How much money do you earn p/a, roughly? | With <5 years industry experience I am making $ 115,000 USD + bonus a year. |
Do you enjoy your work? | I am very fortunate to have the opportunity I do. I enjoy my job and it provides well for my family. I can sit inside on hot/cold days or go play with very large equipment if things get boring. Couldn't imagine not being in the oilfield. |
Do you need a specialized degree to do this kind of work? I have a Geology degree but I didn't have any particular specialization in college. | You are not required to be an accredited engineer or what not to do the work, but I don't think anyone would hire a non-engineer for an engineering position. |
| I think the new standard for geologists to work in industry is to have a masters. Again, not a requirement but my understanding from talking to the Geos is most companies won't accept anything less. |
Yeah, I'm definitely no engineer and unfortunately I never got my Masters. Never could figure out what I wanted to do. | How old are you and what type of experience do you have now? Big companies have different requirements for themselves than smaller mom & pop operations. Are you in an area that's busy with oil & gas activity? |
I'm late 20's, no oil/gas experience (I've done all environmental consulting to date) and live in Southern AZ. | The area you're in is probably the biggest hurdle to overcome. I don't know of anyone out that way who I could hook you up with to talk to. Sorry. |
Can you explain the process behind extracting oil from tar sands and why we don't have the technology for it today? | Preface with: I do not work those sands. I specialize in high temperature/high pressure (HTHP) formations. Someone involved more intimately with them could give a better answer. The technology to extract oil from tar sands does exist - its just there are easier places to get hydrocarbons from for the time being, which means a dollar goes further elsewhere. |
| Basically my understanding is the hydrocarbon is simply too viscous to flow through a rock matrix. In fact it is so viscous that it requires cutting with liquid hydrocarbons in order to be able to pump it through pipelines. |
| There are methods of increasing the temperature of the oil underground so that is becomes less viscous (steam floods for example) but those require extensive planning, maintenance and a very high capital investment. Even then, I am not sure of the % of oil that can be recovered from what is initially in place. |
| I'll do some asking around for you if you want and message you a response. |
| ETA: Here's a video from Cenovus who is a big player in the oil sands. In this example they are using steam to heat the oil to decrease the viscosity and letting gravity drain it to a well beneath for production. |
| Link to www.cenovus.com |
Sure. That would be awesome. | Luck of the draw really. The company I work for is large enough to be able to afford the increased capital to chase HTHP stuff. But whether its tight shales or very permeable sands its all a variation of the same, you know? The thought processes and operations don't change. Specialized sounds a bit douchey - let's go with "I mainly focus on HTHP". |
How did you get to specialize in HTHP formations? | With how hot the market is right now, most companies are taking whatever they can get in terms of experience. If you are trying to transition to a company that predominately works tight shales of course it makes it easier to sell yourself if you have experience in that area - but at the end of the day, it all falls under the same roof. |
Also, how much does it differ between the conventional and unconventional oil and gas industry - in terms of job prospects, pay and expertise needed? | I have worked over-, normal-, and under-balanced formations all for the same company. They pay me the same regardless. |
How did you get your job? (did you make lots of contacts at uni etc) | I spend a lot of time on the computer (writing procedures, checking information, approving invoices), going to meetings or talking on the phone. Pretty much the typical office job. |
With oil being a non renewable resource, what will you do when reserves are low or run out? | I did not intern with any companies and so when it came time to look for a job, I applied to ~ 10 places. The company that hired me had just gone through some folks leaving and were needing people. I was lucky to get hired on. Most of the time it would not have happened that way. I figure we will not see that in my lifetime. If we do though, with all the things that come from petroleum products we use on a daily basis, there will be plenty of other people up shit creek too, not just those in oil and gas. |
Source: organic matter from a long time ago that was trapped in the rock during deposition and became what we know today as hydrocarbon after millions of years of increasing pressure and temperature. Pathway: Permeable rock capable of allowing fluid to migrate upwards. | The point is that the same impermeable layers that have kept the oil/gas from migrating upwards all these years, can also contain my fracture. We know what our layers are all the way from surface to our target zone, and are capable of using tools to log across these zones during drilling and obtain these rock properties. There are mathematical models (models are not the end all be all though, question anyone who tells you they are) which can be used to predict fracture geometry to an extent. |
