Method and system for circulating fluid in a well system

The present invention relates to a method for circulating drilling fluid in a drilling system and a system for circulating drilling fluid in a drilling system.

Underground coal deposits, also known as coal seams, contain significant amounts of methane. The production and use of methane from coal deposits has been going on for many years. However, major obstacles prevent the extensive development and use of methane deposits in coal seams.

For example, one of the problems in producing coal seam gas may be the difficulty sometimes posed by drilling under overpressure conditions caused by low reservoir pressure and made worse by the porosity of the coal seam.

In both vertical and horizontal surface drilling operations, drilling fluid, also known as drilling mud, is used to remove cuttings from the wellbore to the surface. The drilling fluid exerts a hydrostatic pressure on the formation which, if the pressure of such a formation is exceeded, may result in the loss of drilling fluid entering the formation. This manifests itself in the entrainment of the grooves from the drilling of the formations, which tend to clog pores, fractures and fractures that are needed for gas production.

Some methods are available for drilling under vacuum conditions. The use of a gas such as nitrogen in the drilling fluid reduces the hydrostatic pressure, but other problems may arise, such as increasing the difficulty of maintaining the desired pressure conditions in the well system while slowing down and joining the drill pipes.

According to the invention, a method for circulating drilling fluid in a wellbore system is characterized in that:

a first fluid is pumped through the segmental wellbore which segmental wellbore intersects a vertical wellbore in a node at least proximate the subterranean zone, a second fluid is conveyed down the vertical bore through a production line, the production line having an opening in the node so that the second fluid flows out from a production conduit at the node, the fluid mixture being returned to the top of the vertical bore outside the production conduit, wherein the fluid mixture comprises the first fluid. and adjusting at least the flow rate or composition of the second fluid supplied downstream of the vertical wellbore to regulate the bottom pressure to achieve negative pressure, balanced pressure or positive pressure drilling.

In a preferred embodiment, the method of circulating drilling fluid in a wellbore system is characterized in that:

a first fluid is pumped through a segmental wellbore, the segmental wellbore crossing a vertical bore in a node at least proximate to the subterranean zone, a second fluid is supplied down the vertical bore outside a production pipe located in the vertical wellbore, the production pipe having an opening in the subsoil; a node, where the liquid mixture is introduced into the production conduit opening at the node and returned to the top of the vertical borehole through the production conduit. and which fluid mixture comprises the first fluid, and at least the flow rate or composition of the second fluid supplied downstream of the vertical wellbore is adjusted to regulate the bottom pressure in order to achieve negative pressure, balanced pressure or positive pressure drilling.

Preferably, these methods drill a vertical surface to subterranean wellbore, drill a segmental surface to subterranean well using a drill pipe, drill a node drainage hole in the subterranean zone, the first fluid comprises drilling fluid, pumping the first fluid comprises pumping drilling fluid through the drill pipe when drilling a drainage hole, and the drilling fluid flows into the drill string at least in the vicinity of the drill bit of the drill string.

Preferably, supplying the second fluid downstream of the vertical well comprises supplying gas downstream of the vertical wellbore.

Preferably, the fluid mixture further comprises at least one of the components: gas supplied downstream of the vertical wellbore, subterranean fluid, and subterranean groove.

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Preferably, the method further comprises regulating the operation of pumping drilling fluid through the drill string to form a fluid seal, the fluid seal including a fluid level that opposes gas flow from the subterranean zone to the upstream well member.

Preferably, the fluid level opposes the flow of gas from the subterranean zone containing the coal seam or hydrocarbon reserves, and the second fluid supplied downstream of the vertical bore contains pressurized air.

On the other hand, the system for circulating drilling fluid through the boreholes is characterized by the fact that it includes:

a vertical borehole extending from the surface to the subterranean zone, a segmental borehole extending from the surface to the subterranean zone, the segmental borehole crossing a vertical borehole in a node at least near the subterranean zone, a drainage hole extending from a node in the subterranean zone, a drill pipe situated within the segmental well, which drill pipe is used to drill the drainage hole, drilling fluid supplied by the drill string and flowing from the drill string at least adjacent to the drill string, a production line located within a vertical wellbore, the production line having an open end at the node, fluid flowing down the vertical well, which flows from a production line at a node, the liquid mixture returning to the top of the vertical bore outside the production line, which fluid mixture contains drilling fluid after the drilling fluid exits the drill string, and wherein at least the flow rate or fluid composition provided downstream of the vertical wellbore is adjusted to regulate the bottom pressure of the system to achieve negative pressure, balanced pressure, or overpressure drilling .

