As I read it, there are two additional factors that would make any hydrocarbon discovery in the Tikorangi formation here at Matuku particularly interesting.
Firstly, there is the linkage between fractured limestone reservoir and the degree of reservoir porosity. Basically, the porosity in a limestone reservoir is provided through the chemical reduction of the limestone by reaction with aqueous CO2. So the aqueous CO2 flows through the initial fracture planes and dissolves the limestone, thereby creating increasingly larger voids in the rock.
And since early production out of a hydrocarbon kitchen is mainly CO2 and water we therefore have the circumstances in place [near kitchen as modelled by the JV] to create significant reservoir potential in the Tikorangi. Later production from the kitchen is hydrocarbon and this would then migrate into the voids, displacing the aqueous CO2 and hopefully creating an accumulation of hydrocarbon.
The second factor concerns the likelihood of there being structure within the Tikorangi that will necessarily trap any hydrocarbon that is migrating into [again, hopefully] an extensive void system in the rock. The three target horizons at Matuku are seen as drape structures that have formed over an underlying local basement high. Therefore basically, as height above basement increases the degree of drape diminishes until finally there is no drape and hence no further potential of there being a drape structure. The D Sand may have a small drape structure [the JV has not provided any quantification] and so possibly the Tikorangi could also have some very minor structure in this way.
However maybe the Matuku limestone might be offering a much bigger prize. Some 20km to the east is the Whitiki Fault, and this is the fault which provides the western flank to the Maui B oil accumulations. So we then have to ask could the Whitiki also be acting as a fault seal to the Matuku limestone, provided of course that there actually is hydrocarbon within the Tikorangi Formation. Also there would need to be some northeastern bound to this potential limestone structure, otherwise the hydrocarbon would migrate away updip. However we would also have to presume that there will necessarily be some natural stratigraphic bound in this direction as we move away from the effects of the compressive thrusting forces that have [yet again, hopefully] produced fracture in the limestone at Matuku.
OXX Price at posting:
21.5¢ Sentiment: None Disclosure: Held
