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GEOL6350-Advanced Structural Geology - Day4 AM 02-26-2022
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00:13 Let's see, are you seeing that slide topics of in false heels?
00:19 . Okay, good. Okay. we're here in the, in the
00:32 , we'll talk about false heels for an hour. We'll do it combination
00:36 lectures and exercises per usual and then have an hour lunch break. Mm
00:44 . Okay, so for false we're talking about the seal capacity of
00:52 fault and what are the fault dependent and the fault dependent column heights that
00:59 can seal based on those faults so um the fault, the total fault
01:11 planet enclosure is equal to the distance the highest elevation contour that hits the
01:18 . So in this case it would This one About 300. The difference
01:23 that and the deepest spill point, would be here at this 550.
01:30 . The default dependent column height is difference between the highest contour that intersects
01:35 fault in the gas water or oil contact, so that may or may
01:40 equal. Third the deepest spill point . And we're going to differentiate static
01:48 capacity from dynamic false your capacity. false real capacities. What faults trapped
01:55 geologic time scale? Um what hydrocarbon rides or pressure is going to fall
02:01 and what other potential fault dependent column ? And this is a function of
02:06 fault. Rock, capillary entry dynamic fault steel capacity refers to the
02:12 potential faults on the production time So this is about what kind of
02:18 fault flow will occur during production and is a function of the fault,
02:22 permeability. The pressure difference across the and these dynamic pressure differences are much
02:30 greater than the static, false real . And we'll talk about why that
02:38 mm hmm. So here I've got cross section seismic section gas, water
02:45 here, reservoir here, top seal , fault here, In in cross
02:52 . This is my four way dip . This is my fault dependent closure
02:57 these two. Combined to be the dependent the total column height. So
03:02 dip closure and the fall dependent hall equals the total column height.
03:09 alright, so static false heels. ? So four rocks, false phone
03:18 do have prosecuted permeability. They're not tight like glass. And it's the
03:24 effect that creates the seal capacity. You see a thin section of a
03:29 here. Uh huh. A lot porosity adjusted to the fault, green
03:35 reduction and much lower porosity in the . But you still see finite amounts
03:41 ferocity within the fault zone. So are not not glass like seals.
03:49 what creates the seal capacity is this ? We talked about this for top
03:55 . It's the buoyancy pressure that's required the hydro current to displace the water
04:01 the pore throats and that's a function the poor throat size. The wedding
04:10 of the, of the water and the inter facial tension of the hydrocarbon
04:18 in the inter facial tensions. For and gas are different. And on
04:22 right here, I have a graph inter facial tension versus depth. And
04:28 is fellas this line, methane or follows this line. And you see
04:37 oil and gas have different interface So for the same fault rock at
04:43 same depth, it can hold different for oil and for gas.
04:54 Alright, so this is a plot fault rock permeability versus host rock
05:00 So each one of these points represents permeability measurements of a corpse look like
05:07 , Where one is a permeability measurement the unfolded rock and the other is
05:13 permeability of the fault face at the the ends of the core in what
05:20 see or that um there's several orders magnitude reduction permeability between the original host
05:30 and fault rock, the yellow dots are cataclysmic sides. These are very
05:37 into gross roxbury, mm hmm sandstone little or no clan. The grease
05:44 are sand stones with varying amounts of in them. And what this shows
05:49 that the reduction for the cataclysm sites less than the reduction for the um
05:59 clattering rocks, what we call phyllo framework fault rocks rpf frs mhm.
06:06 these are these are the silty but these are the clay rich
06:11 These are the clay poor reservoirs. any case there's Up to 1,
06:18 , 3, 456 orders of magnitude and permeability between the original host truck
06:24 the fault rock some. So the silicate framework fault rocks, the shale
06:40 the Shelley fault rocks. Shelly reservoir lie down in this gray cloud and
06:46 ACL a sites with little or no lie up here in the, in
06:51 yellow cloud. And these are the that are typically used for these cataclysms
06:57 for quite poor and philo silicate framework rocks for the clay rich fault rocks
07:04 these have a much greater reduction in than the cattle place sites. All
07:12 . So we're going to look at examples of juxtaposition analysis and examples of
07:18 ceiling falls. And what we'll see that ceiling faults include sand on sand
07:25 contacts, carbonate and carbonate fault thrust faults and active or critically stressed
07:31 . All of these can be good falls. So I have a cross
07:41 here to explain what just a juxtaposition is. I have a sand,
07:47 sand b fault, sunday, sandy and wherever the uh huh sans are
07:56 was across the faller where I have sand on sand juxtaposition. If the
08:05 the traveling capacity was limited by those , the oil, water contacts would
08:10 up here. There would be no , water, no oil, water
08:15 in this guy. If these faults completely, total water contacts could be
08:21 deeper if the sand on sand fall field. All right. So a
08:32 analysis, it's kind of a a view of a fault. So here's
08:38 fault. I just described juxtaposition analysis looking head on onto the fault plane
08:47 well look at both sides of the in those juxtaposition analyses. What I'm
08:52 here is just the up thrown So there's my up thrown sand
08:57 There's my up thrown sand B. lines represent the cut off lines where
09:02 top of the sand, it's the where the base of the sand,
09:05 the fault. Um and the oil contact would project onto the fault at
09:13 elevation. Okay, now, if look at both sides of the
09:22 I'll get a view like this where I have the up thrown A here
09:28 the down thrown A. Here shown the dashed line so that the dash
09:33 here now represents the cut off of down thrown sand with the fault.
09:40 all along here I have a sand sand juxtaposition where the down thrown
09:48 Is still in full contact with the thrown A. Here the downturn A
09:55 in juxtaposition with the up thrown So this contact represents this contact
10:06 So now we're looking at both sides the fall with just the football side
10:12 one half the down front side and . So it's kind of a sandwich
10:18 . What's called an allen section or T in one section or just addition
10:22 of the fault. Okay, here's complete text composition section where I have
10:32 overthrown a here in the background. up thrown be here in the
10:36 the down thrown A here and the thrown be here. So here,
10:43 , in between the dash line, the solid red line below, there's
10:48 on sand, juxtaposition of the down B. And the upfront beat.
