Patent Application
20170275954
The present disclosure relates generally to drilling systems, and particularly to a drilling system for oil and gas exploration and production operations. More specifically, the present disclosure provides a seal pressure compensation mechanism for a lower rotary seal assembly of a rotary drilling device.
Directional drilling in oil and gas exploration and production has been used to reach subterranean destinations or formations with a drilling string. One type of directional drilling involves rotary steerable drilling systems that allow a drill string to rotate continuously while steering the drill string to a desired target location in a subterranean formation. Rotary steerable drilling systems are generally positioned at a lower end of the drill string and typically include a rotating drill shaft or mandrel, a housing that supports the rotating drill shaft, and additional components that seal a space between the housing and the rotating drill shaft from entry of drilling fluids and other debris. Under normal operating conditions, a hydrostatic pressure exerted on the drill string increases with drilling depth. What is needed is a seal pressure compensation mechanism for a lower rotary seal assembly located at a lower end of the drill string.
Implementations of the present technology will now be described, by way of example only, with reference to the attached figures, wherein:
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure.
In the following description, terms such as “upper,” “upward,” “lower,” “downward,” “above,” “below,” “downhole,” “uphole,” “longitudinal,” “lateral,” and the like, as used herein, shall mean in relation to the bottom or furthest extent of, the surrounding wellbore even though the wellbore or portions of it may be deviated or horizontal. Correspondingly, the transverse, axial, lateral, longitudinal, radial, and the like orientations shall mean positions relative to the orientation of the wellbore or tool. Additionally, the illustrated embodiments are depicted so that the orientation is such that the right-hand side is downhole compared to the left-hand side.
Several definitions that apply throughout this disclosure will now be presented. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “communicatively coupled” is defined as connected, either directly or indirectly through intervening components, and the connections are not necessarily limited to physical connections, but are connections that accommodate the transfer of data, fluids, or other matter between the so-described components. The term “outside” refers to a region that is beyond the outermost confines of a physical object. The term “inside” indicates that at least a portion of a region is partially contained within a boundary formed by the object. The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other thing that “substantially” modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The terms “comprising,” “including” and “having” are used interchangeably in this disclosure. The terms “comprising,” “including” and “having” mean to include, but not necessarily be limited to the things so described.
The term “radial” and/or “radially” means substantially in a direction along a radius of the object, or having a directional component in a direction along a radius of the object, even if the object is not exactly circular or cylindrical. The term “axially” means substantially along a direction of the axis of the object. If not specified, the term axially is such that it refers to the longer axis of the object.
The term “drillpipe” means any conduit that extends downhole to support drilling operations. The drillpipe is coupled to a drill bit provided at the downhole end of the drillpipe. The drillpipe may include a drill string, coil tubing, or any other conduit that extends downhole to support drilling or workover operations. The drill string may include drillpipe of pre-determined lengths, such as 30 feet, 90 feet, or the like. The coil tubing may include continuous piping of several hundred feet or greater or less.
“Processor” as used herein is an electronic circuit that can make determinations based upon inputs and is interchangeable with the term “controller”. A processor can include a microprocessor, a microcontroller, and a central processing unit, among others. While a single processor can be used, the present disclosure can be implemented over a plurality of processors, including local controllers provided in a tool or sensors provided along the drillpipe.
According to one example, open-hole operations are employed during well construction. The open-hole operations typically include forming casing strings, such as a surface casing and intermediate casing. If a well is determined to be viable, then well completion may include forming a production casing for cased-hole operations.
Disclosed herein is a seal pressure compensation mechanism for a rotary seal assembly provided on a downhole portion of a drillpipe. The rotary seal assembly may include a seal carrier having grooves that seat a primary rotary seal and a barrier seal. The primary rotary seal may be positioned between a rotating drilling shaft or mandrel and a non-rotating housing of the drillpipe to form a seal between internal and external components of the drillpipe. The barrier seal may be positioned between the rotating drilling shaft and the non-rotating housing of the drillpipe and may be situated further downhole and closer to the drill bit as compared to the primary rotary seal. The primary rotary seal and the barrier seal are oriented relative to each other such that the barrier seal reduces exposure of the primary rotary seal to drilling fluid and other debris originating from outside the drillpipe. Thus, the barrier seal may be provided to increase a life span of the primary rotary seal. One of ordinary skill in the art will readily appreciate that the rotary seal assembly may include a seal carrier having grooves that seat a plurality of primary rotary seals and/or a plurality of barrier seals.
