80. Can a magnetometer detect cracks in an oil well?
I came across a webpage of your information while researching about fluxgate magnetometers. I am hoping you may be able to provide some insight into this project.
I am involved in the oil and gas industry in Western Canada particularly in the fracture stimulation of oil and gas wells. I am looking for an alternate method to detect the induced fractures in the formation. As a background if you are not familiar with the technique, high pressure pumpers pump a slurry down the wellbore through holes in the steel casing over the zone of interest. They pump at high enough pressures to fracture the rock and fill the fractures (1 to 10mm wide) with the sand laden slurry. We currently add a radioactive tracer to this slurry and run in the wellbore after the fracture treatment is done to "see" where the fracture has gone. Typically these fractures can extent 1 to 500 meters away from the wellbore and grow vertically 1 to 100 meters in height. The current method of fracture detection only identifies the radioactive material up to 20 inches away from the wellbore. It would be advantageous to be able to map the direction, length and width of the fractures for their full length.
Based on this limited explanation do you see potential for some type of magnetometer to be useful in this application. Keep in mind there is steel casing in the wellbore. As well we could add magnetic particles to the slurry which could in effect make the fracture a magnetic conduit?
2 February 2006
I tried hard to figure out a way magnetometers could help you, but could not find any. Even with highly magnetized material, the field gets rapidly weaker with distance, and quickly gets undetectable..
If the slurry were highly conducting electrically, you could perhaps put a high voltage pulse on the pipe and see how "echoes" of the pulse is received at various locations on the ground--a bit like an EKG. However... high voltage electricity near oil and gas is not a good idea, and electrical properties of the slurry are probably not much different from those of the surrounding rock.
I believe that magnetometers were used for a long time in prospecting for gas an oil in Canada, and one of the pioneers was Lawrence Morley, who made a great name in science: he was the first to suggest that the magnetic stripes on ocean-floor rock came from gradual spreading of such rocks, which led to the current view of plate tectonics. I wrote about that in
and in more detail in
The journals refused to publish Morley's article, considering it too far out. A little while later Vine and Matthews arrived at the same conclusion, had it published, and for a long time they alone were given credit, before the world learned about Larry Morley.
I hope he is still with us today: we met once and I found him charming. More about him at
http://www.ryerson.ca/~oars/morely.htm (that's the spelling there!)
February 19th is his birthday--go ahead, raise a toast to him on that day!
81. Telling about magnetism
I am a Junior at Gabrielino High School in San Gabriel, California and am currently working on an expository speech about magnetism for our nationally renowned speech team. I will then memorize the speech, create presentation boards for it, and enter with it a state-wide competition. Last year, I placed 9th best expository speaker in the state of California.
An expository speech is basically an educational speech, and I've found it difficult to thoroughly explain the workings of magnets and magnetism in simple words, without sounding confusing. I am specifically looking for current breakthroughs, inventions, and/or other interesting facts to keep my audience engaged. That's what I hope you can help me with.
I currently have three points: History, Science (which explains how magnets work), and Society (which explains why magnets are important in our world: Maglevs, MRIs, etc.)
If you had 10 minutes to tell an audience everything there is to know about magnets, what would you say?
I cannot write your speech for you, but you may perhaps get ideas from the questions and answers on my web site, all actual correspondence (selected from many more as being the most interesting). Some thoughts:
--Most people do not know much about magnetism, and feel it is a mysterious force. It is actually well understood.
--Many people have heard that the Earth's magnetic field may reverse polarity, and are afraid of it happening soon, and causing great danger. Neither is true.
--Magnetism has a long history of usefulness to humanity, from the magnetic compass (would Columbus have reached America without it, or even dared sail west?) to computer disks and electric machinery. All generators of electric current use magnetism, as do transformers which make it possible to transport electric power across the country at high voltage and small loss, later (with other transformers) reducing the voltage for safe home use.
--We once believed that magnetism was just the property of special iron and minerals. It is actually intimately connected to electricity. The world as we know is held by 4 fundamental forces--gravity, electricity and magnetism (two sides of the same force, responsible among other things for light and radio phenomena), and two kinds of forces holding together atomic nuclei. Thus it is one of the foundations of the natural world.
--We once believed the Earth was special, being magnetic. Now we know most planets are magnets (Jupiter's is 20000 times stronger than Earth), sunspots are magnetic, pulsars and other distant objects, and magnetism is widespread in the universe. We still don't know all the processes responsible--but that's why physics is a frontier science.
Take it from there. Make number 1!
82. Does North-South orientation slow down iron corrosion?
I was told today something apparently known to a few contractors. Namely, metal placed north and south is a lot less likely to be eroded than when placed east and west. Any comments?
I know of no magnetic effects which affect corrosion, but if the effect is indeed observed, maybe there exists a different explanation.
Suppose you build a bridge, using I-beam girders. If the girders point north-south, the sun shines on one side in the morning and on the opposite side in the afternoon, keeping them dry.
On the other hand, a girder placed in the east-west direction will have its northern side in the shade all day. With rain, dew or snow, that side may stay wet much more frequently, and water promotes its corrosion.
83. Why two magnetic poles and not more?
I am a student at a Turkish university. For one of my lessons I need an information about earth's magnetism. My question is:
"Why does the earth has two magnetic poles, north and south? What is the reason for this? If possible there will be another poles?"
There may also exist more magnetic poles--it all depends on the sources of magnetic field. The only requirement is that the amount of magnetic flux (see below) leaving the Earth equals the one re-entering it. For the definition of magnetic flux, see
As for defining the magnetic pole, several versions exist--here let's take the simplest, the point where the magnetic force is perpendicular to the surface of Earth.
The Earth has two poles, because among all the magnetic sources inside the Earth, the strongest ones are those associated with a two-pole structure: see
and in more detail
However, some people speculate that during magnetic reversals, when the two-pole (dipole) source gets weak (and finally reverses direction), for a while the other sources dominate, and more poles can exist. You might say this situation exists on the Sun, which has a weak global dipole field, but in addition also has concentrated fields in sunspots, creating additional local "magnetic poles" by the above definition.