Many people believe that when oil well production declines, a workover team arrives, pulls out the tubing, replaces the pump, and flushes the well, and production should resume. But reality is often different. Some wells recover production after workovers; some stop production again after a few days; and some wells get worse with each workover, eventually becoming unusable.
Why do the same workovers yield such different results? Is the problem really with the workover process?
In fact, in most cases, workover failures aren’t due to inadequate skills, but because the problem wasn’t identified beforehand. Many people treat workovers as a maintenance job, while truly excellent workover engineers never rush to run tools or pull out the tubing. They first consider: Why is this well’s production declining? If the cause isn’t found, even the most advanced workover techniques are merely treating the symptoms, not the root cause.
Today, we’ll start with the essence of workovers and discuss what problems they truly solve.
Well workover is not simply construction work; it’s a systematic solution to wellbore problems.
01 What exactly is well workover?
Many newcomers to oilfield work have a misconception. They believe that well workover is simply fixing broken parts. For example:
- If the pump breaks, replace the pump;
- If the tubing leaks, replace the tubing;
- If the sucker rod breaks, re-run it;
- If the tubing string is stuck, unstick it.
These tasks are certainly part of well workover, but they are not the true purpose. True well workover is essentially a comprehensive project to restore the well’s production capacity and improve its working condition.
In short: Well workover is not about fixing equipment, but about restoring the well’s production capacity.
Equipment is merely a tool for achieving production. What truly needs to be restored is the entire underground production system. You can think of an oil well as the human body.
- The oil reservoir is like the lungs.
- The wellbore is like the blood vessels.
- The pump is like the heart.
- The sucker rod is like the nervous system.
- Surface equipment is like the limbs of the human body.
If it’s just a heart malfunction, replacing the heart can solve the problem. But if the real problem is a blocked blood vessel, even ten hearts won’t allow the body to function properly. The same applies to oil wells. Often, what appears to be a pump malfunction might actually be:
- Reduced formation fluid supply;
- Severe wax buildup in the wellbore;
- Sand accumulation burying the pump;
- Tubing string wear and leakage;
- Casing deformation.
If the root cause isn’t found, simply replacing the pump and sucker rod will quickly lead to the well shutting down again after the workover. This is what many people mean when they say, “The more you work over, the worse it gets.”
What does a well workover truly need to address? A good well workover engineer first considers three questions:
First: Why did the well shut down?
Second: What is truly affecting production?
Third: How long can stable production be maintained after the workover?
Only by clearly answering these three questions does the workover plan have any meaning. Otherwise, even the most brilliant workover summary may just be an ineffective workover.
Here’s a very typical example. An oil well initially produced 8 tons of oil per day. Later, this dropped to 3 tons. The on-site assessment was: “The pump is broken.” A well workover was arranged. The workover included:
- Running in the tubing string;
- Replacing the pump;
- Running it into the well;
- Opening the well.
Result: For the first three days, daily production recovered to 7 tons. Less than a week later, it dropped back to 3 tons. A second well workover was conducted. The pump was replaced again. The result was the same.
Finally, technicians re-analyzed the situation. They discovered the real cause wasn’t the pump, but rather long-term sand production in the formation, with sand constantly burying the pump. The pump wasn’t broken; the working environment was.
If the sand problem had been addressed during the first well workover, the second and third workovers could have been completely avoided.
Therefore, well workover is not just about repairing equipment, but also about improving the well condition.
02 Well Workover is a Systematic Project
Modern oilfields increasingly emphasize the concept that well workover is not a solitary operation, but rather part of the entire oil production system. A successful well workover requires the collaborative participation of multiple professionals, including:
- Geological engineers analyze reservoir conditions;
- Reservoir engineers evaluate development effectiveness;
- Production engineers determine production parameters;
- Workover engineers design the construction plan;
- On-site construction personnel strictly adhere to the procedures.
A problem in any link can affect the final result. Therefore, excellent well workover engineers not only understand construction but also production. They know when to work over wells, when not to, and when working over wells could negatively impact well lifespan.
Well workover involves not only wellhead equipment but also the entire wellbore production system.