The barrier seal may be radially positioned between the rotating drilling shaft and the housing. According to one example, the barrier seal may be provided adjacent or proximate to the downhole end of the housing and may contact a wear sleeve provided on the rotating drilling shaft. In this way, the housing may define a compartment or container for the contents located therein. According to one example, the compartment may be an enclosed compartment when sealed.
The drill bit 110 is located at the bottom, distal end of the drillpipe 112 that supports various components along its length. During the open-hole operations, the drill bit 110 and the drillpipe 112 are advanced into the earth 104 by a drilling rig 120. The drilling rig 120 may be supported directly on land as illustrated or on an intermediate platform if at sea.
The wellbore 102, which is illustrated extending downhole into the Earth's layers, and any components inside the wellbore 102 are subjected to hydrostatic pressure originating from subterranean destinations or formations. The hydrostatic pressure acting on the drillpipe 112 provided inside the wellbore 102 is identified as formation hydrostatic pressure. The hydrostatic pressure originating from within the drillpipe 112 is identified as backpressure hydrostatic pressure. As the drilling depth increases, a hydrostatic pressure differential may develop between the outside formation hydrostatic pressure and the backpressure hydrostatic pressure. For example, the hydrostatic pressure differential may increase as the drilling depth increases. If the hydrostatic pressure differential acting on the drillpipe 112 is not compensated, then hydrostatic pressure differential may crush the drillpipe 112 and/or force minerals, such as oil and gas, into the drillpipe 112. In either situation, the effect of the hydrostatic pressure differential may disrupt drilling operations.
The lower end portion of the drillpipe 112 may include a drill collar proximate the drilling bit 110. The drill bit 110 may take the form of a roller cone bit or fixed cutter bit or any other type of bit known in the art. Sensor sub-units 130, 132 are shown within the cased portion of the well and can be enabled to sense nearby characteristics and conditions of the drillpipe, formation fluid, casing, and surrounding formation. Data indicative of sensed conditions and characteristics is either recorded downhole, for instance at a processor (now shown) for later download or communicated to the surface either by wire using repeaters 134,136 up to surface wire 138, or wirelessly or otherwise. If wirelessly, the downhole transceiver (antenna) 134 may be utilized to send data to a local processor 140, via surface transceiver (antenna) 142. The data may be either processed at processor 140 or further transmitted along to a remote processor 144 via wire 146 or wirelessly via antennae 142 and 148. A surface installation 170 may be provided to send and receive data to and from the well via repeaters 134,136. The data may include well conditions such as formation hydrostatic pressure, backpressure hydrostatic pressure, well depth, temperatures, or the like. For purposes of completeness,
With reference to
The rotary seal assembly 202 provides a transition between the stationary housing 335 and the rotating driveshaft 310. The seal carrier 302 also may include a recess portion that receives a bearing 308 that facilitates rotation of a driveshaft 310 relative to the rotary seal assembly 202. The driveshaft 310 may include a conduit 312 therethrough for passing drilling fluid through an interior of the driveshaft 310 during drilling operations. The conduit 312 may be tubular or hollow to permit drilling fluid (mud) to flow therethrough in a relatively unrestricted and unimpeded manner. The driveshaft 310 may be formed from any material suitable for and compatible with rotary drilling. According to one example, the driveshaft 310 may be formed from high strength stainless steel.
With reference to
Returning to
As a point of reference, the hydrostatic pressure during downhole operations may exceed 20,000 pounds per square inch (“psi”). Without a seal pressure compensation mechanism for the seals, the barrier seal 304 and the primary rotary seal 306 may be subjected to large net pressure differentials during downhole operations. Under such conditions, the barrier seal 304 and the primary rotary seal 306 may deform and fail. Due to size limitations within the drillpipe 112 in the area proximate to the barrier seal of 304 and the primary rotary seal 306, it may not be feasible to employ balance piston structures to hydrostatically equalize these seals.
