广西苗儿山大厚度水敏性地层冲洗液技术研究及应用

Research and application of drilling fluid technology for thick water-sensitive formations in the Miaoershan area of Guangxi

摘要:

广西苗儿山地区铀矿找矿潜力巨大，但局部地区地层复杂，存在大厚度水敏性地层及破碎地层，钻探施工中频繁遇到孔壁坍塌及钻孔超径等难题，导致孔内事故频发，严重影响施工进度。因此，对该地区水敏性岩心进行了矿物成分和微观特征分析，分析结果表明水敏性地层含有大量蒙脱石、高岭石、水云母等粘土矿物，且微裂隙发育，水化膨胀严重。针对以上问题，通过室内实验评价，优选了新型成膜护壁材料，进一步研制了护壁性良好的成膜护壁冲洗液体系，其最优配方为：5%成膜A剂+3%成膜B剂+1.5%改性沥青+1%随钻堵漏剂+1%封堵剂+0.6%增粘剂+0.2%包被剂。该冲洗液API滤失量为5~8 mL，相对膨胀降低率达到87%以上，可有效抑制水敏性岩心水化膨胀，护壁效果明显。该技术在苗儿山地区3个试验钻孔成功应用，顺利钻穿水敏性地层，未发生岩心分散、孔壁坍塌等问题，取得了良好的应用效果，初步形成了针对该地区水敏性地层的成膜护壁冲洗液技术。

Abstract:

The potential for uranium exploration in the Miaoershan area of Guangxi is enormous， but part of the formations are complex， with large thickness of water-sensitive and broken formations. During drilling construction， difficulties such as hole wall collapse and excessively large bore diameter occur frequently， leading to frequent accidents in the hole， which seriously affect the construction progress. Therefore， mineral composition and microscopic characteristics of water sensitive cores in the area were analyzed. The analysis results show that there are a large amount of clay minerals such as montmorillonite， kaolinite， hydromica， etc. in the water-sensitive formations， and the microcracks are developed with serious hydration expansion. To solve above problems， new materials with film forming and wall protecting functions were optimized through indoor evaluation experiments， and a drilling fluid system with good wall protection performance was further developed， which consists of 5% film-forming agent A， 3% film-forming agent B， 1.5% modified asphalt， 1% plugging agent while drilling， 1%sealing agent， 0.6% viscosifier， 0.2% coating agent. The API filtration loss of this drilling fluid is 5~8mL， and the relative expansion reduction rate reaches over 87%. This drilling fluid can effectively inhibit hydration expansion of the water-sensitive formations， and the wall protection effect is significant. This technology has been successfully applied in three boreholes in the Miaoershan area， smoothly drilling through water-sensitive formations without any problems such as core dispersion or hole wall collapse. Good application results have been achieved， and a film forming and wall protection drilling fluid technology has been preliminarily formed for water-sensitive formations in this area.