03 What is the Difference Between Well Workover and Drilling?
Many non-oilfield personnel, and even newly hired employees, often confuse drilling and well workover. In reality, although both use derricks, hoisting systems, and wellhead equipment, their work objectives are completely different.
The simplest way to understand it is: drilling is “building a well,” while well workover is “maintaining a well.”
The task of drilling is to drive a new well from the surface to the target formation underground, completing casing installation, cementing, and well completion, creating conditions for subsequent oil production.
Well workover is different. It deals with wells that are already in production. It is no longer responsible for finding oil-bearing formations, but rather for resolving problems that arise during production, restoring or increasing the well’s production capacity.
In short: drilling determines whether a well can be built, while well workover determines whether a well can maintain stable production in the long term. Drilling focuses on “building the well.” During drilling operations, the primary concerns are:
- Whether the formation is drilled smoothly;
- Whether the wellbore trajectory conforms to the design;
- Whether the casing can be run smoothly;
- Whether the cementing quality meets standards;
- Whether the completion meets production requirements.
Once drilling is completed, the well is ready for production. However, this does not mean that it can maintain stable production indefinitely. Well workover focuses on whether a well can continue producing. After a few years of production, an oil well may experience various problems:
- Fatigue fracture of the sucker rod;
- Corrosion and perforation of the tubing string;
- Deep well pump failure;
- Wax and scale buildup in the wellbore;
- Sand buildup causing pump jamming;
- Casing damage;
- Water flooding leading to decreased production.
If these problems are not addressed promptly, they can lead to reduced production or even well shutdown. The task of well workover is to implement appropriate technological measures to restore the well to normal production.
Therefore, in the mid-to-late stages of oilfield development, well workover is often just as important as drilling. Many mature oilfields are producing fewer and fewer new wells, while the workload of well workover continues to increase. Improving the production stability of older wells is often more economical and efficient than drilling a new well.
04 Why do some oil wells get worse after workover?
Many people believe that more workovers will eventually solve the problem. In reality, more workovers do not necessarily mean better results.
Every tripping of the tubing string and every downhole operation has an impact on the wellbore and formation. Without accurate problem diagnosis, simply replacing equipment repeatedly not only increases operating costs but may also introduce new risks, such as:
- Increased wear due to repeated tubing friction;
- Reservoir contamination from multiple well washes;
- Increased well control risks due to frequent tripping of the tubing string;
- Extended well downtime due to repeated operations, impacting production.
Truly excellent well workover is not about speed or quantity, but about accurately identifying and resolving the problem in one go. This is the biggest difference between excellent well workover engineers and ordinary construction workers: they focus not only on the construction process but also on the entire lifecycle of the well.
05 Why do oil wells need workover?
Many people think that well workover is simply “fixing what’s broken.” In reality, in the oilfield, the real decision on whether to workover is not whether the equipment is broken, but whether the well can still produce normally. From the moment a well is put into production, it is constantly in an environment of high temperature, high pressure, corrosion, and abrasion. Thousands of meters underground, a problem with any component can lead to the shutdown of the entire well. Therefore, well workover is not an accidental occurrence, but an unavoidable part of oilfield development. According to statistics from most onshore oilfields in China, the main causes of well workover fall into the following categories:
- Tubing string damage
- Pump malfunction
- Sand jamming
- Wax buildup
- Scale buildup
- Water flooding
- Casing damage
These may seem like different problems, but they all ultimately lead to the same result: decreased oil well production, or even complete shutdown.
1) Tubing string damage – the most common problem in well workover
If we compare an oil well to the human body, then the tubing string is the “blood vessels” that transport crude oil. Crude oil flows from underground to the surface through the tubing. The sucker rod moves up and down daily, constantly working inside the tubing. A normally producing oil well may have its pump pumping unit pumped dozens of times a day, totaling millions of reciprocating movements per year. Over time, the tubing and sucker rod will constantly rub against each other. This is especially true for deviated wells, directional wells, and horizontal wells. The wear rate will be significantly accelerated. In addition, there is corrosion. Many oil wells contain:
- Carbon dioxide
- Hydrogen sulfide
- High-salinity formation water
The long-term effects of these media will cause the tubing walls to become thinner and thinner. This eventually leads to:
- Leakage
- Perforation
- Fracture
The most common phenomenon on-site is: Daily fluid production was originally 80 cubic meters, suddenly dropping to 40 cubic meters. The pump dynamometer becomes abnormal. The casing pressure changes. In many cases, at this point, it’s not the pump that’s broken, but rather the tubing that has leaked. A well workover requires:
- Retrieving the entire tubing string;
- Inspecting the location of the damage;
- Replacing the damaged tubing;
- Reassembling the tubing string if necessary.