In a second embodiment, the system for circulating drilling fluid through the wells is characterized in that it comprises:

a vertical borehole extending from the surface to the subterranean zone, a segmental borehole extending from the surface to the subterranean zone, the segmental borehole crossing a vertical borehole in a node at least near the subterranean zone, a drainage hole extending from a node in the subterranean zone, a drill pipe situated within the segmental well, which drill pipe is used to drill the drainage hole, drilling fluid supplied through the drill string and flowing out of the drill string at least adjacent to the drill bit of the drill string, a production line located within a vertical borehole, the production line having an opening in the node, the fluid flowing down the vertical well outside the production pipe, a liquid mixture flowing into the production conduit opening in the node and returning up the vertical borehole through the production conduit, which fluid mixture comprises drilling fluid after the drilling fluid exits the drill string, and wherein the flow rate of fluid supplied down the vertical well is changed to regulate the system bottom pressure to achieve negative pressure, balanced pressure, or positive pressure drilling.

Preferably, fluid supplied downstream of the vertical well comprises gas supplied downstream of the vertical wellbore.

Preferably, the fluid mixture comprises at least one of the following components: gas fed down the vertical borehole, subterranean fluid, and subterranean grooves.

Preferably, the system further comprises a fluid seal in the member wellbore, the fluid seal including a level of fluid that opposes gas flow from the subterranean zone to the top of the member wellbore.

Preferably, the fluid level opposes the flow of gas from the subterranean zone containing a thin coal seam or hydrocarbon resource.

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Preferably, the fluid supplied downstream of the vertical well comprises compressed air.

Preferably, the articulated wellbore is horizontally offset from the vertical surface wellbore.

Technical advantages of particular embodiments of the present invention include a method and system for circulating drilling fluid through a wellbore system that includes supplying gas downstream of a substantially vertical wellbore.

The flow rate of gas supplied downstream of a substantially vertical wellbore may be varied to achieve drilling under vacuum, balance pressure, and gauge pressure.

Accordingly, the susceptibility of the drilling operation and the recovery process can be improved.

Another technical advantage of particular embodiments of the present invention includes a fluid level in the articulated wellbore which acts as a fluid seal to resist the flow of formation fluid from the drill rig during the drilling process. Formation fluid that has been contained may contain a toxic gas such as hydrogen sulfide. Accordingly, drilling equipment and personnel can be isolated from the flow of toxic gas to the surface, thereby increasing the safety of the drilling system.

Yet another technical advantage of particular embodiments of the present invention is a method and system for circulating drilling fluid in a wellbore system that comprises pumping the fluid mixture up a substantially vertical bore through a pump column. The fluid mixture may include drilling fluid used in drilling processes and slots from the subterranean zone. Subterranean gas can bypass the pump column, allowing this gas to be recovered or burned separately from other fluid in the drilling system. In addition, the rate of pumping the fluid mixture up a substantially vertical borehole may be varied to achieve drilling under vacuum, balance pressure, or overpressure conditions.

Other technical advantages of the present invention will be apparent to those skilled in the art from the figures, descriptions and claims set forth below.

The subject of the invention is illustrated in exemplary embodiments in the drawing, in which Fig. 1 depicts fluid circulation in a wellbore system where fluid is supplied down a substantially vertical wellbore through a production conduit in accordance with an embodiment of the present invention; Figure 2 shows fluid circulation in a wellbore system where fluid is supplied downstream of a substantially vertical wellbore. and the fluid mixture is recirculated up the wellbore through a production conduit in accordance with the embodiment of the present invention, Fig. 3 depicts fluid circulation in a wellbore system where the fluid mixture is pumped up a substantially vertical bore through a pump column in accordance with an embodiment of the present invention. Figure 4 is a flowchart illustrating an exemplary method of fluid circulation in a wellbore system in which fluid is supplied. down a substantially vertical bore through a production conduit in accordance with an embodiment of the present invention, and Fig. 5 is a flowchart illustrating an exemplary method of fluid circulation in a wellbore system wherein the fluid mixture is pumped up a substantially vertical bore through a pump column, according to an embodiment of the present invention.

Fig. 1 shows the circulation of fluid in a wellbore system 10. The wellbore pattern comprises a subterranean zone which may contain a coal seam. It should be understood that other subterranean zones may similarly be accessed using the dual well system of the present invention for the removal and / or production of water, hydrocarbons, gas and other fluids in the subterranean zone and for treating minerals in the subterranean zone prior to mining operations.

