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@anniegu3366 2 күн бұрын
Dear Prof. Espinoza, I have a question might be a silly one. For the Mohr circle (effective stress) part, wasn't the change in pore water pressure were not considered for layers above (overburden/vertical stress). So why the change in porewater pressure would also case the theta33 increase? Or the situation has been changed... Thank you so much...
@ashitkumarsahoo2140 3 күн бұрын
For the sigma yy- for x>c the equation tends to be negative infinity instead of positive infinity, also for x<c the equation is not defined as it will come in terms of iota in denominator , kindly clarify...
@dnicolasespinoza5258 2 күн бұрын
You are right, the plot shown around ~22:20 follows the mechanics convention (tension positive). That equation is not valid for x<c, so it should not be used. The solution has been coded here: colab.research.google.com/drive/1huIgVsyv1PvyNpXyFnZ9u-Ta1zp6Pbti
@ashitkumarsahoo2140 2 күн бұрын
@@dnicolasespinoza5258 thank you , your lectures are helping me a lot.
@davidalejandrosegurasaboga942 17 күн бұрын
Very valuable knowledge, thank you for sharing.
@Adam-K4 Ай бұрын
@21:00 the equation is valid only at the free surface, right? Because you crossed out the other two terms in the equation #3.
@TalesBy_moonlight-pm2jw Ай бұрын
Thanks a lot for these videos. They are truly awesome. Please I need some help with calculating the vertical stress Sv for well logs with density values greater than 2.3g/cc. I used the equation TVDSSDepth * 1 * (BulkDensity / 2.3) for the topmost row. Then Sv1 * 1 * [Avg(BulkDensity2 : BulkDensity1) / 2.3] * [Depth2-Depth1] for row 2 and below. However I get Sv values all greater than 1.0psi/ft. Most tomes the values are up to 1.2psi/ft. In addition. the trend decrease with increasing depth. This doesn’t seem correct and I need your help explaining this please. Please note that I have tried these equations with a different well density log with values less than 2.3g/cc and everything seems perfectly fine. Advance thanks for your help.
@dnicolasespinoza5258 Ай бұрын
There is nothing wrong with Sv gradientes > 1 psi/ft. This just means the rock is heavier than ~2.3 g/cc. Heavy low-porosity rocks can get to dSv/dz up to ~1.3.
@TalesBy_moonlight-pm2jw Ай бұрын
Thanks a lot for your prompt response 👍
@afsar9974 2 ай бұрын
Hi Prof! Thank you for your lectures . They are very helpful . Can you please refer me to the lecture where u have discussed wormhole generation and propagation due to sand production
@trahuynhmai7985 2 ай бұрын
Thank you for sharing your lecture, I have a question, may you answer this? I have the orientation of SHmax for a deviated well is 170N-S so when I calculate sigma_rr, now my theta is 170 degrees, isn't it?
@trahuynhmai7985 2 ай бұрын
In a deviated well, I have azimuth in the drilling report is 261.14 degrees at depth, so in your coordinate system, sigma= 261.14 degrees, isn't it??
@benvanzon3234 2 ай бұрын
Great video explaining this theory! I'm studying and preparing for my graduation thesis regarding the simulation of phonons, and that required some new material's science theory!
@dnicolasespinoza5258 2 ай бұрын
Typo alert [25:22]: should be du_2/dx_1 instead of du_2/dx_2
@saravanankrish9423 3 ай бұрын
Sir , why do we take average of the strain rate , why not take the sum of the strain . It baffles me so much
@dnicolasespinoza5258 2 ай бұрын
The explanation is at time 20:00 and 25:00. Be careful with the use of the word "rate" as it usually refers to variation in time.
@SH0493 3 ай бұрын
Hi Sir. I'm just confused. I just noticed that the linear equation you used in this video is different from the spring 2020 lecture which leads to different values of TVDSS even it was the same example.
@dnicolasespinoza5258 3 ай бұрын
The linear equation is a fast and simple approximation, which does work for all cases. I may have chosen a slightly different interval in the 2020 video. Anyway, the right solution is to interpolate point by point. It's not practical to do this in Excel, but can be easily done in Python/Matlab/etc. Here is the solution: colab.research.google.com/drive/1cs_zWFIOLWl5_p0X7V_m8nqDES8NTKkG
@SH0493 3 ай бұрын
@@dnicolasespinoza5258 Thank you sir. Your lectures help me a lot since I'm interested in learning geomechanics.
