Description:The present invention related to “Replacement of Bypass Valve by Valvular Conduit in Cement Retainers”

FIELD OF INVENTION
[001] Cement Retainers are frequently used in hydrocarbon wells for cement squeeze operation. Cement Retainer is essentially an equipment which enables the isolation of the hydrocarbon well segment above the depth it has been deployed at. This allows the cement squeeze operation to be done selectively to the well segment below the setting depth of the Cement Retainer. Conventional Cement Retainers have a Bypass Valve which requires a stinger (run on a Tubing/Drill Pipe) to shift it down thus opening the ports in the bottom guide of the Cement Retainer allowing cement to be pumped below the Cement Retainer. Bypass Valve in normal condition also acts as a check valve not allowing the fluids below to migrate above the Cement Retainer. The moving parts in Bypass Valve, requirement of stinger requirement to shift it frequently causes field failures when bypass valve does not move or stinger does not engage with bypass valve or after cement squeeze operation the bypass valve does not come to its original position upon disengagement of the stinger. These failures can damage an entire section of the hydrocarbon well or sometime the loss of entire well causing significant financial losses to exploration & production company.

BACKGROUND OF INVENTION
[002] Cement is used in almost all hydrocarbon wells to isolate a section of a pipe string or well bore. The most common cementing operation is to cement a pipe string or casing in a well bore to secure the pipe string and seal off the contents of formations penetrated by the well bore. This is often called primary cementing and involves pumping cement into the casing and then pumping a wiper plug down the casing so it pushes the cement out of the bottom of the casing through a float shoe or collar into which the wiper plug latches. The cement travels upwardly through the annulus between the casing and the well bore and ultimately sets up to secure the casing in the well bore and seal off the formations penetrated by the well bore.
[003] Conventionally, a cement retainer is run on the bottom of a work string and comprises slips to set the retainer against the casing, a seal to seal between the casing and the cement retainer and a bypass valve that can be opened by manipulation of the work String to allow cement to be pumped through the cement retainer and through the perforations. After a desired amount of cement is pumped through the cement retainer, an amount of water or completion fluid is pumped into the work string to displace cement in the work String and cement retainer. After the cement sets up, the cement retainer and work String are pulled from the casing. Naming this tool a cement retainer is quite descriptive because its function is to retain cement behind the casing and prevent it from flowing back into the inside of the casing.
[004] The primary cementing may involve casing cementation. In particular, primary cementing may be the cementing that takes place soon after the lowering of casing into the hydrocarbon formation and may involve filling the annulus between the casing and hydrocarbon formulation with cement. The secondary cementing may include various cementing operations in which cement is pumped into a well during drilling or production process. Secondary cementing can involve remedial cementing such as squeeze cementing.
[005] The bypass valve in cement retainer allow the circulation of fluids while running in the hole and after the packer is set. This bypass valve is operated by a cement stringer at the end of work string. The moving parts in bypass valve and the requirement of stringer to shift it frequently often cause failure of non-movement of bypass valve. In certain situations, a high negative differential pressure may cause backward flow which may disturb the cement cake. Sometimes the stringer does not engage with the bypass valve which frustrates the cement squeezing operations. In certain situations, after the completion of cement squeezing operation, the bypass valve does not get relocate to its original position upon disengagement of the stringer. This is likely to result in the damage of the entire section of hydrocarbon well or sometimes the permanent loss of the entire well.
[006] In certain situations, the moving parts of the components used in cement squeezing process such as bypass valve, stringer gets jammed due to debris, rusting, and hostile environmental condition inside the hydrocarbon well.

SUMMARY OF THE INVENTION
[007] The main objective of the present invention is to replace the bypass valve used in cement retainer by valvular conduit at bottom guide in order to solve all the problems associates with prior art available of bypass valve in cement retainer. The use of valvular conduit eliminates the dependency on stringer during the cement squeezing operations. The new invented cement retainer consists valvular conduit inside the cement retainer bottom guide which further can be deployed in hydrocarbon well and subsequently in cement squeezing operation.
[008] With the use of new cement retainer with valvular conduit at its bottom guide there shall be no requirement of moving parts unlike prior art available in the form of bypass valve where the bypass valve is required to shift down to open the ports and then vice versa to close the ports. Since the moving parts of bypass valve gets jammed inside the hydrocarbon well which cause financial losses millions of USD and sometimes it result in permanent shut down of the hydrocarbon well.
[009] The valvular conduit at the bottom guide of the cement retainer act as a passive check valve which is a non returnable valve. These valvular conduit operations are considerably quicker than waiting on bypass valve to shift down and open the ports and relocating the bypass valve to its original position. This will cause the faster cement squeezing operation due to non dependency upon the stringer and bypass valve. Thus, depending on the depth involved, squeeze jobs as disclosed may be conducted several times quicker than conventional squeeze jobs. Given a cost of $30,000/day for a land rig or USD 100,000/day for a large offshore rig, time is obviously money.
[010] The present invention of new cement retainer with valvular conduit at its bottom guide eliminates the chances of failure as unlike the prior art available of bypass valve and stringer. There is no possibility of the valvular conduit gets jammed as it does not contain any moving parts.
[011] The another objective of the present invention is to provide an improved cement retainer with better cement squeezing operations.
[012] The another objective of the present invention is to expedite the cement squeezing operations by reducing the dependency upon bypass valve and stringer associated with it.
[013] These and other objects and advantages of this invention will become more apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS
[014] Figure 1 is view, illustrating a prior art conventional cement retainer being used in cement squeezing operations. The components of the conventional cement retainer are marked as (1) Cement Retainer; (2) Body of the cement retainer; (3) Bypass valve; (4) Port; (5) Bottom Guide.
[015] Figure 2 is a view, illustrating the present invention of replacing the bypass valve by valvular conduit at the bottom guide of the cement retainer. The valvular conduit at the bottom guide is marked as (2) which is the heart of the cement retainer system.
[016] Figure 3 is a view similar to figure 2, illustrating the function of valvular conduit in bottom guide of cement retainer which works as check valve which is non returnable. The flow of fluid which is in the form of slurry of cement from top to the bottom and the upward movement is restricted by the cement valvular without any bypass valve and stringer.

