How the Silixa Carina Sensing System is being used for ongoing CO2 storage monitoring in Otway, Australia. This cutting-edge far-offset VSP survey provides high-resolution data for advancing Australia's efforts in deep geological storage of carbon dioxide.

 

Project Introduction

The Otway Stage 3 Project, led by Project CO2CRC's Otway research facility, is at the forefront of Australia's endeavors in deep geological storage of carbon dioxide (CO2), the primary greenhouse gas. The project aims to establish an advanced monitoring system underground, utilizing up to five new wells. The ultimate objective is to develop a lasting, reliable, and cost-effective solution that provides high-resolution, on-demand seismic data for top-quality 4D imaging of CO2 plume movement.

Challenge: Limited Imaging Range of VSP Measurements

While Challenge DAS has proven to be a valuable seismic tool for this project, it has certain limitations. Although it offers detailed measurements that cover the entire wellbore for each shot, most VSP measurements have a limited imaging range, capturing only a small area around the wellbore. Although the range can be expanded by using far-off source points, the signal quality often falls short of extending the seismic image, even when employing standard wireline geophone sensors.

Solution: Silixa's Carina Sensing System

To overcome this challenge, Silixa's advanced Carina Sensing System has been implemented. This system significantly enhances the signal quality of DAS measurements, surpassing conventional geophones in various seismic applications. With a 20dB (100 times) increase in performance, as confirmed during a baseline VSP survey at the Otway research site, the Carina Sensing System offers superior capabilities for seismic imaging.

Results

The images below compare shot gather data from a standard wireline geophone tool and the Carina Sensing System at two different shot points. Figure 1 shows data from 700m away, Figure 2 from 1800m away. A single 26,000lbs vibroseis truck using a 6-150Hz, 24sec sweep was the source.

Carina Data Offers More Detail and Stronger Reflection Energy

Both figures clearly demonstrate that the Carina data provides more detail and stronger upgoing reflection energy compared to the geophone data, despite using the same number of stacked shots. The Carina Sensing System consistently delivers high-resolution data with excellent signal quality.

Figure 2, located 1800m away from the wellhead, displays distinct and consistent reflected energy, even at receiver positions close to the well bottom. Typically, VSP measurement post-processing imaging excludes this shot distance due to the low signal quality obtained with standard geophones. However, the enhanced performance of the Carina Sensing System has the potential to alter this practice, potentially enabling the capture of comprehensive and detailed subsurface images in a single shot.

Figure 1 a) 700m offset, Geophone Z component; b) 700m offset, Carina Sensing System
Figure 2. a) 1800m offset, Geophone Z component; b) 1800m offset, Carina Sensing System

Read more about the CO2CRC project and the researchers behind it here: https://espace.curtin.edu.au/bitstream/handle/20.500.11937/65735/263958.pdf

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