Why We Love Elemental Geology

When a stereoscopic microscope, tweezers, sample probe, some chemicals, and an ultraviolet lightbox were the ‘state-of-the-art’ in cuttings evaluation equipment, mud-loggers and geologists did a very good job in identifying drilled formations all things considered. Similarly, when coach-and-horses and sailing ships were the ‘state-of-the-art’ in transportation, they also did a very good job transporting people and goods from place to place.

 

But times change.

 

In the mud-logging world, Diversified Well Logging (DWL) is embracing X-Ray Fluorescence as the new ‘normal’ for realtime sample evaluation. Driven in part by the demand for better geological information in unconventional formations that are difficult to impossible to examine accurately under the microscope, elemental analysis can be used to accurately determine the elemental, mineralogical, lithological, and geomechanical properties of a sample. With this quantitative data, we will know exactly what the formation is and where we are in it. No more fifty shades of grey, but a wide range of ‘colorful’ elements.

 

 

With what DWL is calling Hybrid Mud Logging, our field geologists will be able to respond to wellbore issues with more certainty. Where answers to downhole questions used to include a ‘maybe’ or a ‘possibly’, we will now have rock solid evidence. For example:

 

Q1: Why am I now drilling slowly when I am in the same formation?   My gamma ray and visual cuttings descriptions are the same. Is the bit or motor failing? Are there hole cleaning issues? Do I really have to waste time and money and trip out of the hole to check?

A1: Realtime geochemical analysis with XRF will help determine the cause.   Evidence of biogenic or authigenic silica – siliceous/quartz cement will affect the ROP. Evidence of carbonate cement can also affect the ROP. Subtle changes in the clay type that will lead to swelling can affect the ROP. Or no change in lithology at all would indicate there is a hole cleaning, bit or motor problem. Whatever the answer, there is evidence to back it up.

 

Q2: I am starting to see an increase in cavings, but where are they coming from?   The cuttings seem to be the same. Do the new formations have stability issues? Are the cavings coming from destabilized formations up-hole? Is hole geometry or drill-string configuration involved? Should mud properties be changed?

A2: Hybrid Mud Logging with elemental cuttings analysis can help answer the questions.  The elemental signature of the cavings will definitely confirm their origin. The exact zone the cavings are from will determine if hole or pipe geometry is a contributing factor. And a change in mineralogy / clay type of the new formation can indicate a mud property change is needed.

 

 

Q3: I am geosteering but now, 750 feet away from TD, my gamma ray tool has failed.  Do I trip out of the hole to change the tool and waste time and money? Do I drill ahead blindly, possibly deviate out of the target and maybe lose the footage for production and waste money drilling? Or, shall I call TD short, definitely lose the 750 feet for production, but save the drilling costs?

A3: With Hybrid Mud Logging, the other option would be to Chemosteer the final 750 feet.  A trip would be avoided, and the uncertainty surrounding the possible loss of a productive section of hole would be avoided.

 

These are just three examples of how quantitative elemental analysis of the cuttings can greatly improve the decision-making process and bring value that far outweighs the cost. There are many more. In general, of course, it comes down to operators wishing to improve their returns on investment. Hybrid Mud Logging will do that.

 

One final example with Hybrid Mud Logging and Chemosteering is estimated to have saved an operator at least $10 million. A third well on a pad intersected an unexpected change in structure above the target, identified with realtime elemental cuttings analysis. Quick interpretation allowed the well-path to be altered and by Chemosteering the reservoir target was successfully intersected. If the change in structure had not been identified, a $10MM sidetrack would have been necessary.

 

Diversified has embraced the future and is now pioneering its Surface Measurement While Drilling services (Hybrid Mud Logging, Chemosteering, Automated Remote Mudlogging). In short order, we believe that our clients will appreciate the new service benefits as they see their geological knowledge grow along with the profitability of their wells.

Gas Quality, Control and Analysis

Since early days of the oil industry, gas liberated from the formation during drilling has been looked at as a means to predict what type of hydrocarbons are lurking in the reservoir. Various ratios and procedures have been tried and tested with various measures of success in reservoirs around the world. The major lesson learned is that every reservoir is different, and that you just can’t trust things to be exactly the same from one place to another.

With the rise of the machines - downhole MWD/LWD ‘machines’ – work with gas ratios as a serious predictive tool slowed down or stopped, becoming another arcane tool of mud-logging folk; a source of data that was always present but rarely used in earnest. Granted, the accuracy of gas data depends on a number of factors that include, at a high level, the formation itself, drilling mud, drilling parameters, lag time calculation, and gas extraction and measurement equipment, but despite the various possible drawbacks, gas data, especially the ratios, is still very useful when looked at in the right way. (And strangely, that right way includes a certain amount of squinty-eyed skepticism.)

 

Diversified Well Logging uses a process that allows daily collaboration between the wellsite, the regional office, and a squinty-eyed data analyst who provides a triple-check of the gas data. This triple-check assures DWL and their Clients that the data is good, and that any issues have been addressed in a timely manner. Quality is important.

In the unconventional, tight formations that are currently drilled in North America, DWL uses gas curves and ratios to (1) aid as a primary quality check, and (2) evaluate what is going on downhole. The traditional ratios, with their traditional setpoints may not point directly to the type of hydrocarbon in place, but they can still be used to

  • Pick or corroborate formation tops
  • Indicate subtle changes in ‘homogenous’ formations
  • Indicate major changes in formations
  • As an aid in geosteering (preferably along with DWL’s Chemosteering)
  • Indicate potential changes in formation fluids
  • And, with squinty-eyed skepticism, point directly to the type of hydrocarbon in place

As a cost-effective formation evaluation technique, DWL believes that gas analysis provides important insights into the downhole environment.