10:53 that would be this contact and cross . So we're going to use these
11:01 sections to help understand what's happening with to false heels along these faults.
11:11 , All right. So when we at actual ceiling falls in juxtaposition
11:17 we see CNN sans healing faults are over the world. Gulf of Mexico
11:23 and deep water. A deep water brazil, abundant sand on sand contacts
11:30 the night. The *** delta both the shelf and the deep water.
11:35 hmm. The North Sea, we examples of sealing faults on fields in
11:40 northern North Sea, the Central North and southern North Sea. Similarly,
11:45 see them in Oman in brunei and northern Carnarvon Basin in northwest shelf of
11:58 . So, here's some, here's examples, mm hmm. Cross sections
12:03 four different fields in this first one fault here, reservoirs here here
12:13 here and so along each of these contracts. You've got to different reservoirs
12:20 With a large pressure difference across the here on this first fault contact.
12:25 got a pressure difference at 190 psi the second one, we've got a
12:30 P of 2 70 C. The one delta P. Of 224
12:35 S. I. In the last , a pressure difference of 52
12:40 True on field number two here. looking at seismic section, the fault
12:48 up thrown sand here, down thrown here and on the down thrown
12:54 we've got a gas bearing sand in with a wet sand, non gas
13:00 sand on the other side of the . So here we've got a sand
13:04 sand contact, Sealing a column height about 350 ft. Gas hydrocarbon column
13:14 here we've got another one with a field fall there one sand here,
13:20 percent here here, this blue sand juxtaposed with yellow sand here And there's
13:28 pressure difference across that contact of about . See between the two sides of
13:33 fall here in this last example, number four, stand here, stand
13:41 , stand here, Mhm. Oil sand here. Oil bearing sand
13:49 the fall down throws on these guys sentences and contacts here here and
13:57 Come on, uh huh. In one we've got an 800 ft fault
14:05 column in the sand and wet sand the other side. So false
14:10 a big tom height difference. when I talk about the pressure
14:15 I'm referring to pressure differences as shown . So here we've got one of
14:20 pressure depth diagrams pressure here, depth , the blue line represents the water
14:27 gradient. The red line represents the . Canadian, this would be
14:33 this would be oil. And these differences refer to this difference between the
14:40 pressure in the gas column, gas or the oil column in the hydrostatic
14:46 in the in the water. Like that's the pressure difference that we're referring
14:50 here. Mm hmm. Okay, an example from deporting brazil, mm
15:03 . Normal closure here, false here here forming a graven in cross
15:10 That's the top of the reservoir That's the base of the reservoir
15:15 mm hmm. And here you've got flat spot showing the oil water
15:21 So this is all oil filled in and in this upper part of the
15:27 , this base of legacy in sand juxtaposed with the the reservoir sand so
15:34 his fault. This sand is juxtaposed this sand. Mhm. There's no
15:40 on the down thrown side of the in the sand. So the difference
15:46 the oil on this side and the on this side means that this fault
15:51 sealing this vaulted ceiling and in this it's a column height of several 100
15:58 here. Mhm. This is an from the central North sea reservoir
16:11 reservoir here. Gas water contact on up thrown side here. Guess water
16:16 on the down throw inside here, base of the reservoir is here,
16:22 the basically the TD of the Mm hmm. In this section of
16:29 fall, we've got a gas bearing on one side of the fault versus
16:33 wet sand on the other side With 605 ft difference in the gas.
16:38 contacts across the fault here. a ceiling fault trapping a couple of
16:45 ft of gas on the sun fall here's an interesting one from the Northern
16:55 Sea. This is from the turn at the top of the reservoir is
17:00 here in yellow. The base of reservoir is shown here in red and
17:05 see it's down dropped across several of falls here. When we get to
17:11 fall, there's a small difference in oil water contact across this fall from
17:21 50 on this side of the fall 81 34 this side of the
17:28 but there's also a large difference in Water pressure gradient. So the water
17:34 gradient on this side of the fault 500cc creator. Then the hydrostatic pressure
17:40 on this side of the phone. here we have an example of the
17:43 that's for the hydro current seal and hydraulic seal, Its seeming both mm
17:49 , a difference in the hydrocarbon column a difference in the actual water
18:00 Here's an example from the southern North , from the alien Republican reservoir.
18:06 the here's the field here, faults here and here. Top of the
18:13 here, no closure on this side this fault. Oh, top of
18:21 reservoir. Down throughout here. Salt seal on top of the reservoir
18:27 And this is interesting because we see gas water contact difference across this
18:34 But these bounding falls are seals, , big big pressures. Alright,
18:49 this is an example of juxtaposition section this is from a field in the
18:53 delta where we have lots of reservoir cares. So we're looking at the
18:59 of the fall in both the up side of the fall and the down
19:03 side of the fall. The up shales are shown in brown's here through
19:11 , down thrown shales are shown by orange colors here here here and and
19:17 here, wherever you see. White this juxtaposition section is where you have
19:24 sand contact across the fault. We've sand in the down thrown side and
19:29 on the out thrown side where there's on the in these red polygon.