For highly corrosive wells, more and more oilfields are now adopting:
- Internally coated tubing;
- Corrosion-resistant tubing;
- High-strength alloy tubing;
The goal is to extend the well workover cycle.
2) Pump Failure – The Most Easily Misdiagnosed Problem
Many field personnel have developed a habitual way of thinking. If the well isn’t producing oil, the first reaction is: replace the pump. In fact, not all production stoppages are due to pump problems. The pumping unit is a core downhole lifting device. After prolonged operation, the following issues may occur:
- Plunger wear;
- Pump barrel wear;
- Fixed valve failure;
- Traveling valve leakage;
- Sand abrasion;
- Seal failure.
True pump failure generally exhibits several characteristics: First, a significant change in the dynamometer card. Second, a gradual drop in fluid level. Third, a continuous decrease in pump efficiency. Fourth, a significant decrease in production.
If you rush to replace the pump because of a slight decrease in production, you are likely to misjudge the situation.
There was once a well where the pump was replaced three times in one year. Each time, production recovered for a few days, only to decline again.
Finally, analysis revealed that the real problem was not the pump, but a decrease in formation fluid supply capacity. Replacing the pump multiple times was pointless. This is why more and more oilfields require the following before well workover:
- Dynamic fluid level testing;
- Dynamometer analysis;
- Production analysis;
- Well temperature testing;
To the greatest extent possible: Diagnosis before construction.
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3) Sand Production and Pump Stuck – A Common Problem in Many Old Oilfields
For loose sandstone reservoirs, sand production is almost unavoidable. When formation sand particles continuously enter the wellbore, they first deposit at:
- Pump inlet;
- Pump barrel;
- Bottom of tubing.
Minor issues: Pump wear. Severe issues: The entire pump seizes up. On-site symptoms typically include: a sudden increase in pumping unit load, increased current, and abnormal suspension point load. In severe cases, even the sucker rod may break.
Many people, upon seeing a pump stuck, immediately replace it. However, if the sand production problem isn’t addressed, the new pump will quickly seize up again.
The real questions to consider are: Why is sand production continuing? Is the production pressure differential too high? Have sand control measures failed? Has the formation changed?
An excellent well workover plan involves more than just pulling the pump out of the well. More importantly, it involves integrating reservoir and production processes, employing comprehensive measures such as sand flushing, sand control, and adjustments to production regimes to reduce the recurrence of similar problems.
4) Wax Formation – The Most Common Cause of Production Reduction in Winter
Many high-wax crude oils flow normally when underground temperatures are high. However, as they rise along the wellbore, the temperature drops. Wax crystals gradually precipitate and adhere to:
- The inner wall of the tubing;
- The surface of the sucker rod;
- The pump inlet.
Over time, the effective diameter of the tubing becomes increasingly smaller. What used to be able to pass 100% of the fluid may eventually only be able to pass half. This manifests in the field as:
- Changes in pump pressure;
- Increased current;
- Gradually decreasing production;
- Difficulty starting the pump;
- Increased rod string load.
The fundamental reason for production reduction in many oil wells during winter is wax formation. For different well conditions, the following methods can be used:
- Hot washing;
- Wax scraping;
- Chemical wax removal;
- Adding pour point depressants;
- Optimizing production parameters.
Prevention is often more economical than treatment. Establishing a reasonable wax removal cycle can effectively reduce operating costs and downtime compared to waiting until severe blockage occurs before well repair.
5. Scale Formation – An Easily Overlooked “Chronic Disease”
If wax formation is like “cholesterol,” then scale formation is more like “vascular calcification.” With increased production time, ions such as calcium, magnesium, barium, and strontium in the formation water easily form scale after changes in temperature and pressure. These deposits adhere to:
- The inner wall of the tubing;
- The pump;
- Perforation channels;
- The near-wellbore zone.
