【作者】 王宁健；

【导师】 刘怀山；

【作者基本信息】 中国海洋大学 ， 地球探测与信息技术， 2008， 硕士

【摘要】 随钻地震技术是一种新兴的井中地震技术,它利用钻井期间钻头的振动作为井下震源,通过安装在钻柱顶端的先导信号传感器和埋置在井旁地表的检波器来分别接收经钻柱和地层传播上来的钻头信号,然后通过互相关等方法得到地下的地层信息,因此也称为随钻VSP或钻头地震。随钻地震不但结合了地面地震和井中垂直地震(VSP)的优点,而且具有自身独特的优势,它不干扰钻井工作,不占用钻井时间,无检波器下井风险,特别是能实时预测钻头前方的构造细节和地层压力,减少钻探风险,降低钻井成本,提高勘探开发的经济效益。由于牙轮钻头在信号采集、处理等方面的优势,现阶段随钻地震测量主要采用的是牙轮钻头。研究发现,牙轮钻头轴向作用力产生P波和SV波,横向作用力产生SH波,SH波振幅相比于P波和SV波的振幅很小,在典型的钻头尺寸和地震频率下,SH波振幅要比SV波振幅小三个数量级。由于在钻柱顶端和地面接收到的信号是连续的随机信号,因此只有将两个信号互相关才能得到反映地下构造的有效信息。但是由于先导信号是在钻柱顶端接收到的,它不可避免地受到了井场噪声和钻柱传输效应的影响,因此如何衰减井场噪声、如何消除钻柱的传输效应是随钻地震信号处理的关键问题。通过井场噪声调查发现,井场噪声有一些明显的特点,因此可以根据井场噪声的特点进行有针对性的衰减。钻柱的传输效应也是影响钻头信号的一个重要因素,其主要包括钻柱对钻头信号能量的吸收、井架顶端虚反射和钻柱内部多次反射,这些因素都会对钻头信号造成严重的影响。通过先导信号反褶积可以较好地消除钻柱的传输效应,将先导信号反褶积应用于模拟资料和实际资料,取得了理想的效果。相关作为钻头信号提取效果分析和应用的重要方法,由于计算速度、实时性等方面的原因可能无法将两个长信号一次运算完成,通过分段相关叠加的方法可以较为灵活地划分长信号,然后对应相关叠加起来,模拟试验验证了这种方法的可行性。更多还原

【Abstract】 Seismic While Drilling (SWD) is a new borehole seismic technique,which uses the vibrations produced by a drilling bit as a downhole energy source.Its signals are recorded by pilot sensors attached to the top of the drill string and by receivers located at selected positions around the borehole,so SWD can also be called Vertical Seismic Profile While Drilling or Drill Bit VSP. SWD has not only the advantages of the Surface Seismic Survey and VSP,but also its own advantages of no interruption to drilling and no risk to the borehole,and especifically it can predict the subsurface conditions ahead of the drill bit without drawing the bit out of the hole,and can also provide the seismic images for real-time survey,so it is a very good way to reduce the drilling risks and to enhance the economic benefit in petroleum exploration and exploitation.In the present SWD survey,roller-cone bit is widely used because of its advantages in signals recording and processing.The axial force of roller-cone bit generates P wave and SV wave,while the horizontal force generates SH wave, whose amplitude is much smaller than that of P wave and SV wave by three orders for typical bit size and frequency.The signals we get at the top of the drill string and at the surface are continuous,so only after crosscorrelation can the useful information be available.But in fact the pilot signals recorded at the top of the drill string are inescapably influenced by the noises and the transmitting effects of the drill string which perform as frequency abnormality and high-velocity multiples.So how to attenuate the noises and eliminate the transmitting effects are the key problems in SWD signals processing.According to noise survey,the noises at well site have some characteristics which can lead to attenuating methods.The transmitting effects of drill string are also important factor which include the drill string’s absorption to the drill-bit signals,the ghost reflection at the top of derrick and the multiple reflection in the drill string.Based on the characteristics of the transmitting effects,this paper develops the pilot deconvolution to eliminate the transmitting effects,which can get good results in both simulating data and real data.Meanwhile,in the examination and the application of the drill-bit signals,a more flexible correlating method which includes division,correlation and stack is proposed and verified by simulating data.更多还原