19:38 these white areas, this is where have hydrocarbons on the throne side of
19:42 fault. So here we have a santa santa contact here we have another
19:49 stand on sand contact here we have ceiling. Sand on sand contact where
19:56 sand and Justin position on both sides the fall and hydrocarbons only on the
20:00 front side of the fault. Mm . And one of the important things
20:07 this is that variations and throw or thickness will not eliminate ceiling sand on
20:13 contacts. Some, some people argue this, the sand and sandy carter's
20:22 are an artifact of not having the graffiti, right or not having
20:28 shale thickness is right or not having throw right. And then in
20:32 if you have the correct throws, , the correct strong graphic sections,
20:36 would have no sand on sand You're where you can see from this
20:40 that if you if you move these if you vary the throw, if
20:46 vary the thickness of the shells with sand, you won't eliminate these white
20:51 on the juxtaposition section, you might them around a little bit but you
20:56 eliminate them completely. So this is just an artifact of the construction of
21:02 juxtaposition section. All right, thrust concealed. This is an example from
21:13 cusiana field in Colombia rows of are shown in yellow oil leg here,
21:19 cap here um thrust faults all through section here, mhm and this this
21:28 fall Which is actually active today is 700 ft of gas and 800 ft
21:33 condensate. So it's the, even it's a thrust fault, even though
21:39 an active fault. It's still ceiling column heights. Alright, this is
21:47 example from the Canadian foothills from the Valley field. You see the reservoir
21:53 water bearing here. Oil blank Gas cap here, main thrust fault
21:59 here in red and this this thrust is trapping several 100 ft of gas
22:05 oil along the, along the So it's another example of the ceiling
22:10 fall. This is an example from dig boy field, the assam basin
22:18 India. It's an active fault. Naga thrust here. Yeah. Field
22:25 here in this hanging Oleanna klein Oil contacts are somewhere down in here several
22:32 m deeper. Then the fault cut . So here, so this is
22:36 example of a ceiling thrust fall and active ceiling thrust fault. And
22:49 mm hmm. No one emphasized Active or critically stressed, false
22:54 We talked about the cusiana example Um, and then this whole complex
23:00 thrust fault is so active That the only last about 18-24 months before they're
23:06 off by the movement along the And and this what when we first
23:15 that we did a calculation to we thought the wells would not pay
23:21 , but the wells produce such high of oil and condensate that they proved
23:28 they payout and Like 60, 60-90 . So even though the wells don't
23:35 more than a year. Um, very highly profitable, correct. This
23:40 an example from the gulf of the Eugene Island 3 30 posey field
23:45 , we've got a big normal It forms part of the trap here
23:50 trap trapping reservoirs here and here and . So exactly that it's a ceiling
23:57 and it's active. This fall extends to the sea floor and offsets the
24:01 light here at the sea floor. this fault is active today, but
24:06 still trapping on pressure's up to 300 . S. I. And Trapping
24:14 total 300 million barrels recoverable field. , come on. Two. Um
24:30 someone has been published in the literature critically stressed faults can seal. We
24:34 saw these two examples of that and idea is that a critically stress fault
24:41 one where the stress circle intersects the envelope. No, and these stress
24:49 would cause shear failure along the faults this failure envelopes here and the slope
24:57 this mine Is about .6 - This is the cross plot of data
25:06 was used to conclude that critically stress leak. And so here we have
25:12 same kind of more cool diagram with normal stress here shear stress along the
25:19 here. The failure envelopes from you one and musicals .6 here, all
25:27 hollow circles here represent sealed non leaking and fractures, the different colors represent
25:34 and fractures for different wells from 2, 3 different wells represented by
25:39 green, the blue and the The leaking faults and fractures in these
25:45 occur in this region is identified by filled in symbols. And so they
25:51 above The failure envelope. Euro And the conclusion was that these faults
25:57 leaking because of this data. Mm . But And in fact, each
26:06 of these three wells is it? in a a volcanic rock or genetic
26:13 . And the flow is only occurring the fractures. And if you calculate
26:19 equivalent permeability of those fractures, The of those fracture systems is 10 to
26:25 -3-10 to the -6 military sees. even though leakage is occurring, it's
26:34 , very tight. It's very, slow. Mm hmm. It's not
26:39 that we would see in a a reservoir. Mm hmm. So,
26:46 this conclusion is kind of an artifact looking at only the only faults and
26:53 in created crocks crystalline rocks. okay, so this is an example
27:04 a carbonate on carbonate false field. is from cretaceous carbonates in the gulf
27:11 Campeche closure here with the high Downing thrust fog here. I know
27:20 want to contact here and and And so this trust fall is sealing
27:29 415 year fault dependent columns in in the football to the thrust.
27:36 then this normal for in the carbonates sealing a a couple 100 m difference
27:44 the oil water contact across this So here we have both ceiling thrust
27:50 and sealing normal faults all in a reservoir. Okay, so I mentioned
28:01 for static false heels, we need static false heels and faults are dependent
28:06 the capitol reentry pressure and we measure parental pressures in plugs like this where
28:13 take these core plugs, put them a centrifuge and measure what pressures you
28:20 to go up to to get the fluid to invade the fault rocks.