Unlike sandblasting, which causes a sudden well shutdown, scale formation gradually decreases production. Many wells only experience a slight decrease per year, which may not seem significant. However, after several years, production may be reduced to only half of the designed capacity. Therefore, many oilfields regularly conduct:
- Water quality analysis;
- Scale formation trend prediction;
- Scale inhibitor injection;
- Chemical descaling.
Controlling problems in their early stages is more economical than large-scale well workovers later.
06 Three Questions You Must Answer Before Well Workover: Finding the Right Cause is More Important Than a Perfect Workover
There’s an old saying in the oilfield: “Well workover isn’t scary; what’s scary is not knowing why you’re working on it.”
Many well workover failures aren’t due to poor skill, but rather because the workover plan is based on flawed judgment. It’s common to see this on-site: A well stops producing. The workover team arrives. They run the tubing, replace the pump, flush the well, unclog the well… the workover is complete, and production resumes. A few days later, production drops again. So, a second workover. A third workover. Finally, everyone concludes: “This well can’t be worked on.”
In fact, this statement should often be revised to: “From the very first workover attempt, the real problem wasn’t identified.”
Truly excellent well workover engineers will answer three questions before developing a workover plan.
The first question: Why did this well stop producing?
This is the starting point for all well workover work. Many on-site personnel like to answer directly:
- The pump broke;
- The rod broke;
- The tubing leaked.
These are all just symptoms. The real questions to answer are: Why did the pump fail? Why did the rod break? Why did the tubing leak? For example, a sucker rod breaking could have many underlying causes, such as:
- Long-term rod string fatigue;
- Excessive well inclination causing uneven wear;
- Pump jamming leading to a sudden increase in load;
- Inappropriate stroke and frequency selection;
- Incorrect rod string assembly design.
Simply replacing the sucker rod doesn’t eliminate the root cause. Another rod breakage is only a matter of time. For example, a well had its tubing replaced twice in three consecutive months. The third inspection revealed that the tubing wasn’t of poor quality. The real cause was a large dogleg angle in the wellbore, leading to long-term friction between the tubing and casing, eventually causing it to wear through. After optimizing the tubing string and centralizer arrangement, similar problems didn’t occur for several years. Therefore, every failure has a root cause. Well repair should focus on fixing the cause, not just the symptoms.
The second question: What truly affects production?
Many people believe that if a well isn’t producing oil, there must be something wrong downhole. In reality… Factors affecting production can be divided into three levels. The first level: Formation problems. This is the most easily overlooked and also the most difficult to solve. Examples include:
- Decreased formation pressure;
- Reservoir contamination;
- Water channeling;
- Water flooding;
- Formation blockage;
- Fracture closure.
Even with a well repair, it’s difficult to completely restore production.
For example, a well’s daily crude oil production dropped from 12 tons to 3 tons. The work team suggested replacing the pump. After analyzing reservoir data, technicians discovered that two nearby water injection wells had been over-injecting for a long time, causing the well’s water cut to rise rapidly. The real cause was a development conflict, not the pump. Simply replacing the pump wouldn’t change the outcome. Finally, after adjusting the injection-production relationship, production gradually recovered.
The second level: Wellbore problems. This is the most important problem to solve during well repair. Examples include:
- Wax deposition;
- Scale buildup;
- Sand deposition;
- Tubing string leakage;
- Casing damage;
- Pump jamming.
These problems… Generally, with proper construction, production can be restored, making it the type of well repair with the highest success rate. The third layer: Surface problems. Often, there’s no problem downhole; the real fault occurs on the surface. For example:
- Pump unit imbalance;
- Motor failure;
- Gearbox damage;
- Belt slippage;
- Control cabinet malfunction;
- Pipeline blockage;
- Gathering and transportation system failure.
There was once a well that had no production for three consecutive days. The site staff assumed, “The pump is broken,” and prepared to repair the well. Later, maintenance personnel discovered that only the wellhead oil pipeline was frozen and blocked. After repairing it, normal production resumed, and the well repair was cancelled, saving tens of thousands of yuan in construction costs. This illustrates the importance of analysis.
