The new technology that allows us to drill in formerly impossible places and produce wells in formerly unprofitable formations make this a very exciting time to be in the “patch.” The ingenuity of the drillers and engineers, plus the world demand for hydrocarbons, has not only allowed, but forced the industry to stay on the cutting edge of innovation.
Back when (nearly) most wells were vertical, wireline tools simply were lowered
in the hole; gravity did the work. Now, with horizontal drilling, the laterals
might be 5,000 feet to 10,000 feet or even 20,000 feet long; we can’t just
lower the tools in the hole. They must be pumped down inside the drill pipe or
tubing. This has required the re-engineering of most of the tools. Some tools
work best in open hole, and have to be redesigned to work inside pipe. Some
tools use a tractor mechanism to crawl through the pipe or hole.
Since most horizontal wells are hydro-fracked to produce their maximum
potential, very carefully sized frac sleeves are installed in the production
liner to regulate the size and direction of the frac. These all must be
considered when running tools, as the normal I.D. of the liner is reduced the
deeper in the hole you go.
These and many other factors make fishing operations in directional holes
anything but boring. Freepoint and back-offs can be very challenging in the
laterals because torque and stretch can be almost completely absorbed by pipe
friction going around the curve. Very often, we are right up against the torque
or stretch values to get any movement downhole.
Another interesting difference between straight hole fishing and fishing in a
directional hole is jar placement. Normally, jars are run as close to the fish
as possible to maximize the impact and the likelihood of freeing the fish. I
can run my jars in the vertical sections of the hole, or out in the lateral,
but not in the curve. Jars, and the drill collars that go with them, are very
stiff assemblies, and don’t go around the curve easily. Plus, they are made
from very high-tensile-strength steel that does not like to be bent. It is
possible to stress the jars to failure, leaving a polished chrome mandrel
sticking up that is very difficult to fish. This usually leads to a
come-to-Jesus meeting with the company man. The solution is to run the jars
above the overshot, up in the vertical section of the hole. Since drill collars
really don’t like to work in the curve, we usually run heavy-weight drill pipe
between the jars and the primary catch tool. The downside: This pipe is
elastic, and absorbs some of the impact of the jars. This lessens the
likelihood of freeing the fish. So far, I have been lucky, and recovered fish
up to 800 feet from the jars. I generally run a bumper sub right above the
primary catch tool. Bumper subs are shorter and a little more flexible than
fishing jars, and can be manipulated to provide a pretty good lick in most
All of these factors are pushing the limits of present technology and
metallurgy. It looks like about 75 percent of my fishing jobs are in the curve.
A couple months ago, I was finishing up a job about suppertime, and looking
forward to a decent meal and a full night’s sleep when I got a call to go to
another well site for a simple pick-up job. Since I hadn’t learned the area
very well yet, I programmed my trusty GPS to guide me. Turns out the rig was 280
miles away in central Montana.
I got up there about 3 a.m., pretty much exhausted. I told the company man that
the well looked gassy, and he ought to circulate for at least three hours, and
be sure to make some coffee before he woke me up.
When I woke up and returned to some semblance of humanity, he told me the rest
of the story. It seems that he had a problem in the curve, in the 7-inch
casing. He thought it was collapsed, so he ran a string mill to fix it. It
turns out the casing was completely parted, and the string mill had gone into
open hole and milled up about 7 feet of casing. The lower portion of the casing
had fallen to the low side of the hole, due to a poor cement job. I went in the
hole with an overshot to catch the fish, which was a 6 1⁄4-inch bit, a bit sub,
and one joint of drill pipe that had twisted off after drilling only 10 feet
outside the casing shoe. I took me five hours of manipulation to get my tools
into the lower part of the casing. I engaged the fish right where it was supposed
to be, and started out of the hole. When we got to the bad spot in the casing,
it took a while to get through.
When we got out of the hole, we realized we had lost the fish in the parted
area of the casing. I made some changes to my tools, and went back in the hole.
Sure enough, the fish was right above the bad spot in the casing. I manipulated
the tools for a while until I could make progress down the hole. I intended to
push the fish to bottom, make a secure catch and pull it out. When I got to
bottom, the tools didn’t stop. We went down exactly the length of the fish and
bottomed out on open hole. When we came out of the hole, we realized that we
had pushed the fish outside the casing, which propped it up, making near
perfect alignment with the upper part. We ran a drilling assembly to bottom,
and started drilling ahead – job complete.
You never know what you are going to find on a fishing job, and often the
customer doesn’t give you the rest of the story until you are in the middle of
something. One thing I can tell you is that it’s never boring. ND
The World According to Wayne: Fishing in the Curve
November 1, 2011