What is the first thing we do when we start a well? Punch a big hole through all of these impermeable zones with our drilling rig. | In the image above they are sigma 1, 2 & 3. When we frac a well we are overcoming the minimum local stress regime and parting the rock. Imagine we have a balloon sealed inside the block that we are pressuring up on. We would overcome sigma 2 first and the rock would split in half perpendicular to sigma 2, right? |
The photo above shows a representation of the drilling casing program. Basically, as we drill deeper and deeper into the Earth, every so often we stop and run steel pipe into our hole. We then cement up the backside (annulus) of the pipe before continuing deeper. | The above photo shows an outcrop of rock depicting layering. Now imagine we initiated a fracture where his left hand is and our minimum stress is perpendicular to your computer screen - that means the fracture is going to grow parallel to the layers. |
I am considering the field of petroleum engineering. I hope you can answer some of my questions. First off, what is your work schedule like? Do you move around a lot? I am planning on a degree in mechanical engineering, will that cover my needs? Is there a lot of competition as far as getting a job? Do you enjoy your job? Would you recommend it? | My particular job, no. I could travel but I have a family and choose to be with them. I work ~ 50 hours a week, almost all of it in the office, but am available to field calls 24 hours a day. |
| There are essentially two routes you could take out of school: working for a service provider or for an owneoperator. The operator of a well oversees each operation - leasing land, drilling, completion, production - and calls out service providers as needed for the various work (drilling rig company to do the drilling i.e.).The best analogy I can think of is that of a construction general/sub contractors. Working for an operator typically pays a bit more than working for a service company. |
| With the recent boom in the industry, more and more companies are hiring non-petroleum engineers. It used to be you would have a hard time finding work as a non-PETE but you very well could land on something now. Not sure how long that will last though. I actually started out as mechanical as well but changed my major along the way. Engineering classes are basically the same up until the last 3 semesters or so just so you know. |
| Internships are huge in this business. If you are able to hook up with an operator for a couple of summer internships, it shouldn't matter what your major is. Without having an internship you will most likely have a hard time landing a job with an operator out of school. |
| I am very fortunate to have the opportunity I do. I enjoy my job and it provides well for my family. I can sit inside on hot/cold days or go play with very large equipment if things get boring. Couldn't imagine not being in the oilfield. |
Was the college you graduated from highly competitive? Was it difficult to find employment after graduation? And finally, how important is the specific 'Petroleum engineering' degree? I ask because only one college in canada offers it while all others offer whats called Mineral engineering. Would it be difficult to find employment as a PE with an Mineral E degree? | I can't speak to what Canadian based companies look for. But there are quite a few big operators in your country that you could call up and ask those type of questions. Not sure if you guys have career fairs up that way, but down here they are a big here and would be another chance to touch base with the companies in your area. Seriously, just call up one of the guys up there and ask to speak to someone in HR that deals with college recruiting. That's your best bet for the right info. |
Have you seen the documentary Gasland, and if so what was your overall assessment of the movie? | I watched about 3 minutes of it and turned it off. |
Yeah, my impression of the trailer was that it was completely a waste of time, then I watched the first 10 minutes. Seemed too propagandic (is that even a word) to me. | Propagandaish maybe? :p Yea I'm in the same boat. It was way too one-sided to sit through. |
Why wouldn't a rich enough company explore cleaner renewable energy? Last time I checked nobody complained of wind gusts because of wind power :-/ | That's a fair point. I'd argue that the thing to remember is that hydrocarbons don't just provide energy. Petroleum products are in almost everything you touch. That computer sitting in front of you is proof of that. |
| Link to www.pbs.org |
| Unless we as a society plan to quit using things that are made up of derivatives (or come up with a substitute) there will always be a demand. Why not try to answer using the most efficient ways we know how? |
Fracking in Canada right now is highly controversial, there was actually a riot last week. The long term affects are still relatively unknown with many feeling it's not worth the economic boom. Does Texas and the surrounding states face as much controversy? | Short answer: no. Oil and gas is HUGE in Texas. It may be the friendliest state for companies to operate in. The industry has been here for over 100 years, and it is such a commonplace thing now that no one thinks twice of it. OK,KS,LA,MS are all similar when it comes to acceptance. |
| I'd say the closest state to us with well known opposition would be Colorado. They do have protests and I know of folks who have had to have security escort them to their vehicles when leaving work due to harassment by locals. |
