Casinjacs are state of the art hydraulic jacks that are used worldwide to raise and lower strings of pipe from 2 3/8" OD to 36" OD and to lift or lower loads up to 1,000,000 pounds. Casinjacs are mounted on a wellhead or other suitable structure to support the size and weight of the pipe involved. We also manufacture equipment for use with Casinjacs such as hydraulic power units, intensifiers, valve stands, and other custom fabrication work.
Uses and Benefits
Removing Wellhead Slips
Removing the wellhead slips requires that the pipe string be lifted to take the string weight off the wellhead slips. The force required to move the pipe upward may be greater than the safe pull force of a workover rig and sometimes even greater than a drilling rig. A Casinjac can be used to safely apply the necessary pull force.
Factors contributing to the required lift force are:
- The pipe is stuck at a shallow depth
- The work-over or drilling rig is not rigged up over the hole.
- The wellhead slips are binding in the wellhead.
- The total weight of the pipe string
- The pull sub is not straight
- Why stress your rig - let our Casinjac handle the heavy lifting.
- Mast support - Matting boards used to support the masts during rod and tubing work are often not adequate for casing pulling.
- The ground support is diminished when the hole around the wellhead is too large. Rain wets and softens the ground around and under the matting boards or cellar beams making it spongy and causing it to subside when a load is applied.
- If the pipe parts up the hole or above the ground the energy released puts the rig and personnel in danger. Pull subs should be inspected carefully before use, they should have a usable pipe collar on top, be the proper grade and weight and also be of sufficient length.
- Under heavy loads the drilling lines and the draw works chains
A Casinjac is mounted on the wellhead and is not subject to the limitations of matting boards, cellar beams, masts, drilling lines, draw works chains and soil conditions. Using a tool that is designed to handle heavy loads safely is not only more safe but more profitable.
Working with Casing
In order to maximize the recovery of casing it is important to work the casing. Working the casing involves lifting and lowering the casing using a Casinjac and lifting and dropping the pipe using the work-over rig. This process conditions the hole and allows greater pipe movement up and down the hole. This process is continued until the casing no longer moves downward. The casing is then in a worked down condition. Sometimes it is necessary to move the casing up and down using the Casinjac in order that the rig can pick up the casing upward enough to work the casing down effectively. Usually the forces used to work the pipe do not exceed 80% of the listed tensile strength of the casing and/or its joint strength whichever is less. The work-over rig is used to work the pipe down hole by picking it up and dropping it to effect a spudding action which allows the pipe to move down through areas in the hole which are impeding pipe movement. The casing can be marked using a crayon which can be used to monitor pipe movement. When the casing quits moving upward or downward a free-point procedure can be performed to determine the amount of free pipe.
Free-pointing is a method of determining the free-point of a pipe string. The free-point being the down-hole location of a point above which the pipe can be parted and pulled without exceeding the safe pull force of the pipe. Experience has shown that the free-point determination is subject to the limitations of the equipment and procedure.
Basically what is required to determine the free-point is as follows:
- The ability to apply an adequate pull force and to measure it accurately.
- The ability to maintain this pull force at all times as the pipe moves up-hole.
- The ability to accurately measure the pipe stretch that results from an applied stretch force.
- The ability to measure the relative pipe movement at a given section of pipe down-hole when a stretch force is applied.
- The ability to apply enough pull force to cause it to move at the lowest possible depth while not exceeding the safe pull force of the pipe.
- The ability to work the pipe down after each free-point determination and before another free-point is attempted.
Current methods in use to free-point pipe strings are:
Using work-over rigs. The work-over rigs pull the string weight, set the brake and mark the pipe. The rig then pulls an additional amount of force (stretch force) and marks the pipe again. The distance between the marks represents pipe stretch caused by the stretch force.
The problems encountered when attempting to free-point with a work-over rig are as follows:
- The inherent inaccuracy of weight indicators and the infrequent calibration of same.
- The work-over rig is incapable of maintaining a constant pull force as the pipe moves up-hole. The inability to maintain a constant pull force as the pipe moves up-hole results in an inaccurate stretch determination.
- When the rig's pull force increases the rig "squats". its wire rope stretches, and the matting boards/cellar beam subsides. It is not possible to determine the effect on the stretch measurement these variables cause.
- Sometimes the work-over rig cannot pull the string weight, sometimes it cannot pull the string weight plus a reasonable stretch force. and often it cannot pull the string weight plus two consecutive stretch forces much less a third consecutive stretch force.
- The use of electric wire-line tools to free-point. This method is used to free-point stuck drill pipe and to free-point casing in work-over operations and is used less often during plugging and abandonment work. Usually a drilling rig or a work-over rig is used to move the pipe string, The free-point tool measures pipe movement over a narrow range (about 6 feet or so). The free-point tool is positioned in the hole where it is assumed that the pipe is 100% free, the rig applies a specified pull force and the tool indicator is adjusted to read 100%. The tool is then lowered to a lower depth, the pull force is applied, and another reading is taken to indicate pipe movement and compared to the initial reading. The tool is lowered to different intervals and readings taken until no pipe movement is indicated,
The following has been observed when free-pointing using wire-line tools and methods.
- A pull force is chosen that is within the capabilities of the work-over rig or drilling rig and often well below the safe pull force of the pipe string being free-pointed. The pipe could move at a lower depth is the pull force is sufficient.
- The pipe string is not worked down prior to the application of the specified pull force and the attendant free-point measurement. This often results in a free-point indication the top of a down-hole area of tightness rather than the maximum free-point depth.
- If the wire-line procedure applied a safe pull force that would assure the movement of all free pipe and if the procedure worked the pipe down after each free-point observation, this method should provide good information.
- When the pull force is applied by a work-over or drilling rig the repeat ability and accuracy is suspect due to reasons previously cited.
Free-pointing with a Wellhead Casinjac
A Wellhead Casinjac can be equipped with instrumentation to accurately measure and apply necessary forces and to accurately measure the pipe stretch resultant from these forces.
- The safe pull force can be applied resulting in the movement of the maximum amount of pipe at the safe pull force.
- The pull can be held constant as the pipe moves up-hole, allowing for observing an accurate stretch measurement resulting from a given pull force.
- Consecutive stretch forces can be applied and their respective stretch
These observations lead to the following reasonable conclusions:
- If the free-points observed are nearly the same the pipe is stuck at one point.
- If the free-points are greater as more stretch force is applied the pipe is partially stuck up-hole and the free-point lowers as the pipe is pulled through tight spots.
- If the free-point depths diminish as the stretch force increases then the hole is probably deviated and the pipe becomes wall stuck as it tries to align itself.
- Using a calibrated digital pressure indicator and an encoding linear transducer lift forces and pipe movement can be measured as accurately as any method currently available.
- If the pipe sting is a combination string, it is necessary to know the amount and weight per foot of each segment and where it occurs in the string.
- Repeating a specific pull force and working the pipe down after each free-point procedure can be easily done using a work-over rig and a Casinjac.