28:28 , and one of the problems is these core plug measurements are not representative
28:34 the whole fault. Here we've got core plugs, Whereas we're looking at
28:40 that are kind of eight km wow or more tens of kilometers in length
28:49 within those faults. Well, we have garage sales like this or like
28:55 where the dog's owner is very So we have different juxtapositions, different
29:01 of garage within the fault. And we need some practical proxy that we
29:09 use to estimate the catholic central pressure faults like this. So we've applied
29:22 different types of garage equations to those to try and understand this. One
29:28 called the shale gouge ratio. The is called clay smear potential. Mm
29:34 in the shell gouge ratio calculates the content of the fault based on the
29:42 content of the rocks that have slipped the fault and the in the clay
29:49 and then the displacement of those rocks the clay content of the false hitting
29:55 the horizons hitting the fault. So I've got a cross section cartoon showing
30:03 and white shales in the brownish color , as shown here And here,
30:12 got a 10 ft sand juxtaposed with on the other side. The displacement
30:20 this point in the fall Is about ft from here to here. Within
30:26 100 ft through a window. This ft thickness of shale has slid past
30:33 that point. So the Shell God here is 90 ft of sand divided
30:40 1990 ft of shale Divided by 100 of sin, or about 90 as
30:46 go up and down the fault. the throw varies in the strategic issues
30:50 that shell God ratio will vary and go down to the base of the
30:55 sand here, the shell guide ratio will be 90 divided by 120's will
31:02 a little lower than the shelf God . Here on this part of the
31:08 . Mhm And so in the simplest , the shell gas ratio equals the
31:14 feet of shale drag past each point the fault, divided by the throw
31:18 that point. When the throw gets , relative to the strata graphic thicknesses
31:25 becomes equal to about 1 - the to gross of the whole section,
31:30 hmm. The clay smear potential is completely different. What the clay smear
31:37 is trying to measure is the length a continuous shale smear that's dragged out
31:44 the fault zone. And the idea that in an extension, all setting
31:49 normal vertical load on the shell belts be greater than the normal stress across
31:55 fall and that will result in shale squeezed like toothpaste into the, in
32:02 fault zone, giving you a continuous smear. It's kind of like stepping
32:08 a toothpaste tube and squeezing shale into fault zone. And this is this
32:18 is observed in ah in some coal clay pit mines in onshore e in
32:26 europe. So these to represent two different phenomenon. This is kind of
32:33 average garage composition. This is a measure of the continuity of the
32:40 smears that might occur in the fault . Okay, now, the we
32:51 another definition of SGR that accounts for clay content in the rocks in
32:58 this is based on the fact that the reservoir rocks and the shales contain
33:05 amounts of clay. Mhm. in fact, the way we calculate
33:13 shale gas ratio is it's equal to sum of the volume of clay in
33:19 rock divided by the thickness of so that by the throw of that
33:27 . So here we've got a reservoir rock, oh, With a clay
33:34 and 15%. And the thickness of here we've got to shale with,
33:41 quite content of on 14% and the of four and so on. And
33:48 we take each one of these and a summation of the volume percent.
33:55 times the thickness divided by the throw that interval. And so what we've
34:08 to try and calibrate those uh, smear in shale god's racial potentials.
34:15 at known ceiling falls and calculate the God's ratio and the clay smear potential
34:20 the faults where we know their ceiling know what pressures their ceiling. This
34:26 an example of one of those fields you see hydrocarbon accumulations in the colored
34:35 , gas in the green oil legs the red. So we've got hydrocarbons
34:40 here, here, here and here in each case they're trapped in part
34:47 sealing falls. For example, this accumulation is trapped in part by this
34:55 . This gas accumulation is trapped by set of faults. The oil leg
35:01 is trapped by false here in false and out of the plane. Such
35:07 all along the false here. So one of these is a definitely assuming
35:13 where we can calculate the shell placing your potential and compare that to
35:18 colonizing pressures that the faults are Okay, so this is an example
35:28 section from one of these calibration studies . Each one of these colored horizons
35:36 a reservoir she'll pair. So we've a lot of reservoir she appears with
35:42 undercover during sands and wet sands within section. We have a lot of
35:48 control constraining the reservoirs and the pressures we've got excellent sizing data constraining the
35:57 on the trees. So all that goes into constructing 3D models like
36:06 We're looking at a 3D model where is what this surface is. One
36:10 the reservoir horizons and false services are here here here and here and
36:17 We can see where that reservoir horizon the fall. We see the up
36:21 own side of the fault here at upfront cut off the down thrown cut
36:25 here. And so we can use , use these to construct juxtaposition sections
36:34 to quantify the throw in the, the throw and the show graduate showing
36:39 place where potential along fault like Right? So this is an example
36:50 one of those juxtapositions sections. You the up thrown shales in the dark
36:56 for down thrown shales in the lighter here, wherever you see the sand
37:02 sand contact here or wherever you see white, that's where you have a
37:07 stand contact and where you see the is where you see hydrocarbons on one
37:12 of the fall and saying reservoir on other side of the farm. So
37:18 we've got a sand on sand ceiling here we've got another sin on sand
37:23 contracts. Right? So when we when we make these sections overall the
37:34 are that we very commonly observed sand sand contacts like these with big differences
37:41 column plates across the fault and they be rationalized away by varying the strategic
37:47 or varying the the throw on the section. We also see that sand
37:54 shale fault traps can be under filled faults and thrust faults can trap large
38:01 rights and pressures and all this implies false. He'll capacity must be dependent
38:06 the gouge on the properties of the , hence that's why we look at
38:11 show graduation inflation, your potential. ? So this is an example of
38:19 of the exhibition section. We're looking way at the plane of the
38:25 These are my up thrown shales, are my up thrown sands where they
38:30 their hydrocarbon bearing where they're white, non hydrocarbon bearing. And then these
38:35 contours represent the shell God ratio contours the fault and what this shows is
38:42 she Oh God ratio. The contours as you go up and down the
38:46 and as you go along the strike the fault as the throw varies and
38:51 the thickness of the sand and shell , you get variations in the shell
38:55 ratio along the plane of the But this is an example of juxtaposition
39:06 showing a sand and shale leaking So, um wherever you see these
39:17 brown streaks looking at both sides of fall, sorry, with the up
39:23 up throwing shells in the brown up thrown sands in the white and
39:27 here in the brown, light brown representing down thrown sands down throwing
39:34 I'm starting down throwing shells. So these yellowish stripes, we have a
39:40 sand on the other side of the juxtaposed with only shale on the other
39:44 of the fault and it's not trapping hydrocarbons here where we've got the red
39:50 white, we have gas sands on upstream side of the fault, juxtaposed
39:55 both sand and shale on the down the side of the farm. If
40:01 come down to this reception on a fault, these stripes represent where I
40:09 sand on the up thrown side of fall and his trail on the down
40:13 side of the fall. The original water contacts in these sands are here
40:18 here, so far above the nearest and sand potential leak points. So
40:25 we have sand on shale trapped that under filled with respect to the,
40:33 maximum possible closure provided by santa, shale seals. So these are sand
40:40 shell fault juxtapositions that are limiting the accumulations in these reservoirs. All
40:55 okay, so what this shows is the comb height is dependent on the
41:00 , capillary entry pressure. The mythology juxtaposed across the fault is irrelevant.