| Hydraulic fracturing is not a new process - its been around for over 50 years. In recent years it has become more mainstream I suppose due to mass media and sensationalism (youtube videos of people lighting tap water on fire - something they could do 100 years ago by the way). Most of the time I have found those with the loudest voices against it, know nothing of the science behind it... |
Is that tap water thing real, btw? is it due to the water being actually full of liquid petro-chemicals or just NG letdown through the pipes? | The stuff in those videos is a result of shallow coal bed methane formations where gas percolate up into the ground water. There are rebuttal videos to those where people go in areas without any oil/gas activity and light river water on fire for instance. |
| So yes, people can light their tap water on fire. But they are able to do so not because of something humans did, but because gas is naturally migrating upwards into their water supply. It has been going on for thousands of years. |
If a community would like to complain about the two main types of contamination you mentioned, either a chemical runoff or fracking into an aquifier - what kind of evidence would they need? That is, what would be considered conclusive proof that the fracking operations in the area caused considerable environmental degradation? | That's tough to say without knowing the specifics. The general idea though, would be to get samples taken before/after the activity in the area. These could then be analyzed and a determination made based off the findings. |
| The most recent case I can think of around that topic was the Pavillion field in Wyoming. Here's a link with some info on it (granted its from the operator who was accused of causing the damage, but I like this because it lists why they refute the claims). |
| Link to www.encana.com |
| I should point out that the EPA discontinued their study, so there would seem to be some merit to the disputes listed by Encana. There are a ton of other sites with info on this case on the web if you want to do some more reading. |
| Truthfully though, you will not be able to find a case in which fracturing was the sole cause of an aquifer contamination. Barring a shitty cement job done during drilling, the physics behind a frac job don't support that type of anomaly. We can go more into the specifics of that if you would like. |
| If you are talking about chemical runoff, or behind pipe (bad cement job) communication - in which fluids migrate up the wellbore into shallower zones - I fully acknowledge the potential that exists for aquifer contamination. But it won't be the induced fracture downhole itself. |
Can you talk a little about why the physics don't support a sole cause of aquifer contamination? Interesting AMA, thanks for doing it. | Link to www.gaslandthemovie.com |
| Link to fracfocus.org |
| Granted the depth of the target formation could be closer to the water bearing zone, but take the first photo with a grain of salt. |
| First thing we need to talk about is what makes a reservoir. Let's stick with conventionals since they are a bit easier to talk about. So three things have to exist for us to have a reservoir by definition: a source, a pathway, and a trap. |
| Source: organic matter from a long time ago that was trapped in the rock during deposition and became what we know today as hydrocarbon after millions of years of increasing pressure and temperature. |
| Pathway: Permeable rock capable of allowing fluid to migrate upwards. |
| Trap: A 'cap' if you will that blocks the further migration of fluid towards surface. |
| So by its very nature a reservoir could not exist without something that keeps fluids from migrating further uphole. The trap has sealed the fluid for millions of years, why would it suddenly give way? The only way that gas could get closer to the surface (and aquifers) if it a pathway was created. |
| What is the first thing we do when we start a well? Punch a big hole through all of these impermeable zones with our drilling rig. |
| Link to www.propublica.org |
| The photo above shows a representation of the drilling casing program. Basically, as we drill deeper and deeper into the Earth, every so often we stop and run steel pipe into our hole. We then cement up the backside (annulus) of the pipe before continuing deeper. |
| For this particular example there are 3 steel barriers, one with cement behind it, protecting the ground water from contamination from below. Typically the minimum set depth for the surface casing is a state requirement and is dependent upon the water table. We are required to test the casing/cement job for integrity prior to continuing operations to ensure everything is holding. |
| So although we did create a pathway for the gas to travel to surface on, our casing/cementing program should keep the various zones separate. However, there are times when shotty cement jobs allow for crossflow communication and can in fact contaminate the ground water. This is due to drilling practices though, not hydraulic fracturing (we haven't gotten to that step yet). |
| Hydraulic fracturing is used for one purpose: to increase a well's productivity. Productivity is just a fancy word describing how much fluid we get for a given pressure drop i.e q (flow rate) / (P initial – P flowing). |
| Let’s put it into something we can picture. Out in my backyard my son has a kiddy pool filled with water covered with a lid I cannot take off; that is my reservoir. You approach me and say you will give me $1 / gallon of water I can give you that I take out of the pool. Hell of a deal I think and I head off to get your water. Now reservoirs, just like pools, come in all different shapes and sizes. The important thing to remember is compared to the diameter of the hole we drill (called ‘wellbore’ – varies by area but typically <12”), the reservoir is HUGE! Its like a coffee straw compared to my kiddie pool, or if I have a really big reservoir, a coffee straw compared to an in ground pool. Needless to say I’ve got a ton of water to get out of the pool, and a very small straw to do it with. |