The third question: Is this well worth repairing?
This is a question many people easily overlook. Not all shut-in wells are worth repairing. Some wells cost hundreds of thousands of yuan to repair, and after repair, they might only restore a few tons of oil before shutting down again after a few months. Such wells are not economically efficient. Modern oilfields increasingly emphasize that technical feasibility does not equate to economic rationality.
Before well workover, in addition to technical analysis, economic benefits must be calculated. This typically involves considering:
- How much remaining recoverable reserve is there?
- How much will the workover cost?
- How much increase in production is expected after the workover?
- How long will it take to recoup the cost?
- How many years of stable production can be maintained after the workover?
If a well workover costs 800,000 yuan, but the expected increase in oil production is only 400,000 yuan, then even if the technology is successful, it is an economic failure. Conversely, some wells, although more difficult to work on, may increase daily production by 5 tons, allowing for cost recovery within six months. Such wells are worth the investment. Excellent workover engineers not only develop workover plans but also consider the overall development benefits of the oilfield.
07 A Real Case: Why Did Three Consecutive Well Workovers Fail?
A pumping well in an old oilfield experienced a drop in daily production from 9 tons to 2 tons. Initial analysis: Suspected pump wear. Workover content: Replaced pump. Production resumed for 5 days. Production decreased again. Second analysis: Suspected tubing leakage. Workover details: Replaced part of the tubing. Production resumed for 10 days. Well shut down again.
Before the third well workover, the technical team reviewed well history data, dynamometer cards, fluid level tests, and production dynamics. They ultimately discovered that the well had been producing sand for a long time, with sand constantly burying the pump. The previous two workovers had not thoroughly flushed the sand, nor had sand control measures been optimized.
The third workover adjusted the plan:
- Thoroughly flushed the entire well with sand;
- Replaced the pump;
- Improved sand control measures;
- Adjusted production parameters to reduce production differential pressure.
After the workover, the well maintained stable production for over a year without recurring similar problems.
This case illustrates that: a correct well workover plan is more important than the speed of workover; identifying the problem is more important than replacing equipment. Chapter Summary: Many people understand well workover as “equipment repair.” In reality, well workover is first and foremost a diagnostic process. A successful well workover typically follows this logic: anomaly detection → cause analysis → problem location determination → economic feasibility assessment → workover plan development → workover implementation → follow-up results. Truly mature well workover management doesn’t pursue “fastest repair,” but rather accurate repair on the first attempt and long-term effectiveness.
08 Common Well Workover Techniques: Every step has a purpose; never perform work for the sake of work.
Many newcomers to the well workover industry have a misconception. They believe that well workover is simply performing every procedure: running the tubing string, changing the pump, cleaning the well, washing the well, scraping wax… as if the more steps, the more thorough the workover.
In fact, well workover is not about piling up techniques, but about selecting the most appropriate measures for the problem. Each well workover technique has its own applicable conditions. Using it correctly can restore production. Using it incorrectly not only wastes costs but may also damage the wellbore, contaminate the reservoir, or even cause an accident.
Truly excellent well workover engineers never ask, “What processes can be performed on this well?” Their first question is, “What processes does this well truly require?”
I. Running and Retrieving the Tubing String—The First Step in Almost All Well Workovers
If well workover is a surgical procedure, then running and retrieving the tubing string is opening the “surgical passage.” This is because the vast majority of downhole tools:
- Pump
- Water distributor
- Packer
- Fishing tools
- Well gauges
Must be lowered into the well via tubing. Therefore, whenever downhole equipment replacement is involved, the original tubing string usually needs to be retrieved. However, many people easily overlook one issue: retrieving the tubing string itself is a risk.
For example, long-term tubing corrosion, worn couplings, thread damage, and significant well deviation can all lead to:
- Tubing string jamming;
- Tubing string breakage;
- Tool falling into the well;
- Increased well control risks.
Therefore, before each tubing string run-out, a thorough analysis is necessary:
- What is the well depth?
- What is the tubing string structure?
- Is there a risk of a stuck drill bit?
- Is it necessary to prepare retrieval tools?
The more thorough the preparation, the lower the on-site risk.
