Efficiency and Innovation for Borehole Seismic Acquisition in a Well Completed with Permanent Fiber: DAS Technology for Saving Time and Minimizing Risk

Abstract

Abstract Efficiency is a key factor on any operation. In this paper, we introduce the heterodyne Distributed Vibration Sensing (hDVS), which is an innovative technology based on fiber optic system to improve the duration of borehole seismic operations. We designed a survey aimed at comparing standard downhole geophone accelerometers measurements to i) optical fiber seismic installed inside the hybrid Wireline cable and ii) optical fiber clamped permanently to the well completion tubing. This comparison was conducted using a standard rig source VSP in association to advanced Offsets VSP. The purpose of the study was to evaluate this innovative technology and to assess the feasibility of drastic operation time reduction without compromising output data quality. To better evaluate the readiness of the technology, we decided to compare three distinct types of downhole measurements and designed a specific advanced acquisition which allowed us to compare various configurations. Consequently, the borehole seismic acquisition performed in the MR-SE1 well located in Makhrouga field (Tunisia) was split into two phases. Phase #1: during open-hole Wireline logging, using the standard downhole geophone accelerometers (VSI) and fiber optic seismic cable (single-mode cable) installed inside the Wireline logging cable (called hybrid Wireline cable). Phase #2: at the departure of the drilling rig, using a fiber optic seismic cable (single-mode cable) installed permanently along the intelligent completion. The results highlight the effectiveness of the hDVS technology with a proven decrease on operation timing, with reliable and good SNR recorded data. Nowadays, efficiency is a key requirement for any data acquisition process. The heterodyne Distributed Vibration Sensing (hDVS) is an innovative technology designed to achieve such effectiveness by making the Vertical Seismic Profile (VSP) a matter of minutes instead of hours, as using standard downhole equipment, without compromising output data reliability and allowing the measurements repeatability (no well interventions required). Finally, based on the quality of the dataset acquired, further analysis can be conducted for imaging purpose by analyzing the reflected waveforms, which could bring additional information and could change the way we are operating.