Search found 27 matches

by Michael_Seman
Fri Jun 19, 2020 6:42 am
Forum: Oil and Gas Exploration
Topic: The U.S. Has Already Lost More Than 100,000 Oil And Gas Jobs
Replies: 9
Views: 1386

Re: The U.S. Has Already Lost More Than 100,000 Oil And Gas Jobs

PGS cut 40% of their staff and are closing London, Perth and KL. Ion-GX handed out paycuts and furloughs. Weatherford is only just out of chapter 11 and had a big job cut round in April. Schlumberger just had a big layoff round. My LinkedIn feed is pretty grim at the moment... Downunder seem to be ...
by Michael_Seman
Fri Jun 05, 2020 4:10 am
Forum: General Geophysics and Geoscience
Topic: Filters used in signal analysis, FIR or IIR?
Replies: 3
Views: 343

Re: Filters used in signal analysis, FIR or IIR?

The FIR filter would be zero-phase in seismic processing. In real-time applications, it would be delayed a little so becomes linear phase. The IIR filters would be used if you wanted a minimum phase filter, or to simulate analogue recording filter. Although in practice, the phase response is only va...
by Michael_Seman
Fri Jun 05, 2020 3:51 am
Forum: Oil and Gas Exploration
Topic: bad SPS files (Friday afternoon whinge)
Replies: 1
Views: 272

bad SPS files (Friday afternoon whinge)

I got a line recorded on an Aram Aries (presumably the original model, as it was in the early noughties) and the XPS file is crap. It has typical records saying channel 1-240 but receiver 101-343, which is inconsistent. Anyway it is explained by some hand-written notes revealing a gap in the spread....
by Michael_Seman
Sun May 17, 2020 8:10 am
Forum: Near Surface Geophysics
Topic: Archaeologist searching for thousands of unmarked graves in Australia's cemeteries
Replies: 4
Views: 307

Re: Archaeologist searching for thousands of unmarked graves in Australia's cemeteries

Where I live there is an old pioneer cemetery only 1 km from the CBD. The basketball courts of a girls school was built over one end of it a long time ago. I presume that must have been the poor folks end with timber crosses that rotted away. Anyway, the old school stood empty for years, and a prope...
by Michael_Seman
Fri May 15, 2020 8:56 pm
Forum: Oil and Gas Exploration
Topic: does anybody use CGM plots anymore?
Replies: 1
Views: 184

does anybody use CGM plots anymore?

I gather paper plots have have dwindled away - I have seen quite a few plotters in rubbish skips the last few years. Recently I tried demo versions of two programs which are supposed to support CGM*PIP format (used for seismic data). One of them worked properly, but the other didn't. I guess it is s...
by Michael_Seman
Fri May 15, 2020 8:35 pm
Forum: General Geophysics and Geoscience
Topic: Seismic aperture and taper
Replies: 4
Views: 364

Re: Seismic aperture and taper

Not wishing to complicate matters, but you could also have a taper by angle as well as horizontal distance. An algorithm might not be accurate over all angles, so for example you might use angles up to 60 degrees, and taper down to nothing at 65 degrees. But at depth, the horizontal aperture becomes...
by Michael_Seman
Wed Apr 29, 2020 6:19 am
Forum: General Geophysics and Geoscience
Topic: Volcanic eruption soon in Iceland?
Replies: 0
Views: 306

Volcanic eruption soon in Iceland?

Southwestern Iceland has had a lot of earth tremors and even ground movement. Looks like magma is moving. If a major volcanic eruption occurs, at least there isn't much airline traffic to disrupt at the moment.
by Michael_Seman
Fri Mar 13, 2020 8:54 pm
Forum: Oil and Gas Exploration
Topic: is exploration dead at $35/barrel?
Replies: 1
Views: 3220

is exploration dead at $35/barrel?

Although I noticed that natural gas price has recovered to February levels.
by Michael_Seman
Fri Jan 10, 2020 4:41 am
Forum: Oil and Gas Exploration
Topic: Vibroseis Trucks
Replies: 1
Views: 2546

Re: Vibroseis Trucks

Look at the paper
"Comparison of explosive and vibroseis source energy penetration during COCORP deep seismic reflection profiling in the Williston Basin"
Geophysics 61(1):211-221.
their conclusion was 20 to 30 km, but that was with pretty big effort (8 vibs and 30 sec sweep length)
by Michael_Seman
Fri Jan 03, 2020 6:53 am
Forum: Oil and Gas Exploration
Topic: receiver spacing less than one meter?
Replies: 0
Views: 5544

receiver spacing less than one meter?

I had a look a promo video:
https://www.youtube.com/watch?v=VW2BFJKGgmU
One slide claims 1.3 million sensors for 24 streamers 10 km long. Even with 4 components (XYZ + P), that works out to sensor spacing of 0.8 m.
Sounds insane, unless somebody got a decimal place wrong.
by Michael_Seman
Mon Jun 10, 2019 7:04 am
Forum: General Geophysics and Geoscience
Topic: CMP aliasing and removal
Replies: 9
Views: 4487

Re: CMP aliasing and removal

Thanks, Micheal_Seman for the comment. Please, could you explain a bit more what you mean by skimping on p-values? Rather you need a small increment between p-traces. "slowness" p=dt/dx So on the far offset, you need p increment small enough to get 2 samples in the period of your highest frequency ...
by Michael_Seman
Sun Jun 09, 2019 1:11 am
Forum: General Geophysics and Geoscience
Topic: CMP aliasing and removal
Replies: 9
Views: 4487

