Thoughts on Interference testing, connectivity et al.., page-5

Ya

Do you have any idea how much of the central SNE area contains the blocky sands?  In trying to make my own assessments of how much recoverable oil SNE could hold and what each appraisal well might prove up I did run into a few problems:

1.  The identical images below are labelled NW to SE by Cairn and West to East by FAR and no km scale is indicated to help relate these images to others where a scale is given:

CAIRN


FAR


2. Quite apart from the previously alluded to fact that the outer contour for the oil water contact given by FAR encloses a much bigger area than that given by CNE, the different directional indications in the two images above does seem to lead to potentially quite different interpretations as you extrapolate in your minds eye the different NW to SE or W to E directions in the image below:

FAR


Obviously it may not be as simple as that either way as the structure in three dimensions may be more complex, but one is tempted to conclude that if the NW to SE version is correct then there are larger areas of blocky sands to the North of the structure (where also the amplitudes seem strongest) and that a larger proportion of the northern area might include both blocky sands instead of just the one.
   
3. With respect to how much of the area might contain two blocky sands I note that FARs N/S seismic cross section seems to indicate only one blocky sand at both SNE 1 and SNE 2. FAR may say that the images are “just illustrative”, but we know there is only one blocky sand at the SNE 1 location and FAR’s N/S image below certainly does not seem to suggest that this situation is changed at SNE 2, consistent with FAR’s dip away of the blocky sands to the East.

FAR


But if the blocky sand dip away was to the SE as per Cairn one might expect both the blocky sands at SNE 2?  Also I would have thought they would want to test both blocky sands??
  
4. I have been looking at all this in the process of trying to work out how much recoverable volume each appraisal well might prove up, and how much of the total prospect might be made up of blocky sands which are illustrated in the cross sections as continuous and how much might be made up of the thinner wispy (discontinuous?) sands only.

In arriving at their current 330mb 2C Cairn have stated in the CMD presentation that:

“In terms of recovery factor, we have a wide range at this point of time and as I say that also depends on the nature of the sands. We expect very high recovery factor in the blocky sands, with a favourable mobility ratio with the light oil and water you’d expect good recovery. In the thinner sands we might get less efficient recovery and so we’ve deliberately discounted our overall recovery for that until we collect some more information in the appraisal programme”

So, in assessing the potential for further increases in SNE recoverable volumes, the percentage of the prospect that contains thin sands only is important because if it is a relatively large percentage the productivity and recoverability of the thin sands becomes a major factor. Also it is worth noting that the statement above indicates that Cairn have included thin sands in their 330mb estimate (but not apparently FAR’s claimed additional thin sands).

Cairn have stated that they will be flow testing both the thick and thin sand sections separately at SNE2.

pj