lost their oil, page-30

** corybas 1 - is it risky? ** Hello,

I've been doing a bit of work from the ARQ website.
Here are some points to consider in assessing how risky or otherwise the well is:

We've been told the following:

1. "Corybas 1 will evaluate the potential of the upper High Cliff Sandstone which was not penetrated in Central Yardarino 1 but forms the productive horizon in Hovea 2, where it flowed gas at 13.5 million cubic feet per day."

2."The well will also provide information on the Irwin River Coal Measures known to be gas bearing in the area but generally of poor reservoir quality."

From the Corybas "Technical description" I think the following is very interesting.

"The upper High Cliff Sandstone is largely untested on the Yardarino Terrace where Corybas 1 is located, with only two wells penetrating the section and no drill stem tests undertaken."

And "The nearby Central Yardarino 1 was drilled to test the Dongara Sandstone in 1995 but failed to intersect hydrocarbons at that level and was not deepened to the upper High Cliff Sandstone level. Log analysis from the two penetrations of the upper High Cliff Sandstone on the Yardarino Terrace indicates good reservoir quality with ambiguous hydrocarbon saturations (most likely gas)."

From this I think the key is:
"Log analysis from the two penetrations of the upper High Cliff Sandstone on the Yardarino Terrace indicates good reservoir quality with ambiguous hydrocarbon saturations (most likely gas)."

That to me indicates ARQ, based on log analysis, know that there is:
1. "good reservoir quality" and
2. hydrocarbons are present.

ARQ continues:

"The Corybas 1 well will test the upper High Cliff Sandstone at a location which has been seismically interpreted to be close to the highest structural elevation on the Yardarino Terrace for this unit."

Based on past log analysis, I start to wonder whether the well is really high risk?

In addition, ARQ mention a further objective:

"..to evaluate the commercial potential of the Elegans gas accumulation in the Irwin River Coal Measures. The Irwin River Coal Measures produce gas in the nearby Dongara Field and are interpreted from existing well intersections on the Yardarino Terrace to have substantial quantities of gas in place (up to 400 BCF) in relatively poor reservoir in an accumulation known as the Elegans resource. This gas accumulation has never been satisfactorily tested and the Corybas well has been designed to gather information which will allow the appropriate geological, engineering and economic studies to be undertaken with a consistent modern data set to allow a decision to be made on the possible commercial exploitation of the resource. The section will be drilled with a similar mud system used for the recent Dongara Arranoo wells and two cores will be cut in the section. It is also planned, if appropriate reservoir and gas shows are encountered, to conduct open hole drill stem tests of these cored zones. Once these data are fully interpreted after the completion of the well, a decision will be made on the next phase of the evaluation..."

As we can see there are a number of objectives. ARQ already have "interpreted from existing well intersections on the Yardarino Terrace" that there are "substantial quantities of gas in place (up to 400 BCF)."

I suspect the well may not turn out to be such a high risk play. However, only time will tell.

Cheers,
SP.