Not applicable.
Not Applicable
This disclosure relates generally to the field of fluid transfer devices. More specifically, the invention relates to fluid transfer devices usable in so-called managed pressure drilling or dual-gradient drilling systems.
U.S. Pat. No. 8,783,379 discloses a so-called “barrierless” fluid transfer device wherein a power fluid is introduced into and removed from one or more pressure containment vessels. Movement of the power fluid into and out of the pressure containment vessel(s) causes corresponding, opposite movement of working fluid into and out of the pressure vessel(s) to move the power fluid from a system inlet to a system outlet, and wherein energy of the power fluid is transferred to the working fluid. In the fluid transfer device disclosed in the '379 patent, no physical barrier is disposed between the power fluid and the working fluid. Mixing of the power fluid and the working fluid is minimized by selecting dimensions of the pressure vessel selected with respect to a rate of movement of the power fluid into and out of the at least one pressure vessel.
One aspect of the present disclosure related to a fluid transfer device for use in wellbore drilling that includes at least one pressure vessel having a fluid port at a bottom thereof for entry and discharge of a working fluid or a power fluid and a fluid port at a top thereof for entry and discharge of a power fluid or a working fluid. The pressure vessel has no physical barrier between the power fluid and the working fluid. Valves are coupled to the power fluid port for selective introduction of the power fluid into the at least one pressure vessel. Valves are coupled to the working fluid port such that the working fluid is constrained to flow in only one direction.
Other aspects and advantages of the invention will be apparent from the description and claims which follow.
A seal 30 may be provided in the upper end of the riser pipe 16. The seal 30 can be a Hydril brand Bag Type BOP such as Type GL or GK shown in the 1978-79 Composite Catalog, Pages 36-40. To decrease wear on the seal 30 during operation, an optimal section or joint of polished drill pipe can be threaded into the drill string 28 just below the kelly or top drive (neither shown for clarity of the illustration) and kept in that position during the drilling of a well. A light-weight fluid conduit 32 is connected at a selected point 34 to the interior of the riser pipe 16 and extends to a pump 36 and a supply of lightweight fluid (not shown) which may be on the drilling vessel 10. Lightweight in the present context means a fluid having a specific gravity lower than the specific gravity of a drilling fluid (“mud”) pumped into the wellbore as will be further explained with reference to
A return mud flow line 38 hydraulically connects into the annulus of the riser pipe 16 at a selected position above the wellhead 18, e.g., at outlet 35, and extends to mud return tanks and facilities 40 which may be disposed on the drilling vessel 10. The return mud line 38 can be one of the “kill and choke” lines with appropriate bypass valving for a fluid transfer device system 42. A fluid transfer device system 42 according to the present disclosure may be hydraulically connected in the lower end of the return mud return flow line 38.
In
The lightweight fluid 33 may, for example, be sea water, which has a specific gravity of approximately 8.6 pounds per gallon or the lightweight fluid 33 may be a gas such as nitrogen gas. The drilling mud 37 which it replaced may have specific gravity as much as 18 pounds per gallon or more. Without the system shown in
Regardless of what kind of light fluid 33 is used (liquid or gas), pressure sensors may be used to control the interface level 45 by measuring the hydrostatic head of the fluid above the pressure sensor (not shown for clarity). In such cases the seal 30 may be omitted. See U.S. Pat. No. 7,677,329 issued to Stave and incorporated herein by reference.