II. Replacing the Pump – Not All Production Reductions Require Pump Replacement
Many oilfields have a joke: “If the well isn’t producing oil, replace the pump first.” It sounds like experience. In reality, this thinking has harmed many wells. Pumps are indeed wear parts. After long-term operation, the following may occur:
- Plunger wear;
- Valve ball seal failure;
- Pump barrel scoring;
- Sand abrasion.
But before actually replacing the pump, it’s crucial to first confirm: Is the problem with the pump? On-site assessment typically involves:
- Dynamometer diagram;
- Dynamic fluid level;
- Current changes;
- Pump efficiency analysis;
- Historical production data.
A comprehensive judgment is made. If the problem is simply insufficient formation fluid supply or wellbore blockage, even replacing the pump won’t restore production. Therefore, replacing the pump is not the goal; restoring lift efficiency is.
III. Retrieval Tools – The Most Experienced Testing Technique in Well Workover
What’s the biggest fear at a well workover site? It’s not the complexity of the work itself, but rather objects falling into the well. For example:
- A sucker rod broken in the well;
- Tubing disengaged;
- Tools falling into the well;
- A broken wireline.
These all require retrieval. Retrieval may seem like simply removing objects, but in reality, it demands a great deal of experience. First, you must determine: What fell in? Where did it fall? What is its position? Is it buried in sand? Only with accurate judgment can the appropriate tools be selected. Common retrieval tools include:
- Retrieval spear;
- Retrieval tube;
- Retrieval basket;
- Magnetic retrieval device;
- Milling shoe;
- Grinding shoe.
Different tools are for different types of objects. If the wrong tool is chosen, not only will the object not be retrieved, but it may also cause secondary falls. This is why many complex retrieval operations require on-site supervision by experienced well workover engineers.
IV. Unblocking – The Most Patient-Required Process in Well Workover
“Stuck.” These are the two words almost every well workover team dreads hearing. Stuck drill bit. Stuck tubing. Stuck pump. Each one affects the workover process. There are many causes of sticking, such as:
- Sand accumulation;
- Casing deformation;
- Wellbore narrowing;
- Wax buildup;
- Formation collapse;
- String bending.
Many young workers’ first reaction is to increase the pull-up force. In reality, this is the most dangerous because it exceeds the safe load of the tubing string, easily causing rod breakage or tubing breakage.
Truly standardized unblocking generally follows these steps: analyze the cause, determine the sticking point, calculate the safe load, and develop an unblocking plan. If necessary, use a shock absorber, circulate sand, or perform chemical treatment. Gradually release the sticking, rather than blindly forcing it.
V. Well Cleaning – A Crucial Measure to Ensure Wellbore Flow
Many people understand well cleaning as: “Put the next tool to the bottom.” It’s not that simple.
The main purposes of well cleaning are threefold: First, to check the wellbore for blockage. Second, to verify the wellbore dimensions. Third, to remove minor obstructions.
For example, if it is discovered before construction that the well gauge cannot reach the bottom smoothly, it indicates that the wellbore may have:
- Reduced diameter;
- Scale;
- Sediment;
- Foreign objects.
Forcibly lowering the tubing string can easily lead to jamming. Therefore, many construction plans include well cleaning first. Although it is not as noticeable as pump replacement, it is a crucial step to ensure the smooth progress of subsequent construction.
VI. Well Washing – The Most Easily Underestimated Process
Many people think that well washing is simply flushing the well clean. In reality, the purpose of well washing is far more than that. Standard well washing mainly includes:
- Removing sediment from the bottom of the well;
- Removing mud;
- Removing mechanical impurities;
- Restoring the wellbore’s flow capacity;
- Creating conditions for the next stage of construction.
Different well conditions require different methods. For example, for general wells, reverse circulation well washing is often used. For wells with severe leakage, a positive circulation well washing method may be used.
During the well washing process, the most crucial factor is not time, but the returned fluid. Only when the outlet fluid is essentially free of mechanical impurities and the properties of the inlet and outlet fluids are basically consistent can it be said that the well washing has met the requirements. Many well workovers are ineffective not because of pump replacement failure, but because the well was not properly cleaned.