By way of comparison, a separate tool pressure compensation system is typically employed within drilling tools to prevent large net pressure differentials from developing on the drillpipe 112 during downhole operations. The tool pressure compensation systems are designed to include various seals that counteract external hydrostatic pressure acting on the drillpipe 112. If not properly equalized, the external hydrostatic pressure may deform the drillpipe 112, which may cause drilling tools located within the drillpipe 112 to fail.
According to one example, drilling tools provided within the drillpipe 112 may include a tool pressure compensation system, such as a pressure-responsive piston and a pressuring pump. The tool pressure compensation system may include a balance piston that hydrostatically equalizes the pressure of components inside the drillpipe 112 against hydrostatic pressure exerted on an outside surface of the drillpipe 112. One of ordinary skill in the art will readily appreciate that mechanisms other than pressure-responsive pistons may be employed to compensate for any pressure differentials.
With reference to
With reference to
A check valve may be designed to open to enable fluid flow therethrough when a differential pressure across the check valve exceeds a crack pressure. For example, the fluid flow may be enabled in a single direction through the check valve. According to one example, the check valve may include a screen on the inlet side to prevent large particles from entering into and clogging the check valve. Furthermore, the check valve may be designed to close to block fluid flow therethrough when a differential pressure across the check valve is below the crack pressure. According to one example, when the valve 502 situated between the primary rotary seal 306 and the barrier seal 304 opens, it may draw fluid such as oil into the aperture 402 formed between the primary rotary 306 seal and the barrier seal 304. Any pressure differential between the primary rotary seal 306 and the barrier seal 304 may be equalized when the valve 502 opens and fluid may fill the aperture 402. According to one example, the valve 502 may be designed with a predetermined crack pressure. For example, the crack pressure may be in a range of 50 psi to 1,000 psi. Alternatively, the crack pressure may be in a range of 100 psi to 1,000 psi. One of ordinary skill in the art will readily appreciate that the valve 502 may be designed to support various crack pressures.
According to one example, a downhole tool may include a pressure compensation mechanism to counteract the hydrostatic pressure acting on the downhole tool. For example, if the hydrostatic pressure is 20,000 psi during downhole operations, then the pressure compensation mechanism of the downhole tool may generate a 20,000 psi back pressure to counteract the hydrostatic pressure acting thereon. Alternatively, the pressure compensation mechanism of the downhole tool may generate a 20,000 psi back pressure plus some additional back pressure to counteract the hydrostatic pressure acting thereon. For example, the additional back pressure may be in a range of 1 psi to 200 psi. Accordingly, the pressure compensation mechanism of the downhole tool may generate back pressure in a range of 20,001 psi to 20,200 psi to counteract hydrostatic pressure of 20,000 psi. One of ordinary skill in the art will readily appreciate that other values may be employed for the additional back pressure.
Returning to the example above, if the hydrostatic pressure is 20,000 psi during downhole operations, then the pressure compensation mechanism of the downhole tool may generate a 20,000 psi back pressure to counteract the hydrostatic pressure acting thereon. In this example, no additional back pressure is being applied. If a valve 502 having a crack pressure of 1,000 psi is selected, then the pressure within the aperture 402 may be equalized to approximately 19,050 psi, which is the value of the crack pressure below the internal pressure of the drillpipe 112. In this example, 19,050 psi is approximately 1,000 psi below the 20,000 psi internal pressure of the drillpipe 112. Furthermore, with the aperture 402 equalized to 19,050 psi, the pressure exerted across the barrier seal 304 is approximately 950 psi (or 20,000 psi−19,050 psi). Additionally, if the aperture 402 is equalized to 19,050 psi, the pressure exerted across the primary rotary seal 306 is approximately 1,000 psi (or 20,000 psi−19,050 psi).
