Using the noise generated by the drill-bit as a source, the Drill-bit seismic while drilling (DB-SWD) technique can provide a valuable real-time and on-site information during drilling, which is of great significance for the exploration and development of oil and gas reservoirs.
Recently, XU Liwen, a doctoral student from the Institute of Acoustics (IOA) of the Chinese Academy of Sciences, along with his supervisors and other researchers, proposed a new wave field separation method, which can numerically decompose the source wave field in horizontal wells and image the formation around the horizontal borehole.
The paper entitled “Green’s Function Retrieval with Marchenko and Inter-Source Seismic Interferometry Method for Drill-Bit Seismic While Drilling” was published in the Journal of Geophysics and Engineering.
The wave field separation method is the basis of the seismic borehole techniques. For deviated or horizontal wells, it is not feasible to separate up-going and down-going waves using the conventional filtering method at only one vertical depth, as the high deviated drilling trajectory induces a similar moveout for both up- going and down-going reflections.
Based on the principle of reciprocity, researchers proposed a method of using the bit and surface data to separate the bit wave field.
Figure 1. The up-going (a) and down-going (b) wave fields. (Image by XU Liwen)
The new wave field separation method uses the direct wave field as the bond to retrieve the one-way wave field. The proposed scheme only needs the single-component wave field data recorded on the ground. It is a complete data-driven method, which effectively reduces the cost. Furthermore, the formation around the well is imaged by using the retrieved virtual one-way wave field.
Figure 2. Images obtained with the surface and the retrieved data. (Image by XU Liwen)
Numerical simulations successfully demonstrated the accuracy of this method, which provide theoretical guidance for the seismic while drilling.
This research was supported by the National Natural Science Foundation of China (No. 11574347, 11734017, 91630309, and 41274134).
XU Liwen, CHEN Hao, ZHANG Xiumei, WANG Xiuming. Green's Function Retrieval with Marchenko and Inter-source Seismic Interferometry Method for Drill-Bit Seismic while Drilling. Journal of Geophysics and Engineering (Volume15, June 2018, Pages 2047-2059).DOI: 10.1088/1742-2140/aac095.
Institute of Acoustics, Chinese Academy of Sciences, 100190 Beijing, China