VII. Wax Scraping – Seemingly Simple, but Requires Timing in High-Wax-Containing Oil Wells.
As production time increases, wax layers continuously adhere to:
- Tubing;
- Sucker rod;
- Pump inlet.
The wellbore becomes increasingly narrow, eventually affecting fluid production. At this point, wax scraping is necessary. However, wax scraping is not a case of “the more, the better.” Too little scraping results in a thicker wax layer. Too frequent scraping increases construction costs and may even increase tubing wear. Mature oilfields generally develop a reasonable wax scraping system based on:
- Crude oil wax content;
- Temperature changes;
- Historical wax deposition cycles;
- Production data.
The key is to maintain maintenance on a schedule, not wait until it gets clogged before addressing it.
09 Five Common Mistakes Made on-Site
Similar problems recur every year at well workover sites.
1. First, failing to analyze well history before developing a workover plan.
Ignoring historical data often leads to repeated mistakes.
2. Second, over-reliance on experience and neglect of data.
Dynamometer charts, fluid level tests, and pressure data are often more reliable than subjective judgment.
3. Third, addressing only the symptoms, not the root cause.
Replacing the pump without controlling sand production; washing the well without addressing the source of scaling.
4. Fourth, failing to track results after workover.
Many well workovers lack data tracking such as production, dynamometer charts, and pump efficiency, making it impossible to evaluate workover quality or accumulate experience for future workovers.
5. Fifth, neglecting standardized construction practices.
Even a small violation can lead to tools falling into the well, well control risks, or equipment damage, resulting in losses far exceeding the workover cost. In summary, there is no “best” well workover technique, only the “most suitable.”
Truly excellent well workover is not about performing every technique imaginable, but about precisely selecting measures based on the well condition to solve the real problem with minimal cost.
From running the tubing, replacing the pump, fishing, and freeing stuck tubing, to well cleaning, well washing, and wax scraping, each technique is merely a means to an end, not the end itself.
10. How Do Excellent Well Workover Engineers Analyze Well Conditions?
The future of well workover will no longer be about physical strength, but about judgment.
Many believe that the greatest ability of a well workover engineer is familiarity with downhole tools, understanding of construction techniques, and the ability to handle complex accidents. These are certainly important. However, those who have worked in the oilfield for many years know that the biggest difference between an ordinary well workover engineer and an excellent one often lies not on-site, but before arriving at the site.
Ordinary engineers see the fault. Excellent engineers see the cause behind the fault. Ordinary engineers study “how to repair.” Excellent engineers study “why to repair.”
What truly determines the success rate of a well workover is not the size of the workover team, nor the sophistication of the equipment, but whether the construction plan is based on a correct well condition analysis.
1) Truly excellent well workover engineers all have a fixed set of analytical approaches.
Many newcomers like to ask as soon as they arrive on-site, “When will construction begin?” Experienced engineers, however, often begin by saying, “Show me the data for this well from the past year.” Because wells don’t suddenly develop problems. All faults have a gradual development process. Therefore, analyzing well conditions begins with learning how to interpret data.
Generally, at least the following should be reviewed:
(1) Production Dynamics:
- Daily Oil Production
- Daily Fluid Production
- Water Cut
- Casing Pressure
- Oil Pressure
- Dynamic Fluid Level
- Pump Efficiency
These data, taken together, form the well’s “health check report” over a period of time. For example: a continuous decline in daily fluid production and a continuous increase in water cut indicate that the issue may not be equipment failure, but rather a change in the reservoir’s fluid supply capacity.
(2) Well History Data:
What has been done on this well? When was the pump replaced? When was the well flushed? When was sand flushing performed? When did rod breakage occur? This data is crucial. Many well problems are already documented in historical records.
For example: three rod breakages in one year indicate that the problem may not be rod quality, but rather: well deviation, uneven wear, or an unreasonable flushing design.
(3) Well Workover Records
Excellent engineers will focus on: How was the previous well workover performed? What tools were used? What problems were encountered during the workover process? How long did it take to recover after the repair? If the well was shut down again three months after the last well repair, it indicates that the first well repair likely did not solve the fundamental problem.
2) Analyze the well condition on-site; don’t just focus on the wellhead.