By comparison, without the seal pressure compensation mechanism, the pressure within the aperture 402 may remain at atmospheric pressure of approximately 15 psi during downhole operations. Under similar conditions as described above, with external hydrostatic pressure of 20,000 psi and internal backpressure of 20,000 psi, the pressure exerted across the barrier seal 304 would be approximately 19,985 psi (or 20,000 psi−15 psi). Furthermore, the pressure exerted across the primary rotary seal 306 would be approximately 20,985 psi (or 20,000 psi−15 psi). Under these pressure conditions, the barrier seal 304 may collapse, which may allow drilling fluid 160 to penetrate into the aperture 402. Once the drilling fluid reaches the aperture 402, then the drilling fluid 160 may contact the primary rotary seal 306. Direct contact between the drilling fluid 160 and the primary rotary seal 306 may cause damage and eventual failure of the primary rotary seal 306.
The seal pressure compensation mechanism described herein provides several advantages over existing piston compensation mechanisms employed for seal pressure compensation. For example, as compared to existing piston compensation mechanisms having a pressure-responsive piston, the seal pressure compensation mechanisms described herein offer reduced size due to the relief port 307 and valve 502 being smaller in size compared to the pressure-responsive piston mechanism. Additionally, the seal pressure compensation mechanism described herein draws oil from the tool pressure compensation and therefore does not require a separate reservoir. By contrast, existing piston compensation mechanisms employed for seal pressure compensation require a separate reservoir and a separate oil fill.
According to one example, the rotating driveshaft 310 generates heat that dissipates into adjacent components during drilling operations. The heat may cause oil within the aperture 402 to thermally expand and exert counter-pressure or back pressure against any oil flowing through the relief port 307 illustrated in
With reference to
According to one example, the relief port 607 may fluidly couple the aperture 402 to an area external to the drilling tool. For example, the relief port 607 may fluidly couple the aperture 402 to an area exposed to drilling fluid or mud. By providing a fluid path external to the drilling tool, the relief port 607 and valve 602 may prevent pressure lock from developing due to thermal expansion of oil within the aperture 402 inside the drilling tool.
According to one example, the rotary seal assembly 202′ may include both the relief port 607 and valve 602, along with the relief port 307 and valve 502 (not illustrated). In this configuration, the relief port 307 and valve 502 perform seal pressure compensation as discussed above. As discussed above, the relief port 607 and valve 602 coupling the aperture 401 to the drilling fluid prevent pressure locking due to thermal expansion. Additionally, the seal carrier 302′ may include a cross-drilled port 611 to account for any size differential associated with introducing the valve 602 into the seal carrier 302′. If cross-drilled port 611 is provided, then pressure plugs 613 may be employed to plug the cross-drilled ports 611. One of ordinary skill in the art will readily appreciate that other techniques may be used to appropriately size the seal carrier 302′. Alternatively, one of ordinary skill in the art will readily appreciate that any sizing adjustments may be avoided altogether if the seal carrier 302′ is appropriately sized during manufacture.
Returning to
The method 800 may include detecting a preselected pressure differential (block 802). For example, the valve may be configured to detect a pressure differential of 1,000 psi. The valve may be configured as described above. The method 800 may further include opening a valve upon detecting the preselected pressure differential (block 804). For example, a check valve may be opened when the preselected pressure differential is detected. The method 800 also may include releasing pressure through a relief port provided between the primary rotary seal and the barrier seal. The valve may release pressure in a single direction through the relief port (block 806). Additionally, the method may include closing the valve when an actual pressure falls below the preselected pressure differential (block 808). In this way, the oil passing through the valve may be shut off to prevent depletion of the oil supply.
Numerous examples are provided herein to enhance understanding of the present disclosure. A specific set of examples are provided as follows. In a first example, a downhole rotary seal assembly is disclosed that includes a seal carrier having an inner surface; an outer surface; a first groove dimensioned to receive a first seal at the inner surface; a second groove dimensioned to receive a second seal at the inner surface; an aperture defined on the inner surface between the first groove and the second groove; a relief port positioned between the first groove and the second groove, the relief port being positioned to fluidly couple the aperture and the outer surface; and a valve provided in the relief port.
In a second example, there is disclosed herein the downhole rotary seal assembly according to the first example, wherein the first groove is positioned uphole of the second groove and wherein the first seal is a primary rotary seal and the second seal is a barrier seal.
