This project reports on the geochemical evaluation of the Harvey-1 stratigraphic well, as part of the South West Hub demonstration project.
Two gas samples from a potential source of CO2 (CSBP and BOC in Kwinana) that may be used for a pilot scale test have been analysed and found to contain almost pure CO2 , in excess of 98.3 mol.%. The carbon isotopic composition of this gas is δ13C -37.6 ± 0.28 ‰, which is quite distinct from other background natural sources of CO2 and might act as a tracer in the future.
Rock samples were extracted and the uppermost sample in the Yalgorup Member contained the highest concentration of liquid hydrocarbons (304.9 mg/kg rock). Other samples contained an order of magnitude less. Relative to commercial scale oilfields this amount is negligible, indicating that there is no active source rock of quantitative significance surrounding this well. This indicates that there is unlikely to be any form of basin resource conflict in relation to oil or gas finds in the immediate area. It is also possible that the hydrocarbons may have come, in part, from drilling mud contamination.
Only one unconfined formation water sample was recovered from the well at 856 m and it was also extensively contaminated by drilling fluids (Figure B).
The sample from Harvey-1 is therefore on a mixing line between the drilling mud and the shallow bore water used.
Preliminary modelling of potential reactions in the Lesueur Formation samples suggests that the rocks have some capacity to maintain circum-neutral conditions, until all albite is converted to dawsonite (Figure A), with the removal of dissolved Na. Only after this point, do changes in pH occur. These reactions illustrate the importance of clays and feldspars contributing to changes in the mineralogy. These preliminary models contain a large number of assumptions (e.g. formation fluid chemistry is unknown).
Core-flood analyses have been conducted to evaluate chemical and physical changes to some of the Lesueur Formation samples. One experiment conducted provided detailed analyses of core flood effluents far in excess of previous literature . Improved core flood experimental setup has allowed increased sampling and detailed geochemical analysis of > 60 cations and anions to monitor changes in chemistry when subjected to CO2 injection. This workflow has provided “time-lapse” chemical data that enables us to see discrete changes in the mineralogy caused by the passage of CO2