The Midland Basin Field Test - Results for the Geolite/Das Hybrid System and the Surface Linear Vibrator

Mature electrical geophone technologies for active and passive borehole seismic are challenged to address emerging permanent monitoring needs like CO2 storage, geothermal, production optimization, High Pressure - High Temperature (HP-HT) reservoir surveillance and induced seismicity detection. Optical technologies (including Distributed Acoustic Sensing (DAS) and Fiber Bragg Grating (FBG) based Optical Point Sensors (OPS)) are investigated as candidates to complement or eventually replace geophones for borehole seismic acquisition (imaging or monitoring). Permanent seismic sources are needed for 4D monitoring. The GeoLite project is designed to evaluate such an innovative approach, combining DAS and FBG based Optical Point Sensors. After an initial shallow borehole prototype test in 2020, stronger downhole tools were built and tested in field conditions in 2024 and 2025 in the Midland Basin to record induced seismicity and to perform seismic borehole imaging. DAS was embedded in the GeoLite cable to combine the two optical technologies in a single array. It was deployed in parallel with a standard geophone wireline tool. It was the first time that such a design was considered for passive and active seismic evaluation. It comprised: two observer wells, a hybrid borehole optical system (DAS/ Slim multicomponent multilevel FBG array), a standard geophone borehole array, a network of surface stations, a Vibroseis source truck and a permanently anchored automated seismic source. Active and passive seismic were acquired by all systems. The experiment established the operational feasibility of GeoLite as a wireline tool. Broadband seismic data were acquired across both campaigns. Stronger coupling for this light tool was identified as an improvement for future wireline operations. For permanent deployment inside the casing, the small size of the FBG sensor is an advantage. Surface station records confirmed the limited detectability for small events from surface compared to borehole sensors.