The present invention relates to oilfield drilling devices and methods, and specifically, to an apparatus and method for inducing under balanced drilling conditions by artificially lifting the drilling fluid and the formation fluid with a jet pump assembly affixed to an inner casing section while simultaneously drilling with a drill bit and drill pipe that passes through the jet pump assembly.
In order to produce fluids such as oil, gas, and water from subterranean rock formations, a well is drilled into the fluid-bearing zone. Most wells are generally drilled with a drilling rig, a drill bit, a drill pipe, and a pump for circulating fluid into and out of the hole that is being drilled. The drilling rig rotates and lowers the drill pipe and drill bit to penetrate the rock. Drilling fluid, sometimes referred to as drilling mud, is pumped down the drill pipe through the drill bit to cool and lubricate the action of the drill bit as it disaggregates the rock. In addition, the drilling fluid removes particles of rock, known as cuttings, generated by the rotational action of the drill bit. The cuttings become entrained in the column of drilling fluid as it returns to the surface for separation and reuse. The column of drilling fluid also serves a second purpose by providing weight to prevent seepage from the formation into the well. When the weight of the column of drilling fluid is used to prevent seepage, the hydrostatic pressure of the column of drilling fluid exceeds the pressure contained within the formation, a drilling condition referred to as over balanced drilling.
A desired condition when drilling is to prevent drilling fluids from penetrating the surrounding rock and contaminating the reservoir. Another desired condition is to allow any fluid such as oil from the reservoir being drilled to flow into the well bore above the drill bit so that production can be obtained during the drilling process. Both of these conditions can be achieved by lowering the bottom hole pressure, or in other words, lowering the hydrostatic pressure that is exerted by the column of fluids in a well bore to a point that is below the pore pressure which exists within a rock formation. Lowering the bottom hole pressure within a well bore while drilling below the formation pressure to accomplish either of these goals is called under balanced drilling.
Conventional under balanced drilling intentionally reduces the density of fluids contained in the well bore. In conventional under balanced drilling, the reduction in the density of the fluids causes the hydrostatic pressure of the fluid column to be lower than the pressure contained within the pores of the rock formation being drilled. When a reduction in density causes the hydrostatic pressure of the fluid column to be lower than the pressures contained within the pores of the rock formation being drilled, fluids in the reservoir may flow into the well bore while it is being drilled. Under balanced drilling has gained popularity in the upstream oil and gas industry because it does not allow the drilling fluids to penetrate the surrounding rock and damage the permeability of the reservoir.
The under balanced condition is usually achieved by injecting a density reducing agent such as air, nitrogen, exhaust, or natural gas into the fluids that are being pumped down the drill pipe during the process of drilling a well. The injected gas combines with the drilling fluid and reduces its density and thus lowers the hydrostatic pressure that exists in the annulus between the drill pipe and the wall of the well bore. The concentric casing technique is a common method for delivering the gas to the bottom of the well by utilizing a second string of casing hung in the well bore inside the production casing. The injected gas flows down to the bottom of the well through the outer annulus created by the two strings of casings. The drilling fluid, delivered via the drill pipe, and any produced fluid combine with the injected gas as it flows upwards through the inner annulus between the second or concentric string of casing and the drill pipe. The process may be reversed such that the inner annulus is used for injection and the outer annulus is used for well effluent. The use of gas as a density reducing agent has distinct disadvantages. First, if air is used, the risk of down hole fires and corrosion problems are invited. Second, if an inert gas such as nitrogen is used, the expense may be prohibitive. In either case, the cost of compression that is required by all types of gas at the surface is significant.
Another method for lowering bottom hole pressure is by artificially inducing lift to remove fluids from a well by using a jet pump and a power fluid. The use of jet pumps is common in production operations where drilling activity has stopped. In this case, the drill pipe and drill bit have been extracted and a jet pump is lowered into the well on the end of a tubing string. A surface pump delivers high-pressure power fluid down the tubing and through the nozzle, throat, and diffuser of the jet pump. The pressure of the power fluid is converted into kinetic energy by the nozzle, which produces a very high velocity jet of fluid. The drilling and production fluids are drawn into the throat of the jet pump by the stream of high velocity power fluid flowing from the nozzle into the throat of the jet pump. The drilling and production fluids mix with the power fluid as they pass through the diffuser. As the fluids mix, the diffuser converts the high velocity mixed fluid back into a pressurized fluid. The pressured fluids have sufficient energy to flow to the surface through the annulus between the production casing and the tubing that carried the jet pump into the well.
While jet pumps are used for removing fluid from a well by lowering down hole pressure in production wells, the advantages of under-balanced drilling would be enhanced significantly if a jet pump could be combined with drilling operations. The jet pump could be employed to achieve under-balanced conditions while the drill string is down in the hole and the drill bit is operating. By using a power fluid such as water, the disadvantages of gas could be avoided altogether thereby increasing safety and decreasing costs. Attempts have been made to place jet pumps into drill bits. However, when the jet pump is placed in the drill bit, the drilling fluid serves a dual purpose and becomes the power fluid before entering the nozzle of the jet pump. When the power fluid and the drilling fluid are one in the same and enter the nozzle of the jet pump, the extreme abrasiveness of the drilling fluid can cause the jet pump to wear out prematurely.
What is needed beyond the prior art is a jet pump connected to a concentric casing string that will induce artificial lift while allowing the drill bit to operate independently of the jet pump. What is further needed beyond the prior art is a jet pump connected to a concentric casing string that will keep the power fluid separate from the drilling fluid until after the power fluid has passed through the nozzle of the jet pump.