41:08 on sand, concealed sand on shell wait in this cartoon cross section.
41:12 have reservoirs shown here in yellow oil shown here in red gas cap shown
41:18 in green fault zone, shown here gray. And so what we're seeing
41:23 these observations is the ceiling capacity is on the capital's central pressure of the
41:29 zone here. Alright, uh so simplification that we used to estimate the
41:44 God ratio is something called the triangle in these diagrams, we take a
41:51 official or gamma ray walk like this slide it past itself and calculate the
41:58 guard ratio that would result from sliding sand shale sequence across the fault against
42:06 felt and the shale gas ratios are as colorful contours on these diagrams and
42:17 we can use these as a simplified to calculate the shell God ratio from
42:23 single well and from varying throw So this is how much a much
42:30 way to calculate the show God ratio the juxtaposition sections I showed you with
42:35 the complex contours across it. This another example where I've taken this blog
42:44 slid it past itself to create this diagram plot, hmm. The way
42:50 works is you really see the up sand here, the down thrown stand
42:56 and the shell God ratio within this varies as a function of the throw
43:03 plotted across the bottom here and you visualize the throw is increasing as I
43:08 from left to right across here. throw is the sand to this,
43:13 is low at this point becomes greater this point and uh creates a juxtaposition
43:22 at that point where the throw is to the shale thickness between the
43:27 All right, so from this, can estimate the shell gouge ratio as
43:32 function of only one log a log the throw along the fault. All
43:44 , So here's an example of how , how these work. So,
43:48 my log. All right, 200 ft thick sand here. And
43:58 is the triangle diagram created by sliding long past itself. And the way
44:05 read this is to extrapolate your area interest in this case that thomas and
44:11 extract like that horizontally across the triangle . And then read off the show
44:17 shows for various throws using the thrill at the bottom of the diagram.
44:24 the intersection of this point says that show God ratio with the top of
44:29 sand with 2500 ft to throw is yellow color, which is Only 20
44:36 30 If I increase the throw up ft shown here, The Shell God
44:45 at the top of the sand is to increase to about 50 sure.
44:52 as we go out with the increasing of throw, you see these values
44:56 smeared out so they start to approach constant values with large throws.
45:08 okay, so you have this in slide pack for exercises. I want
45:12 to try reading this Shell guard ratio , the triangle diagram and tell me
45:20 the shell got ratio At the top the 300 ft stand On a fault
45:26 a 100 ft of throat. So ahead and um pull out these diagrams
45:37 from the slide back or work off screen here. And that's doing what
45:41 the show God ratio for? I with a 100 ft of throw
46:39 Yeah, Okay. Um close .6 .7. So if I take the
46:49 of the sand and I extrapolated across And then I look at the value
46:54 I've got 100 ft of throw, between .6.5.6 shown here in the blue
47:02 and .7 showing here. So 60 or 70 for the show God
47:08 at the top of the sand With ft of throw, mm hmm For
47:14 same sand in the middle of the . Same fault with 100 ft of
47:20 . The shell God's ratio is much . It's only 10 to 20% shown
47:25 the red contours on here. And the throw increases further on the shale
47:34 ratio is going to, it's actually decrease as it gets further because this
47:41 sand, we'll get dragged down into with this football sand decreasing the show
47:47 ratio. So for the for the of 100 ft of throw, The
47:54 got direction was going to be 60 70 and it's going to vary both
47:58 and down the fault and with throw the fault, Are you just identifying
48:06 sand based on the log characteristics of gamma ray? Yes. Okay.
48:14 . Um and you can you can better to use a take the gamma
48:20 log and actually converted to avi shale to have your petro physicist do
48:24 But you can use just a gamma log as well, an unconverted gamma
48:30 log. And that's that's what I'm here, I should have explained that
48:35 we're looking at a the shale log the sand here has about 5% play
48:46 5% share within it. And then shells are blocked over here, Where
48:51 have 80 or 90% clay within the . Okay, alright, so in
49:06 calibration studies, what what's been done to compare the or clay smear potential
49:13 the show God's ratio along the fall the pressure differences across the fall.
49:19 the pressure differences are calculated from these death diagrams where I have the water
49:26 is shown here, Gas pressure, pressure oil pressure here and from these
49:33 depth plots. I can calculate the difference across the fall at any point
49:39 I have different hydrocarbons and checks position water in juxtaposition with the hydrocarbons.
49:45 sometimes there will be two different oil in juxtaposition that there will be a
49:50 difference between them across the fault, though there's oil on both sides of
49:55 fault. Okay, so this this an example of that we're here.
50:05 looking at a just decision section where this area I've got Sand on Sand
50:12 with the show graduation for about And I can compare that .6 to
50:18 pressure difference between the water bearing sand one side of the fall and the
50:23 bearing sand on the other side of fall. Mhm. Now um go
50:35 . This is an example of one those plots where I've got the shell
50:39 ratio here first is the pressure difference delta P on the Y axis here
50:45 . The pressure differences in bars it's in C. And you see
50:50 are pretty messy plots with big cloud data down in here. And what
50:58 , what we're interested in finding is top of that data cloud.
