Open hole fishing is one of the most time consumed operation because it involves a lot of unknown down hole conditions. In order to have successful fishing operation, it is imperative to fully understand about the open hole fishing tool. The video training below provided by Weatherfor is considered as one of the best fishing operation video training. Additionally, the full video transcription is provided to help people understand this topic.
Open Hole Fishing Transcription
Open hole fishing involves the removal of unwanted objects from the wellbore. The objects can be tools, equipment, and broken pieces of drill, pipe, bits or tribunals. Open hole fishing begins following a backoff and a drill string at or above the stock point of the fish in the wellbore leaving an accessible fish top. The fish can be removed using special tools and techniques.
A screw-in sub is one of the most common fishing tools. Its modified pin can be used to catch an undamaged fish. The overshot tool because of its versatility is frequently used in fish recoveries. Its simple design included circulating and releasing action as well as a 360 degree catch of the fish.
Normally, the overshot or screw in sub is connected to the bottom of the bumper sub and fishing jars on the fishing assembly. As the tool is lowered over the fish, the top of the fish passes through the tool into the ball. When the assembly is raised, grapples engage the fish at a lower point and it is worked free and pulled upward. If the top of the fish is bad, twisted or broken, it should be dressed off to provided clean top so grapple can insecurity firmly. Dressing off is achieved with a skirted or hollow food mill. Several types of mills are available for this purpose and other jobs.
In a washed-out hole, use of a hydraulic knuckle joint located above the overshot kicks out under pump pressure to increase the sweep of the overshot to facilitate capture of an elusive fish. With a severe washout, a wall hook guide run on the bottom of the overshot, further improves the search and capture of the fish. When the fish cannot be dislodged by pulling with the overshot, a jarring assembly run in the fishing strain can be activated to strike heavy blows either up or down on a stock fish to freak. The down action is achieved with a bumper jar, essentially a slip joint with a sliding stroke. The impact, enhanced by the weight of drill collars above the bumper jar results in a sharp blow with the fishing string. Dropping the string quickly produces a sharp downward blow on the fish. This jarring action is especially effective in free e-seated pipe or a string that is stuck as a result of an upward blow.
In many cases are stuck fish will require a powerful upward jar to free. Hydraulic fishing jars permit an impact.
The impact produced by hydraulic jar depends on the amount of pulled taken on the tour before it drips. As indicated earlier, the impact of a hydraulic jar is enhanced by the weight of drill collars placed above the tool. A jar accelerator further intensifies the effect of a jar at any depth. It is especially effective in shallow fishing operations where elasticity present in longer drill strings is not in any way. The use of an accelerator also keeps the energy of the jar impact from being lost up hole.
When a fish is stocked in and cannot be jarred or work free, a widely used practice called washover is employed. The washover operation is the most successful way of freed of fish and requires expert judgment both in pipe selection and in its proper running applications. As modern whole conditions are critical, in many cases of bit drip may be necessary to condition the hole prior to running the washpipe.
Essentially, washover operations involve a pipe string that slips over a stuck fish allowing fluid to circulate in the annulus between the fish in the inner wall of washover pipe. Fluid under pressure flushes out debris cut loos by the rotary shoe run on the bottom of the washover pipe. The washed over fish secured by an overshot or screw in sub and then he backed off and removed to the surface. The washover pipe selected requires an inside diameter large enough to accommodate the fish and an outside diameter they can rotate without sticking in the open hole and still allow circulation.
Various types of weatherford rotary shoes are available. Each shoe is custom designed for a particular procedure. Tooth-type shoes for example, are recommended when the formation to be cut is relatively soft. When metals such as tool joints or stabilizer blades must be cut, the rotary shoe is dressed with tungsten carbide or diamonds internally, externally or both, tailored specifically. And improper choice could severely damage the fish, complicating the recovery operation. Occasionally with drill pipe maybe plug usually by mud. Cutting the free drill pipe with a mechanical outside cutter run on the washpipe will remove the obstruction and establish a clean, workable top. Following the washover, the washpipe is pulled up and the shoe removed and replaced by a mechanical outside cutter. Run into the well and over the freed fish, the cutter is engaged. With a slight upward string, cutter knives are fed through the wall of the drill piped fish and the fish is parted. Rotation has then stopped and the cut piece of fish is recovered and pulled to the surface. When the fish is stock off bottom, washpipe spear maybe run in conjunction with the wash wipe and screwed into the fish prior to the washover procedure. This prevents the fish freed by the washover operation from dropping to the well bottom and damaging the well board, drilling string or drilling bit.
Open hole fishing also involves the retrieval of the junk at the well bottom. Junk is defined as any unwanted material in the hole that hampers operations such as accidentally dropped tools, metal debris and parts of equipment including cones from drill bits. A commonly used retrieval tool is the fishing magnet. Fishing magnets are especially cost effective for retrieving smaller ferrous objects such as bitcones, slips and mill cuttings. Permanent magnets have circulating ports around the outer edge so that fill and cuttings can be washed away exposing the junk for proper magnetic contact. Magnets are furnished with plush guides, lipped guides or mill guides which help in washing and securing the junk. The magnet is lowered to the well bottom while circulating and then pulled to the surface. This activity may be repeated until wellbore is cleared of all junks
Where junk pieces cannot be caught by a magnet consists of nonferrous metals, Weatherford employs specialized to junk baskets depending on the type of formation encountered. These retrieval tools consist of three basic types. The simplest to use is called a boot basket. It is run directly above junk mill or a junk bit the cuts the junk into small pieces. Fluid circulation deposits these pieces into the basket which is raised to the surface. In soft to medium formations, according-type basket commonly known as a globe basket can be run to cut a short core in the bottom of the well. This core as well as any junk contained is held in place by retaining fingers and removed to the surface. In hard formations, a jar powered or reverse circulating basket is a highly effective tool. Lowered to the bottom, it rotates slowly with circulation to flush samplings from the junk. A ball is dropped into the drill pipe and pump down until the ball sits in the retriever. The flow of the fluid is diverted to outside the tool which causes two things to occur and establishes reverse circulation and venture effect which then creates a partial vacuum inside the junk basket. These two forces propel the junk into the basket. Captured junk is secured by hymns retaining fingers. This action continues until all junk is removed from the hole.