Antelope-4 ST-1

[petrengr1]

I was a little disappointed that no one responded to the post I put up last night so I am putting it up again under a new thread in case it was lost in the other string. And I will add a little to it.

Here is last night’s post:

“Another little morsel for you to cogitate on about Antelope-4. Please refer to http://tinyurl.com/p5bttdy slide 6. If this interpretation is correct and if they do kick Antelope-4 a ½ km south from the vertical well, as I have suggested, the pay section will be 100% high porosity dolomite from the top of the pay zone to the gas/water contact. The logs will give us the best reading yet on the gas/water contact in this high porosity rock and if there is any oil or high liquid content in this reservoir it should be in this high porosity reservoir rock near the gas/water contact. You will see that the cartoon on slide 6 tells us the distance from Antelope-1 to Antelope-5 is 2.5 km. You can use this measurement to estimate where the bottom of Antelope-4 will be at the gas/water contact if they do kick the well ½ km to the south.”

I believe that there is a chance that Antelope-4 ST-1 may be significant. Why? Because we have never drilled a well that had high porosity rock at the gas/water contact. In all of the other wells we have very low porosity limestone at the level of the gas/water contact. As a consequence the gas/water contact is a transition zone due to capillary action. With limestone, very low porosity, transition zone, and fresh formation water it is very difficult for the logs to show an accurate gas/water contact. The level of the gas/water contact is very important because it is the bottom of the pyramid which is the field. GLJ had determined that the gas/water contact was at –2,228 meters sub sea. On the latest presentation they are using a gas/water contact of –2214 meters sub sea or a difference of 14 meters (46 feet). Fourteen meters spread over the entire area of the field is a significant volume. We need to have this number determined as accurately as possible before turning the appraisal information over the resource calculators.

When we have high porosity rock at the gas/water contact it is much easier for the logs to come up with an accurate depth for  the gas/water contact.

Before  I talk about liquids let me say that I believe this is just a gas reservoir based on all of the data we have been given. 

However, it is interesting to remember that we have had some oily cores and  some oil reported in the mud while drilling one or more of the wells. We have discussed many times that if there is an oil column it will be right above the water. In low porosity low permeability rock it is possible that oil could be present in the tight rock  but it would not flow out of the rock due to the low permeability and low porosity. To complicate the matter further we might have high permeability fractures in the same low porosity low permeability rock which is at or near the water contact. In such a case the water might flow through the fractures while the oil  remains immobile. We have never had an opportunity to test the formation near the gas/water contact where we have high porosity high permeability rock. As you know the high porosity dolomite is the very best of the reservoir rock. We have never had a well that had 100% high porosity dolomite. That seems to be what is indicated by http://tinyurl.com/p5bttdy slide 6 for the Antelope-4 Sidetrack-1. If their cartoon is a correct interpretation, Antelope-4 Sidetrack-1, which may only have 309 meters (1,014 feet) of gas column at the vertical well site, may contain more gas than most of the up dip wells due to the extraordinarily good reservoir rock. Further, getting back to the liquids and remembering the oily cores and oil in the mud, we know that if there was ever any oil in this reservoir it will accumulate above the water contact by gravity separation due to the differences in the weight of water, oil and gas. Where the oil might have been immobile in the low porosity rock it will be mobile in the high porosity rock. Also there has been a lot of discussion about the gas/liquid ratio improving with depth but we have never been able to see much evidence of that because all of the gas we have been testing is coming from the top of the reservoir with very little or none from the low porosity rock near the gas/water contact. So this may be our first chance to see what kind of movable hydrocarbons are present right at the gas/water contact. Maybe the best we should hope for  is a higher gas/condensate ratio but, in any case it will be interesting to see what they find and report.

[Bevo]

Thanks Pet, easy to picture with your discription

[sageo]

Pet -Good afternoon to you ,sir. Sorry I missed your addition to your post last evening.( ...getting too darn old !) Your recent "adds" are more interesting and educating . All your points were great,but a few were exceptional....as in "Fourteen meters spread over the entire area of the field is a significant volume". Next,.".We have never had a well that had 100% high porosity dolomite. Then, paraphrasing, Ant 4 ST may only have 1,014 ft. of gas at the vertical well site,but could contain more gas than most of the up dip wells because of high porosity and high permeable rock . If our believed conditions do exist at Ant 4 ST and the slope does now give us more , better quality results, please forgive "my french" but we could have another "dy - no - mite" well on our hands .[ When Ant 4 ST is finished,am hoping the "slope " of the pps is upward ! ] Pleasant evening to you .

[admin]

As always, interesting take, Pet. A 309M high porosity dolomite column, that sounds pretty exciting, especially for the implications you add (determining more accurately the gas/water level, have better rock for liquids, or even oil, if present, to flow).

How sure can we be at this stage that it is indeed all a high dolomite column? Thanks.

[petrengr1]

As always, interesting take, Pet. A 309M high porosity dolomite column, that sounds pretty exciting, especially for the implications you add (determining more accurately the gas/water level, have better rock for liquids, or even oil, if present, to flow). How sure can we be at this stage that it is indeed all a high dolomite column? Thanks.

Admin- GLJ had concluded that the field had a high porosity limestone cap above a layer of high porosity dolomite. That is the same that IOC is showing at http://tinyurl.com/p5bttdy slide 6. From this slide it appears that the dolomite section is thick enough to reach all the way to the gas/water contact if the well can be kicked a wee bit down dip to the south or southeast. Since Antelope-4 hit dolomite at the top of the pay zone it looks like we will have dolomite all the way from Antelope-4 to the gas/water contact. As a matter of fact it looks like we will have a fairly big area of dolomite south and east of Antelope-4. I refer you to http://tinyurl.com/q2lzmbq slide 10. On this slide they show the reef rim in yellow. All of the reef rim (yellow) down dip from Antelope-4 to the south and east to the gas/water contact should be dolomite. This map must have been drawn before they drilled Antelope-4 or they have an error on the map. The slide clearly says they intersected the top of the reservoir at1,911 meters sub sea true vertical depth (TVD). But the map shows the well at about 1,830 meters sub sea TVD. That is just a passing comment. Anyway all of the reef down dip from Antelope-4 should be dolomite. This map was revised as we have discussed before and the latest map is shown at http://tinyurl.com/p5bttdy slide 6. They do not show much area southeast of Antelope-4 on this map and they not show enough to include the dotted line for the gas/water contact.

Remember that the gas/water contact is being reported at 2,214 meters sub sea so everything above that should be full of gas (or other hydrocarbons). All of this map to the southeast of Antelope-4 is above the gas/water contact and contains gas (or other hydrocarbons). I would like for them to core the last 100 feet or so above the gas/water contact at Antelope-4 ST-1 to check for oil shows. Or maybe they will start coring if they get good fluorescence (indicating oil) in the drill cuttings.

Do you remember when they used to show us maps like this? http://tinyurl.com/ntr7ff8 slide 22. That flat area (red) in southeast of the field is what we are still talking about.

Remember I am like Sgt. Schultz. I know nothing!! I am just commenting on the slides and information presented by the Company.

[admin]

Well, as Sgt. Schultz's go, you're one of the best, for all I can make out. Thanks for that.
I was actually re-reading the MS presentation with Hession, and it's exhibit 6 (or slide 11, if you will). 33M core of the top shows excellent dolomite. Logs of another 118M suggest it extents. There is 158M to drill to gas/water which we don't know the rock quality perhaps, or maybe we do from (reprocessed?) seismics or gravity gradiometry. But we'll soon find out.