厚松散层小口径钻探护壁与提效技术

Borehole wall protection and efficiency enhancement technology for small-diameter drilling in thick loose strata

摘要:

在皖北阜阳、亳州等厚松散层覆盖区，钻探中缩径、坍塌等孔内事故率>80%。通过分析松散层特性，揭示了孔壁“水化膨胀?颗粒运移?泥皮破坏”连锁失稳机制。提出冲洗液滤失量≤5 mL/30 min、泥皮黏聚力>8 kPa为关键控制指标，可保障长裸眼钻进超3个月。研发了KPAM+NH₄?HPAN+PAC?LV+超细碳酸钙复合冲洗液体系，形成“分层施策+随钻封堵+短程提钻”工艺。4个钻孔验证表明：孔壁稳定系数由0.51提至0.89，事故处理时间缩短100%，机械钻速提高32.8%，台月效率突破800 m。成果可为同类厚松散层钻探提供技术支撑。

Abstract:

In thick loose overburden covered areas such as Fuyang and Bozhou in northern Anhui， the incidence of downhole accidents including borehole shrinkage and collapse during drilling exceeds 80%. By analyzing the characteristics of loose layers， this paper reveals the chain instability mechanism of borehole walls dominated by "hydration expansion-particle migration-mud cake failure". The key control indicators are proposed， including the filtration loss of flushing fluid ≤5 mL/30 min and mud cake cohesion>8 kPa， which can ensure the safety of long open-hole drilling for more than three months. A composite flushing fluid system consisting of KPAM， NH₄-HPAN， PAC-LV and ultrafine calcium carbonate is developed， and a technical process featuring "layered targeted treatment+plugging while-drilling+short tripping" is formed. The verification of four test boreholes shows that the borehole wall stability coefficient increases from 0.51 to 0.89， the accident handling time is reduced by 100%， the mechanical drilling rate is increased by 32.8%， and the monthly drilling efficiency of a single rig exceeds 800 m. The research results can provide technical support for drilling engineering in similar thick loose overburden layers.