| No big deal I think, I’ll just put in a bunch of straws and suck out of more than one. The catch is that a straw may cost me a week’s worth of sucking, or a month, or a year before it pays itself off. I can’t afford to put too many in the pool, or it will take too long to pay out. I decide that 5 straws is an economic compromise, so I put my straw in the pool (drill my hole) and start sucking (producing the well). |
| Now there are two important differences between my kiddy pool analogy and the real world that we need to understand. |
| The first is that not every well I drill in the real world will be equal. Some will produce more than others, and some not at all. Some straws I bought will never pay for themselves. |
| The second point to make is that unlike water flowing freely in a pool, the fluids in my reservoir cannot move so readily. In my analogy the straw would be the limiting factor in how much fluid I could move (frictional pressure loss associated with such a smaller inner diameter). In reality though my wellbore can move however much fluid I can throw at it, the problem is getting it there. That is, the connected pores in the rock do not line up perfectly to my straw. There are tight spots, backtracking, dead ends and all sorts of things that the fluid has to fight. Not only that, but once you get to the base of the straw there are some other effects. We can mimic these behaviors by placing a maze around each straw that restricts how much fluid I can suck. So now this maze, and no longer the straw, is the limiting factor in how much water I can move. |
| So here I am sitting in my backyard, with 5 straws spaced around the kiddie pool sucking away (don’t forget we added the maze). My wife walks out, sees me and asks how would I like to decrease the amount of effort (pressure drop) it is taking to suck a certain volume? She says she will create a path that completely bypasses the maze and can increase how easily the water flows to the straw by 4 times. Not only that, it is only a third the price of a new straw. |
| That is what hydraulic fracturing does to a well. It creates a pathway for the reservoir fluids to bypass the permeability of the rock – a one lane country road – and jump on an 8 lane highway headed straight for the straw. For the same amount of pressure drop, I can move much, much more water. |
Has their been an influx of petroleum engineers over the past few years? I know for a while a bunch of websites were saying it has the highest paying starting salary, so I figured lots of people would begin to major in it. | According to this there are only 23 accredited schools in the US that offer petroleum engineering (PETE) as a major. |
| Link to www.myplan.com |
| Compare that to mechanical engineering numbers (using the same site) of 296 schools, and you can see it is a not so common field. I think most people do not know about the option, and if they did, wouldn't be able to attend a school without moving. |
| I know of companies that were hiring non-petroleum engineers (chemical,mechanical even some industrial) to work PETE jobs just because there were not enough PETE graduates. I'd be curious to see if that trend continues. |
You covered chemical runoff. Care to tackle the "fracing into an aquifer below ground" part? It seems conspicuously absent. | Its in a comment below. Here's a copy/paste. It was late last night when I wrote it so its a little too long for this type of interaction, so feel free to ask for more clarification. |
| First a bit of background. If you want to skip straight to the frac part, scroll down. |
| Link to www.gaslandthemovie.com |
| Link to fracfocus.org |
| Granted the depth of the target formation could be closer to the water bearing zone, but take the first photo with a grain of salt. |
| First thing we need to talk about is what makes a reservoir. Let's stick with conventionals since they are a bit easier to talk about. So three things have to exist for us to have a reservoir by definition: a source, a pathway, and a trap. |
| Source: organic matter from a long time ago that was trapped in the rock during deposition and became what we know today as hydrocarbon after millions of years of increasing pressure and temperature. |
| Pathway: Permeable rock capable of allowing fluid to migrate upwards. Trap: A 'cap' if you will that blocks the further migration of fluid towards surface. |
| So by its very nature a reservoir could not exist without something that keeps fluids from migrating further uphole. The trap has sealed the fluid for millions of years, why would it suddenly give way? The only way that gas could get closer to the surface (and aquifers) if it a pathway was created. |
| What is the first thing we do when we start a well? Punch a big hole through all of these impermeable zones with our drilling rig. |
| Link to www.propublica.org |
| The photo above shows a representation of the drilling casing program. Basically, as we drill deeper and deeper into the Earth, every so often we stop and run steel pipe into our hole. We then cement up the backside (annulus) of the pipe before continuing deeper. |