As shown in Figure 1, a substantially vertical bore 12 extends from the surface 14 into the subterranean zone 15 of the target layer. A substantially vertical borehole 12 intersects and delves into the subterranean zone 15. A substantially vertical borehole 12 may be aligned with a corresponding casing 16 that terminates at or above the level of the coal seam or other subterranean zone 15.

The widened recess 20 may be formed in a substantially vertical bore 12 at the level of the subterranean zone 15. The enlarged recess 20 may have a different shape in various embodiments. The enlarged recess 20 provides a node for the intersection of a substantially vertical bore 12 by the segmental bore used to form a drainage hole in the subterranean zone 15. The enlarged recess 20 also provides a collecting point for fluids discharged from subterranean zone 15 during working operations. A vertical portion of substantially vertical borehole 12 extends below the enlarged recess 20 to form a sump 22 for the enlarged recess 20.

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A segmental wellbore 30 extends from surface 14 into an enlarged recess 20 of a substantially vertical wellbore 12. The segmental wellbore 30 includes a substantially vertical portion 32, a substantially horizontal portion 34, and a curved or radial portion 36 connecting vertical portion 32 to horizontal portion 34. Horizontal portion 34 lies substantially vertical. in the horizontal plane of subterranean zone 15 and intersects the enlarged recess 20 of substantially vertical wellbore 12. In a particular embodiment, the articulated wellbore 30 may not include a horizontal portion, for example when the subterranean zone 15 is not horizontal. In such a case, the articulated wellbore 30 may include a portion substantially in the same plane as the subterranean zone 15.

A segmental wellbore 30 may be drilled using an articulated drill pipe 40 that has a suitable downhole motor and drill bit 42. The drill rig 67 is at the surface. A Drill Measurement Device 44 (MWD) may be mounted in articulated drill pipe 40 to adjust the orientation and direction of a drill hole with the motor and drill bit 42. The substantially vertical portion 32 of the segmented wellbore 30 can be aligned with the corresponding casing 38.

After the enlarged recess 20 is cut by the segmental wellbore 30, drilling is continued through the enlarged recess 20 using drill string 40 and suitable horizontal drilling equipment to drill a drainage hole 50 in the subterranean zone 15. The drainage hole and other such wells are sloped, undulating or other slopes of a thin coal seam or subterranean zone 15.

During the drilling process for drainage hole 50, drilling fluid (such as "drilling sludge) is pumped to the bottom of articulated drill string 40 using a pump 64 and poured from the drill string 40 adjacent the drill bit 42, where it is used to flush the formation and remove it. cuts from this formation. The drilling fluid is also used in the drill bit 42 in cutting the formation. The overall flow of drilling fluid through and out of the drill string is indicated by the arrow 60.

The wellbore system 10 includes a valve 66 and a valve 68 in the piping between the articulated wellbore 30 and the pump 64. The valve 66 is open as drilling fluid is pumped down the articulated drill pipe 40 during drilling. When making connections to articulated drill string 40, when releasing the drill string, or otherwise when desired, valve 68 remains open to allow fluid (i.e., drilling fluid or compressed air) to be pumped down the articulated wellbore 30 out of the articulated drill string. 40, in the annulus between articulated drill string 40 and the surfaces of member wellbore 30. Pumping fluid downstream of the articulated wellbore 30 out of articulated drill pipe 40 when no active drilling is taking place, such as during connecting and releasing the drill string, enables the operator to maintain the desired bottom pressure in the articulated wellbore 30. Furthermore, fluids may be delivered through either valve 66. and valve 68 at the same time, if desired. In the embodiment shown, the valve 68 is partially open to allow fluid to flow down through the segmented wellbore 30.

When the pressure in the segmental wellbore 30 is greater than the pressure in the subterranean zone 15 ("formation pressure), the well system is considered to be under overpressure. When the pressure in the segmental wellbore 30 is less than the pressure in the formation, the wellbore system is considered to be under a negative pressure. When drilling under overpressure conditions, the drilling fluid and entrained grooves may be lost and enter the subterranean zone 15. Loss and entry of drilling fluid and cuttings into the formation is not only costly due to the loss of drilling fluids that need to be replenished, but risks clogging the pores in the subterranean zone that are needed to evacuate gas and water from that zone.

Fluid, such as compressed air or other suitable gas, may be supplied downstream of substantially vertical wellbore 12 through production conduit 80. In the illustrated embodiment, gas is supplied through production conduit 80, however, it will be understood that production conduit 80, in other cases, is In exemplary embodiments, other fluids may be provided. The gas may be supplied through the production line using an air compressor 65, a pump, or other means. The gas flow is generally indicated by arrow 76. The production conduit has an open end 82 at the enlarged cavity 20 such that gas flows from the production conduit at the cavity 20.

