萨哈林NV3井长筒取心技术

Long Barrel Coring Technology for the Well NV-3 in SakhaLin Island

NV-3井所在区块属于亚极地海洋环境,年钻井时间窗口十分狭窄。该井在取心钻井时,面临取心段长、时间紧等困难。为提高NV-3井的取心作业效率、缩短取心作业时间,根据该井所处地层的实际地质特点,制订了长筒取心作业方案,优选了取心钻头、岩心爪、取心筒等关键工具和装置,设计了取心筒组合方式,提出了能保证施工安全的关键技术措施,建立了取心内筒倒旋圈数和钻具安全提升高度计算公式。应用表明,建立的计算公式符合实际情况,选择的长筒取心工具和采用的技术措施效果良好,取心平均机械钻速达到8.4m/h,平均岩心收获率达到99.9%。这说明,长筒取心技术可有效克服亚极地海域时间窗口狭窄的束缚,能显著提高取心效率。

Well NV-3is on the shelf of Sakhalin Island,Russia,a location characterized by a sub-Arctic offshore climate.Every year the drilling time window is very short due to the harsh conditions.Here the coring duration must be as short as possible.In order to improve the coring efficiency and reduce the coring time of Well NV-3,the long barrel coring technology was used based on the geological features of relevant formation.Under this scheme,key tools were selected,including coring bit,core catcher and coring barrel,to form an optimal coring barrel assembly.Further,key technical measures were proposed for ensuring the operation safety.Moreover,the formulas were established to calculate the number of reverse cycles and the safe lifting height of drill tools.Practical applications showed that the formulas were satisfactory to the practical conditions,and both the coring barrel assembly and technical measures were efficient,contributing average ROP of 8.4m/h in coring operation and the recovery rate of the core up to 99.9%.Accordingly,the long barrel coring technology could overcome the limitations caused by the short drilling time window in the sub-Arctic offshore climate and greatly improve the coring efficiency.