August SPE WA Lecture: Well-based Monitoring of a CO2 Plume in a Carbon Dioxide Storage Project

Carbon dioxide (CO2) capture and storage is the subject of ongoing research in which several techniques are being evaluated to monitor the progress of the injected CO2 through the selected formation(s). Of the formation properties desirable for CO2 storage, one of the most important is the presence of an effective trapping mechanism to ensure the CO2 remains in place and does not escape to neighbouring formations or to the surface. Therefore, to confirm that the CO2 plume can be detected and leaks outside the target formation identified, various monitoring techniques must be assessed. One such technique was tested at the CO2CRC Otway Research Facility in southwest Victoria, and it is the subject of this presentation.
Pulsed neutron logging has been used for reservoir monitoring in the oil business for over 40 years. Conventional techniques rely on the measurement of the thermal neutron capture cross section (Sigma) in saline formation water of known or assumed salinities and/or the salinity-independent carbon/oxygen (C/O) ratio in oil densities and porosities of sufficient magnitude to enable calculation of the oil and water saturations.
Prior to 2004, the limited sensitivity of Sigma to oil vs. gas and of C/O measurements to water vs. gas precluded quantitative gas saturation and the differentiation of gas from oil and fresh water. Recently developed interpretation techniques using pulsed neutron gamma ray ratio-based measurements overcome these limitations and enable quantification of gas saturation in fresh, brackish or saline water, oil and three-phase environments.
This paper presents the results of a programme conducted in late 2015 and early 2016 to monitor an injected CO2 plume. The workscope comprised a base log and a post-injection log in the injection well and a post-injection log in the neighbouring monitoring well. The results show that the combination of the pulsed neutron capture measurement, Monte Carlo tool response modelling, and the interpretation technique is able to locate and quantify the CO2 plume. In the injection well, this was accomplished in the presence of complex completion hardware. The data also show that the measurements enable the location of leaks within the completion, in this case, by detecting CO2 trapped under a packer.

Speaker: Roger Marsh-Geoscience Manager, Baker Hughes, a GE company in Perth, Western Australia

Roger Marsh is Geoscience Manager for Baker Hughes a GE company in Perth, Western Australia.  He has more than 15 years of field experience in open and cased hole services.  Since 1995, he has overseen field trials for various services including the RPM prototype. He is a Chartered Engineer, a member of the SPWLA, SPE and IET.  He received a BSc in Electronics and Electrical Engineering from the University of Manchester.