Current StatusandDevelopment TrendofLook-Ahead While Drilling Technology

Yan Sen ^1，2 Gao Wenkai²Zhang Xiaohui³Wang JiajinZhang Chunhua²Jia Hengtian²Cao Chong² （1.PetroChinaResearch Instituteof PetroleumExplorationamp;Development;；2.CNPCEngineering TechnologyRamp;DCompanyLim ited;3.CNPC Daqing Drilling Engineering Company）

Abstract：Asone ofthe key emerging technologies in the fieldof logging while drilling （LWD），the lookahead wiledrilling（LAWD）technologycan perform real-time detection on undrilled formation in frontof the bit， effctively reducing therisk of drilling accidents and improving drilling efficiency.In this paper，theLAWD technology was clasified，the working principles of electromagnetic LAWD，acoustic LAWDand seismic LAWD were introduced，and their respective advantages and disadvantages were compared.The development history of LAWD toolsand instruments was brieflydescribed，andtheir application was analyzed.Moreover，itis indicated that the fusionof multiple methods is a key trendof LAWD technology in the future.Finally，the folowing suggestions are put forward：（1） the electromagnetic LAWD technology should develop towards multi-frequency and multi-spacing measurement mode；（2） the research on the phased array acoustic LAWD theoryand technology should be strengthened，or the technology such as enhancing the look-ahead acoustic wave energyby pre-positioning the ultrasonic transducer should be explored to laya technical foundation forthe developmentof subsequent acoustic LAWD instruments；and（3）the research and development of VSPwhile driling technology，including the development of high-accuracy sensors and the exploration of using downhole vibroseis to replace drill-bit source should be increased，so as to overcome the problem of PDC bit source.The research results provide technical support for the efficient and safe development of oil and gas resources in China.

Keywords： LAWD;LWD； seismic while drilling; electromagnetic wave;acoustic LAWD； stratigraphic prediction; phased array

0 引言

随钻测井技术（LoggingWhileDrilling，LWD）是一种在钻井过程中通过将测量仪器集成于钻具中进行作业的技术，能够执行传统电缆测井作业，同时具备将数据即时传回地面的能力[1]。随钻前探技术作为LWD技术发展的方向之一，实现针对钻头前方未钻地层信息的测量及预测。与地质导向技术不同，地质导向技术主要针对水平井而言，水平井地质导向主要依靠径向测量来保证钻头始终在储层中钻进。随钻前探技术的目的主要是及时了解钻头前未钻开地层信息，保障安全钻进，提高钻进效率，其主要用于直井中卡准地层。随钻前探技术根据测量方式主要分为随钻电磁波前探、随钻声波前探以及随钻地震前探3类。笔者在简要分析不同随钻前探技术方法原理的基础上，重点对随钻前探工具和仪器研发进展进行了综述，并介绍了当下先进前探技术应用的典型案例。同时对比分析了国内外的技术现状，并对下一步随钻前探技术的发展提出建议，以期为我国油气资源的重要高效开发提供技术支撑。

1随钻前探技术工作原理与分类

1.1随钻前探技术工作原理

1.1.1随钻电磁波前探

随钻电磁波前探技术基于随钻方位电磁波测井技术发展而来，其通过测量不同源距接收线圈间的感应电动势的幅度比和相位差来反演地层信息，工作原理如图1所示。随钻电磁波前探仪器除了配备轴向线圈以外，还加装了倾角和正交的线圈，测得的电压信号中包含多重方向分量信号；……