DETAILED DESCRIPTION
[017] The present invention relates to cement retainers for use in hydrocarbon wells drilled into the earth to squeeze a material known in the field as cement through perforations in a well casing. Referring to figure 1 which is illustrating the cement retainer being run into the hydrocarbon well inside casing which has been cemented in a well bore by a cement shealth. The bypass valve (3) referred in figure 1 is used as a check valve which prevents the fluids below to migrate above the cement retainer. The upper stringer is attached to bypass valve and used to move the bypass valve in cement squeezing operations. The stringer run on a tubing or drill pipe to shift it down thus it open the ports in the bottom guide of the cement retainer allowing slurry of cement to be pumped out below the cement retainer for cement squeezing. The port and bottom guides are illustrated as (4) and (5) respectively in figure 1.
[018] In the conventional cement retainer as illustrated in figure 1 the bypass valve and use of stringer many times causing failure of cement squeezing operations due to jamming of its parts. The bypass valve and stringer associated with it in the cement retainers are deployed inside the hydrocarbon well at a very low depth somewhere around 3,000 meters to 6,000 meters depending upon the surface rig or offshore rig. This sometimes cause the jamming of the bypass valve and stringer due presence of enormous debris, high pressure, rusting and hostile environmental situations inside the hydrocarbon well, which cause slurry of cement and other microfluids to flow backward and cause failure of cement squeezing operations. There were many situations where the cement squeezing operations failed due to jamming of bypass valve and stringer which further becomes impossible to extract them to the surface and consequently cause the shut down of the hydrocarbon well permanently. This cause huge financial losses in the exploration of hydrocarbons.

[019] In certain situations the stringer does not get engaged with bypass valve which cause delay in cement squeezing operations. The cement squeezing operation is naturally a time consuming process as cement requires time to get hard. However, if the stringer does not get engaged with bypass valve, this cost financial losses upto of $30,000/day for a land rig or USD 100,000/day for an offshore rig.
In another situation after the cements flows through bypass valve passage to the bottom guide of the cement retainer, the stringer requires to shift it frequently which sometimes cause displacement of the bypass valve from its original position. In such a situation it cause malfunction of cement retainer and whole cement squeezing process gets failed. These failures cause the significant delay in the process causing delay in production of hydrocarbons and sometimes damage the whole hydrocarbon well permanently.
[020] With the application of present invention as illustrated in figure 2 the bypass valve is removed from the new cement retainer and the valvular conduit is added at the bottom guide of the cement retainer. This valvular conduit works similar to bypass valve but it is non moving and naturally act as a check valve and non returnable valve with flow of slurry of cement moving from top to bottom only. This prevents the upward flow of slurry of cement and thus it works with all advantages of bypass valve and without any support of stringer. This valvular conduit is a non moving material and therefore it does not requires to get shift frequently. The flow of valvular conduit at the bottom guide is illustrated in figure 3. In this way the replacement of bypass valve by valvular conduit results in improved cement retainer by removing all the problems associated with the prior art available.
, Claims:We claim
1. Replacement of bypass valve by Valvular Conduit in Cement retainer prevents the dependency upon the stringer to frequently shift the valve to control the flow of slurry of cement.
2. The replacement of bypass valve by valvular conduit in cement retainer as claimed in claim 1 where the valvular conduit does not contain moving parts and thus it does not get jammed inside the well.
3. The replacement of bypass valve by valvular conduit in cement retainer as claimed in claim 1-2 improves the cement retainer by eliminating the possibility failure of cement squeezing due to disengagement with stringer as it independent works as a non returnable valve without having the requirement of stringer.
4. The replacement of bypass valve by valvular conduit in cement retainer as claimed in claim 1-3 makes the cement squeezing process quicker by preventing failure and reducing the time in shifting of bypass valve with stringer.