伊位克鲁迈拉定向井井身结构优化

Wellbore Structure Optimization of Directional Well in Rumaila Oilfield

为提高鲁迈拉钻井效益,降低施工风险,减少非生产时间,开展了伊拉克鲁迈拉油田井身结构优化。采用由内而外、自下而上的设计方法,根据地层压力情况,结合地质特点和施工难点,确定了一开进入Dammam层顶6m,二开进入Sadi层8～15m,三开钻过储层50m完钻的三层套管井身结构。根据鲁迈拉油田开发实际需求和后续作业管柱尺寸,确定各开次钻头和套管尺寸。通过套管柱安全性分析发现,采用L80级套管既要满足施工操作,又要满足抗外挤安全系数不小于1.125、抗内压安全系数不小于1.10、抗拉安全系数不小于1.25的技术需求,且各开次管柱均可顺利下入。通过该项技术在25口井上的成功应用,平均建井周期缩短15.33d,平均非生产时间比例降低了8.6个百分点。研究结果表明,伊拉克鲁迈拉油田井身结构优化技术,解决了多层漏失、大段页岩坍塌、含硫水侵等问题,确保了复杂地质条件下的安全钻进。该技术有助于提高鲁迈拉整体钻井技术水平,具有广阔的市场前景和推广价值。

In order to improve the drilling benefits,decrease the risk and reduce nonproductive time in Rumaila Oilfield of Iraq,the wellbore structure in Rumaila Oilfield was optimized.The design of operation method of drilling from inner to outer layer and from bottom to up layer was adopted.According to the formation pressure,combined with the geological characteristics and drilling difficulties,in the 1 st spudding 6 m was drilled above the top of Dammam Formation,in the 2 nd spudding 8 to 15 m was drilled in Sadi Formation and in the 3 rd spudding 50 m was drilled through the casing structure.As for the actual development requirements and subsequent casing string sizes in Rumaila Oilfield,the sizes of drill bits and caings were determined.It was found out from casing safety analysis that L80 casing could be used for meeting requirement of operations and the requirements that the safety factor of resistance to external extrusion was not less than 1.125,the safety factor of resistance to internal extrusion was not less than 1.10 and the safety factor of resistance to tension was not less than 1.25,and the casing strings could go through smoothly in each operation.The technology was successfully used in 25 wells,by which the average well construction cycle was shortened by 15.33 days,the average non-productive time ratio was reduced by 8.6 percent.The research results show that the optimization of wellbore structure in Rumaila Oilfield resolves many operating problems and complexities resulted from multi-zones circulation loss,large shale collapse,sulfur-bearing water invasion and so on,it ensures the safety drilling in complex geological conditions.This technology is able to assure the safe drilling under the complex geologic conditions.It is helpful for improving the drilling level in Rumaila Oilfield and has broad market prospects and promotion value.It provides the technological supports for the drilling and exploration teams of CNPC to hold the market in Iraq.