SideTrack Coring Tool
Qsine often works with companies that have new ideas but lack the engineering and product development skills to convert them into real products. This project is an example of how Qsine acts as a Research and Development division of Foothills Diamond Coring for a very innovative tool.
Unfortunately I cannot give a lot of details on this project. Even though the SideTrack is patented, there are many trade secrets I am afraid I would unveil if I talked about it or showed photos. So I will try and keep the story about the events that happened, even if I cannot present the particular problems and corresponding solutions... and there have been many! The SideTrack is still not in commercial use but recent development and testing is starting to make it look like it may be close.
Rob Zeer is the motivational force behind the SideTrack. His company Foothills Diamond Coring click here is an oilfield services company that provides coring services. Coring (in a conventional sense) is the act of entering a well borehole once it has been drilled to a point of interest, then cutting a "doughnut hole" of up to 10 meters in length and finally retrieving it to the surface. The rock is analyzed and provides invaluable information about the oil reservoir.
One of the constant problems that Rob observed with conventional coring is the inexact science of choosing the core point or the depth at which a core sample should be taken. In the traditional process, the core point must be chosen before or during drilling. Then once the core point depth is reached, normal drilling is stopped, the drill bit is replaced with the coring apparatus and a core is retrieved.
While it sounds simple, making the decision as to where to stop drilling is a difficult decision to make solely because there is very little information to base a decision on. In areas where drilling has been successful and reservoir parameters are known, geologists can make educated guesses. These guesses are often wrong where there is high variability in the geology. In the case of exploratory wells, there is may be geophysical surveys or no data at all to work with. Quite often drilling will go right through the reservoir before reaching the core point. There is currently no way to retrieve a large core sample once this happens.
The ideal situation is to core once the hole is completely drilled and tested and the exact point of interest can be pinpointed from the test data. There currently is a tool that blasts small cups into the side of the well and retrieves small samples. The rock that comes back is about the same size as the end of your thumb and has very limited usefulness for analytical testing.
Rob's idea is to create a tool that can retrieve a large core sample from the side of a well bore. The basic idea is to:
- run the tool to the point of interest
- activate it causing a sideways push on the core head
- rotate the drill string and have the cutting head cut sideways into the wall of the well
- plunge the cutting head while rotating to cut the core
- stop at the end of the core barrel travel
- break the core
- deactivate the side shift of the core barrel
- retrieve the core and tool up the well bore
This seems like a simple enough task but keep in mind that, typical to drilling tools, all of the functionality has to fit into a diameter of 6-1/2 inches, work in a high pressure, temperature and vibration environment all while being hundreds to thousand of meters in the ground where it cannot be seen, heard, touched, smelled nor tasted! For this reason, if something goes wrong in the well, it is never known what has actually happened. When tools are extracted, we look at the tool for clues to deduce what may have happened.
I am not sure exactly when the SideTrack project actually started. It was 1994 when Qsine got involved and I know Rob had been working on it for several years before he got to us. When he arrived, Rob had actually built and was testing his prototype of a second concept. In fact, why we first got involved was simply to help him find a replacement for a hydraulic valve that was apparently leaking fluid and draining his hydraulic power while the tool was being run into the hole. As we worked on the problem, we discovered that the problem was not really in the valve but was a flaw in the concept of another part in the tool.
The flaw was that at high well bore pressures, the hydraulic fluid would get trapped in the tool. The concept worked okay at low well pressures, so it was decided to carry on with shallow testing. We had the tool apart at our shop and as we inspected things, we found some damage as well some parts that looked fragile for what they were doing. I did some quick numbers I warned Rob that I thought this might break or that might break. When they did break during the shallow well tests, Rob seemed impressed that I could forewarn him of the problems. I then realized that the tool was laid out strictly on geometry and not on engineering calculations. We still had to do a bit of this later down the road. It is hard, if not impossible, to be accurate with numbers on a tool as complicated as this. If the design got dicey and what we wanted did not fit, the choice was either quit or tries with the best that could fit. This is where I have to really hand it to Rob. If I told him it was out and out a no go, he would back away and we would find something else. When we really got into a jam and I told him it was dicey, his response was "Let's try it, watch it and we'll learn". While it was risky, it was reasonably educated risk and often a failure revealed some clue that took us to the next step.
One of the failures, broken ears on the coring head, actually resulted in the loss of the main tool body. After a long try at fishing for the tool, Rob decided there were enough things wrong with the concept to leave it in the watery grave and start fresh.
We helped layout, design and detail a new tool. This time the hydraulic power source was designed so that it was not overwhelmed by high well bore pressures. We could activate the old tool reasonably well but deactivation was done by pulling very hard on the tool. It was hard on the tool and unreliable.