It may be an arcane tool of mud-logging folk, but it is a very good tool.

Gas, used alongside our XRF service allows us to offer HYBRID MUD LOGGING … Hybrid Mud Logging used alongside our Geosteering service allows us to offer CHEMOSTEERING … and along with hi-data-density AUTOMATED REMOTE MUDLOGGING, if hi-data-density cuttings sampling is needed, we offer Operators the full benefits of …

SURFACE MEASUREMENT WHILE DRILLING (SMWD) – Bridging the gap between Seismic and Downhole logs.

A Straw Too Many

This is not going to be about the damage to the environment caused by the proliferation of plastic straws (but I do recommend that paper ones be used - they are being sold again you know - or just sip from the glass - glasses are specifically designed to be sipped from.)

No. This is an article about some other wastefulness - over-drilling.

The popular phrase of the moment in the unconventional world seems to be 'Parent-Child Relationship Issues'. That is, just like real-life human families, the more children you have, the faster the poor parent's resources will be sucked dry. There has to be a sensible limit both in the amount of wells poked into a formation and children running around the house.

For the last two weeks or so, the SPE's 'Journal of Petroleum Technology' has run pieces on the increasing focus on shale production with the 'Parent-Child' thing being the major issue. The salient point in the last article I read was that unless fewer wells were squeezed into a certain area of rock, then those wells will start to produce less and less - quickly. Just think about it - give ten kids a straw each (a paper straw remember) and only one glass of lemonade, well, no-one's going to be happy.

Straws are cheap. Ten wells sunk into the ground are not. They cost a lot of money to drill and they cost a lot of money to fracture and complete. If well number 1 just happens to be sucking a lot harder on its 'straw' than well number 10, or 3, or 7, or whichever, hopefully the returns from well number 1 compensate for the drilling and completion costs of the other poor performers.

Now, according to a recent Spear's blog-post I saw, the average number of wells per pad throughout the continental USA is in fact about 3 or 4. That doesn't sound bad, but of course there are pads with up to 10 wells and some with only 1. In either of these extreme cases, there must surely be room for improvement. Lets save some drilling costs and only poke 6 'straws' into our reservoir here, or lets add a couple more into our 1-well pad here, and hopefully tap into some hidden hydrocarbons.

The question of course is how many children are needed, how much are they going to cost, are they going to be useful or just a drain, and where on earth should they be put for the most benefit? Unfortunately, for geologists working on plans for a productive field, the answers to such well-centric questions can often be hard to answer because the data may not be there. You just don't know. You think you know. But you don't. You're just making the best choice you can with the information that you do have.

I mean, look at the picture on the left. Lots of wells, many of which are probably heading down and into the same target formation. A target that has been deemed good with some probably low resolution seismic data, some wireline and/or LWD data, and some excellent core data from an 8-inch pilot hole somewhere or other in that picture. What needs to be remembered is that an 8-inch cylinder of rock at point 'A' will not fully represent points 'B' through 'Z'. Geology is a tricky thing, (and coming back to the children theme) every well, like every child will be different. They need to be watched pretty constantly!

Alright then, back to the issue of wastefulness. What would it be worth if improved geological knowledge could be achieved on a pad, field, or region? What if that knowledge helped in the drilling of correctly spaced wells allowing a fracture program to be designed without fear of damaging parent or sibling wells. This would have to make life easier, less uncertain, and would probably save money. Unnecessary wells would not have to be drilled and there would be savings on ineffective fracturing. I'll also throw out for debate the supposition that production might be enhanced, and the whole project would become more profitable.

But how do we improve our knowledge? How do we gain the geological certainty needed to place each well correctly? Because it is geological certainty that is needed. Pretty much every article agrees that it's the rocks that hold the key to better performance, but, apart from that 8-inch cylinder of rock in the middle of a vast expanse of West Texas or wherever, we do not have much to look at, scientifically speaking.

There are ways to get the data of course. Wireline, LWD, cores - methods that are used in vertical pilots, but probably not so much in the laterals. Hey - we hit the target our 8-inch cylinder of rock from several miles away told us to hit and the cuttings sort of look the same, so we're good right? Plus, that wireline, LWD, and core stuff is way too expensive to run in every well. Let's just rock along with the status quo.

What if there was a better way? The initial problem is clear - money wasted and production compromised. The answer to this is also clear - better geology from every well drilled. Which raises the secondary problem of having to spend a bunch of money to get the better geology. So ... the better way is?

The better way is to get quantitative, scientifically accurate data that can be used for correlation, interpretation, use in geological models, etc., etc., from every sample on every well, and, here's the best part, at a price that fits every cost-conscious operator's budget. It combines old-tech with new-tech and some hard work and a lot of expertise.

Diversified Well Logging LLC., is calling this 'Hybrid Mud Logging', a 'Surface Measurement While Drilling (SMWD)' service. No more subjective lithology percentages or descriptions on the mud-log, but accurate modelled mineralogy or lithology, allowing integration with geosteering, and of course, real-time, cross-field correlation which can let you know whether or not you have one child too many draining your resources, or whether you could possibly fit in one more before you quit your pad.

Bottom line; SMWD from Diversified provides the geological certainty that can save operators hundreds of thousands of wasted dollars, while adding millions through better production at a cost that makes the service hard to ignore.

Forget the status quo - Diversify your Well Logging.