纳微米封堵钻井液提升页岩油极窄间距井簇井壁稳定性研究与实践OA

Aiming at the technical challenges encountered in drilling the horizontal wells with extremely narrow cluster spacing(1-5 m)in the low-maturity Chang 73 shale oil reservoirs of Zhengning Block in Ordos Basin—namely wellbore instability and lost circulation triggered by high illite/smectite mixed-layer content,well-developed microfractures and low compressive strength of target reservoirs—a water-based anti-sloughing drilling fluid system designated CQ-Seal was developed.This system adopts self-developed micro-nano plugging agents and inhibitors for drilling fluids,with plugging formulation optimized via Box-Behnken response surface methodology experiments.Laboratory evaluations were conducted to characterize its plugging capacity,inhibition performance,and effect on the compressive strength of rock core samples.Test results demonstrate that the CQ-Seal water-based drilling fluid achieves a cuttings recovery rate of 96.3%,a shale swelling rate as low as 1.7%,and a reduction in rock core compressive strength of less than 10%after immersion.Field applications were carried out across five horizontal wells within Zheng 75 horizontal well cluster.The drilling fluid density was reduced to 1.13-1.30 g/cm3,the hole enlargement ratio was merely 5.4%-6.3%,the average drilling cycle reached 16.56 days,and the casing run-in success rate in one attempt hit 100%.By synergistically enhancing nanoscale physical plugging and organic potassium salt inhibition,the CQ-Seal system substantially improves wellbore stability for shale oil well clusters with ultra-narrow spacing,delivering technical support for the efficient development of low-maturity shale oil resources.