套铣技术优化及其在渤海油田大修井中的应用

Optimization and Application of Washover Technology in Bohai Oilfield

套铣存在施工持续时间长、卡钻风险高、受井况及落鱼材质影响制约施工效率等缺点。为此,针对渤海油田井况,通过数学建模和室内试验模拟井下套铣作业,对套铣管柱进行力学、水力学和材料学分析计算,得到了适合井眼直径、轨迹及落鱼材质的套铣工具尺寸、钻具组合的选择方法,以及影响套铣时效的钻压、转速和排量等重要参数的优化计算方法。采用该方法对套铣技术进行优化,优化后的套铣现场应用结果表明,在防砂井和注水井大修施工时,采用分段套铣解卡技术成功率很高,而且对于出砂、结垢和落物等造成的卡钻适用性较强;现场下入套铣筒数量一般不能超过10根,应根据现场条件随时调节套铣参数;若套铣落鱼产生大量钻屑,则套铣液黏度应达到45 s以上;若遇到突发情况,一定要将套铣管柱起出到生产层段之上,并活动管柱以防止卡钻。

The efficiency of washover operation is restricted by long duration, high-sticking risk, well condi- tions and fish materials. To solve these problems, for well conditions in the Bohai Oilfield, downhole washover op- eration was simulated through mathematical modeling and laboratory tests to analyze the mechanics, hydraulics and materials of the string. The methods were obtained to select proper washover tool size depending on borehole diame- ter, trajectory and fish material and to optimize and calculate the important parameters （ e. g. WOB, rate of revolu- tion and displacement） that may affect washover efficiency. Washover tools are optimized by these method and ap- plied in the field. The results show that, for workover operations of sand wells and injection wells, the section washover stuck freeing technology has a high success rate and strong applicability for sticking caused by sand prob- lem, crustation or fish. The number of washover pipe should be generally less than 10, and washover parameters should be adjusted according to field conditions. If there are a large amount of fish cuttings, washover fluid viscosity should be higher than 45 s; if an emergency situation occurs, washover string must be tripped above the produc- tion layer and moved to prevent sticking.