Modeling of Acoustic Reflection Imaging Logging Based on Least-square Reverse Time Migration

In recent years, the acoustic reflection imaging logging technique (ARILT) has become a research hotspot in evaluation of fractures and holes reservoirs close to borehole. The conventional ARILT can generally detect structures within 20 meters, and has certain limitations on describing complex structural boundaries. In this paper, the least-square reverse time migration (LSRTM) is introduced into ARILT on the premise of matching logging observation systems and calculation parameters, which will improve the effective imaging range and imaging precision nearby the well area. Based on the realization of migration algorithms and processing flows, the article applies the algorithms to typical models and one actual data, and focuses on analyzing the imaging effects of different frequencies, depths and migration methods. It is found by comparing the imaging results that (1) the effective imaging algorithms are the key to the imaging accuracy of ARILT. LSRTM not only has a high resolution, but also can reveal the horizontal change of the structures; (2) Excitation source's frequency is an important factor affecting the resolution of imaging as the result that the higher the frequency, the higher the image resolution, but the high frequency will lose detecting depth; (3) LSRTM can effectively detect structures within 23 meters under the given logging observation parameters in this paper.