The overhaul construction of oil and water wells is complex, difficult and requires high technical requirements. And there are many reasons and types of underground accidents. Frequent downhole accidents are generally divided into three categories: technical accidents, downhole sticking accidents and falling objects accidents. When handling, we must find out the nature of the accident, find out the cause of the accident, take corresponding technical measures and properly handle it. All process accidents occur in the process of construction, which can be handled in advance according to the cause of the accident, and downhole sticking accidents and falling objects accidents are the main downhole accidents that affect the normal production of oil and water wells. It is also a large number of common underground accidents, and the following aspects should be done well when dealing with them.
1. Clearly grasp the current situation of underground accidents, understand what kind of accidents happened, the time and reason of the accidents, and whether they have been dealt with. If the accident of falling objects in the well is handled, the shape, size and nature of the falling objects should be made clear.
2. Accurate selection of tools and equipment for handling accidents.
3. Discuss and formulate the construction plan repeatedly and write the construction design book.
4. Prepare construction tools, equipment, materials, etc. , and organize and divide the work of construction personnel.
5. Carry out the construction in strict accordance with the requirements of the construction design, be careful in the construction, do it while groping, and do a good job in the admission of construction records and materials. 1. Type of falling object
According to the names and properties of falling objects, the types of falling objects in the well mainly include: pipe falling objects, rod falling objects, rope falling objects and small falling objects.
2. Salvage of pipeline falling objects
Before fishing, we must first master the basic data of oil and water wells, that is, we must understand the drilling and oil production data clearly, and find out the well structure, casing situation and whether there are early objects. Secondly, find out the cause of falling objects and whether there is deformation and sand surface burial after falling into the well. Calculate the maximum load that may be reached during fishing, and reinforce the derrick and guy rope pit. It is also necessary to take into account that after catching falling objects, if they get stuck underground, there should be preventive and solving measures.
The commonly used fishing tools are female cone, male cone, spear and slip fishing tube. The fishing steps are as follows:
(1) Visit the underground lead mold to find out the position and shape of the falling objects.
⑵ According to the falling objects and the size of the annular space between the falling objects and the casing, choose appropriate fishing tools or design and manufacture fishing tools by yourself.
(3) Compile the construction design and safety measures, salvage according to the construction design after being approved by the relevant departments according to the reporting procedure, and draw a sketch of downhole tools.
(4) When fishing, the operation should be stable.
5) Analyze the salvaged articles and write a summary.
3. Fishing rod-shaped falling objects
Most of these objects are sucker rods, as well as weighting rods and instruments. Some objects fall into casing, while others fall into tubing.
(1) Salvage the tubing.
It is relatively simple to salvage the broken sucker rod in the tubing. For example, when the sucker rod is pulled up and down, the sucker rod can be lowered to salvage the buckle or slip cylinder. If it cannot be salvaged, the tubing can be pulled out.
⑵ fishing in casing
Fishing in casing is more complicated, because the inner diameter of casing is large, the rod is slender, the rigidity is small, it is easy to bend and trip, and the shape of falling into the well is complicated. When fishing, you can use a sliding fishing tube with a hook, guide shoes or loose-leaf fishing tackle to fish. When the falling object bends in the casing, it can be fished with a fish hook. When the falling objects are compacted underground and cannot be salvaged, they are milled with a sleeve milling cylinder or a grinding shoe, and sundries are salvaged with a magnet fishing device.
4. Salvage of small falling objects
There are many kinds of small objects, such as steel balls, pliers teeth, cones and screws. Although this kind of falling object is small, it is extremely difficult to salvage. Tools for salvaging small objects mainly include magnet fishers, grab buckets, reverse circulation fishing baskets, etc. There are many reasons for sticking, so there are many kinds of sticking, such as sand sticking, wax sticking, falling object sticking, casing deformation sticking and cement solidification sticking.
1. Shaka processing
For wells with short sticking time or serious sticking, the downhole string can be lifted and lowered to loosen sand particles and alleviate sticking accidents.