The flow rate of gas or other fluid supplied downstream of substantially vertical wellbore 12 may be varied to alter the bottom pressure in the articulated wellbore 30. In addition, the composition of the gas or other fluid supplied downstream may be altered to alter the bottom pressure.

By varying the bottom pressure in the segmental wellbore 30, desired drilling conditions, such as vacuum, balanced pressure, or overpressure drilling, can be achieved.

The drilling fluid pumped through the articulated drill pipe 40 mixes with gas or other fluid supplied through the production line 80 to form a fluid mixture. The fluid mixture flows up a substantially vertical bore 12 outside the production conduit 80. Such fluid mixture flow is generally indicated by arrow 74 in Figure 1. The fluid mixture may also include slots from subterranean zone 15 drilling and subterranean fluid 15, such as water. or methane.

The drilling fluid pumped through the articulated wellbore 30 out of the articulated drill string 40 may also mix with gas to form a fluid mixture flowing up the substantially vertical wellbore 12 out of the production conduit 80.

The segment wellbore 30 also includes a fluid level 39. Level 39 may be formed by adjusting the rate of pumping fluid by the pump 64 and / or the rate of fluid introduction by the air compressor 65. This fluid level acts as a fluid seal to provide resistance to the flow of fluid in the formation, such as a toxic gas from the formation (e.g. example, hydrogen sulfide), upstream of the member 30. Such resistance is due to the hydrostatic pressure of the fluid level in the member 30. Thus, the drilling rig 67 and its personnel can be isolated from the formation fluid which may contain toxic gas flowing up and out of the articulated well 30 at the surface. In addition, the larger ring in substantially vertical bore 12 allows the cuttings to return to the surface at a lower pressure than when the cuttings are returned upstream of the articulated wellbore 30 outside of articulated drill pipe 40.

The desired bottom pressure may be maintained during drilling, even when additional rings of articulated drill string 40 are required as the amount of gas pumped down the substantially vertical wellbore 12 may vary to offset the change in pressure resulting from the use of additional rings in the drill string.

Fig. 2 illustrates fluid circulation in a wellbore system 410 in accordance with an embodiment of the present invention. The pattern 410 is similar in many respects to the well pattern 10 of FIG. 1, however, the circulation of fluid in the pattern 410 is different from that of the pattern of the wells 10. The pattern 410 includes a generally vertical borehole 412 and a segment borehole 430. a substantially vertical bore 412 in enlarged cavity 420. A segment wellbore 430 includes a substantially vertical portion 432, a curved portion 436, and a substantially horizontal portion 434. The segmental wellbore intersects the enlarged recess 420 of substantially vertical wellbore 412. A substantially horizontal portion 434 of segmental wellbore 430 is drilled through subterranean zone 415. drill pipe 440, which includes a downhole motor and drill bit 442. A drainage hole 450 is drilled with an articulated drill pipe 440.

The drilling fluid is pumped through the articulated drill pipe 440 as described above with reference to Fig. 1. The overall flow of such drilling fluid is indicated by arrow 460. The drilling fluid may mix with the fluid and / or chutes from the subterranean zone 415 after the drilling fluid flows out of the borehole. articulated drill pipe 440. By using valve 468, fluids may be conducted downstream of articulated bore 430 outside articulated drill pipe 440 during a joining or release operation or other circumstances as desired, such as the falling fluid shown in FIG. 1.

Fluid, such as compressed air, may be supplied downstream of substantially vertical bore 412 in the annulus between production conduit 480 and the surface of essentially vertical borehole 412. In the embodiment shown, gas is supplied downstream of essentially vertical bore 412 outside production conduit 480, however, it should be understood that other fluids may be provided in other embodiments. Gas or other fluid may be supplied by an air compressor 465, pump, or other device. Gas flow is generally indicated by arrow 476.

The flow rate of gas or other fluid supplied downstream of substantially vertical wellbore 412 may be varied to alter the bottom pressure in member wellbore 430. In addition, the composition of gas or other fluid supplied downstream of substantially vertical wellbore 412 may be varied to alter the bottom pressure. change of the bottom pressure in the segment bore 430,

Desired drilling conditions, such as drilling under vacuum, balanced pressure, or overpressure, can be achieved.

