The Oil Drum | The Status of North Ghawar

217 comments on The Status of North Ghawar

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Euan Mearns on April 7, 2007 - 12:24pm

GaryP - thanks for this amazing work.

I was wondering if you would care to comment on what exactly the "saturation profile" is showing. Based on 4D seismic, it seems that the authors are saying that the Arab D is being depleted so slowly that differences in impedence are not detectable from one year to the next.

(Note that Gullfaks is a giant oilfield Norwegian N Sea and that the Tarbert is the uppermost sandstone reservoir of the Brent Group)

You indicate that the dry oil column in Uthmaniyah is around 120 ft thick - and accepting that as valid would point to the summary saturation model posted by Bob yesterday (and reposted by Stuart here) is showing dry oil at top reservoir and not necessarily a full dry oil column.

Notwithstanding that, the layer of oil shown in your profile seems to tie in with the big tongue of oil on the saturation model..

Different folks tend to look at this in different ways. Some think "My God" Ghawr is dying - which is of course true. Others, like me tend to think - thank God look at all that oil that is left after 50 years of production.

It seems to me that by replacing vertical wells with horizontals (to limit water production) that Aramco will be able to maintain oil production here for a number of years yet.

Taking the Uthmaniyah tongue as 20 miles long, 5 miles wide, and 100 ft thick I get 279 billion cubic ft of rock. At 5.6 ft3 per bbl I get 50 billion bbls of rock, at 18% porosity and 89% water saturation I get 8 billion barrels in place or around 4 billion recoverable.

At 1 million bbls per day, this will be gone in 11 years (very roughly).

It doesn't seem very much to me - I've been generous with length and breadth, probably conservative with depth. If anyone would care to check the sums...

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garyp on April 7, 2007 - 12:36pm

Euan,
Personally I skipped over the discussion of acoustic velocities etc. Something for those with more knowledge than I. I focused on the 2004 simulation run with a big area of zero change in water %age. I contend that this is the dry oil area, a reasonable assumption I think. Cross section and area plot seem to tie up in the plots above.

With regard Uthamniyah and horizontal drilling, see the posting I just made below on what a patent app has to say about Uthamniyah faults. This might shed some light on why the oil has a high water cut at the peak, but not downslope.

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Fractional_Flow on April 7, 2007 - 3:39pm

Next stop Uthmaniyah.

Euan...

As you know Saleri says Ghawar was 48% depleted at 55 billion. That leaves 60 billion barrels of field reserves.

He gives an aggressive 13.9 billion for AD/s, and the Haradh at 900kBOPD is 10 billion over 30 years. That's 24 billion at 1/1/04......

Houston we have a major problem with Uthmaniyah and your numbers (mine are similar- maybe wrong as well).... especially at a billion barrels per year. 2 MMBOPD AD/s, .9 Haradh, 2.7 Uthmaniyah.

Thanks for your contributions here.

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totoneila on April 7, 2007 - 6:51pm

Hello TODers,

Great work by all!

I refer everyone to Garyp's great find:

http://www.blackwell-synergy.com/doi/pdf/10.1111/j.1365-2478.2004.00473.x

"Houston we have a major problem with Uthmaniyah"

I think we need more information on the moving mud wave in the pressurized waterfront [in all areas of Ghawar] as it pertains to horizontal/vertical permeability/porosity ratios--could the mud wave be making the waterfront behave more like a breaking wave than a rising tide through the payzones?

General carbonate reservoirs have greater permeability and porosity as you go from payzone bottom to top. The mudwave is clogging the bottom making it easier for ever increased waterfront vertical permeability through ever more porous payzone toprock. Increased injection pressure maybe making it very hard to keep the mud moving causing a waterfront 'breaking wave action in the reservoir sweep.

Sorry, wish I had more time, but busy today. Please flog this mud wave implication as best as you can--Good luck!

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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Euan Mearns on April 7, 2007 - 7:59pm

Bob - I've not forgotten about your question on a tilted contact - but it is a complicated question to answer - which evidently has been discussed by the SPE for 30 odd years - so I'm not sure that I can contribute a huge amount in a short post.

Suffice to say this:

1. Any aquifer (water) pressure gradient across the field related to a tilted contact is unlikely to be significant to the present debate on reservoir depletion. Variations in pressure caused by production and injected water are likely to be over riding.

2. The geological processes responsible for the tilted contact will be very important in understanding the "hydrodynamics of the reservoir" and how it responds to production.

I know this won't help much but the key issues right now are the size of undrained reserves in good quality reservoir in Northern Ghawar.

