Boring or penetrating the earth – Processes
Reexamination Certificate
1999-02-19
2002-04-09
Dang, Hoang (Department: 3672)
Boring or penetrating the earth
Processes
C166S370000, C175S215000, C175S324000
Reexamination Certificate
active
06367566
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method and apparatus of hydrodynamically controlling well-bore fluids down in oil and/or gas wells to prevent uncontrolled well blowouts while maintaining any desired degree of fluid dynamics underbalanced, neutral balanced, or overbalanced conditions for drilling, completion, or work-over operations in such wells.
BACKGROUND OF THE INVENTION
Well bore drilling is commonly performed by one of two techniques, namely overbalanced drilling and under balanced drilling. Overbalanced drilling refers to a well drilling process in which the drilling mud is maintained at a pressure greater than the formation pressure to inhibit the flow of fluids in the formation into the well bore. Under balanced drilling, in contrast, refers to a well drilling process in which the drilling mud is maintained at a pressure less than the formation pressure, thereby permitting formation fluids to flow into the well bore. Under balanced drilling techniques are gaining wider acceptance in the drilling industry because of the significantly lower likelihood of damage to the formation during drilling compared to overbalanced drilling techniques. When the drilling fluid has a greater pressure than the formation pressure, the formation can be damaged by penetration of drilling fluids into the formation or into formation fractures.
During the drilling, completion, and work-over operations in oil and gas wells, down-hole formation fluids entering the well bore may cause the well-bore fluids to be blown out of the well bore, which may result in an uncontrolled and hazardous well blowout or in very difficult operating conditions for the later work in the well bore. To prevent such uncontrolled blowouts, the operator/owner of the well typically circulates into position in the well bore a heavy enough fluid (i.e., drilling mud) to create a well-bore fluid pressure sufficient to exceed the current pressure of the formation fluid adjacent to the well bore, thereby preventing (i.e., killing) the flow of such formation fluid into the well bore. This process of circulating or injecting a fluid into the well bore of sufficient weight to prevent formation fluid from entering the well bore is commonly called “killing the well”, which results in well-bore fluid at the surface well head having no significant pressure.
This common practice of killing the well preparatory to tripping drill pipe or production equipment in or out of the well bore often results in serious damage to the formation around the well bore or adjacent to any fractures connected to the well bore. When the well is killed for any purpose, the wellbore fluid at higher pressure than the adjacent formation fluid will flow into the adjacent formation, resulting in reduction of the rock permeability to the production of formation fluids. In many formations, this reduction of permeability to formation fluids in the zones invaded by well-bore fluids may result in permanent or long-term damage to the well productivity. This damage is especially serious if a producing well, completed by hydraulic fracture stimulation, is killed because the killing well-bore fluid then may invade and damage the formation adjacent to the entire length and height of the hydraulic fracture.
As an alternative to killing the well with a heavy well-bore fluid, the drill pipe, production tubing or other equipment may be stripped in or out of the well under high well-head pressure through a snubbing unit. This procedure is expensive and complicated. Furthermore, if the well is shut-in under high pressure while stripping pipe or equipment in or out of the well through a snubbing unit, the liquids at the bottom of the well bore may be injected into the formation adjacent to the well bore and adjacent to the hydraulic fractures. In the zones invaded by these bottom-hole well-bore liquids while stripping through the snubbing unit, the rock permeability to the formation fluids may be severely damaged as described above.
In order to prevent damage to the producing reservoir formations, it is desirable not to kill the well by injection of well-bore fluids and not to shut-in the well with any liquids in the well bore as previously commonly done for the purpose of tripping drill pipe, production tubing or other equipment in or out of the well bore. To prevent reservoir damage from the invasion of well-bore liquids into the formation adjacent to the well bore or adjacent to the hydraulic fractures, it is desirable to maintain the down-hole well-bore fluid pressure at a level less than the then current pressure of the formation fluids in the adjacent reservoir rock. These fluids should flow only from the formation into the well bore or fracture and never from the well bore or fracture into the formation.
SUMMARY OF THE INVENTION
An objective of this invention is to provide a system for maintaining or regaining effective control of the well-bore fluids by circulating down hole a hydrodynamic control fluid through a dual path circulation system to prevent well-bore blow-outs under any drilling condition of underbalanced drilling, neutral balanced drilling, or overbalanced drilling, whether drilling ahead or while tripping the drill pipe out of the hole.
Another objective of this invention is to provide a system for maintaining a low or near-zero surface fluid pressure on the annulus fluid surrounding the drill pipe at the well head to permit the drill pipe to be rotated or moved up or down in the well bore while drilling ahead or tripping in or out of the hole without needing any high-pressure well-head rotating seal or pipe stripping seal and while maintaining any desired bottom-hole, well-bore pressure and any desired formation fluid flow dynamic condition in the lower portion of the well-bore.
An objective of this invention is to provide a system for under balanced drilling a well while substantially continuously maintaining the production (i.e., flow) of formation fluids into the well bore throughout all phases of the drilling operation, including tripping the drill string in and out of the well bore, while avoiding stripping the drill string in or out of the well head under significant or difficult high well-head pressures. During all phases of the drilling operation, the down-hole well-bore fluid pressure is not allowed to significantly exceed the formation fluid pressure adjacent to the well bore and, thereby, is not allowed to kill (i.e., stop) the continuous flow of formation fluids into the well bore and is not allowed to inject any non-formation fluids into the formations adjacent to the well bore.
Another objective of this invention is to provide a system for performing well work over, maintenance, completion, and recompletion operations in a producing oil and/or gas well, including the tripping of tubing and tools in and out of the well bore, without killing the well or stopping the continuous production of formation fluids into the well bore and without having to strip the tubing and tools in or out of the well head under significant or difficult well-head pressures. During all phases of these operations, the well-bore fluid pressure maintained at a level that does not significantly exceed the formation fluid pressure adjacent to the well bore and, thereby, is not allowed to kill (i.e., stop) the continuous flow of formation fluids into the well bore and is not allowed to inject any non-formation fluids into the formations adjacent to the well bore or adjacent to the hydraulic fractures extending from the well bore.
Another objective of this invention is to provide a system for performing any of the prior stated objectives without using a snubbing unit or other such surface pressure containment equipment to trip pipe and equipment in and out of the well bore.
Another objective of this invention is to provide a system for performing any of the prior stated objectives while being able to trip pipe and equipment in or out of the well bore without any produced formation fluids flowing out through the open well head through whic
Dang Hoang
Sheridan Ross PC
LandOfFree
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