The most important part of running a proactive well servicing regimen, (the backbone if you will) is conducting a proper, thorough well review prior to repair. Without properly familiarizing yourself with the well, you are unable to proactively repair it. You must be able to identify and address any recurring failures or weak spots. This will go a long ways in extending your run life.
Experience
During my tenure at NAL, the company took a very progressive approach and was consistently growing. Over the years, we took over numerous small companies, adding their properties to our cache. This ever-increasing well count taught me a lot in regards to taking a proactive approach.
One well in particular stands out in my mind. Shortly after taking over another field, this well (which shall remain unnamed to avoid pointing any fingers) went down with a seized pump. Upon review, I found that in the 3 years prior, a service rig had been brought in 10 times for repair. When I went through each of the prior repairs, I found a variety of failures (pump seizures, top end damage, etc.) With the various causes of failure, upon first inspection you might think this well just had a run of bad luck. However, upon further review, after digging through all of the workover reports, I managed to find some indication that fill had been tagged above the perfs. This created a few problems, if you didn't suck any sand directly into the pump then you had to tap it, as it was being starved of fluid. Although the failures ranged in cause, all of them were directly related to the perfs being covered and the pump landed high. During the first workover after we took over, we cleaned out the sump, lowered the pump, and didn't have to put a rig back on the well for a few years. The cleanout cost a little more during that one workover, but we potentially avoided 9 more workovers (if the failure rate were to continue.) Taking a proactive approach saved significant workover expenses over the well's life.
Workover Reports
The first thing I do when conducting a well review is to obtain and review the historical workover reports, day by day. This is a time consuming job and can be quite monotonous, but you need to understand the well as thoroughly as possible. The workover reports will tell you quite a bit of the story if you know what you're looking for. You need to identify not only the cause of failure each time, but also make note of all of the inspections conducted along the way.
Tubing
You want to know what condition the tubing was found in, and what depths the poor joints were found at. It is also important to note what grade of tubing was installed at what depth after the workover, in order to trend future failures. There are different strategies of approaching the new BHA after a workover, so you will find different qualities of tubing landed at different depths, from one well to the next. There are also varying opinions on what quality of tubing to re-use in a well, and what to send to junk. Sometimes I will use blue band tubing on low risk applications. Where-as, other times I will only re-use yellow band. Typically red & green band are always sent away as "junk."
I have used all different types of strategies, depending on the specific situation at hand.
Rods
As with the tubing, you also need to trend what condition each rod was in every time it's pulled out of the well. It can be helpful to draw diagrams side by side (from one workover to the next), comparing any wear spots, failures, etc. You need to note if and when any rods were replaced, and it's also important to recognize rod grade, scraper type/length/spacing. There can also be outside parameters that may have impacted failure, such as wax, sand, corrosive fluids, tapping, side loading, etc.)
Note: Some people will put used rods from the boneyard back into service. But, I've always had the philosophy that unless that rod has been into a qualified facility and had a quality inspection, there's too much risk in putting it in the ground. One rod failure will offset the cost of buying quite a few new rods.
Bottomhole Pump
A bottomhole pump can fail due to numerous reasons, and it can be very time consuming to trend every detail on each specific pump that has been used over the years. Some pump companies provide access to their software tracking each individual pump, and this can be extremely helpful. This way you can track material compositions, pump style, accessories, etc. A couple of obvious, but important details you want to review with your pump are diameter and length. More often than not, pump sizes remain the same over time. Alot of times, people will just order the same pump that's in the ground and "round-trip" it. This is a pet-peeve of mine. If you're spending all this money to get a well back online, don't you want to keep it running as long as possible? What I like to do is pull the pump, send it to town for inspection, make any necessary changes/upgrades and then run it back in the ground.
When we were busy enough and had multiple repairs in the cue, we would pull a pump and send it to town in the afternoon. It would get inspected and repaired or replaced, and sent back to site for the morning to run in the well. Then in the afternoon we would move to the next well and repeat the process.
Wellbore deviation
No matter what any driller or tool push might try to tell you, no wellbore has ever been drilled perfectly straight. Just because you're dealing with a "vertical well", that doesn't mean it's straight! If you think about the nature of drilling itself, that drill bit will follow the path of least resistance. I have found significant side wear damage on pumps,rods & tubing located in many "vertical wells" over the years. If you really want to know what your wellbore looks like, you can conduct deviation surveys via wireline. However, if you have a good history on the well, I find it more economical to just trend occurrences over time. Then you can either avoid those depths, or design to withstand the side loading.
Fluid Characteristics
Wellbore fluid characteristics can change over time. Just because you have not had any historical wax or scale issues in the past, doesn't mean you don't have those issues now or won't develop them in the future. This is another reason to wait for your inspection results before repairing the pump or building a new one, you might find something that you can design around. Scaling tendencies can be impacted by things like chemical introduction or waterflood breakthrough. You can combat scale by coating your pump components to deter it from setting up. Paraffins & asphaltenes will also change over time, so you might want to add rod scrapers or maybe some exotic downhole tools to avoid letting it drop out (with which I have had mixed results.)
Depending on the problem and well characteristics, you might also want to add a capillary string while you have the bottomhole equipment out of the ground. So gathering as much data as possible while you go is very valuable.
Deliverability
The amount of production provided by a well over time declines, of course. Therefore, it can be important to review fluid levels, GOR, and other production specific data points, to see how the well is performing at the current stage of its life. As mentioned above, you might be able to decrease the pump size, pumpjack stroke length, spm, etc. In some cases, you may also find the the GOR increases and the fluid volume decreases enough that a plunger lift could be installed. My personal preference is to switch over to plunger lift if you can. You burn less fuel, have significantly less maintenance costs, and often will even see a production uptick.
As you can see, the well review portion of the workover process is very time consuming, but is very important in taking a proactive approach. I have tried to summarize the components, but in actuality there is alot more to each step. It takes alot of time to complete a proper well review, but if done thoroughly you can save your company significant amounts of $$ in the long run.
If you'd like some assistance in reviewing your wells, whether they're still producing or you've encountered a failure, please reach out.
Cheers, Kalcy
(403) 391-3758
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