51:06 And the reason for that is if take a cross section like this with
51:13 oil, water contact here as you up into the up in the
51:19 the buoyancy pressure difference is going to , its gonna increase like this across
51:24 fault as you go higher into the on an str on a plot of
51:32 versus that pressure difference. The show ratio will kind of bounce around for
51:41 relatively, you know, small range values until it hits the, until
51:48 hits the maximum ceiling capacity, what's the weak point and then it will
51:54 off like this giving you the big of data that we see over here
52:00 all the points over here are not important. It's just the ones that
52:06 the maximum pressure difference along here that the maximum seeming capacity. Okay,
52:18 this is an example of the the SGR faulty calibration plot. And this
52:25 been published in a lot of different and the different each, each dot
52:33 here represents a the ceiling, the contact on a fault. So you
52:41 a lot of data coming up like and hitting the maximum here and then
52:46 off somewhere to the right. And these maximums that were interested in.
52:52 maximums seem to be divided based on depth sugar. The blues here give
52:59 this maximum envelope for depths less than km. The red here gives you
53:05 maximum for 3-3 and a half court . The green data cloud here gives
53:11 the maximum for 3.5 to 3.5 for kilometers, 3.5 to 5.5 kilometers.
53:19 to estimate the ceo capacity based on show God's ratio you come down
53:26 find your show got a great show extrapolate that up until you hit the
53:32 curve for your reservoir. Let's say less than three km you would come
53:38 , go up, hit the blue line and then extract like the maximum
53:42 from the, from the Y axis or here. Here. It's the
53:47 values here in bar here. It's . Okay. All right.
54:02 one of the, one of the that we've learned is that computer,
54:07 scatter is pretty much independent of a of different variables that initially were thought
54:14 be important. And that's shown by fault behavior matrix where there are different
54:22 here based on the reservoir fishies and alien from real shallow marine deepwater carbonate
54:32 the structural setting, extension and contraction strike slip and so on. And
54:38 the Y axis represents whether these are , poorly consolidated or consolidate well
54:45 Welcome back its hands. And what find is that in fact we have
54:49 same shell God ratio maximum pressure trend of all these variables. All
55:02 If we do the same thing with smear potential, we don't see any
55:07 and this is a thought for CSP potential shown here versus pressure difference shown
55:16 all the points from the same fault gave us the SDR calibration and you
55:21 there's really no calibration here and kind increase to maximum along the side,
55:28 this part of the cloud. And it's constant with increasing place near
55:33 So there's not a good correlation between spear potential concealing capacity. Okay,
55:41 hmm. Okay, so another another point here based on these known ceiling
55:51 , I'm based on this SGR calibration and data. What pressure difference
55:57 fault with 0% str hold up 3.5 burial depth. Mhm. Mhm.
56:37 . So for 0% s gr You're here at the 0% SGR on the
56:44 axis. And you follow that up where where you intersect this blue line
56:52 . Unless I'm sorry, this red for 3.25 kilometers 3 to 3.5
56:59 So at 0% str you can still up to about .2345. About half
57:06 bar pressure difference. Even with the guard ratio of zero, That would
57:12 equivalent to about about eight p. . I. Okay, so here's
57:22 , I've written out the answer, strap plate this up to where the
57:27 line hits the fault. Mhm. and uh extrapolate that across to here
57:33 get seven c. So even where got a sand on sand contact with
57:40 no Shell God ratio with 0% str can still hold a seven of seven
57:48 . Which is a equivalent to about columns of well and we convert the
57:55 into column feet. Using this equation them seven C. And divided by
58:03 pressure difference between the water column, oil column here Yielding about 47 column
58:09 of oil. Mm hmm. Okay. Let's see. Um
58:21 So based on the on the triangle analysis that we did, What Delta
58:27 . Canna Fault with 100 ft of and three list 3 km burial hole
58:33 the top of this 300 ft thick . So from the previous discussion we
58:40 that the SGR at the top of stand Would be about 60-70%. So
58:47 what pressure difference can that fault It would be around 1000 P.
59:50 . I. Yeah. Yeah around P. S. I. So
59:57 find the 60% share God's racial value here. And follow it up to
60:02 you intersect the blue line for less three km burial depth. And you
60:07 that blue line right at about 1000 . S. I. So that
60:11 graduation with 60% can hold a very relatively high pressure of thousands. Which
60:18 be equivalent to 67 100 column feet oil. So potentially a huge column
60:25 of oil across there. Yeah. , dynamic false fields. Mm
60:36 So um we talked about static false and those being dependent on the capital's
60:44 pressure. Now, we're gonna talk dynamic false heels that are dependent on
60:49 permeability. Mm hmm. Here we a thin section of a fault.
60:55 see the unfaltering rock here, the rock here. The faulted rock in
61:02 . And yes, you see a of grain size reduction reduction and
61:09 And so you have some reduction of from here to here. But within
61:14 zone you still have some finite Alright, in this these are this
61:27 an example of a dynamically ceiling So, we're looking at a field
61:30 the gulf of Mexico. The reservoir by the dark colored loop here Reservoir
61:40 Jamari log shown here in the green along this fault this reservoir is juxtaposed
61:47 itself across the fall. Small through , much less throw than the actual
61:53 thickness. And despite that this well the fault, I saw 6000 psi
62:02 over over only eight months. So is the decline curve showing bottom hole
62:08 as a function of time. And see that this initial very rapid drop
62:13 the tailing off and then when the is shut in the pressure starts to
62:18 up again. So what we're seeing that this small throat fault is acting
62:24 a very strong baffle during production. ? All right. So here's another
62:35 . This is again from the turn in the northern North Sea. The
62:39 of the reservoir shown here in yellow shown here in black stepping the reservoir
62:46 well, we have reservoir reservoir juxtapositions all of these thoughts. Prior to
62:53 , there was no pressure difference across faults. After Several months of
63:00 there were pressure differences of 800 to psi across these falls. And at
63:08 point, was there any sort of breakdown where the pressure difference caused catastrophic
63:14 of the false field? This is example. This is from the eager
63:22 in the Central North sea. The is here in the sub thrown fault
63:27 . You can see the gamma ray here, top of the reservoir here
63:33 the basis of the reservoir and about td here. So, we've got
63:37 and sand contacts all along the false . Reservoir was a very high net
63:45 gross high porosity and moderate permeability is 50 million Darcy's production from this.
