透率
返排
气井
岩心
压裂液
增产措施
气层
鄂尔多斯盆地
地层
气藏
Computer simulation
Fracturing (oil wells)
Mechanical permeability
Petroleum reservoirs
Thermal effects