For the treatment of wells with serious sand sticking, firstly, when lifting, slowly lift the load to a certain value, immediately lower it and unload it quickly; Secondly, after lifting and lowering activities for a period of time, tighten the pipe string and brake it, so that the pipe string is suspended for a period of time under tension, and the tension is gradually transferred to the lower pipe string. Both forms may be effective, but each activity should be stopped for 5 ~ 10 min to prevent the pipe string from breaking due to fatigue.
Other methods can be used to deal with sand card, such as reverse circulation card, well flushing card, strong lifting card, jack card, reverse sleeve milling card, etc.
3. Handling of falling objects stuck
Falling objects and sticking refers to the sticking of downhole tools caused by tongs, slips and small tools falling into the well.
When dealing with falling objects and sticking drill, do not lift it forcibly, so as to avoid sticking drill and complicate the accident. Generally, there are two treatment methods: if the stuck pipe string can rotate, it can be lifted gently and rotated slowly. Crushing the falling objects, so that the downhole string is stuck; If the above methods fail, you can straighten the top of the fish with a wall hook before fishing.
4. Remove the casing card
Shell deformation, damage, etc. Due to stimulation measures or other reasons, downhole tools are damaged by mistake, resulting in sticking. When handling, pull out the pipe string above the sticking point, and the sticking can not be released until the casing is repaired. In the middle and late stage of oilfield development, with the extension of production time and the increase of workover times, casing damage will occur one after another. After the casing is damaged, it must be repaired in time, otherwise it will lead to downhole accidents.
1. Inspection and measurement of casing damage
The main contents of casing inspection include: casing inner diameter change, casing quality, wall thickness, casing inner wall condition, etc. In addition, check and determine the position of casing coupling, etc.
2. Repair of deformed casing
Repairing deformed casing by plastic method.
(1) pear-shaped forming machine (also known as tube expander)
Lower the expander to the deformed well section, and gradually expand the deformed part by the expansion force of the drilling tool. The transverse distance that can be inflated at one time is only 1 ~ 2mm, and tools are frequently changed.
⑵ Casing forming machine
This tool is widely used and is a good shaper.
Casing shaper is a special tool, which is used to repair casing deformation in the well, such as flattening, depression, etc., and restore it to a near normal state.
The casing forming machine consists of an eccentric shaft, a cone head, a ball and a plug for fixing the cone head. The eccentric shaft is equipped with three rollers, namely an upper roller, a middle roller and a lower roller. Run the tool into the deformed part of the casing, rotate and apply appropriate pressure, forcing the cone head and roller to squeeze the deformed pipe wall of the casing with great lateral force to achieve normal diameter and roundness.
Casing scraper: Casing scraper is used to remove any deposits, irregularities or burrs in oil well casing, so as to clear the obstacles for future operations.
3. Casing subsidies
Subsidies can be taken to repair oil wells with perforated or broken casings. After repair, the inner diameter of the casing is reduced by about 10mm, and the one-time construction can be subsidized by 10 ~ 70m, the casing size is subsidized by 60 mm ~ 273 mm, and the subsidy depth is from 5m to 3900m. ..
(1) Subsidy management
Generally, the wall thickness of the subsidy pipe is 3mm, and there are large ripples in the longitudinal direction. The tubes are wrapped with 0. 12mm thick glass fiber cloth and bonded with epoxy resin, and each tube is 3m long. When in use, the length of the lower pipe can be welded on site according to the design requirements, and the front outer wall of the lower pipe is coated with epoxy resin.
(2) subsidy tools
It is mainly composed of centralizer, sliding sleeve, upper hammer, hydraulic anchor, piston barrel, fixed piston, piston, upper plug, piston rod, stretching pipe and tube expander. Casing drilling is mainly used to repair oil wells with serious faults underground. This kind of complex well is difficult to be effectively treated by general methods. In order to repair dead wells and improve the utilization rate of oil wells, casing sidetracking technology must be adopted.
In-casing drilling is a set of technology that the inclinometer is fixed at a certain depth in the oil-water well, a window for milling and deflecting the cone is opened on the side of the casing by using the inclined plane, then a new borehole is drilled from the window, and then the liner is run for cementing. Casing drilling technology is the application of directional drilling technology in oil and water well overhaul.
The main tools for drilling in casing are inclinometer, inclinometer, milling cone, drill bit, dropping joint, cementing rubber plug, etc.