(11-18-2015, 05:48 AM)ArtM72 Wrote: Pet - Would you mind addressing my concern that soon we will have triangulated pressure tests in a very permeable formation and knowlege of the actual boundaries of that formation (eg specific fault locations) are of much lesser if not little consequence? Just how can pressure tests be of any value when adding a seventh well to a formation can resolve a 30% pressure testing error? Thx as always.
Art- As I have stated earlier I do not trust the accuracy of the pressure gages for such a small amount of gas produced. I guess they are not so interested in the actual pressure as they are the pressure change for a given amount of production. The pressure change at Antelope-5 was 0.061 psi at a depth of 1,644.6 meters drill depth and the pressure change at Antelope-1 was 0.08 psi no depth indicated. Based on the well bore diagram at
http://tinyurl.com/ovhqeft page 20 I believe the pressure gauges were set near the X landing nipple at about 2,347 meters drill depth. They set three gauges in each well. I would never suggest that anyone would manipulate anything to make the numbers come out like they wanted but it seems a little strange that they used the lower gauge at Antelope-5 and the “average” at Antelope-1. I would like to know what each of the three gauges showed in each well. That might give us a better idea about the accuracy of the gauges for such a small change in pressure. I would also have expected the larger pressure change to be at the producing well Antelope-5 instead of the “listening” well Antelope-1. With such small pressure changes and such a relatively small amount of gas produced we would also have to worry about the “exact” amount of gas produced for use in the calculation. As mentioned before the weight of the gas is about 0.075 psi/foot. One foot of gas weighs as much or more than the pressure change recorded. For this calculation to work on a very large reservoir we need a much larger volume of gas produced and a much larger pressure change so that it can be measured accurately. After we produce 10 or 20% of the gas and record the associated pressure drop then this method would give an accurate number.
What the connectivity test did do successfully is prove connectivity. This should be confirmed again with the up coming test with both Antelope-1 and Antelope-4 as listening wells. Proving connectivity removes a lot of “uncertainty” in the minds of the engineers making the reserve calculation. So the test is worthwhile just to prove connectivity. To run this test is not a big deal because I do not see how it could cost very much.
What is very important in the reserve determination is the Area of the Field, the thickness and amount (area-wise) of the high porosity limestone and dolomite and the porosity of this upper limestone and dolomite. In order to know the area of the field we need to know the location of the western fault. Since they have given us three choices of the location of the fault based on seismic it seems they can not tell exactly where it is located based on seismic and gravity surveys. The only sure way to find the fault is to keep drill to the west until we find it. Antelope-7 also may not locate the fault but it will determine whether or not we have the full reservoir thickness or if we have drilled through the fault. So not finding the fault would probably be the best outcome because that would mean the fault is still further west.
On another subject.... While looking at
http://tinyurl.com/ovhqeft I came across page 12 which brought back some fond memories. These samples are shown with descending depth from left to right. As you may be aware they are now using -2,214 meters sub sea for the gas/water contact. These DST’s were taken from the following depths:
DST No. 11 -2100 to -2149 meters sub sea 9.9 MMCFD with 149 BPD condensate or 15.1 Bbl/MMCFD
DST No. 12 -2125 to -2203 meters sub sea 2.6 MMCFD with 40.6 BPD condensate or 15.6 Bbl/MMCFD
DST No. 13 -2176 to -2203 meters sub sea No gas recorded but recovered a little oil.
DST No. 14 -2220 to -2253 meters sub sea 1.4 MMCFD with 23.8 BPD condensate or 17 Bbl/MMCFD
The lowest test is below what they are now calling the gas/water contact at -2,214 meters sub sea.
Maybe Antelope-4 will confirm that the gas/water contact is lower than -2,214 meters sub sea. GLJ used -2,228 meters sub sea for the gas/water contact. Maybe the logs in the good porosity (hopefully) at Antelope-4 will give us our best indication of the true gas/water contact so far.
Even though they recovered black oil on DST No. 14 the liquid/gas ratio was still pretty low (or the gas/oil ratio is pretty high at 59,000 cu.ft./Bbl) it looks like we will still have a "gas condensate" reservoir or a very thin oil column right above the water contact.