| For this particular example there are 3 steel barriers, one with cement behind it, protecting the ground water from contamination from below. Typically the minimum set depth for the surface casing is a state requirement and is dependent upon the water table. We are required to test the casing/cement job for integrity prior to continuing operations to ensure everything is holding. |
| So although we did create a pathway for the gas to travel to surface on, our casing/cementing program should keep the various zones separate. However, there are times when shotty cement jobs allow for crossflow communication and can in fact contaminate the ground water. This is due to drilling practices though, not hydraulic fracturing (we haven't gotten to that step yet). |
| Why Frac? |
| Hydraulic fracturing is used for one purpose: to increase a well's productivity. Productivity is just a fancy word describing how much fluid we get for a given pressure drop i.e q (flow rate) / (P initial – P flowing). |
| Let’s put it into something we can picture. Out in my backyard my son has a kiddy pool filled with water covered with a lid I cannot take off; that is my reservoir. You approach me and say you will give me $1 / gallon of water I can give you that I take out of the pool. Hell of a deal I think and I head off to get your water. Now reservoirs, just like pools, come in all different shapes and sizes. The important thing to remember is compared to the diameter of the hole we drill (called ‘wellbore’ – varies by area but typically <12”), the reservoir is HUGE! Its like a coffee straw compared to my kiddie pool, or if I have a really big reservoir, a coffee straw compared to an in ground pool. Needless to say I’ve got a ton of water to get out of the pool, and a very small straw to do it with. |
| No big deal I think, I’ll just put in a bunch of straws and suck out of more than one. The catch is that a straw may cost me a week’s worth of sucking, or a month, or a year before it pays itself off. I can’t afford to put too many in the pool, or it will take too long to pay out. I decide that 5 straws is an economic compromise, so I put my straw in the pool (drill my hole) and start sucking (producing the well). |
| Now there are two important differences between my kiddy pool analogy and the real world that we need to understand. |
| The first is that not every well I drill in the real world will be equal. Some will produce more than others, and some not at all. Some straws I bought will never pay for themselves. |
| The second point to make is that unlike water flowing freely in a pool, the fluids in my reservoir cannot move so readily. In my analogy the straw would be the limiting factor in how much fluid I could move (frictional pressure loss associated with such a smaller inner diameter). In reality though my wellbore can move however much fluid I can throw at it, the problem is getting it there. That is, the connected pores in the rock do not line up perfectly to my straw. There are tight spots, backtracking, dead ends and all sorts of things that the fluid has to fight. Not only that, but once you get to the base of the straw there are some other effects. We can mimic these behaviors by placing a maze around each straw that restricts how much fluid I can suck. So now this maze, and no longer the straw, is the limiting factor in how much water I can move. |
| So here I am sitting in my backyard, with 5 straws spaced around the kiddie pool sucking away (don’t forget we added the maze). My wife walks out, sees me and asks how would I like to decrease the amount of effort (pressure drop) it is taking to suck a certain volume? She says she will create a path that completely bypasses the maze and can increase how easily the water flows to the straw by 4 times. Not only that, it is only a third the price of a new straw. |
| That is what hydraulic fracturing does to a well. It creates a pathway for the reservoir fluids to bypass the permeability of the rock – a one lane country road – and jump on an 8 lane highway headed straight for the straw. For the same amount of pressure drop, I can move much, much more water. |
| Frac Mechanics |
| Any combination of forces on an object can be represented by three principal directions. |
| Link to petrowiki.org |
| In the image above they are sigma 1, 2 & 3. When we frac a well we are overcoming the minimum local stress regime and parting the rock. Imagine we have a balloon sealed inside the block that we are pressuring up on. We would overcome sigma 2 first and the rock would split in half perpendicular to sigma 2, right? |
| So a fracture will always grow perpendicular to the least principal stress. |
| Link to www.southampton.ac.uk |
| The above photo shows an outcrop of rock depicting layering. Now imagine we initiated a fracture where his left hand is and our minimum stress is perpendicular to your computer screen - that means the fracture is going to grow parallel to the layers. |
| Although no formation of rock in nature is homogeneous, for our purposes we will assume it is. You will notice that on either side of our target layer, we are bounded by rock that looks significantly different. There are two mechanical properties of rock we are concerned about when it comes to fracturing: Young's Modulus and Poisson's Ratio. Basically how stiff our rock is, and how much flex it has. So we have a layer of rock, our target zone, with a certain YM and PR bounded by rock on either side with a different YM and PR. |
