$PEAK - TriOil Announces... Paddler. - $PEAK - InvestorVillage
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Msg  11219 of 61179  at  9/28/2010 9:37:51 AM  by

GreatSwami


 In response to msg 11216 by  paddler
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Re: TriOil Announces... Paddler.

Now you have asked a really interesting question Paddler - and i am at a loss for something useful to offer? The art of reading wireline logs - or squiggly line-ology as one of my mining friends used to call it - is something that is both relatively simple at one level and yet really complicated once you start to peel back the layers. Understanding and manipulating wireline log information comes under the great heading of Petrophysics - and it it is a huge and burgeoning, rapidly evolving branch of understanding the near wellbore environment.
 
There used to be some very good (and quite easily readable) manuals available from Schlumberger that walk you through the basic fundamentals of wireline log evaluation - and while parts of the manuals are quite scary with all kinds of fancy algorithms and charts to navigate showing how the interpretations are worked through from the raw data through various correction factors for mud, borehole geometry and invasion factors to tease out some solutions - they can be read and something learned without having to get too deep into all the mathematical hocus pocus. However I cannot think of any general all purpose readable text books that put wireline logs into the realm of general understanding - or which give a comprehensive overview for the layperson? Some excellent books on sedimentary geology such as Richard Selley's "Elements of Petroleum Geology" show how some well logs can be used to discern sedimentary environmental information from log character. But I must confess I know of no book that basically does a "Wireline Logs For Dummies" kind of Cook's tour through this discipline? Or provides a real and useful generalist's overview of the arena?
 
Part of the problem is that while all wireline log curves measure some physical property of the near well bore environment - none of them measure anything fundamentally revealing directly. All measurements have multivariate - or non-unique - solutions. Many of the data sets produced must be corrected for mud properties and borehole geometry and interpreted using a priori knowledge of what rock type is being investigated. And yet even with all this stuff - the basics are really quite simple and much can be done (with caution) from some very simple generalisations. If anyone out there knows of any good treatise on this please add a link and we can all perhaps benefit?
 
In the good old days when the basic logging suite was pretty well fixed with a few simple standard logging devices evaluation was done with paper copies of the well logs and the basic Schlumberger Manual charts (Or Dresser/Computalog etc). Nowadays there are a lot of newer "more better" logging devices and techniques - and the log data is digitally captured and subjected to all kinds of cross plotting techniques requiring large number crunching abilities to produce what can be considered the most likely probablistic solutions to the many non-unique possible sets of outcomes. However - even with all that raw number crunching power some unusual mineralogy in the rocks themselves can create all kinds of havoc and mischief in the detailed petrophysical computer output and interpretation. The skilled Petrophysicist corrects these but running many possible iterations of the many possible outcomes using data gleaned by close review of the wellsite geological lithology plots as well as relying on years of prior experience with certain formations to reduce the uncertainties in the raw mineralogical assumptions used.
 
For myself - I have gathered a pretty good understanding by spending over 30 years looking at the very detailed way a drill bit grinds its way through the formations together with the produced mud gas logs - and then forcing a correlation between the drill rate logs, the mud gas logs, the drill cuttings smorgasboard of lithologies represented and the wireline logs run after each well drilled. This feedback proces of comparing the wireline log data (having been taught the fundamentals in University Petrophsics courses and spending a good many years with the Manuals running through the corrections and charts) with the striplog data well by well, year over year in a wide variety of environments means that I can often review a suite of logs and get an understanding of what they mean that is better than that derived from a technician just taking the raw wireline data - running it through all the appropriate Petrophysical sieves and producing a generic lithology, porosity and fluid phase plot. (Although - given good quality raw data - these automatically generated interpretations are now getting exceedingly good...)
 
Anyway I digress. The basics and "Big Picture" stuff is quite simple - even if the details are devilishly complicated. Perhaps that is the book I should write?
 
I have great empathy for your position Paddler as I have spent many years working with both Company Geologists - and trying to train up field Geologists - and the hardest job i ever get to tackle is getting them to properly understand what the "Squiggly lines" actually show and perhaps mean? For me this understanding is essential because by understanding what they mean I can go into a completely new area to me and with a couple of offset log data sets know almost precisely what to expect and where before we drill anything. The only thing I cannot tell from the wireline logs is the colour of the rock - but that I can guess from other "learnings!" But there are unfortunately all too many seasoned geologists that still cannot do a good job with these things - other than the most basic generalities?
 
I'll try to look for something - maybe I'll post some topics here? Basic "Squiggly line-ology stuff? I'll return to this - but for now its time to get my morning report together and off to town!
 
GS


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11222 Re: TriOil Announces... Paddler. Bigbadoil 1 9/28/2010 12:10:52 PM






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