In a third example, there is disclosed herein the downhole rotary seal assembly according to the first or second examples, wherein the valve is a check valve having a predefined crack pressure.
In a fourth example, there is disclosed herein the rotary seal assembly according to any of the preceding examples first to the third, wherein the seal carrier further comprises a second relief port positioned between the first groove and the second groove, the second relief port being positioned to fluidly couple the aperture and an area outside the downhole rotary seal assembly.
In a fifth example, there is disclosed herein the rotary seal assembly according to any of the preceding examples first to the fourth, wherein the check valve is a one way valve.
In a sixth example, there is disclosed herein the rotary seal assembly according to any of the preceding examples first to the fifth, wherein the seal carrier is dimensioned to fit over a driveshaft.
In a seventh example, there is disclosed herein the rotary seal assembly according to any of the preceding examples first to the sixth, wherein the seal carrier further includes at least one cross-drilled port and at least one pressure plug provided in the at least one cross-drilled port.
In an eighth example, a downhole rotary seal assembly is disclosed that includes a primary rotary seal; a barrier seal; and a seal carrier having an inner surface; an outer surface; a first groove dimensioned to receive the primary rotary seal at the inner surface; a second groove dimensioned to receive the barrier seal at the inner surface; an aperture defined on the inner surface between the first groove and the second groove; a relief port positioned between the first groove and the second groove, the relief port being positioned to fluidly couple the aperture and the outer surface; and a valve provided in the relief port.
In a ninth example, there is disclosed herein a downhole rotary seal assembly according to the preceding eighth example, wherein the first groove is positioned uphole of the second groove.
In a tenth example, there is disclosed herein a downhole rotary seal assembly according to any of the preceding examples eighth to ninth, wherein the valve is a check valve having a predefined crack pressure.
In an eleventh example, there is disclosed herein a downhole rotary seal assembly according to any of the preceding examples eighth to tenth, wherein the seal carrier further comprises a second relief port positioned between the first groove and the second groove, the second relief port being positioned to fluidly couple the aperture and an area outside the downhole rotary seal assembly.
In a twelfth example, there is disclosed herein a downhole rotary seal assembly according to any of the preceding examples eighth to eleventh, wherein the check valve is a one way valve.
In a thirteenth example, there is disclosed herein a method according to any of the preceding examples eighth to twelfth, wherein the seal carrier is dimensioned to fit over a portion of a driveshaft proximate to a drill bit.
In a fourteenth example a method is disclosed for equalizing pressure at an aperture positioned between a primary rotary seal and a barrier seal during downhole operations, the method includes detecting a preselected pressure differential between the aperture and an internal pressure; opening a valve upon detecting the preselected pressure differential; releasing pressure through the valve provided in a relief port located between the primary rotary seal and the barrier seal; and closing the valve when an actual pressure falls below the preselected pressure differential.
In a fifteenth example, there is disclosed herein the method according to the fourteenth example, wherein the pressure is released through the relief port in a single direction.
In a sixteenth example, there is disclosed herein the method according to the examples fourteenth and fifteenth, further comprising detecting a second preselected pressure differential between the aperture and an external pressure; opening a second valve upon detecting the second preselected pressure differential; releasing pressure through the second valve provided in a second relief port between the primary rotary seal and the barrier seal; and closing the second valve when a second actual pressure falls below the second preselected pressure differential.
In a seventeenth example, there is disclosed herein the method according to the examples fourteenth and sixteenth, wherein the valve is a check valve that automatically opens and closes based on the preselected pressure differential.
In an eighteenth example, there is disclosed herein the method according to the examples fourteenth and seventeenth, wherein the releasing pressure through the relief port includes passing oil through the relief port.
In a nineteenth example, there is disclosed herein the method according to the examples fourteenth and eighteenth, wherein the oil fills an aperture defined between the primary rotary seal and the barrier seal.
In a twentieth example, there is disclosed herein the method according to the examples fourteenth and nineteenth, wherein the preselected pressure differential is greater than 25 pounds per square inch.
The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size and arrangement of the parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms used in the attached claims. It will therefore be appreciated that the embodiments described above may be modified within the scope of the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/059088 | 10/3/2014 | WO | 00 |
