DESC:A liner hanger drillable packoff bushing conventionally seals between the liner hanger and the running tool, and thus between the liner and the running string or work string, which conventionally may be drill pipe. A packoff bushing is particularly required during cementing operations so that fluid pumped through the drill pipe continues to the bottom of the well and then back up into the annulus between the well bore and the liner to cement the liner in place. During cementing operations, the seal body of the packoff bushing is fitted in the annulus between the liner hanger and the running tool, and includes OD seals for sealingly engaging the liner hanger and ID seals for sealingly engaging the running tool. Packoff bushings are preferably retrievable with the running tool to prevent having to drill out the bushings after the cementing operation is complete. Also, a packoff bushing is preferably lockable to the liner hanger by locking within a profile to prevent the bushing from moving axially with respect to the liner hanger. If the packoff bushing is not lockable to the profile of the liner hanger, the bushing may get "pumped out" through the top of the receptacle, thereby losing a cementing job.
Conventional DPOB currently being used worldwide has Aluminum as material of construction. This material often causes a significantly problem in drilling-out causing rig downtime of many days sometime causing significant financial losses.
Several challenges are faced in the design and operation of these bushing devices. First, the bushing is exposed to fluid pressure during cementing operations from the fluid which is passed down through the inner conduit and released into the liner conduit. This fluid pressure is significant, tends to push the bushing and/or the inner conduit upwards through the interior of the liner conduit and must be counteracted in some manner, usually by anchoring the bushing in the liner conduit. As the internal fluid pressure increases the cross section ovality and wall thickening decrease due to use of aluminum material in construction of DPOB.
Since the bushing is intended to provide a seal between the liner conduit and the inner conduit, it occupies a significant amount of space inside the liner conduit. Therefore, the conventional DPOB based on aluminum material are difficult to get modified due to higher cost and it takes longer period of time.
Longer Drill out time of conventional DPOB as aluminum has higher strength which cause slow production of oil and gas wells due to longer rig downtime
The prior art describes several attempts at designing cement bushings or packers for use in association with liner hanging apparatus which can be anchored in the liner conduit and then removed from the liner after use along with the liner hanging apparatus.
None of the prior art references outlined above fully address the problem of high cost and rig downtime due to using of aluminum as material of construction of DPOB.

The main object of the present invention is to provide Composite Drillable Pack off Bushing, which obviates the drawbacks of the hitherto known prior art as detailed above.
Another object of the present invention is to provide reduce the rig downtime and increase the production of hydrocarbons in oil and gas well.
Still another object of the present invention is to provide reduction of financial cost in the production of hydrocarbons in oil and gas well.

Achieved outcome of the present invention is Composite Drillable Pack off Bushing which is completely new type of drillable pack off bushing. The material of construction of this Composite Drillable Pack off Bushing is composite material made up of glass-reinforced epoxy resin. The drill-out time of this composite material drillable pack off bushing is less than sixty (60) seconds which essentially eliminates the drawback associated with conventional DPOB made of Aluminum material. Composite Drillable Pack off Bushing provides a method of sealing off the liner top to allow for cementing. It is supplied pre-installed inside a Sub to give it a plug and play feature. Composite DPOB is constructed from specially formulated Composite Material designed to withstand high differential pressures and high temperatures. The drill-out time of Composite DPOB is 1-5 minutes and its produces powder like cuttings which can be cleaned-out of the well easily. Composite DPOB completely eliminates all problems associated with drill out of conventional Aluminum DPOB. Pre-installed inside a sub, Composite DPOB is generally run directly below the liner top packer or the setting sleeve, and above the liner hanger. Its most common configuration is Box up and Pin Down. It has moly-glass chevron seals to seal on the OD of a slick stinger that is connected to the bottom of a running tool. When using this pack-off, piston forces are significantly reduced below what conventional PBR or swab cup seal assemblies yield. There is a long lead in taper on this product that facilitates re-entry if necessary.
However, strength of the composite material is significantly less compared to metal like Aluminum. Therefore, the unique design is invented for this composite drillable pack off bushing to sustain the high fluid and gas pressure below the surface of the earth in oil and gas well. The design was invented after several rounds of testing in simulated oil/gas well conditions. Testing of Composite drillable pack off bushing has been done successfully at 5,000 psi pressure and 350 Degree Fahrenheit temperature passing all test parameters. The combination of using the composite as material of construction of drillable pack off bushing and unique design has eliminated the drill-out drawbacks of the current conventional drillable pack off bushing.
As an additional advantage, the composite material generates very fine powder like cuttings upon drill-out so these can cleaned-out of the well very easily.

The present invention is illustrated in figure 1 to 2 of the drawings accompanying this specification. In the drawings like reference numbers /letters indicate corresponding parts in the various figures.

,CLAIMS:1. Invented composite drillable pack off bushing reduces the rig downtime and increase the production of hydrocarbons.
2. Invented composite drillable pack off bushing consists of glass-reinforced epoxy resin as composite material which sustains 5000 PSI pressure and high temperature upto 400 Degree Fahrenheit in oil and gas well.
3. Invented composite drillable pack off bushing’s drill time is below five minutes.