I've looked at probably 500 video surveys with perforations and have nearly always seen a crown around the perf on the inside of the casing unless the zone underwent a frac with proppant pumped into the perfs, or a scraper run to smooth off the perfs,
@jlwhittaker We did a number of tests with casing at the surface. We placed casing inside a 55 gal drum, filled the casing with cement and perforated. We work with perforating at an angle to increase the number of bedding planes in contact with a perforation. We get a smooth perforation on the inside, without a crown or burrs of any type. Could it be that our perforations are at a given angle and not 90 degrees as in a typical perf job that gives us the smooth inner wall?
Those perforations look a little strange to me. Normally, the inside of the casing has no burrs from perforating, it tends to be smooth. This almost looks like the outside of perforated tubing to me.
As for the problem with the perf's being plugged off, they might not have tried to pump into the CBM and break down the perfs with a fluid. In most cases you have to break down those perf's before they can flow because, yes, of deep cement invasion from the primary cement job.
Why the other perforations are taking in water and gas is because they might have perf'd another zone that is pressure depleted and is of lower pressure than the CBM zone. That is the case most of the time when a zone "drinks" the gas/oil/water flowing up the wellbore. They might have been off in their wireline measurement some and opened the pressure depleted zone. Hope that helps on why the perforation is taking fluid and gas.
Thanks for your comment. I don't know what is in the blocked off perforations. It's possible its cement or also could be some fines from the coal that has bridged off in the perforation. Did you also notice that some perforations are producing gas and water while others are actually taking in water and gas? Very interesting.
That is interesting. If those perforations are associated with a different formation of lower pressure, that maybe the cause. Perhaps as a temporary 'thief' zone until the reservior pressures are lowered. Also, if some cement or coal fines are an issue, it might be worth dumping some acid over the perfs in an attempt to clean that up.
It would be powerful to run a video survey both both before and after an acid treatment on something like this. That's usually the hard part though. If the acid treatment does the job, few go back to take a look and see what changed downhole.
I've looked at probably 500 video surveys with perforations and have nearly always seen a crown around the perf on the inside of the casing unless the zone underwent a frac with proppant pumped into the perfs, or a scraper run to smooth off the perfs,
jlwhittaker 1 year ago
@jlwhittaker We did a number of tests with casing at the surface. We placed casing inside a 55 gal drum, filled the casing with cement and perforated. We work with perforating at an angle to increase the number of bedding planes in contact with a perforation. We get a smooth perforation on the inside, without a crown or burrs of any type. Could it be that our perforations are at a given angle and not 90 degrees as in a typical perf job that gives us the smooth inner wall?
hopeurforfreedom 1 year ago
Those perforations look a little strange to me. Normally, the inside of the casing has no burrs from perforating, it tends to be smooth. This almost looks like the outside of perforated tubing to me.
hopeurforfreedom 1 year ago
As for the problem with the perf's being plugged off, they might not have tried to pump into the CBM and break down the perfs with a fluid. In most cases you have to break down those perf's before they can flow because, yes, of deep cement invasion from the primary cement job.
PetroOmega 3 years ago
Why the other perforations are taking in water and gas is because they might have perf'd another zone that is pressure depleted and is of lower pressure than the CBM zone. That is the case most of the time when a zone "drinks" the gas/oil/water flowing up the wellbore. They might have been off in their wireline measurement some and opened the pressure depleted zone. Hope that helps on why the perforation is taking fluid and gas.
PetroOmega 3 years ago
This is a good camera job video. It appears to me as though a couple of the perforations are plugged off, perhaps due to cement evasion?
bs0d 4 years ago
Thanks for your comment. I don't know what is in the blocked off perforations. It's possible its cement or also could be some fines from the coal that has bridged off in the perforation. Did you also notice that some perforations are producing gas and water while others are actually taking in water and gas? Very interesting.
jlwhittaker 4 years ago
That is interesting. If those perforations are associated with a different formation of lower pressure, that maybe the cause. Perhaps as a temporary 'thief' zone until the reservior pressures are lowered. Also, if some cement or coal fines are an issue, it might be worth dumping some acid over the perfs in an attempt to clean that up.
bs0d 4 years ago
It would be powerful to run a video survey both both before and after an acid treatment on something like this. That's usually the hard part though. If the acid treatment does the job, few go back to take a look and see what changed downhole.
jlwhittaker 4 years ago
I believe you are correct in that- because usually you can tell if it worked or not based on the increase in production!
bs0d 4 years ago
Great Video. Note also fluid going back IN to some of the perfs late in the video.
johnshenry 4 years ago
Wow, you can see the salt water flowing out of the perforated holes in bore
Cr3ater 4 years ago