FROM THE BOREHOLE WALL INTO THE FORMATION – COMBINING BOREHOLE IMAGES WITH DEEP SHEAR WAVE IMAGING TECHNOLOGY

摘要

One major challenge of integrating borehole image andgeophysical measurements is to bridge the gaps betweentheir dissimilar horizontal and vertical resolutions anddepth of investigation. Identifying and characterizinggeological features like bedding contacts and fractures,by combining high-resolution Borehole Imaging (BHI)with Deep Shear Wave Imaging (DSWI) technology,helps to overcome this challenge. It reveal sub-seismicfeatures in the reservoir section that ultimately lead to amore accurate structural model of the subsurface.In this paper, we present a case study showing the fullintegration of both imaging methods. Picked reflectors inthe deep shear wave image allow correlation withcorresponding geological features on the boreholeimage. Identifying the dip and azimuth of a reflectorfrom the measured orientation of the correspondingfeature on the borehole wall enables the rotation of thetool reference frame to be aligned with the sagittal planefrom the deep shear wave image (i.e., the plane in whichthe reflection occurs. Note that the strike of the reflectorequals the azimuth of the sagittal plane). With thisborehole image-based adjustment the sagittal plane ofthe deep shear wave image is shown at its correctazimuth and therefore positioned “correctly” in thesubsurface. Accordingly, our understanding andinterpretation of the DSWI result improves significantly.Although this azimuth can also be obtained via the fourcomponent DSWI data (Tang 2004), this is not always asrobust as the method proposed here. However, ifpossible, it is good practice to compare both methods,also because an “event” picked from a borehole imagelog does not necessarily have to coincide with a similarevent in the DSWI image. The borehole image event maynot continue away from the wellbore and/or theresolution of this borehole image event is far above theDSWI resolution.