Fishing in the Curve

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 us to stay on the cutting edge of innovation.

Back when most wells were vertical (or nearly so), wire line tools were simply lowered in the hole, gravity did the work. Now, with horizontal drilling, the laterals might be 5 to 10 or even 20 thousand 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 must all 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 don’t really like to work in the curve, we usually run heavy-wate drill pipe between the jars and the primary catch tool. The downside is: 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 conditions.

All of these factors are pushing the limits of present technology and metallurgy. It looks like about 75% of my fishing jobs are ‘in the curve’. A couple of months ago, I was finishing up a job about suppertime, and looking forward to a decent meal and a full nights sleep when I got a call to go to another well site for a simple pick-up job. Since I haven’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 their about 03:00, pretty much exhausted. I told the company man  the well looked gassy, and he ought to circulate for at least 3 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 ¼ 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 5 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. 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, it’s never boring…