The invention that meets the needs identified above is a Down Hole Drilling Assembly (DHDA) for inducing artificial lift of the drilling and formation fluid by means of a hydraulic jet pump attached to a concentric casing string and a drill string including a drill bit and drill string that passes through the jet pump. In this design, the drilling fluid and production fluid do not mix with the power fluid until after the power fluid has passed through the nozzle of the jet pump. The jet pump is joined to an inner casing section of a concentric casing string. The jet pump consists of a nozzle, a throat, and a diffuser. The jet pump assembly also contains a bladder that inflates to redirect the flow of drilling fluid from the inner annulus to the throat of the jet pump.
As seen in
DHDA 300 is affixed to inner casing 150 and positioned above packer 140. As used herein, the term jet pump means an apparatus having a nozzle, a throat, and a diffuser which transfers energy from a power fluid to a drilling and production fluid to artificially lift and remove drilling and produced fluids from a well thereby decreasing the hydrostatic weight of the combined fluid column in the annulus between the concentric casing string and drill pipe above the jet pump. Drilling fluid inlet housing 310 screws onto and extends up and out from inner casing 150. Drilling fluid inlet housing 310 has approximately the same inside diameter as inner casing 150 so that drilling fluid 101 may continue to flow up to the surface through inner annulus 230 if desired. Drilling fluid inlet housing 310 also contains drilling fluid inlet 240, which is an aperture in drilling fluid inlet housing 310 that allows drilling fluid 101 to flow into drilling fluid chamber 242. Drilling fluid chamber 242 is an annular region that allows drilling fluid 101 to flow from drilling fluid inlet 240 to pump chamber 216.
As seen in
Bladder 316 is cylindrical and interlocks with bladder housing 318. Bladder 316 has the same outer diameter as the inside wall of drilling fluid chamber inner wall 314. Bladder 316 is made of an expansive material, such as rubber, that expands inwardly from drilling fluid chamber inner wall 314 to drill string 110 when inflated. Bladder tube 332 is screwed into drilling fluid inlet housing 310. Bladder tube 332 extends up through drilling fluid chamber 242 and is screwed into bladder elbow 334. Bladder elbow 334 is welded to drilling fluid chamber inner wall 314. As seen in
As seen in
As seen in
As seen in
CCJP and (DHDA) 300 operates as described only when bladder 316 is inflated as indicated in FIG. 6. When bladder 316 is not inflated, drilling fluid 101 will flow up through inner annulus 230 instead of into drilling fluid inlet 240. When the pressure of power fluid 100 is increased to expand bladder 316 to fit against drill string 110, drilling fluid 101 will no longer be allowed to flow up through inner annulus 230, and will instead be forced into drilling fluid inlet 240. As seen in
The method of inducing lift to remove drilling and production fluid 101 involves injecting power fluid 100 through a nozzle so that when the power fluid exits the nozzle a pressure differential is created that draws in drilling and production fluid 101. The power fluid enters the diffuser where the power fluid combines with the drilling fluid and the production fluid. When the power fluid combines with the drilling fluid and the production fluid, the high velocity power fluid converts the drilling fluid and production fluid to a combined pressurized fluid that now has the energy to flow to the surface. This process reduces the pressure of effluent 102, by reducing the hydrostatic weight of the fluid column above DHDA 300. The reduction in the hydrostatic weight in turn reduces the pressure in well bore 160 below DHDA 300 and allows the production fluid in the reservoir to flow into well bore 160. This method of inducing lift can be utilized during the drilling process and is attached to inner casing 150 rather than drill string 110.
With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
Number | Name | Date | Kind |
---|---|---|---|
270488 | Saunders | Jan 1883 | A |
2201270 | McIntyre | May 1940 | A |
2234454 | Richter | Mar 1941 | A |
2849214 | Hall | Aug 1958 | A |
2946565 | Williams | Jul 1960 | A |
3087558 | Dougherty | Apr 1963 | A |
3208539 | Henderson | Sep 1965 | A |
3924696 | Horlin et al. | Dec 1975 | A |
3948330 | Langford, Jr. | Apr 1976 | A |
4022285 | Frank | May 1977 | A |
4239087 | Castel | Dec 1980 | A |
4436166 | Hayatdavoudi | Mar 1984 | A |
4534426 | Hooper | Aug 1985 | A |
4567954 | Voight et al. | Feb 1986 | A |
4630691 | Hooper | Dec 1986 | A |
4687066 | Evans | Aug 1987 | A |
4744730 | Roeder | May 1988 | A |
5355967 | Mueller et al. | Oct 1994 | A |
5456326 | Raines | Oct 1995 | A |
5562171 | Besson et al. | Oct 1996 | A |
5771984 | Potter | Jun 1998 | A |
5775443 | Lott | Jul 1998 | A |
5836404 | Trujillo | Nov 1998 | A |
5921476 | Akin | Jul 1999 | A |
5992763 | Smith | Nov 1999 | A |
6129152 | Hosie et al. | Oct 2000 | A |
6209663 | Hosie | Apr 2001 | B1 |
6276455 | Gonzalez | Aug 2001 | B1 |
20020170749 | Hoyer et al. | Nov 2002 | A1 |
Number | Date | Country |
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1 288 434 | May 2003 | EP |
Number | Date | Country | |
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20030042048 A1 | Mar 2003 | US |