复杂地质条件下S型定向井的井身结构优化及应用

Casing Program Optimization of Sshaped Directional Well in Complicated Geological Conditions and the Application

摘要:

为提高鲁迈拉油田钻井效益，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研究工作。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6 m，二开进入sadi层8～15 m，三开钻过储层50 m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，并结合行业标准，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≮1125、抗内压安全系数≮110、抗拉安全系数≮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33 d，平均非生产时间比例降低了86%。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、储层渗透率高等引起的施工中井下多发生复杂情况等问题，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，从而为中石油钻探队伍站稳伊拉克市场提供了技术支撑。

Abstract:

In order to improve the drilling economic benefits, reduce construction risk and decrease non-production time in Rumaila oilfield of Iraq, the research on casing program optimization has been carried out. Using the design method of inner to outer and bottom to top, according to the formation pressure and combined with the geological characteristics and drilling difficulties, the structure of 3-layers casing program is adopted, the 1st spud is drilled to 6 m above the top of Dammam formation, the 2nd spud is drilled into 8～15 m of Sadi formation and the 3rd spud is completed at the depth of 50 m after drilling through the reservoir. According to the actual needs of the development of Rumaila oilfield and the string size in subsequent operation, and combined with the industry standard, the sizes of drill bits and casings for each spud are determined. Through the safety analysis on the casing string, it is found that L80 casing can not only meet the operation requirements, but also can meet the technical requirements of the safety coefficients of anti-extrusion not less than 1125, anti-internal pressure not less than 110 and tensile resistance not less than 125, and the casing strings can be put down smoothly in each spud. This technology has been successfully applied in 25 wells, the average construction period is shortened by 1533d and the average non-production time is decreased by 86 percentage. The research results show that the optimization technology of the casing program in Rumaila oilfield of Iraq has resolved many complicated problems resulted from multi-zones circulation loss, large shale collapse, sulfur-bearing water invasion, high permeability of reservoir and some othrers, so as to ensure the safe drilling under the complex geological conditions. This technology is helpful to improve the overall drilling level in Rumaila and has a broad market prospect and promotion value.