How to Read an Oil Well Production Chart
How To Easily Read A Well Log in 5 Minutes Using 'Vi Ko Ko Rules'
Past Dosh Nazlan , Petrophysicist.
Petrophysicists await at the well log patterns, recognize the trends, and and so turn those patterns into reservoir noesis.
Well logs can tell usa many stories about our reservoir. Each colorful line, each curve deflection and each curve blazon create the story of our reservoir.
Each reservoir story is different from one another.
But for sure, every story begins the same fashion. The story starts when the oil and gas, trapped inside the reservoir for million of years, go very excited to come out.
Our main job is to figure out the correct story by using well logs and other lab data to make the storyline better.
When nosotros run well logs, these hydrocarbon pools tell us everything – where they are, how they look like and how much they are, then we know how to get them.
But before we sympathize whatsoever story, we need to exist able to read these well logs.
My first mentor, Ko Ko Kyi, starting time taught me how to read and interpret well logs just past looking at the well log patterns. I want to share the same tips with you today.
It'southward merely a mutual sense, footstep-by-step arroyo in interpreting whatsoever well logs. Simply the results are magical.This is a technique I called'The Ko Ko Rules'.
To make information technology work, you need to have Gamma Ray Log, Resistivity Logs, Density and Neutron logs plotted on the same log plot respectively. And so, by looking at how the curve deflects relative to each other, you can tell the difference between oil, gas and h2o. Isn't that neat?
But first, you need to understand the reasons we run any well logs.
When y'all run a well log, you are interested in:
- locating where you lot reservoir is,
- describing your reservoir, and
- knowing if you have oil or gas in your reservoir.
The rules work and they make sense. The rules could wait likewise simple, only the results could be profound to your work. As long as you could read a graph and could tell the divergence between right and left, or blueish and cherry, then you tin can use these rules.
Some people call information technology monkey rules because they recall it'southward stupidly elementary for an engineer. But I don't intendance every bit long every bit it works for me and helps me do my task well, I am happy. Hopefully, yous'll find it useful too.
Simply, like any other rules, there's always exception. It'south like when you tell your daughter not to play with the ipad all the fourth dimension, but you lot spend too much time on your smartphone! Ouch! You can't blindly employ this rules all the time. It won't work in unconventional reservoirs or in a depression resistivity pay. Simply it's worth a try.
Hither we get:
What you need:
1. Plot triple combo logs in this sequence GR, Resistivity, Density-Neutron. Plot GR in the showtime rails and Resistivity in the second rails. Both curves should be plotted in increasing values from the left to the right. Plot Density-Neutron together on the same track. The values should be decreasing equally we go from the left to the right.
The First Curve
To wait for a reservoir, y'all demand a Gamma Ray log. Unremarkably, your reservoir will give lowGamma Rayreading. High Gamma Ray reading most probably indicates shale zones or non reservoir rocks.
The 2nd Curve
2d, once yous accept located your reservoir, so you desire to run across how skillful your reservoir is. This is by and large washed by means of calculating porosity. A good reservoir typically has proficient overall effective porosity. To be able to gauge whether y'all target reservoir is porous, you need logging tools that tin give you indication of porosity. The most typical porosity tools are density, neutron and sonic. Sometimes, people do go fancy. Then they get for Nuclear Magnetic Resonance (NMR) log and others.
The 3rd Curve
Third, since you know where and how practiced your reservoir is, at present yous must know whether your reservoir contains oil, gas or water. For this purpose, you needresistivity log. In well-nigh cases, if you accept a hydrocarbon begetting zone, your resistivity reading will exist higher than the resistivity reading in water bearing zone (assuming your water is saline). You have to exist conscientious though because if your formation water is fresh, your resistivity reading will be high too. In this case, you demand additional information like getting a formation sample or running a fluid typing log to make sure the types of fluid you take.
2. Plot Density-Neutron in lithology compatible scale: Sandstone or Limestone scales. We will be able to tell the reservoir types, the fluid types and estimate porosity right abroad.
3. Expect at the directions of GR, Resistivity, Density and Neutron curves deflections, either to the right or to the left.
4. Past combinating the patterns of each curve deflections, we can tell the departure between reservoir and non reservoir and/or the fluid types (oil vs gas vs h2o).
Follow the Ko Ko Rules:
1. Look at the directions of the curve deflections (whether to the right or to the left) in these following sequence: GR-Res-Density-Neutron.
1.Tight non-reservoir: Right-Right-Right-Right.
GR-Res-Density-Neutron all deflect to the right.
Why it works: If we are non in a reservoir zone, GR is college due to larger natural radioactivity from U, Thursday, K contents. Resistivity is college due to tightness. Density and Neutron read low porosity.
ii.Shale: Right-Right-Correct-Left.
GR, Res-Den deflect to the right. Only Neutron deflects to the left.
Why it works: GR is college due to larger natural radioactive decay from U, Thursday, Thousand contents. Resistivity is college due to tightness. Density read low porosity. Neutron falsely responds to the clay bound water resulting to higher credible porosity. Yous will come across a reversed Density-Neutron crossover.
Sometimes, the resistivity could deflect to the left equally well, depending on the backdrop of the shale itself. And so it could read, Right-Left-Correct-Left.
Annotation: You might run across a reversed Density-Neutron crossover in dolomite. Over a dolomitic zone, GR reads lower.
iii.Depression porosity (tight) reservoir: Left-Correct-Right-Right.
GR deflects to the left, GR-Res-Density-Neutron deflect to the correct.
Why it works: GR reads lower due to lower radioactivity of Th, K and U. Resistivity, Density-Neutron respond to the tightness of the reservoir (rock quality), rather than to the fluid types.
iv.Water bearing reservoir: Left-Left-Left-Left.
GR-Res-Density-Neutron all deflect to the left.
Why information technology works: GR reads lower due to lower radioactivity of Th, K and U. Resistivity responds to saline formation water. Density-Neutron reads higher porosity in reservoir.
five. Oil bearing reservoir: Left-Correct-Left-Left.
GR and Density-Neutron all deflect to the left. Only resistivity deflects to the right.
Why information technology works: GR reads lower due to lower radioactive decay of Th, Thou and U. Resistivity responds to non conducive hydrocarbon, giving college resistivity. Density-Neutron reads higher porosity in reservoir.
vi.Gas reservoir: Left-Right-Left-Correct.
GR deflects to the left; Resistivity, right; Density left; and Neutron, right.
Why information technology works: GR reads lower due to lower radioactive decay of Thursday, K and U. Resistivity responds to non conducive hydrocarbon, giving higher resistivity. Density gives lower bulk density due to lower gas density. Neutron reads low apparent depression porosity in gas zone due to lower neutron-hydrogen interactions in gas as compared to neutron-hydrogen interactions in water.
Then, at that place y'all become – the 6 Ko Ko Rules in well log interpretation. With these rules, you are able to read whatever logs in no fourth dimension, and effigy out your own reservoir stories!
As always, I don't guarantee it to work all the time. It may not work for freshwater environment, low resistivity pay zones, hot sands, and possibly in some unconventional reservoirs.
Thanks Ko Ko, you dominion!
Source: http://superpetrophysics.com
Source: https://production-technology.org/how-to-read-a-well-log/
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