| So we pressure up on the rock next to his hand, overcome the minimum stress and the rock parts. Now how much of the rock parts is dependent upon how much pressure over the minimum we exerted. If it took 1,000 psi to open the rock and I applied 1,001 my fracture will grow less than if I applied 2,000 psi. This concept of pressure greater than my minimum pressure required to open my fracture is called 'net pressure'. This is the energy that will be used to grow my frac. Let's say I have one gallon of fluid and I pressure up on my rock with a minimum stress of 1,000 to 1,001 psi and my fracture initiates. As soon as I create enough space for that 1 psi to dissipate into, my fracture will quit growing. In order to keep growing my fracture I must continuously inject into it. |
| So back to our photo. I initiated my fracture, and will continuously inject into the formation to keep a net pressure of 100 psi. My fracture begins to grow both out and up. At some point, it will reach the upper and lower boundaries. Because of the varying mechanical properties, the pressure required to grow a frac in those layers may be 2,000 instead of 1,000 psi and the fracture will no longer grow vertically. Sure, the layers could be less than 1,000 psi but I will eventually hit something above and below that will be too hard to breakdown with my 1,000 psi. My frac will quit growing in height. |
| The point is that the same impermeable layers that have kept the oil/gas from migrating upwards all these years, can also contain my fracture. We know what our layers are all the way from surface to our target zone, and are capable of using tools to log across these zones during drilling and obtain these rock properties. There are mathematical models (models are not the end all be all though, question anyone who tells you they are) which can be used to predict fracture geometry to an extent. |
You sort of skirted the question. How confident are you that these things are working to prevent water supplies from being effected. You seem skeptical that the measures in place now are going to prevent the poising of water. Am I wrong in that assumption? | What is the first thing we do when we start a well? Punch a big hole through all of these impermeable zones with our drilling rig. For this particular example there are 3 steel barriers, one with cement behind it, protecting the ground water from contamination from below. Typically the minimum set depth for the surface casing is a state requirement and is dependent upon the water table. We are required to test the casing/cement job for integrity prior to continuing operations to ensure everything is holding. Let’s put it into something we can picture. Out in my backyard my son has a kiddy pool filled with water covered with a lid I cannot take off; that is my reservoir. You approach me and say you will give me $1 / gallon of water I can give you that I take out of the pool. Hell of a deal I think and I head off to get your water. Now reservoirs, just like pools, come in all different shapes and sizes. The important thing to remember is compared to the diameter of the hole we drill (called ‘wellbore’ – varies by area but typically <12”), the reservoir is HUGE! Its like a coffee straw compared to my kiddie pool, or if I have a really big reservoir, a coffee straw compared to an in ground pool. Needless to say I’ve got a ton of water to get out of the pool, and a very small straw to do it with. The second point to make is that unlike water flowing freely in a pool, the fluids in my reservoir cannot move so readily. In my analogy the straw would be the limiting factor in how much fluid I could move (frictional pressure loss associated with such a smaller inner diameter). In reality though my wellbore can move however much fluid I can throw at it, the problem is getting it there. That is, the connected pores in the rock do not line up perfectly to my straw. There are tight spots, backtracking, dead ends and all sorts of things that the fluid has to fight. Not only that, but once you get to the base of the straw there are some other effects. We can mimic these behaviors by placing a maze around each straw that restricts how much fluid I can suck. So now this maze, and no longer the straw, is the limiting factor in how much water I can move. So here I am sitting in my backyard, with 5 straws spaced around the kiddie pool sucking away (don’t forget we added the maze). My wife walks out, sees me and asks how would I like to decrease the amount of effort (pressure drop) it is taking to suck a certain volume? She says she will create a path that completely bypasses the maze and can increase how easily the water flows to the straw by 4 times. Not only that, it is only a third the price of a new straw. Although no formation of rock in nature is homogeneous, for our purposes we will assume it is. You will notice that on either side of our target layer, we are bounded by rock that looks significantly different. There are two mechanical properties of rock we are concerned about when it comes to fracturing: Young's Modulus and Poisson's Ratio. Basically how stiff our rock is, and how much flex it has. So we have a layer of rock, our target zone, with a certain YM and PR bounded by rock on either side with a different YM and PR. The point is that the same impermeable layers that have kept the oil/gas from migrating upwards all these years, can also contain my fracture. We know what our layers are all the way from surface to our target zone, and are capable of using tools to log across these zones during drilling and obtain these rock properties. There are mathematical models (models are not the end all be all though, question anyone who tells you they are) which can be used to predict fracture geometry to an extent. |