Re: CMP aliasing and removal

You are usually better off removing the aliased energy in the shot or receiver domain prior to a CDP sort. Generally for marine data I'd : - use an interpolation module to push the shot-domain trace spacing to 6.25m if you have one available - do a linear tau-P transform with a large number of p-va...
by Michael_Seman
Thu Feb 07, 2019 6:01 am
Forum: General Geophysics and Geoscience
Topic: Vibroseis field correlation in the 1980s
Replies: 7
Views: 2530

Re: Vibroseis field correlation in the 1980s

There's come good papers from University of Calgary on vibroseis phase; they determined that its closer to minimum that zero in practice after correlation, if I recall correctly. Unless you can phase match to wells then phase is a bit of an approximation - the wavelet is always more complex than we...
by Michael_Seman
Sun Feb 03, 2019 8:01 am
Forum: General Geophysics and Geoscience
Topic: Vibroseis field correlation in the 1980s
Replies: 7
Views: 2530

Re: Vibroseis field correlation in the 1980s

What was your "diversity stack" algorithm, Guy?
The definition given in the SEG Wiki is not what the TIMAP (Texas Instruments) used to do. That was more like an AGC before correlation.
by Michael_Seman
Sat Dec 29, 2018 12:47 am
Forum: Oil and Gas Exploration
Topic: slopes for f-k filter
Replies: 1
Views: 2775

Re: slopes for f-k filter

You can't define a dip that will kill that noise without affecting the desired data. Notice that your energy is not centred on the k=0 axis.
Well not with sudipfilter. Maybe sukfilter would work with
k=0,0.01,0.015
amps=1,1,0
by Michael_Seman
Wed Dec 05, 2018 4:34 am
Forum: Oil and Gas Exploration
Topic: geophysics not attractive for undergrads anymore?
Replies: 0
Views: 3075

geophysics not attractive for undergrads anymore?

I was talking to an academic recently, and he told me that they had lots of Masters/PhD students, but very few first and second years.
The university had downgraded geophysics from a department to "a discipline". Seems they consider it about a worthy as a diploma in street theatre.
by Michael_Seman
Fri Nov 09, 2018 9:16 am
Forum: Near Surface Geophysics
Topic: what geophysical methods used for lithium prospecting?
Replies: 1
Views: 2852

what geophysical methods used for lithium prospecting?

Some of the company press releases are a little vague, reporting something like "airborne survey and drilling located a deposit".
About the only method I have seen mentioned is vertical electrical sounding.
by Michael_Seman
Tue Jul 31, 2018 7:16 am
Forum: Oil and Gas Exploration
Topic: how common is LTO nowadays?
Replies: 0
Views: 1013

how common is LTO nowadays?

LTO has won the lion's share in the backup market, but I am curious if it has become dominant tape in the seismic industry. I know there are various state regulations that might specify archives be written on Magstar or whatever. But if I were building a land recording truck today, I would use LTO.
by Michael_Seman
Thu May 24, 2018 6:00 am
Forum: Oil and Gas Exploration
Topic: when did Kirchhoff PSTM originate?
Replies: 1
Views: 741

Re: when did Kirchhoff PSTM originate?

I presume the answer is Schneider's 1978 paper in Geophysics. But I did come across an interesting article on the history of migration.
Since many oil companies were heavily into migration, one of them could have been doing it earlier, but never published it.
by Michael_Seman
Tue Apr 24, 2018 3:39 am
Forum: Oil and Gas Exploration
Topic: when did Kirchhoff PSTM originate?
Replies: 1
Views: 741

when did Kirchhoff PSTM originate?

I came across an article which stated that straight-ray PSTM was formulated by Lynn(1988), but there was no list of references at the end. The only 1988 paper by Lynn is about cascaded migration. There are several papers that year about migration, even one about RTM (about 20 years before it was fea...
by Michael_Seman
Sat Apr 07, 2018 2:20 am
Forum: Near Surface Geophysics
Topic: seismic for mining - what became of it?
Replies: 1
Views: 2714

seismic for mining - what became of it?

There was a company called HISEIS that specialised in seismic surveys for mineral exploration. I noticed that their website is gone.
I presume there hasn't been much interest in it, despite the pickup in exploration for minerals related to renewable-energy.
by Michael_Seman
Sun Jan 21, 2018 5:58 am
Forum: Oil and Gas Exploration
Topic: F-K spectrum
Replies: 4
Views: 1029

Re: F-K spectrum

I am not familiar with Echos, but your fk plot has label "after filter" and it looks like you have passed the low-velocity noise. I would expect to see energy around the 0 wavenumber line, corresponding to the refelctions around 1.5 seconds.
by Michael_Seman
Sat Dec 23, 2017 3:13 am
Forum: General Geophysics and Geoscience
Topic: Stack specific traces with SU
Replies: 1
Views: 618

Re: Stack specific traces with SU

A while since I used SU, but you use module SUWIND to select traces just before stacking.
So assuming they are sorted by shot,
suwind key=tracf min=10 max=15
by Michael_Seman
Sun Dec 10, 2017 7:40 am
Forum: Oil and Gas Exploration
Topic: Cadzow/SSA filtering
Replies: 3
Views: 737

Re: Cadzow/SSA filtering

I put up some examples here:
http://processing-seismic.xyz/cadzow.html