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totoneila on April 8, 2007 - 5:26pm

Hello TODers,

http://www.spe.org/elibinfo/eLibrary_Papers/spe/2006/06EURO/SPE-98847-MS...
-------------------------------
ABSTRACT/details behind paywall =(

Water Production Management Strategy in North Uthmaniyah Area, Saudi Arabia

A water management strategy was initiated in the North Uthmaniyah area of Ghawar field in late 1999. The strategy main objectives are to reduce operating expenses associated with water handling and avoid capital investment required for the expansion of water handling facilities while engendering a more efficient recovery process. The strategy was implemented through four initiatives: operating of high water cut wells on a cyclic basis, conducting rigless water shut-off jobs, drilling horizontal sidetracks of existing vertical completions and drilling wells with partial penetration completions. [There is much more detail in the abstract, please read]
-------------------------------

http://home.entouch.net/dmd/ghawar.htm

Specifically, I refer you to the second graphic of Alexander: http://home.entouch.net/dmd/ghawarwaterfront.JPG

Does the oilwell placement make sense? I expected a more even spacing, or else well concentration along the top of the incline [the eastside injection well pattern just above the bottom tarmat makes sense]. Also, can someone access the graphics and charts in this article [I can't]:

http://www.oilandgasnewsworldwide.com/bkArticlesF.asp?IssueID=115&Sectio...
---------------------------------------------
[Selected excerpts]

Robert Phelps, Richard Black, Harold Triebwasser, Ali Al Shahri and Fahad Al Ajmi of Saudi Aramco discuss ways to integrate data to identify high-stratiform permeability regions in the 'Uthmaniyah area of Saudi Arabia.

A PROJECT was undertaken at Saudi Aramco to develop a quantitative definition of super-K; map this quantitative definition of super-K and compare to other geological and reservoir properties; determine a possible correlation between the data in order to determine what parameters may be influencing super-K events; and use 3D visualisation to review the data to determine if there are trends or similarities in the data.

Using all open-hole flowmeters in the 'Uthmaniyah area, a Fluid Flow Index (FFI) was calculated.

To better understand the quantity of data used in this study it is important to note that there were 1,366 'Uthmaniyah wells analysed.

This represents about $82 million-worth of open-hole logging cost. A total of 799 wells had flowmeters run at a total cost of $16 million, of which 462 wells were open-hole flowmeters.

The majority of these wells had several and some as many as 16 open-hole flowmeters. Since a data point is taken at every 0.3 m interval, measuring both water and oil, this translates into approximately 2.5 million data points that were used in this study.
-----------------------------

But, I want F-F,SS, and Euan, plus interested others to see this MOTHERLODE OF GHAWAR INFO [WARNING 540 page PDF]:

http://pangea.stanford.edu/~jcaers/theses/thesisJoeVoelker.pdf
----------------------------------------------
page 54 -- placement of all wells in Ghawar
page 106-120 --UTHM waterflood detail and super k

The rest of the PDF is extreme detail that I haven't had time to study.

Other links here:

http://pangea.stanford.edu/~jcaers/publications.html

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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garyp on April 8, 2007 - 6:23pm

Well that puts paid to me doing any real work tomorrow.

Can I point to two papers that result from the trawl to find the original paper for the oil and gas ref.

Integration of Data to Identify High-Stratiform Permeability Regions is the original paper, complete with pretty pics.
&
Simulation of Super-k Behavior in Ghawar by a Multi-Million-Cell Parallel Simulator

There are many more illuminating papers via here. These are Aramco's own papers and there are lots of bits of data to ingest.

-----
Edit: And Fractional Flow REALLY needs to comment on this paper:
Equations for Water/Oil Relative Permeability in Saudi Arabian Sandstone Reservoirs

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totoneila on April 8, 2007 - 6:27pm

Hello TODers,

When you use the PDF magnifying tool to zoom in on the oil wells on page 54 of the Motherlode link--alot more detail becomes visible.

Does it show OWC at the various stratigraphic levels inside the well, gas condensate output for some, Horizontals & MRC?

What details do the shapes, and colors mean for each extraction well? for each injection well? Is there any way to figure this out?

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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garyp on April 8, 2007 - 7:27pm

Bob, and anyone else looking at the data, I heartly suggest going through the Aramco Journal of Technology. There is much there that informs and provides evidence that can be pieced together.

The page 54 oil well pic doesn't tell me much, the resolution is too low. However there is enough in the JoT articles to give a fairly complete picture I think.

As an example Simulation of Vertical Fractures and Stratiform Permeability of the Ghawar Field provides a figure that answers precisely the question of where the Uthmaniyah map and cross section output we have goes.

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totoneila on April 8, 2007 - 9:39pm

Hello Garyp,

Great Job! This area is/has been studied extensively by Aramco because:

From the Motherlode link:
---------------------------------
Moore[55] reported superficial flood front velocities
v = 15 ft=day over an 8 km span
on the Uthmaniyah flood front.

Saudi Aramco (SA), is attempting to resolve observed, massive, unmitigated hydraulic conductivity between injection and production wells separated often by more than 1 km.

The first fundamental fnding: the predominate, repeated waterflood pattern is that of line drive, specifcally under long and thin, rectangular pattern boundaries. Second: Ghawar water injection wells are often inadvertently hydraulically fractured with unpropped fractures [basically, shooting themselves in their own feet!].

We conclude that these conditions exacerbate the problematic super-k condition, that of early water breakthrough. Our hypothesis for the structure of super-k, containing essential discrete fracture network components, naturally leads to a supposition that the two conditions stated above, are conducive to the formation of highly
conductive pathways, consisting of hydraulic fractures at injection wells, connecting to natural discrete fracture systems, culminating in a network that may significantly
affect production well performance, because it resides in a long, thin bounded region, the tight waterflood pattern.
-----------------------------------------------------------

I haven't read everything yet, but Aramco mentions horizontal wells watering out instantly, water over-riding oil, loss of drilling mud, and other anomalies due to widespread DFNs.

