摘要:
涪陵页岩气田前期水平井因导眼和一开井眼尺寸大，导致机械钻速低，并存在一开井塌严重、二开井壁易失稳等问题。为此，在分析涪陵地区钻井工程地质环境特点的基础上，确定了套管必封点，并根据William钻速方程缩小了导眼和一开井眼的尺寸，将表层套管下深从长兴组上提至飞仙关组顶部，二开中完井深由进入浊积砂体3.00~5.00 m，调整为进入龙马溪组地层50.00~100.00 m后下入技术套管，从而形成了优化后的井身结构。涪陵页岩气田水平井自2014年后期开始采用优化后的井身结构，2015年105口水平井与2013年采用原井身结构的30口水平井相比，平均机械钻速提高了65.74%，在井深增大的情况下，平均钻完井周期缩短了20.95%。这表明，优化井身结构后达到了提高机械钻速、减少井下故障、缩短钻井周期的目的。
Abstract:
Due to the large size of conductors and boreholes in the first drilling section in the Fuling Shale Gas Field,the horizontal wells had issues such as low ROP,severe sidewall collapse during the first drilling section,and borehole instability during the second drilling section.Accordingly,the sealing points of casing were determined based on analyzing drilling engineering and geologic features of Fuling Area,based on the William drilling-speed equation,sizes of conductors and borehole of the first drilling section were reduced,the set depth of surface casing was withdrawn upward from the Changxing Formation to the top of Feixianguan Formation,and in the second drilling section,set the depth of intermediate casing was changed from 3.00-5.00 m into the turbidite sandstone to 50.00-100.00 m into the Longmaxi Formation.The optimized casing program has been applied to horizontal wells in the Fuling shale gas since late 2014,as a result,the ROP of the horizontal wells got higher,and drilling cycle was shorted.Compared with the 30 horizontal wells drilled in 2013,the average ROP of 105 horizontal wells drilled in 2015 was improved by 65.74%,and the average drilling cycle was shorted by 20.95% while the average well depth increased,which showed the optimization of the casing program effectively enhanced ROP,reduced the downhole complication and a shortened drilling cycle.
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