Can't get enough of your FAULT-SEAL ANALYSIS (baby).

Can't get enough of your FAULT-SEAL ANALYSIS (baby).

Juan Cottier Juan Cottier
Director & Lead Geologist at MMbbls Limited

There are 3 three things that really grind-my-gears in subsurface discourse; one is when during a partner meeting an overly earnest geologist who is presenting the results of the core programme will sidestep into a set of slides about “the fun fossils we saw in the core” and all of a sudden the room of well-paid/over-paid professionals who are supposed to be developing oilfields begin cooing “ooooh, look, a shell”. Focus guys, focus!

Scoring close behind that on my irritation-o-meter is when towards the end of a discussion on a fault and it’s sealing capability during production somebody will always chirp-up with “it may not seal, but it will probably act as a baffle”. That staggeringly common sentence is purporting to be a technical comment and yet contains two “maybe” words and an un-quantified noun.

The best conference I ever attended, by a Norwegian mile, was the EAGE Fault and Top Seal in Montpelier in 2012. Great speakers, academia and industry, superb case studies, new innovations, plus a fantastic city, sunny weather, strong coffee and an Ivorian restaurant. Fault-seal study is a superb example of combining, mathematics, outcrop-geology, seismic interpretation and probability. Some really smart people have done some really smart work over the last decade … or 2 … or 3. Just within the northern British Isles we have had superb research come out of the Universities of Dublin (John Walsh's Fault Analysis Group), Liverpool (the great, late Manx-man Juan Watterson) and Leeds (RDR Group). Great stuff.

And yet I have never, truly never, been involved with a project where a fault-seal study ever came up with anything better than MAYBE. Sometimes a quantified MAYBE and always a qualified and caveated MAYBE. Except one time, and it was shameful.

Anonymous case-studies are weak things but you’ll have to forgive me this time in order that we protect the guilty. The operator carried out detailed lab tests to augment fault-seal work and assured us most vigorously that the faults sealed, thus allowing the deepest most contradictory OWCs within a number of fault blocks and so a large STOIIP. But, fear not, I bring good tidings of great joy, which shall be to all Partners, the fault-seal study also assured us that under dynamic conditions, at a threshold pressure very early in our operating-window, the faults failed and fluid movement across the faults was pretty well unimpaired thus allowing higher RFs for a lower well-count. A saviour indeed was born. No doubt. No MAYBEs.

So, I ask the question: despite fault-seal analysis being great stuff and advancing year on year, does it ever produce anything more than a MAYBE? Has anyone seen a definitive answer? Or has any person, institute or company carried out enough studies that were tested by wells to claim their methodology is robust? Is the quality of the probabilities better and so acceptable?

Or … am I asking too much, demanding a straight answer to a straight question … always a risky position to take in the subsurface. Is it simply a case of we need to do more work?

To mis-quote the great Barry White: I’ve heard people say that too much of anything is not good for you … but, I don’t know about that … because many times we’ve done fault-seal analysis, and shared fault-seal analysis and made fault-seal analysis … and it doesn’t seem to me to be enough … it’s just not enough for me … it’s just not enough. I can’t get enough of your fault-seal analysis, baby.

PS: Top of my gear-grinding list-of-3 is when a well is casually described as a “technical success” ... thus implying it was a success, rather than a commercial failure.

Photo: Faulted Early Devonian (Crowley 2008) Peel Sandstone Group, West Coast of Isle of Man. Courtesy of Dr D. Burnett.

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