旋转磁场定向测距随钻测量仪的研制与试验

采用水平对接连通井开发煤层气时,为了确保水平井能够与洞穴井准确连通,需要给司钻人员提供准确的导向信息,即需要精确测量2口井的相对距离和方向。通过研究旋转磁场信号强度与相对位置关系,根据正交磁偶极子模型,提出了一种旋转磁场定向测距方法,研制了旋转磁场定向测距仪样机,进行了样机的地面试验和现场试验。该样机主要包括近钻头强磁短节、井下数据采集系统和地面解算系统3部分。地面试验装置包括转速可调的永磁短节台架、姿态可调的数据采集系统台架和轨道正交的50 m×30 m试验场地。地面试验结果表明,30 m以内的定位误差不超过0.1 m。现场试验结果表明,钻头距离洞穴井80 m时就可以探测到有效信号,偏航角平均误差小于1.5°,能够用于连通井的引导钻进。试验结果说明,利用旋转磁场将钻头与洞穴井靶点耦合为一个闭环系统,进行2口井的相对定位是可行的。 

Development and Field Test of Rotating Magnetic MWD Range Finder

During the drilling of horizontal intersection wells for developping coalbed methane,the relative distance and direction between two wells should be measured in real time and accurately to ensure the horizontal well trajectory being intersected with the cave wells,and provide precise geosteering information for the driller.By studying the relationship of signal strength of rotating magnetic field and relative position,a rotating magnetic directional range finding method is proposed according to the model of orthogonal magnetic dipole,and a directional range finding device prototype is developed.It has been tested on surface and at wellsite.This prototype includes near bit permanent magnet sub,downhole data acquisition system and surface interpreting computer.The surface testing device includes a permanent magnet sub bench that can adjust rotating speed,an attitude adjustable bench to fix the data acquisition system,50 m×30 m testing site with orthogonal track.The ground test result shows that the positioning error is less than 0.1 m within a distance of 30 meters.The downhole data acquisition system can receive effective signals when the bit is 80 meters far from the cave well,and the mean direction error is less than 1.5°,it can direct horizontal intersection well drilling.The testing result proves that the distance and direction measurement technique is feasible by coupling the bit and target point of cave well into a closed-loop system with rotating magnetic field.