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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garyp on April 7, 2007 - 4:57pm

Euan,

I've been playing with Uthmaniyah dimensions, doing similar calcs to you. I've got slightly different numbers. Assuming you mean 89% is oil, not water I end up with ~10 billion barrels in place. Isn't there a factor you have to use to take account of gas in oil, etc. I seem to remember a 1.4ish factor?

Uthmaniyah is supposed to produce at 2Mbopd, so assuming 50-60% recovery puts us at 5-6bbl and 2500-3000 days (6.8-8.2 years from 2004). That is 2011-2012, although in reality we should expect a drop off in production and a longer tail. And this assumes nothing major prevents capture of the remaining dry oil.

It does seem a relatively close date and there may be much recoverable oil behind the waterfront - but like you as a rough back of the envelope calc it is worrying. It seems as if 9mbpd rising to 12 is less the order of the day than trying to maintain near the 8-9mbpd level as volumes drop off from the Northern fields.

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Euan Mearns on April 7, 2007 - 6:13pm

89% was a typo.

I took 1 million bpd from Twilight, if it is doing 2 then obviously decline will be significantly more rapid.

One point that leaves me puzzled is the reference to depletion in the Arab D being too slow to monitor on an annual basis using 4D seismic - they say they need 5 years to see it.

On these calculations - going, gone.

So I wonder if the oil column may thicken southwards?

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Fractional_Flow on April 7, 2007 - 6:43pm

Euan-

Wall Street Journal said 5.6 MMBOPD last week.

Saleri said North Ghawar (AD/s) would make 2 MMBOPD at "modest water cuts" for decades to come.

The 3 haradhs are 300 K/ project

That leaves me 2.7 for Uthmaniyah.

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Stuart Staniford on April 7, 2007 - 7:29pm

What about Hawiyah?

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Fractional_Flow on April 7, 2007 - 7:36pm

Damn stuart that is the big mystery.

You had a fractional flow curve which showed a 43% initial water saturation and a 30% residual oil saturation which means it doesn't compare

Then GaryP shows a little oil being pumped (don't jump me) from there.

Gary P I see 2.5 MMBOPD for North Uthmaniyah on your ref... but I have been wrong before.

Now Hawiyah - it is not on any development plan I have seen why was it skipped over.... somebody had to say something once. Maybe it is an active caldera (just kidding). But that is the way they pronounced Hawaii in my Appalachian home.

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totoneila on April 8, 2007 - 10:06pm

Hello SS,

Look at all the wrinkles in the Hawiyah area of the Laherrere 3D---many,many fracture networks. See page 126 of the motherlode link for a quick look at all the Southern Ghawar fractures that will make a uniform waterflood very difficult. Unfractured rock in South Ghawar has lower general perm/porosity so the water will 'look' for fractures to follow. Yikes!

Bob Shaw in Phx,Az Are Humans Smarter than Yeast?

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garyp on April 7, 2007 - 6:51pm

I got 2mbpd from here, figure 2. According to this Uthmaniyah South doesn't really count from a production standpoint. Why? Your guess is better than mine.

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Stuart Staniford on April 8, 2007 - 2:01am

I'm not certain that's a reliable source. At the bottom of his graph where he shows the Ghawar production breakdown, he lists his source as "modeled by Jud", which isn't exactly comforting. I emailed him asking him how he knew, and he hasn't responded. I hate to accuse the guy of anything, but I just have no idea how he would know what the graph claims to know, and since he doesn't say, I don't know what to make of it.

Admittedly, I have no better idea for how the EIA or the IEA come up with production numbers on Saudi Arabia than for how Jud comes up with his numbers for Uthmaniyah, except I suppose that a large government department has more to lose if they make up the numbers, and a longer track record, and everybody else quotes them...

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garyp on April 8, 2007 - 3:01am

I'd agree that the source has question marks associated - but since I can find no other source that really addresses the question, and because it goes up and down with authority (sic) its the numbers I've taken till now.

Put it this way, I've no better idea myself.

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Stuart Staniford on April 7, 2007 - 9:04pm

Greg Croft says the formation volume factor for Uthmaniyah is 1.31 (that is 1.31 barrel of oil seeping into the wellbore become 1.0 barrels of oil in a tanker by the time the gas has all come out of solution).

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Nate Hagens on April 7, 2007 - 5:21pm

.. I get 8 billion barrels in place or around 4 billion recoverable.

At 1 million bbls per day, this will be gone in 11 years (very roughly).

That would assume constant flow rate of 1mbpd. Would that be realistic given this geology or would the last scraps be harder and harder to get to - perhaps averaging 500,000 per day over 20 years?? Or is the way the oil is pushed into that column make the future extraction rate pretty constant?

Ultimately Im asking if we should expect a high flow rate of oil and then a slurping sound, or a gradual (but noticeable) decline? (politics excluded for the moment)

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