Dual-Source Distributed Acoustic Sensing (DAS) for Seismic While Drilling (SWD)

Seismic While Drilling (SWD) is an efficient downhole seismic technology that enhances drilling operations by continuously updating subsurface velocity models and images in real time. By integrating Vertical Seismic Profiling (VSP) with Measurement While Drilling (MWD) systems, SWD improves drilling efficiency and safety, and optimizes well placement. Traditional SWD methods include using drill-bit vibrations as seismic sources and deploying geophones on the surface or a seismic tool package in the bottom-hole assembly (BHA) with seismic sources shooting at the surface. However, these methods have limitations, such as variability in drill-bit sources and delays in accessing downhole seismic data. To address these issues, we develop a Distributed Acoustic Sensing (DAS) technology with dual seismic sources – surface seismic sources and drill-bit vibrations. DAS involves a fiber-optic cable deployed in the well, enabling continuous, real-time seismic signal measurement along its length. This technology replaces conventional geophones and has been proven effective in SWD surveys, as demonstrated in previous studies. The workflow involves cementing a fiber cable behind the casing at an intermediate depth (ID) and acquiring 3D DAS-VSP data to update velocity models and produce high-quality images. As drilling progresses below the ID, DAS-SWD data from drill-bit vibrations is used to refine images, predict pore-pressure variations, and adjust the drilling direction. This iterative process continues until the drill bit reaches the target reservoirs, ensuring safe, accurate, and efficient drilling.