For fairly simple, straightforward oil painting and gas fishing jobs similar as the recovery of pipe inadvertently dropped or left in the hole, an overshot can be used for a nicely fast and affordable recovery. For a more complicated job similar as the recovery of wedged or cemented pipe, or the recovery of several wireline tools – special fishing tools and chops will be needed. When cases similar as these arise, an educated fishing tool driver should be considered.

Junk In Hole

Junk lost in the hole is considered to be a frequent cause of fishing operations. There are numerous possible causes for loose junk to be lost in the hole, still, the most frequent causes are
*The loss of a gemstone bit cone and comportments
*Hand tools or other eclectic objects that are inadvertently dropped from the face
*The loss of comber reamer corridor
*The loss of a hole nature arm and cone
*The loss of an underreamer arm
*The loss of a airman bit during hole opening operations

still, the first step in the recovery of loose junk lost in the hole is to identify what it is, If at all possible. This may be readily determined if commodity has been left in the hole on a trip or has been dropped into the holeaccidentally.However, an print block should be considered, If the type and configuration of the junk aren't known. Once the type and size of the object are determined, a decision can be made if it can be recovered as a single whole piece or whether the object must be mulled( junk shop) or else broken up. It's generally preferable to recover the junk whole rather than in pieces, still, this isn't always possible.

Parted String

One frequent reason for a oil painting and gas fishing job results when there are a twist- off and the drill string corridor due to essence fatigue. Rough running, scarring by tong dies, indecorous make- up necklace, erosion and corrosion performing in a flop in the tube body or cracks that form and enlarge under constant bending and torsional stresses during drilling operations. The most common place for this to do is at the connection of a drill collar, at a crossover, or drill pipe tool joint where the advanced stress position generates a crack.

Stuck Pipe And Their Causes

Quite frequently, circumstances during drilling operations will affect in the drill string getting wedged downhole. Both mortal error and mechanical failures can beget this. The recovery of wedged pipe can be a delicate, time- consuming and expensive operation, thus it's desirable to identify the type of sticking so that the most effective system of recovery may be initiated incontinently. farther discussion of these sticking causes is handed below
*Differential Sticking
*Mechanical Sticking
*Undergauge Hole
*shy hole drawing
*Lost Rotation
*Junk In Hole
*Keyseating
*Crooked Pipe
*Ledges & Doglegs
*Stuck In Cement

Economics Of Fishing

Some fishing jobs can go on for months before the fish is recaptured. After a certain period, still, the cost of fishing operations and lost drilling time come prohibitive. thus, a truly successful oil painting and gas assiduity fishing job shouldn't only be an functional success but an profitable success as well.

opinions made during fishing operations should address an provident result to the problem in the well. Obviously, a shallow hole with little carriage time and outfit invested can justify only the cheapest fishing operation. When the misplaced outfit and tools to be recovered represent a large capital investment, further time and expenditure can be justified. Generally, once these costs reach about one- half of the cost of sidetracking andre-drilling, fumbling operations should be abandoned. One approach used to calculate the number of carriage days that should be allowed for fishing uses the following equation



where

*D = number of days allowed for fishing

*Vf = relief value of fish

*Cs = estimated cost of sidetracking

*R = diurnal cost of fishing tool reimbursement and services

*Cd = diurnal carriage operating cost

Avoiding Fishing Operations & Hazards While Drilling

The secret to a successful drilling program is to avoid the hazards that historically have led to fishing jobs.

*Take all preventives to insure that objects aren't dropped into the wellbore.
*Cover the drilling necklace precisely and learn the limitations of the drilling bottom hole assembly.
*Begin with a full examination( including electro- glamorous ) of the drillstring and BHA.
*Continue a routine conservation and examination program of the BHA by covering operating hours inservice.However, leave it out ”, “ If indoubt.



*Condition the hole and drilling slush previous to drilling bit or BHA passages( check also Pipe tripping procedures). Circulate a high- thick reach if needed to discharge the hole of inordinate drillcuttings.However, spot a high thick lozenge on bottom to adequately suspend solids and contain loose, loose conformation, If needed.
*previous to drilling into a implicit loss rotation zone, circulate a high thick reach to discharge the hole of inordinate drill slices and reduce the effective slush viscosity.
*Make routine wiper exertion passages to gauge the overall hole stability and the condition of possible water sensitive and tight shale sections.
*Precisely ream out any suspected undergauge hole.
*Formulate a plan to recover a downhole assembly should it come wedged or parted.
*force and check all fishing tools that may be needed incontinently. Order missing or imperfect corridor.
*Can the BHA factors be scrabbled? What tools are needed?
*Can it be washed over? What tools are needed?

Preparation For Fishing Operations In Drilling

Anyhow of the cause, the success or failure of the oil painting & gas fishing job greatly depends on the degree of preparedness taken prior to the inception of drilling operations. The following factors should be considered when preparing for a fishing job –

Critical Information

The costs and essential pitfalls of fishing make it imperative that the following critical well-conditioned information and BHA data be recorded in advance of drilling operations incipiency. Continue to modernize the information as needed.


Record every dimension and the position of all drilling tools( as listed below) in the string before they're run below the rotary table. Continue to modernize the information as needed. Maintaining a good record of all critical outfit confines is necessary if an provident oil painting & gas fishing job operations is to be done.

DRILL PIPE – Sizes( OD, ID)

DRILL COLLARS

*Tool Joint OD
*Weights
*Grade
*Volume
*Length
*Connection
*Last examination

STABILIZERS – Size( OD, ID)

REAMERS Type/ periodical No.

DRILLING JARS – Quantity

SHOCK SUB – Fish Neck Length

CORE BARREL – Overall Length

MUD MOTOR – Connection

HOLE Nature – Last examination? SUBS

Fishing Preparation Of Hole And Drilling Fluid

The hole should be conditioned( slush exertion) and the drilling fluid should have the asked slush parcels before starting in the hole with fishing tools. It may be necessary to make a trip with a bit to condition the hole and circulate out filler that has covered the fish. Always circulate and flush the hole first with a high thick lozenge to discharge drill slices and spot a balanced high thick lozenge above the fish to suspend solids previous to trip out for fishing tools.

Type And Details Of Fish

Once it's apparent that fishing operations must be conducted, it's necessary to learn and acquire all applicable information about the fish that's to be recovered. Determine
*The probable cause of failure or reason for junk lost in hole.
*The size, length, quantum, and type of fish( all confines are important).
*The position or top of the fish.( check also Free point index)
*The condition of the top of the fish.
*The mechanical condition of the wellbore covering.
*The condition and stability of the open hole interval down to the top of fish.
*The value or relief cost of the fish if sidetracked and left in the hole.
*The probability of success, pitfalls of failure, and estimated recovery time and cost.

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