'petrengr1' pid='62394' datel Wrote:I have been looking again at the maps presented at the AGM on June 9, 2015. http://tinyurl.com/q2lzmbq Specifically let’s look first at the map on slide 10 which is a pre-drill top reservoir structure map. That means this is what they thought the structure looked like before drilling Antelope-5. Look at the colors on the map and note that the yellow is where they thought the reef was before drilling Antelope-5. Remember that the reef rock contains about 10 or 12 times as much gas as the non-reef rock. They leave these pre-drill colors on all the following maps including those marked post-drill. I would like to call your attention to the amount of yellow (reef) that is northeast of Antelope-1 and east of Antelope-4. We are only interested it the area of yellow that is up dip from the gas/water contact or west of the dotted line which is the gas/water contact. Those two areas represent a huge area of un-appraised reef. Note on this pre-drill map that they think there is some lagoonal rock (green) above the gas/water contact. This pre-drill map shows the gas/water contact as the field boundary on the south and east and faults as boundaries on the north and west.
There is another pre-drill map on slide12 but let’s move on the slide 13 which is a post-drill (after drilling Antelope-5) top reservoir structure map. They leave the old fault on the map (where the colors end) but they put the new location of the fault further to the west as indicated by the red arrows. So they now believe the fault to the west is further west than they previously thought. You will note that the formation still dips toward the west. I have stated previously that I thought the formation might slope up dip in the westerly direction because the Antelope Field is riding on top of a thrust fault and is being pushed upward on the fault plane. As a matter of interest I refer you to the latest presentation http://tinyurl.com/p5bttdy ; slide 6. You will see that on the latest map the formation is no longer sloping down to the west but it is shown to be more or less flat from the line of wells that have been drilled to the fault on the western boundary. Even this more optimistic interpretation may be too conservative in my opinion.
Now let’s go back to the AGM presentation that we were discussing http://tinyurl.com/q2lzmbq , so we know from slide 13 that they think the field is larger because the fault is further west than previously thought. Now let’s have a look at slide 14 and put our attention on the map at the right and pay specific attention to the yellow arrows which they tell us indicate “High quality reef may extend further west”. So they think the high quality reef (yellow color) may extend further to the west making the field much larger because the reef rock contains 10-12 times as much gas as the non-reef rock. The reason they believe this is because Antelope-5, the most westerly well drilled to date, “Intersected best reefal build up to date”. Now let’s move along to slide 15 and again pay attention to the yellow arrows which indicate that they think “High quality reef may extend further east”. Keep in mind that we are only interested in that part of the map that is above or west of the gas/water contact (dotted line). The map again shows the lagoonal rock in green but what we would like to see is that this green area above the gas/water contact is really reefal rock and not lagoonal rock. If this is the case it will again mean the field is larger because the reef rock is where the most gas is found. I have previously stated that I think Antelope-6 will find high porosity limestone and/or dolomite at the top of the pay section. Why would I think such a thing? Because every well we have drilled since Antelope-1 found high porosity limestone and/or dolomite at the top of the pay section. So this green area (lagoonal rock) may not be present at all or it may be further east than shown on the map.
Now let’s go back to slice 10 and have a look at Antelope-4. We know we have 300 meters (984 feet) of gas column at the Antelope-4 location because we know where the top of the zone is and we know the depth of the gas/water contact. They cored 33 meters (108 feet) of dolomite at the top of the zone and drilled another 118 meters which logs indicate to also be dolomite. So they drilled 151 meters (495 feet) of dolomite at the top of the section before the well was suspended. As you know they have recently announced that the well is being side tracked from a depth of 862 meters (2,828 feet). Since the well is being side tracked at such a shallow depth I have speculated that the well is being kicked down dip to the south (or southwest) to see if the dolomite extends further to the south. I believe the bottom of the well will be about 1/2 km from the original Antelope-4 location. They will drill through the formation to the gas/water contact but we do not know if they will have dolomite all the way to the gas/water contact. They have never drilled a well that had good porosity at the level of the gas/water contact. There has been a lot of speculation about the gas becoming richer with condensate with depth but we have never had a high porosity zone to test near the gas/water contact so that we could conclusively determine it the gas is richer with condensate or not. Years ago we thought we might have a thick oil column above the water contact but all of the data suggests that we have gas on water. In any case is would be interesting to have a test near the gas/water contact in a high porosity zone in order to see what the gas/condensate ratio is. Vertical wells drilled on the -2,000 meter sub sea contour line would have a gas column of 214 meters (702 feet). If the zone near the gas/water contact in rich in condensate it might be worth consideration to drill some horizontal wells in the reef rock at a depth of about -2,100 meters sub sea or half way between the -2,000 meter contour line and the gas/water contact.
Enough for tonight. Have good evening/day.
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.
Good night and sleep well.