It is to be clearly understood that the example drilling system shown in
For example, in another drilling system shown schematically in
An adjustable fluid transfer device 130 in the mud return line 132 may provide the ability to control the bottom hole pressure during drilling of the wellbore 90. The fluid transfer device 130 will be discussed below with reference to
A sensor P2 may be provided to measure the bottom hole fluid pressure and a sensor P3 may be provided to measure parameters indicative of the pressure or flow rate of the fluid in the annulus 146. Above the wellhead 125, a sensor P4 may be provided to measure parameters similar to those of P3 for the fluid in the return line 132 and a controlled valve 152 such as an adjustable choke may be provided to hold fluid in the return line 132. In operation, a control unit 140 and the sensor P1 operate to gather measurements relating to the drill pipe 142 pressure to ensure that the surface pump 128 is operating against a positive pressure, such as at sensor P5, to prevent cavitation, with the control unit 140 adjusting the choke 150 to increase the flow resistance it offers and/or to stop operation of the surface pump 128 as may be required. Similarly, the control system 140 together with sensors P2, P3 and/or P4 gather pressure measurements, relative to the desired bottom hole pressure and the pressure and/or flow rate of the fluid in the return line 132 and the annulus 146, necessary to achieve a predetermined pressure at any point along the wellbore 90. More particularly, the control system 140 acting at least in part in response to the data from sensors P2, P3 and/or P4 controls the operation of the adjustable fluid transfer device 130 to provide the predetermined downhole pressure operations, such as drilling, tripping, reentry, intervention and recompletion. In addition, the control system 140 controls the operation of the fluid circulation system to prevent undesired flow of fluid within the system when the fluid transfer device is not in operation. More particularly, when operation of the pumps 128, 130 is stopped a pressure differential may be present in the fluid circulation system tending to cause fluid to flow from one part of the system to another. To prevent this undesired situation, the control system operates to close choke 150 in the drill pipe 142, valve 152 in the return line 132 or both devices. The adjustable fluid transfer device 130 will be explained below in more detail with reference to
In the embodiment shown in
The fluid transfer device 130 may be used in conjunction with any kind of subsea drilling system; riserless tophole drilling (pre-blowput preventer or pre-BOP), riserless post-BOP drilling (as shown in
In some embodiments, the power fluid 69 may be less dense than the working fluid M. In such embodiments, the valves to be explained with reference to
As explained above, in some embodiments the working fluid M may be less dense than the power fluid 69. In such embodiments, valves 66 (explained further below) may be coupled to the ports 71 at the top of the pressure vessel(s) 60, 62. Valves 64 would be coupled to the corresponding ports 71 at the bottom of the pressure vessel(s) 60, 62.
The system shown in
In some embodiments, a device 77 may be included between the wellbore discharge (35 in
When the selected level of working fluid M is reached such that the inlet valve is closed, another power operated valve 74 (outlet valve) may be opened to discharge the power fluid 69 into the water 12. When the power fluid 69 is so depressurized, working fluid M can then flow into the bottom of the pressure vessel 60, 62 until the level of the barrier fluid L reaches a predetermined height inside the pressure vessel 60, 62. One way (check) valves 66 may be provided between the drilling fluid (mud) outlet on the wellbore (35 in
In certain situations, particularly during a gas kick (uncontrolled entry of formation gas into the wellbore), there may be a risk of gas-hydrates forming. The extent of gas hydrate formation will be dependent on the amount of free gas present in the well bore, in combination with the existing specific pressure and temperature near the bottom of the riser.
To prevent hydrate formation, it may be desirable to use a power fluid 69 that has certain chemical properties to resist hydrate formation. Such properties may result in the fact that the power fluid cannot be discharged to the water (12 in
Valves 64 and 66 may be one way vales or combined into two way valves as appropriate.
Near the top of the interior of each pressure vessel 60, 62, a permeable plate 70 such as a perforated plate or other type of flow diffuser may be included to reduce the possibility of the power fluid 69 “jetting” into the working fluid M, thus reducing the possibility of mixing the power fluid 69, the barrier fluid L and the working fluid M.
Generally speaking deep water drilling muds have specific gravity in the 10 to 18 pounds per gallon range or higher, nominally thus being dimensionless specific gravity of 1.2 to 2.16 or greater. Seawater is generally understood to have specific gravity of 1.025, however seawater specific gravity can vary based on pressure, salinity and temperature. In wellbore drilling, the specific gravity of seawater may be slightly greater based on the temperatures and pressures existing along the riser, but could be effectively less that at the bottom of the wellbore if the drill pipe is pulled from the surface. Using 1.025 as the specific gravity of seawater translates to 8.54 pounds per gallon as contrasted with distilled water at 8.33 pounds per gallon or fresh water at a nominal 8.34 pounds per gallon.