63:56 resulted in production Toronto and pressure production delta P, about 6000 psi,
64:04 eventually declined off and built in builds up when the well is shut in
64:10 again, we don't see any sort dynamic catastrophic failure on the false
64:14 We just see the decline and then tailing off of the of the pressure
64:21 . All right, alright, this a cross plat now of shale gas
64:28 versus pressure difference across the fall. aesthetic pressure differences are shown down here
64:36 then here and here and here in red shaded polygons our production in these
64:42 differences. And what this shows is the pressure differences induced by production very
64:51 exceed the pressure differences that we see on the geologic time scale. And
65:01 think that that is an artifact of permeability of the fault gouge. So
65:06 I've got a cartoon cross section shine fault God's own here on down thrown
65:13 here, upstream reservoir here when we the reservoir on one side of these
65:19 , we create a very large pressure across the fall that exceeds that pressure
65:25 exceeds the capital financial pressure and hydrocarbons to bleed through the fall. But
65:32 permeability is so low that it takes long time for these two compartments to
65:39 will operate across the fall. All . And and that's And just we
65:46 see that build up on a production until we shut the wells back in
65:52 let the pressure build up again. , because of this low permeability,
65:57 see these great drawdown pressures in the . Department wants President Boris. All
66:07 . All right. Now, in reservoir simulation models, what we do
66:11 calculate the shell graduation and the Transmissibility for profitability and fortunes of disability
66:19 the fault. So, here's an of a terrorism model. I've got
66:24 faults here. Reservoir shown in the non reservoir shown here in the purplish
66:33 . And so we can use these calculate the the flow between cells and
66:40 restaurant model based on me. She'll rays showing the permeability and what are
66:47 default transmissibility multipliers. Okay, And the fault transmissibility multiplier is defined
66:58 the ratio of the flow between two with a fall in the flow without
67:05 fall. And so this is this . This ratio is going to range
67:10 zero for no flow in one for unmitigated flow. Um and we do
67:20 because in the reservoir models the faults just represented by grid grid intersections.
67:26 not represented by any column of cells the reservoir model. So this FTm
67:33 a proxy for the gouge thickness and that we apply to the restaurant
67:41 And so we can calculate this along fall. We can calculate this ftm
67:48 the fault and projected onto the fall see how it varies right.
67:56 And again, the permeability of fault is orders of magnitude less than the
68:05 of the host rocks. So even we have hyper um reservoirs the fault
68:11 , you're going to have lower permeability our and and cause baffling between The
68:18 sides of the fault, baffling across fault. I'm fine. Alright.
68:26 here's here's another discussion slide. We a fault with the reservoir reservoir juxtaposition
68:32 a very high net to gross reservoir 1000 mila Darcy's permeability. To get
68:38 history manager already says the form must completely closed the fault. Transmissibility multiplier
68:44 be zero mm hmm. From the . What permeability can you reasonably expect
68:51 this fault? So, here, , my reservoir permeability. My host
68:58 permeability is about 1000 military sees. I'm wrong. This why access
69:06 I would expect to have some reduction in the middle of this cloud To
69:11 reduction of maybe 10 of -2. starting with 1000 million Darcy's tom 10
69:18 minus two, I'd still expect to about a 10 mil. It darcy
69:24 rock in there and I would not the fault to be completely closed to
69:29 an FTm of zero. Okay, we can we can use this plot
69:40 the Initial reservoir permeability of 1000 million extrapolated up to the middle of this
69:47 cloud. Hit say the 10 to -2 line and extract played across here
69:53 get the fault rock from the So, I would expect a fault
69:58 permeability of about 10 million Darcy's for situation. And now it's important to
70:08 whether you're dealing with an oil reservoir a gas reservoir. 10 Mila Darcy's
70:14 an oil reservoir is really poor So, this fault would be a
70:20 baffle with an oil reservoir like you have an FTm Greater than zero,
70:27 it would be any .1.2.3, something that for a gas reservoir, a
70:34 minute darcy gas reservoir is a very permeability gas reservoir. So for a
70:40 reservoir, this fault would not be significant baffle at all. Mhm.
70:49 . Any comments or questions on Are you, did you follow the
70:53 on that in the interest of I just walking through it rather than
71:01 you do it yourselves. Okay, , let's go on. Um we're
71:14 look at a variation on this. now we're going to change from a
71:21 net to gross reservoir counterclaim tonight to very low net to gross reservoir Of
71:26 shale and maybe 20%. So now going to be down here in this
71:30 silicate framework fault rocks cloud down here the grays. So starting with 1000
71:38 darcy permeability in the reservoir. What of fault rock permeability could I
71:46 And this time I'll rely on you some feedback. Is it 10 million
72:26 ? I'm sorry. Just repeat. . Is it thousands into 10 per
72:35 . Yeah, Yeah. So 1000 demise for unexpected fall rock permeability is
72:42 1/10 final darcy. So, the between philosophical framework fault rocks, the
72:49 fault rocks in the low behind it fault. Rocks the low, show
72:55 rocks you got a big difference in vault. Rock permeability third.
