08-08-2024, 11:28 AM
(08-08-2024, 10:56 AM)Stewy Wrote: NO POLITICS HERE: I have given facts and my opinions. My opinions are biased obviously by 30+ years of O&G experience, but I hope it is clear that I am not 100% oil company. If a question gets raised that is politically biased, I will quote that I am not responding to it and flag it for moderation. If you wish to discuss, the political sides f this post, feel free to copy this post to P&R for your discussion, but I will not be participating.
Frac'ing is short for fracturing the reservoir. It is a form of reservoir or formation stimulation. Stimulating a reservoir can be as simple as splashing a little acid on an open hole (no casing) reservoir to a "through casing" high pressure multistage proppant "frac" (NOTE: A proppant is a sand grain like material (used to be sand all the time, but now mostly synthetic) which is introduced into a reservoir via natural or artificial fractures.
"Frac"ing as a stimulation technique is over 100 years old. In the early 1900's in Appalachia, the Devonian Shale responded best to a Nitro "frac" or in other words dropping a bomb into the open hole (not kidding). FUN FACT - Over the years operators have attempted to up-science Devonian Shale completions, but results have shown that good ole Nitro still works best, but under more controlled conditions than the early 1900's.
I mention all this to counter the notion that frac'ing is a new thing and a new problem, which it is not.
Wellbore Design (google "wellbore design oil and gas" - images): Wellbores are designed telescopically into the ground with many overlapping steel cylindrical pipes (called "casing"), which are cemented into place. Known aquifers, faults, trouble zones are protected by putting them behind cement and steel. NOTE: The press and the populace in general may think the industry greedy and negligent, but the last thing a company wants is a leaky well, a blow out, accusations of polluting, etc., not because they care, but because a "bad" well is bad for business, which makes them care. However, humans aren't perfect/shyt happens AND on rare occasions an AHOLE company makes the rest of us look bad by being greedy and/or negligent (looking at you BP).
Company Philosophy: Companies are beholden to their governmental and equity stake holders, and not the public opinion of them. Most companies will meet or exceed (not by much) state and federal regulations to avoid litigation. They will not go over and above as that will eat into profits. This is reality.
Cementing of casing/pipe/steel in the ground is the single most important part of drilling a well as it not only protects the geology it protects the humans running the rig. (The failure of the Deep Water Horizon at Macondo was due to a poor cement job, allowed by negligence and greed on BP's part). However, there are all kinds of ways to get poor cement jobs. Bad Design: Cement is designed by engineers in labs to accommodate known reservoir and wellbore condition prior to drilling the well. But if conditions aren't known, then design can fail. Poor Regulation: The amount used and how much formation is covered is based upon design and local (onshore - mostly)/federal regulations. Old Wells: Wells from the 80's and older were beholden to different regulations. Over time cement could break down or companies didn't have the same regulations as they do now. Companies may enter old wells and try new stimulation techniques on them, which modern regulations may not limit properly.
Geologically, when/how can frac'ing be a problem? Well frankly it shouldn't be, but shyt happens. Imagine this: You have a wellbore and it drills an unseen or un recognized fault. The fault crosses the wellbore either in the section that is being stimulated OR more likely in a part of the hole with an improper, poor or just an old cement job. So what can happen is if a high pressure (which most are) "frac" job accidentally intersects an unseen fault, it can open the fault, force fluids into it and essentially lubricate it allowing it to dsitrub it's geologic equilibrium and move.
Frac'ing and Earthquakes: Real or media hype? Oh it's real. See the paragraph above as to how it works. But not every EQ is because of frac'ing. The USGS has seismometers all over the country (and world for that matter), which can detect EQ's that humans can't even feel. EQ's caused by O&G activity have very different patterns (frequency and strength) than those that are naturally occurring. In places like Oklahoma this has bene a big problem.
The meat of the discussion is below<----
Negligence/Ignorance and/or Operator Responsibility: Having worked at multiple O&G companies, I can tell you most are very serious about safety and following regulations. We all say we really REALLY care, but the cynic in me says it's about litigation mitigation. Regardless, operators will follow safety/environmental regulations to avoid fines, litigation and bad press (less important to bigger companies). So how does a problem like the Oklahoma EQ swarms happen if everyone cares so much? Well, for the purpose of discussion we will ignore negligence, as that is an aberration.
Mostly, the answer as I see it is "Unforeseen Circumstances" (UC's for short). What does that mean? Here are a few scenarios of unforeseen circumstances causing a widespread EQ swarm problem.
---Modern Application of frac'ing techniques into old/known formations not previously developed. This can be due to changing economics or an advance in technology. The formation could unknowingly be highly NATURALLY faulted/fractured, which causes the frac job to propagate in an unexpected way into unexpected faults, lubricating them.
---Old Reservoirs with new technology: There could be an old producing formation that behaves in known ways, that has never been frac'd. Frac'ing gets applied to it and for the same reasons mentioned above you get UC's.
---Horizontal Drilling (HDr for short): This I think is possibly the biggest factor. HDr is a technique that follows parallel to a mostly horizontal bed as opposed to normal wells which try to cut through section at a 90 degree angle. This is done almost exclusively in production wells because it is expensive and you have to know where your target is before you drill, whereas in an exploration setting your target is an educated guess, which is why it's called exploring :) . HDr introduces two problems however: #1 - It is often these days being applied to old reservoirs that were previously developed vertically, thus the affect of HDr on long term reservoir condition is unknown; #2 - Greater Exposure to Reservoir Surface Area (which is the point of HDr) also exposes the wellbore to a greater chance of intercepting faults/fractures, which also are generally perpendicular to bedding. In other words a vertical well is very unlikely to encounter an unseen vertical fault, whereas a HDr well could very well cross multiple vertical faults and fractures depending on their and the wellbores orientation in the X/Y domain.
Who's Responsible? Ultimately, I'd say regulators AND the operator. If the operator is following all the rules but gets bit by a UC, they aren't negligent, but is likely responsible. To avoid a long term issue like the Oklahoma EQ swarms, it is the responsibility of the operator to bring the problem to the attention of the local regulators and make changes to account for the UC's. If the operator recognizes and ignores the problem, they are negligent. If the state regulators recognize and ignore the problem they are negligent. And yes you can get an either or condition, as both will lose money with more regulation. So it is in the operators financial interest to collect data and not raise a premature alarm, and the Regulators best interest for the same reason. My point is, that it isn't always the greedy oil company.....the state wants their uninterrupted revenue as well.
Finally:
More on Macondo: Macondo was an anomaly. The industry was horrified by what BP did. Personally I was disgusted. The amount of greed and negligence that went into causing that disaster was turn of the previous century mentality. There were over a dozen safety triggers that were ignored by 7+ individuals on and off that rig, which any one being taking into account would have stopped the disaster, and all were ignored. Note that I was mostly talking above about onshore/state issues. Macondo completely changed offshore/federal regulations. The rules tightened up dramatically. US GoM barrels produced are some of the cleanest safest barrels in the world now. This is a good change IMO.
Phenomenal answer, thanks Stewy. So, earthquakes happen by fluids getting into a fault which lubricates them and makes it easier for them to shift. Is this an accurate understanding?
Also, what does the "stimulation" actually do? Does it just make it easier to extract the resource?