The barrier fluid L fluid specific gravity (SG) may be intermediate to the SG of the power fluid 69 and the working fluid M. In some embodiments the barrier fluid L SG may be roughly midway between the power fluid 69 SG and the drilling mud or working fluid M SG. For example, the barrier fluid SG may be intermediate (midway) between seawater SG if seawater is used as the power fluid 69 and the drilling mud SG when drilling mud is the working fluid M. A suitable range of SG for the barrier fluid L in this example may thus be in a range from about 9.27 to 13.27 pounds per gallon or 1.11 to 1.59 dimensionless specific gravity (DSG). In some embodiments, the SG of the barrier fluid L may be more or less than midway between the SG of the power fluid 69 and the drilling mud (working fluid M) in order to optimize properties of the barrier interfaces for certain considerations, such as minimizing mixing or to enhance mixing with one or the other, improving ‘wiping’ properties within the pressure vessel 60, 62. In some embodiments, the barrier fluid L may be supplemented by a movable disk D which has a SG selected to cause the movable disk D to float on the top of the barrier fluid L or to float on the top of the working fluid M (thus being at the bottom of the barrier fluid L). A movable disk D may further reduce mixing of the power fluid 69, the barrier fluid L and the working fluid M. In some embodiments, a plurality of axially spaced apart disks may be used. Each of the plurality of disks may be axially separated by a rod or support, may be free floating on top of and at the bottom of the barrier fluid L or may be separated, e.g., by magnetic repulsion and/or magnetorheologically active compositions for the barrier fluid L.
The disk(s) D may be made from engineered materials such as plastics, phenolic, composites and or combinations of the materials for both density selection and mechanical/structural/wiping properties. The disk(s) may be, for example:
If the link(s) were long in relationship to the working length of the vessel and working/drilling fluid, then a change in the SG of the barrier fluid L may be used to be used to precisely adjust the bottom hole pressure (BHP) in the wellbore (below wellhead 18 in
More generally, when using an upper and lower disk having different effective densities to create a composite SG, the upper disk should be designed and weighted such as to be slightly ‘lighter’ (less dense) than the barrier fluid L but more dense than the power fluid 69 (e.g., seawater) above. This will cause the upper disk to remain substantially atop the barrier fluid L. The lower disk may be slightly more dense than the barrier fluid L and less dense than the working (drilling fluid) M. This will cause the lower disk to remain substantially atop the working fluid M. These disked could be linked by rod, chain or other device to further control their respective behavior,
The disks should have diameter to thickness ratio so to ensure the upper and lower surfaces thereof remain substantially perpendicular to the longitudinal axis of the pressure vessel and their desired motion. The value of this ratio likely in the range of 2, but will be a factor of the clearance between the disks/pucks and the bore and length of the working chamber.
In some embodiments multiple disks (more than two) could be used within the barrier fluid L to further improve the barrier fluid capacity to act to reduce mixing of the power fluid 69 and the working fluid M. Multiple disks would likely work best in a system where the disks are in some way linked by one or more ‘rods’. The ‘rod’ like device could be singularly mostly in the center of the disks, or the ‘rods’/links could be distributed in a radial fashion between the center and the disk edge.
The barrier fluid L may have a viscosity, polar/non polar solvent activity and surface tension properties such that the barrier fluid L tends to remain in a single contiguous mass; depending on surface tension properties and the polar/non-polar nature of the barrier fluid L it may or may not ‘wet’ the interior walls of the pressure vessel 60, 62. The barrier fluid L may act as a mass of jelly that tends to remain intact after being dropped into a container of fresh water or other fluid as might be considered for the working or drilling fluid. The barrier fluid L may also be a mass of selected SG non-polar liquid, such as oil, that floats within, above or below a water based fluid or other fluid type. In some embodiments the barrier fluid L may be hydrophobic to seawater (or the working fluid) and in the best case also hydrophobic to the drilling mud (working fluid M). The hydrophobic effect is the observed tendency of non-polar substances to aggregate when disposed in polar (aqueous) solutions and to thereby exclude polar liquid molecules from intermixing with the non-polar material.
In yet another embodiment the barrier fluid L may be two fluids where the upper fluid is hydrophobic to the seawater and the lower fluid is phobic to the drilling mud. The two barrier fluids may be slightly phobic with respect to each other; in some embodiments a SG difference keeps the two fluids substantially separated. Using one or more disks as explained above may improve performance.
A fluid transfer device used in a drilling system according to the various aspects of the present disclosure may provide lower maintenance costs, more efficient operation and lower cost to make than similar devices known in the art which rely on solid barriers to separate the working fluid from the power fluid.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
Priority is claimed from U.S. Provisional Application No. 62/420,579 filed on Nov. 11, 2016 and which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62420579 | Nov 2016 | US |