73:04 Just as before you go along the military c line here. Extrapolate up
73:09 something in the middle of great cloud and extrapolate that across To the full
73:15 permeability here giving you a value of .1 million RC. Mhm. All
73:24 now, um there are other functions estimate fault rock permeability as a function
73:33 the Shell God ratio. Yeah, is a plot of shell got ratio
73:40 thought rock for mobility. And these curves published by different, different
73:49 different different researchers. And you they they follow a common trend For
73:57 God's ratio is greater than about 15 20%. When we go to lower
74:02 gallery shows they diverge tremendously from thousands millet Darcy's to less than one
74:12 See, I'm sure these are There's a lot of variation in these
74:22 . And for Shell God ratios Creator about 10 or 15%,, you can
74:29 use these curves but for Shell God less than that, you should use
74:35 firm firm cross plots. Use these , Destiny. What your fall Rock
74:43 is going to be okay. so in the, in the reservoir
74:51 models, the faults are the cell their faces. They're not columns themselves
74:56 their own properties. So that flow two cells is addressed by that fall
75:02 multiplier. All right. So, that that multiplier that fall transmissibility multiplayer
75:13 FTM is simply the ratio of the with the fall divided by the flow
75:18 the fall. So again, that from zero for the no flow case
75:23 one for unimpeded flow. And in reservoir simulator, that can be calculated
75:34 by this function. So the flow these two reservoir cells is a function
75:42 the thickness of the fault down The permeability of that zone and the
75:49 the position window of the area available cross fault flow And the spacing between
75:57 two cell centers in the reservoir Yeah, so now we're looking at
76:08 reservoir model, looking at just the and so each one of these great
76:16 represents a fault where it's completely like along here is where you have
76:23 reservoir reservoir juxtaposition. Come here, . Trans disciplinary multiplier is is
76:29 That's shown by the scale here, you have the red streaks and then
76:35 lighter colors shown up here is where have a reservoir reservoir juxtaposition with a
76:40 fall transmissibility multiplier, The reds are it's between .9 and one. The
76:47 are where it's between .5 or 1.5 .5 and .6. So from
76:56 you can see how that fault transmissibility in that baffling is going to vary
77:02 the strike of the fault and up down the fault. And so that's
77:11 FTm are going to vary as a of the throw the juxtaposition window,
77:15 area available for cross fault flow, area of discharge and the flu
77:21 the fault permeability is a function of str and the Gods own thickness.
77:31 , now, if you go back the the first couple of sessions we
77:35 use these plots to estimate what the garage thicknesses. So this is a
77:41 of displacement versus fault guys thickness And average through this data cloud is about
77:50 that the thickness equals about 1 100 throw. So from the reservoir simulation
77:56 I can calculate the throw and then that to calculate with the go some
78:02 and then you start to calculate the multiplayer, correct. Right now coming
78:11 to this plot for this is the is the equation used to calculate this
78:21 of lines and it shows fault rock as a function simply of displacement in
78:29 shell God ratio and that that gives these curves. This is our this
78:37 function is a similar one. Blue is a is a different one for
78:42 different set of reservoirs but they all basically the same friend. So for
78:48 rocks with vicioso, greater than You could use these trends to estimate
78:55 the fault permeability is. But for God ratios were you? The shale
79:04 is less than 10%. You have much divergence within these functions and for
79:12 you want to come to this this cloud of host rock permeability versus
79:18 rock permeability. And look at the cloud through here in the, in
79:24 average through this cloud is about this the fault rock permeability is about point
79:33 Times the host rock permeability raised to power of .8414. So you can
79:39 this this function for the low show racial rocks to estimate what the fault
79:46 permeability is. All right. Um wait, wait. We kind of
79:57 about this that the, the permeability the fellow silicate framework fault rocks as
80:07 probably got the final silicate framework fault is much greater, much lower.
80:13 reduction is much greater. Then we for the loan into gross cataclysm that
80:22 right. Sure. So given this , given the scenario you have a
80:32 Net to gross reservoir with about 1000 Darcy's permeability. The shield, graduation
80:38 50%. one way to estimate default permeability would be to use this
80:47 In which case you would get that of about 0.1 mil darcy for the
80:52 rock permeability within the highest strikeout ratio . The other solution is to go
81:02 this series of parts And look at show graduation about 50%. So
81:08 you're, you're out here this range solutions says you're Salt rock permeability is
81:14 to be between .001 1.01. And permeability will be a very strong baffle
81:25 oil, but a very minor baffle gas would be a a permeable fault
81:31 the gas reservoir, a very strong in an oil. Um,
81:41 so to summarize this section, static seal refers to the fault traveling capacity
81:47 geologic timescales and that's a function of fault rock capital, very entre pressure
81:53 that that determines the fault dependent column or the vertical height of the hydrocarbon
81:59 . That depends on false field. , Reservoir, reservoir or ST on
82:03 fault, contacts concealed depending on the acted for critically stressed, false concealed
82:10 , false concealed. And these are just empirical observations from, from producing
82:20 , faulty capacity can be calibrated as function of the shale gas ratio,
82:25 not as a function of the place potential dynamic falsetto capacity refers to the
82:31 potential faults on the production time And it's important of course, for
82:36 untrained or under produced 12 blocks in field for determining your full compartment station
82:43 you're welcome for a new field. dynamic pressure differences are much, much
82:50 than a static pressure differences and that's the dynamic delta P. S.
82:55 a function of the fault. Rock rather than the capillary entry pressure.
83:01 fault rock perms are typically 1-5 orders magnitude less and uninformed restaurant firms but
83:08 not lower. So when you're when , when the already wants to set
83:14 effort PM Fault. Transmissibility multiplayer to two, get a history match.
83:21 needs to go back to, he to tell him to go back to
83:23 reservoir model and um look at other besides the fault. Rock permeability,
83:32 dynamic fault seals and reservoir simulations are as fall transmissibility zor ftm. They
83:40 from zero for the no flow case 1 to the unimpeded flow case.
83:45 their functions of the fault, throw just position area, the God for
83:50 ability in the galley zone thickness, of these things can be extrapolated from
83:57 static or dynamic restaurant. Yeah. , so that's it for this
84:04 Any comments or questions, anything you me to go back to?
84:29 well, if there's nothing at this , we can come back to this
84:33 again later through the, through the , we'll take a break for
84:41 Now we ran over with this so let's take give yourselves an hour
84:47 lunch and we'll start again at or
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