中国南海珊瑚岛礁第四系覆盖层钻探取心技术

Coring drilling technology of coral-reef Quaternary overburden in South China Sea

中国南海珊瑚岛礁拥有巨大的资源潜力和科研价值。珊瑚岛礁第四系覆盖层结构为珊瑚砂和珊瑚骨架的松散堆积物,无胶结,钻探取心、成井极端困难。通过南海诸岛礁数百口钻井的施工实践,总结出“套管连续跟进干钻取心技术”,工艺要点为4个步骤循环操作,称为“四步法”。使用该技术:①能确保珊瑚岛礁第四系覆盖层岩心采取率达到95%以上,并基本保持岩心原状性;②能实现在珊瑚岛礁第四系覆盖层中不使用泥浆护壁情况下安全钻进成井,达到避免地层过水通道堵塞、满足抽水试验要求的效果。研究成果对于珊瑚岛礁钻探具有重要的借鉴作用。

The coral-reefs in the South China Sea own huge resource potential and scientific research value.Coral-reef′s Quaternary overburden is composed of the loose accumulation of coral skeleton and coral sand.The poor cementation coral-reef covering layer makes coring and well completion much difficult.Based on the construction practice of hundreds of drilling holes in South China Sea Islands,the technology of"casing continuous follow-up dry coring drilling technnology"is summarized.The key point of this technology is the four-step cycle operation,which can be called"four-step method".It can ensure that core recovery rate of the coral-reef Quaternary overburden can reach above 95%with basically guaranteeing core original state.Also it can safely drill into the formation without using mud protection wellbore in the Quaternary overburden of coral-reef and achieve the goal of avoiding blockage of formation water passage and meeting the requirements of pumping tests.The present research results have significant reference for coral reef drilling.