环保型弱凝胶护壁护心钻井液研究与应用

海域浅层气地质调查和盐湖环境科学钻探在松散砂岩钻探取样工程中，存在孔壁易坍塌、成孔率低等技术难题，为此开展了松散砂岩地层环保型弱凝胶护壁护心钻井液技术研究。通过弱凝胶结构研究及成胶剂、交联剂及抗盐降滤失剂等材料优选，研发了一套环保型弱凝胶护壁护心钻井液，评价了钻井液的流变性、滤失性、抑制性、护心性能、环保性能等性能，并在山西某盐湖环境科学钻探工程进行现场应用。室内及现场应用结果表明：研制的弱凝胶护壁护心钻井液具有良好的流变性、降滤失性、抑制性（岩屑回收率96.3%）、护壁护心性能及环保性能（BOD5/COD比值24.6%，EC50值47950 mg/L），能有效解决松散砂岩类地层孔壁坍塌、岩屑不易携带等问题，在松散地层钻探工程中具有广阔的应用前景。

Research and application of environment-friendly weak-gel drilling fluid for wall and core protection

When drilling and coring loose sandstone in offshore shallow gas geological survey and salt lake environmental scientific drilling project, we often encounter technical problems such as easy collapse of borehole and low porosity. This work researched the environment-friendly weak gel wall-and-core-protecting drilling fluid technology for loose sandstone formation. Through the structural study of weak gel and the optimization of gelling agent, crosslinking agent, and salt resisting fluid loss reducer, a set of environment-friendly weak gel wall-and-core-protecting drilling fluid was developed. The rheological properties, filtration performance, inhibition, core protection and environmental protective performance of the drilling fluid system were evaluated, and the drilling fluid was applied in a salt lake environmental science drilling site. Laboratory experiments and field application indicate that the developed weak gel wall-and-core-protecting drilling fluid has excellent rheological properties, fluid loss reduction, inhibition (rock debris recovery rate 96.3%), wall-and-core-protecting performance, and environmental protecting performance (BOD5/COD=24.6%, EC50=47950 mg/L). This weak gel wall-and-core-protecting drilling fluid can effectively solve the problems of borehole collapse in loose sandstone and cuttings carrying difficulties, which has broad application prospects in loose formation drilling.