@AlanM-it2pi 3 ай бұрын
hello. how can you have porosities in the vicinity of 30% for shales?
@dnicolasespinoza5258 3 ай бұрын
"Shales" is a word generally used to refer to rocks and sediments with high clay content. The shales or mudrocks in this example are relatively young and are undergoing the first compaction process in their life. These are commonly found in all young (~<50 Ma) sediemntary basins.
@AlanM-it2pi 3 ай бұрын
how can you have porosities in your table in the vicinity of 30% to 40% in shales?
@mariogalindoq 3 ай бұрын
Why the model doesn't have cohesion (like Mohr-Coulomb or Drucker-Prager), being the cohesion a fundamental characteristic of a Clay?
@evankias 3 ай бұрын
Prof Espinoza, excellent lecture, thank you for sharing with all of us. Have you posted the lecture you did on the undrained solution?
@evankias 3 ай бұрын
Oops, I think I’ve found it actually, L21 on Diffusivity. Thanks for sharing!
@ahmedadnanaziz2005 3 ай бұрын
I have learned a lot from your lectures Dr.Espinoza , thanks
@mariogalindoq 3 ай бұрын
Could you explain please why the model doesn't consider the cohesion being that one of the most important characteristic of a clay is the cohesion? Thank you in advance.
@mariogalindoq 3 ай бұрын
Could you explain please why the model doesn't consider the cohesion being that one of the most important characteristic of a clay is the cohesion? Thank you in advance.
@KirillGoloviznin 3 ай бұрын
Like for not giving up on the ellipse :)
@carlosbocaz9321 3 ай бұрын
Hola, cuál es el libro guía que utilizas para tus apuntes?
@dnicolasespinoza5258 3 ай бұрын
Mine: dnicolasespinoza.github.io, additional suggested reading is listed in each chapter. Saludos!
@han.splash9648 4 ай бұрын
Hi, I have a structural geology exam coming up and I need some help. Is there any way I can contact you via email to ask for help?
@dnicolasespinoza5258 4 ай бұрын
Typo alert: around minute 5 the correct equation is "Delta q / Delta p' = 3". Thanks to a viewer for pointing out the mistake!
@farahnazabouk2461 5 ай бұрын
Good❤
@atxlax 5 ай бұрын
Are these Kirsch equations, as written, valid for thick wall cylinder testing?
@dnicolasespinoza5258 5 ай бұрын
No, here the external radius has been taken to be infinity. Thick wall cylinder equations need a finite value for the external radius.
@andrikurniawan823 5 ай бұрын
Thank you for Nicolas, Watching this lesson from Indonesia
@phunguyenba4818 5 ай бұрын
Thank you very much for your sharing. Your videos are useful with me
@atxlax 6 ай бұрын
In section 6.2.2, the handwritten equations for \sigma_{rr} and \sigma_{\theta\theta} each have two terms that use \Delta \sigma (=\sigma_Hmax - \sigma_hmin). However, in the typed equations for \sigma_{rr} and \sigma_{\theta\theta} in section 6.2.3, each have only one term that uses \Delta \sigma...where did the second \Delta \sigma term go?
@dnicolasespinoza5258 5 ай бұрын
It goes into the "isotropic" term (sigmaH+sigmah)/2*(1-a^2/r^2). Notice that the average stress (sigma_inf + sigma_inf + Delta_ sigma) /2 = sigma_inf + Delta_sigma/2.
@atxlax 5 ай бұрын
@@dnicolasespinoza5258 (+1) Can you clarify how (sigmaH+sigmah)/2 = sigma_inf + Delta_sigma/2 = sigma_inf + (sigmaH-sigmah)/2? It is probably simple, but I'm not seeing it. For the above relation to be true, i.e., (sigmaH+sigmah)/2 = sigma_inf + (sigmaH-sigmah)/2, this would mean sigma_inf = sigmah...that right?
@dnicolasespinoza5258 5 ай бұрын
@@atxlax Correct, to go from the special cases to the general case: sigma_H = sigma_inf + Delta_sigma; and sigma_h = sigma_inf . Then, (sigma_H+sigma_h)/2 = (sigma_inf + Delta_sigma + sigma_inf)/2 = sigma_inf + Delta_sigma/2
@atxlax 6 ай бұрын
Hand written equation for deviatoric shear stress, sigma_rtheta in section 6.2.2, has leading negative sign while the typed equation in section 6.2.3 does not have the negative sign. Which is correct?