The new tool received a custom designed electronic control. We used an 8 bit microcontroller and a pressure sensor. Sounds simple but it was designed to go into a watery, 15,000 psi, 150°C/300°F environment. The same mechanical activation as the old tool was brought forward. The electronics, via the pressure sensor, could tell when the tool was activated. Also via the sensor, we could detect much gentler pulls on the drill string to cause the deactivation. We also incorporated a timer so that if the control did not sense a deactivation sequence within a given, programmable time, it would automatically deactivate.
The mechanical design of this tool pushed high strength materials to their limits and we constantly had to find innovative ways to squeeze the mechanism into the allowable space. Complex features, off-center in round parts, and complex milling profiles were common and challenging to the machine shops. Qsine's tools are too small for this machine so we farmed out the machining.
This tool had another difficult problem to solve. The hydraulic system required that the control valve have near-zero internal leakage and it needed an electric solenoid that could be powered for up to 10 hours off of battery power. Nothing commercially available had these characteristics.
We experimented with our own valve design. We could get the near zero leakage performance that we wanted but the friction in the valve was too much for our low power solenoid. The solenoid was our own design also. In the end we settled for commercially available valves that were 10 week delivery and then designed the interface to our solenoid.
We re-used the core head and barrel from the original tool. We had mixed success with shallow testing. While we managed to cut core, as we encountered different rock formations we found some things worked well and others did not. One was a feedback system that circulated shiny pieces of Mylar back in the mud flow. When these pieces came back to surface we knew the side extension was complete and could proceed with coring. It was not reliable, sometimes the sparkly pieces came up with full extension other time they did not.
Knowing we could not rely on the feedback system, we took our chances and plunged the core bit even if we did not get our feedback signals. We ran a deep test in a southern Saskatchewan oil well where the feedback system worked and we successfully recovered the core shown to the right. The test shortly thereafter was in central Alberta. This test we did not get our feedback signal, tried to core and our luck ran out. We are quite certain that the formation contained chirt, which is the second hardest substance next to diamond. The core head and barrel were destroyed before the side extension was completed. When we put weight on the string, the core bit landed on the top of the tool and proceeded to destroy it. From the surface we could not tell what was happening. At first it seemed like we were cutting core but then the downward motion slowed dramatically and then stopped.
The tool dragged terribly all the way out of the hole. When it got to surface, we could see that it was a miracle that we even recover the tool. We dragged it over 1500 meters up the hole with the tool hanging only on a 1/8 inch shoulder that the core bit had cut into it.
On the way home from this test Rob and I talked about all the things that had happened. I felt tapped. I remember telling him that I felt I had taken him as far as I could and maybe we needed to find someone else. He felt tapped too. We were not giving up just because of the failed test but by other limitations that came out of our conversation. The core barrel traveled on an arc as it passed through the core head as opposed to a straight line which would have been ideal. We knew this was possible trouble in the design stage and through testing we found that in soft formations it worked okay but in hard formations it fractured the core badly. The other big problem was that the core barrel traveled past the side of the tool and made failures like the one we just had a constant worry.
That test was in 1997 and it was at that point that the project was put on the shelf. Rob and I kept in touch, though not all that often. It was in 2005 that he came back and said he had a new idea.
The core barrel would travel a straight line and did not go past the body. The trouble I had with the idea is that it needed double universal joints and was really an unpredictable mechanism. As skeptical as I was, I helped him layout a concept in which we came up with a very clever mechanism to make the operation possible. Theoretically it had potential to work but there was no way to say definitely if it would or not. I saw it as an overly risky concept to pursue. But Rob being Rob, when I could not show positively that it would fail, he wanted to try. Foothills has an animated movie on their web site that illustrates how the tool works. You can view it by clicking here.
Things had changed at Qsine at that point and we were barely keeping up growth in the fabrication side of the business. We brought in some extra help to tackle Foothill's requirements. Barry Toppings of Toppings Engineering had down hole experience and was brought in handle the bulk of the mechanical work. Thomas Rozek of Polaron was brought in to develop a new concept we had for an electronic activation system for the tool. Both of these companies are really competition to Qsine in their respective fields but it is just an example of how competitors can be complementary as long as they behave like gentlemen.
This time the new system re-used the old tool and had a new coring head/barrel developed. Again testing has been a bit hit and miss but a very nice core (pictured still in the barrel) was succesfully pulled from the first test in an oil well test. You can read about the test on Foothill's web site by clicking here. Continued testing has revealed other problems that have foiled subsequent attempts. These new lessons are making contibutions to the knowledge base that will drive the next design. If you have read our philosophy page, this project is an extreme case where the "100% or you fail" rule holds unconditionally.
Look for updates to this page as results from testing come in.