Many newcomers like to stand at the wellhead and observe: Is there a problem with the pumping unit? Is there any oil leakage at the wellhead? Is the pressure high? These are all important. However, a true well condition analysis should establish a complete troubleshooting logic. Experienced well repair engineers usually judge according to the following order:
Step 1: First determine if it is a surface problem, such as:
- Motor damage
- Gearbox failure
- Belt slippage
- Electrical control system malfunction
- Pipeline blockage
If it is a surface problem, well repair is often not necessary. Maintenance can restore production.
Step 2: Determine if it is a wellbore problem, including:
- Pump failure
- Broken rod
- Pipe leakage
- Wax buildup
- Sand accumulation
- Pump jamming
- Casing damage
These are the problems that truly require well repair.
Step 3: Determine if it’s a reservoir problem, such as:
- Decreased formation pressure
- Reservoir contamination
- Rapid increase in water cut
- Water channeling
- Imbalance in injection-production relationship
Many wells cannot be repaired successfully. It’s not that the workover was a failure, but rather that the problem couldn’t be solved by well repair itself. In this case, solutions should be jointly developed by reservoir, production, and geology professionals.
3) Well repair is not a one-person job, but a team effort.
In the past, in many oilfields, well repair plans were primarily determined by the well repair engineer. Now, there’s an increasing emphasis on multi-disciplinary joint analysis. For example: the well repair engineer is responsible for the construction plan; the production engineer is responsible for the production system; the reservoir engineer analyzes the development effect; the geology engineer analyzes reservoir changes; and the equipment engineer ensures the surface system. Only by combining this information can we truly achieve: one analysis, one operation, one success.
4) The future direction of well repair: from experience-driven to data-driven
In the past, well repair relied heavily on the experience of veteran engineers. A senior engineer could judge the general problem by glancing at the dynamometer card. This experience was extremely valuable. However, as oilfield development enters its mid-to-late stages, well conditions become increasingly complex. Experience alone is no longer sufficient. The future direction of well workover will rely more heavily on data and intelligent analysis.
For example, digital well history management creates a complete database for every workover, test, and malfunction. Subsequent operations can quickly access this database, reducing redundant judgments. Online production monitoring collects data in real time:
- Power
- Current
- Pressure
- Temperature
- Fluid level
Enabling early detection of anomalies. This shifts the focus from “post-workover maintenance” to “pre-failure prevention.” Intelligent fault diagnosis utilizes data analysis models to comprehensively analyze dynamometer cards, pressure curves, and production data.
This assists engineers in quickly determining whether the problem lies with the pump, the tubing string, or the formation, making workover plans more precise. Refined management in the future oilfield will focus not only on workover success rates but also on:
- Whether workover cycles are extended;
- Whether single-well maintenance costs are reduced;
- Whether oil production increases are stable;
- Whether the input-output ratio is reasonable.
Well workover has evolved from a construction operation into a crucial component of oilfield lifecycle management.
11. The greatest value of well workover is not simply fixing a well, but extending its lifespan.
Many believe that the task is complete once workover is finished. In reality, true well workover should only begin after the initial construction phase. Post-workover monitoring is essential:
- Is production stable?
- Has pump efficiency improved?
- Is the dynamometer card normal?
- Has the current recovered?
- Has the water cut changed?
- Has the same fault recurred?
Only by continuously summarizing the causes and optimizing solutions can we truly extend the oil well production cycle and reduce overall development costs. This is why modern oilfields increasingly emphasize lifecycle management.
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12. In conclusion
Oil well workover is one of the most common tasks in oilfield development, and also one of the most easily underestimated. Some understand it as simply replacing pumps, running tubing, and retrieving tools. In fact, these are merely the “actions” of well workover. True oil well workover involves the entire process of analysis, judgment, decision-making, and execution. The success of a well repair isn’t determined by the number of tools used or the number of days the work took, but rather by:
- Whether the problem was accurately identified;
- Whether production capacity was restored;
- Whether the well’s lifespan was extended;
- Whether real economic benefits were generated.
A successful well repair not only restores a well’s production but also creates sustainable and stable value for the oilfield.
(Article Source: Oilfield Production Management – “Why Do Some Oil Wells Get Worse After Repairs? 90% of Well Repairs Don’t Really Solve the Problem”)