@dnicolasespinoza5258 6 ай бұрын
good catch! the typed equation for shear stress $\sigma_{r \theta}$ should have a negative sign. I'm fixing the equation in my master code and should appear in the next release. Thanks!
@traveltoeurope007 6 ай бұрын
Thank you so much sir
@cchrism.7586 6 ай бұрын
Wow!
@danialhussain1336 6 ай бұрын
I am quite relieved after watching your video. Thank you!
@concretemathematics8146 7 ай бұрын
03:33 Why the 1 psi/ft? Why not use the (rho)*(g)*(h) formula? Not all region in the world can be applied with 1 psi/ft.
@dnicolasespinoza5258 7 ай бұрын
1 psi/ft is the stress gradient for mass density 2.3 g/cc = 2300 kg/m3; here it is used as a linear interpolation that captures the actual mass density from the log (e.g., 1.87 g/cc for depth 1750 ft), gravity is included in the calculations, see dnicolasespinoza.github.io/node9.html.
@zeco03 8 ай бұрын
Excellent presentation.
@zeco03 8 ай бұрын
Great job !
@zeco03 8 ай бұрын
Good job
@jhonathanhenaoossa2828 8 ай бұрын
Clear lecture professor Espinoza.... useful for my class on mechanical behavior!
@kaluemeka4194 9 ай бұрын
Wanted to know if there is any where you did anything related to the stress Polygon
@kaluemeka4194 9 ай бұрын
Also the video seems to be cracking? Was there any alternate video to this?
@kaluemeka4194 9 ай бұрын
When drilling a horizontal well in the direction of Shmin.. How do we know when to get a transverse fracture geometry or a longitudinal fracture geometry?
@kaluemeka4194 9 ай бұрын
Does this orientation of hydraulic fracture consider whether it be Longitudinal or Transverse?? Are there any conditions for a horizontal wellbore for having a transverse fracture orientation?
@kaluemeka4194 9 ай бұрын
No audio , can't hear you
@dnicolasespinoza5258 9 ай бұрын
The updated versions are L17, L18 and L19 here: kzbin.info/aero/PLv0npDbE5HXtZbV42aJXzrOsv-V8q_q8_
@clem5474 10 ай бұрын
Master class.. 👏👏
@cheneric6854 11 ай бұрын
Hello, Dr. Nicolas Espinoza! I've been watching a lot of your videos and really learn a lot! I'm a big fan! Can I ask a question in regarding to the stresses when we input into FEM. If porosity is not considered, should we input the effective stress or the total stress as the boundary condition. If we consider the pores of porous media, should we enter the effective stress or the total stress? Thanks!!!
@dnicolasespinoza5258 10 ай бұрын
Hi, the formulation presented in this example solves stresses in solids only. Therefore, it's valid to solve for total stresses in low-permeability porous media or effective stresses assuming pore pressure does not change. A rigorous solution requires implementing poroelasticity in the formulation and solving for pore pressure as an additional unknown.
@nadiasourez8560 11 ай бұрын
Thank you
@JosueA_455 11 ай бұрын
Context - Minute 15.20. How would you explain that from s1 in the M-C plot the characteristic angle can be found in the counterclockwise direction whereas it is clockwise in the 2D representation?
@dnicolasespinoza5258 11 ай бұрын
I don't think it in terms of clockwise or counterclockwise, I think it always as going from the point/plane of sigma_1 to point/plane of sigma_3 (or any other principal stresses). It never fails.
@GauravMishra-hf1pg Жыл бұрын
How is negative volumetric strain dilation and positive compression ? Pl explain
@dnicolasespinoza5258 11 ай бұрын
This follows the typical convention in geomechanics for which compression and contraction are positive and tension and dilation are negative. It is the opposite of conventional mechanics. The models can be applied with the classical mechanics convention though.
@GauravMishra-hf1pg Жыл бұрын
Fantastic
@muhammadm4582 Жыл бұрын
How do you measure tectonic strain?
@dnicolasespinoza5258 11 ай бұрын
It is not measured in practice, it's a calibration parameter, a variable that allows you calibrate the model to field measurements.
@GauravMishra-hf1pg Жыл бұрын
Xcellent , superb explanation , total visualization. Thanks a lot Prof.