Hession has said that the data from Antelope-4 ST-1 and Antelope-5 support the following:
1. The gas/water contact may be lower than previously thought.
2. The western fault is further west than previously thought.
In the absence of information on the subjects I will speculate a little.
The comment about the gas/water contact is probably based on better quality wire line logs, especially if they had better quality formation (higher porosity) at the depth of the gas/water contact. They have been using -2,214 TVDSS lately but GLJ had used -2,228 meters TVDSS. I think the GLJ number is probably about where it should be. We have produced gas on a DST from a depth lower than -2,214 meters TVDSS and perhaps lower than -2,228 meters TVDSS. Antelope-1 ST-1 DST #8 recovered 0.25 Bbl of 43.9 degrees API oil and 150 scf/day of gas from a depth of -2,193meters TVDSS to -2220 meters TVDSS. Antelope-2 ST-2 DST #14 tested the interval -2,220 meters TVDSS to -2,252 meters TVDSS and recovered 1.4 MMCFD and 23.8 BPD of condensate (17 Bbl/MMCF). Also recovered 158 BWPD but it was thought to be load water and not formation water.
Now what was the basis of Hession saying that Antelope-5 supports moving the fault to the west? Please know that the following suggestions are highly speculative.
If we have a look at the map at http://tinyurl.com/q2lzmbq page 13 you will see a post-drill map showing two faults to the west. The first fault is the earlier interpretation and is about 1.5 km west of Antelope-5. The most westerly fault shown on this map is the new interpretation and is about 3.7 km west of Antelope-5.
What additional information could they have to support moving this fault to the west? First they have the new gravity survey data shown on page 13. I believe the black line shown on the gravity graphic is the same as the most westerly fault shown on the map.
I have said in the past that we need as many as three wells that have cut the fault in order to pin down the location of the fault. What I had not thought of until recently is that some of the wells already drilled might have cut the fault. Remember they are using -2,214 meters TVDSS as the depth of the gas/water contact. Below I will list the TVDSS of the total depth reached on all of the Antelope wells:
Well Name Total Depth meters TVDSS Distance Drilled Below GWC
Antelope-1 -2,515 302 meters (989 feet)
Antelope-2 -2,323 109 meters (357 feet)
Antelope-3 -2,483 269 meters (882 feet)
Antelope-4 ST-1 -2,248 34 meters (112 feet)
Antelope-5 -2,307 93 meters (299 feet)
Antelope-6 (planned TD) -2,464 250 meters (820 feet)
Here is my speculation: Why did Antelope-5 support moving the fault west? I think they expected to cross the fault before striking the Gas Water Contact. Since Hession says Antelope-5 supports lowering the gas/water contact the well must have reached the gas/water contact before crossing the fault. They drilled another 299 feet below the gas/water contact. Did they cross the fault? I do not know but it is a possibility.
I believe it is also possible that Antelope-1 and Antelope-3 might have crossed the fault when drilling below the gas/water contact. If so they could have the fault located in three of the wells. I do not think Antelope-6 will reach the fault at the planned TD because the fault dips to the east and Antelope-6 is too far east to reach the fault at the planned TD.
Looking again at http://tinyurl.com/q2lzmbq page 13, if we take the distance from Antelope-5 to the most western fault shown on the map (3.7 km) and the Antelope TD of -2,307 we estimate the depth of the top of the reservoir where the fault crosses at -1,500 meters TVDSS then the angle of the fault would be about 12 degrees. I think the fault angle could be anywhere between 10 and 20 degrees. If they have the data to prove the location of the fault is where they have drawn it on Page 13 we may be able to use that data and go to certification after Antelope-6 without drilling Antelope-7.
Just a lot of wild guesses with the information I can scrape up.
Have a good evening!!