The drilling fluid pumped through articulated drill pipe 440 is mixed with gas or other fluid supplied downstream of substantially vertical borehole 412 outside of production conduit 480 to form a fluid mixture. The fluid mixture flows into open end 482 of production conduit 480 and flows upwardly vertical borehole 412 through production conduit 480. Such fluid mixture flow is generally indicated by arrow 474. The fluid mixture may also include slots from subterranean zone 415 drilling and subterranean zone 415 fluid, such as water or methane. Fluid pumped through the articulated bore 430 out of articulated drill pipe 440 may also mix with gas to form a fluid mixture flowing up essentially vertical bore 412 out of production conduit 480.

Fig. 3 illustrates fluid circulation in a wellbore system 110 in accordance with an embodiment of the present invention. The wellbore pattern 110 includes a substantially vertical wellbore 112 and a segmental wellbore 130. A segmental wellbore 130 intersects a substantially vertical wellbore 112 within an enlarged recess 120. A segmental wellbore 130 includes a substantially vertical portion 132, a curved portion 136, and a substantially horizontal portion 134. The segmental wellbore cuts through the enlarged recess 120. a substantially vertical borehole 112. A substantially horizontal portion 134 of the segmented wellbore 130 is drilled through the subterranean zone 115. The segmental wellbore 130 is drilled using an articulated drill string 140 that includes a downhole motor and drill bit 142. A drainage hole 150 is drilled using an articulated drill pipe 140.

A substantially vertical wellbore 112 includes a column 180 that includes an inlet 182 located within the enlarged cavity 120. The drilling fluid is pumped through the articulated drill string 140 as described above with reference to Figure 1. The overall flow of such drilling fluid is indicated by arrow 160. The drilling fluid may be mix with the fluid and / or chutes from the subterranean zone 150 to form a fluid mixture after the drilling fluid flows from the articulated drill pipe 140.

The fluid mixture is pumped up through a substantially vertical bore 112 through pump inlet 182 and pump column 180 using pump 165 as generally indicated by arrow 172. Gas 171 from the formation from subterranean zone 115 flows up essentially vertical bore 112 to lower pressure areas. bypassing pump inlet 182. Thus, particular embodiments of the present invention provide a method of pumping fluid out of the double well pattern through the pump column and limiting the amount of formation gas pumped through the column. The gas 171 from the formation may be burned at the outlet as shown, or recovered.

The rate of pumping the fluid mixture up essentially vertical bore 112 through the pump column 180 may be varied to vary the fluid level and bottom pressure of the bore system 110. By varying the fluid level and bottom pressure, desired drilling conditions, such as vacuum drilling, can be achieved. balanced pressure or overpressure. A substantially vertical borehole 112 includes a pressure sensor 168 operable to sense pressure in substantially vertical borehole 112. A pressure sensor 168 may be electrically coupled to the motor 167 of pump 165 to automatically vary the speed of pump 165 based on pressure present at certain locations of the wellbore system 110. W In other embodiments, the speed of pump 165 may be manually changed to achieve desired drilling conditions.

When making connections to the articulated drill pipe 140, while releasing the drill string, or at other times as desired, the drilling fluid may be pumped through the articulated wellbore 130 out of the articulated drill pipe 140. The drilling fluid may mix with the fluid and / or chaffing from the subterranean zone 115 to form a fluid mixture pumped upwards of a substantially vertical bore 112 through column 180 of the pump.

Fig. 4 is a flowchart illustrating an exemplary method of circulating a fluid in a wellbore system according to an embodiment of the present invention. The method begins in step 200 where a substantially vertical borehole is drilled from the surface to the subterranean zone. In particular embodiments, the subterranean zone may contain a thin coal seam or hydrocarbon reserves. In step 202, a segment wellbore is drilled from the surface to the subterranean zone. A segment borehole is drilled with a drill pipe. A segmental wellbore is horizontally offset from a substantially vertical surface wellbore and intersects a substantially vertical wellbore at a node proximate the subterranean zone. The node may be in an enlarged recess.

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Step 204 includes drilling a drainage hole from the node in the subterranean zone. At step 206, the drilling fluid is pumped through the drill string during the drainage hole drilling operation. The drilling fluid may exit the drill string in the vicinity of the drill bit of the drill string.

In step 208, gas such as pressurized air is supplied down a substantially vertical borehole through the production conduit. In other embodiments, other fluids may be delivered down a substantially vertical bore through a production conduit. The production line has an opening in the node so that the gas leaves the production line at the node. In particular embodiments, gas is mixed with the drilling fluid to form a fluid mixture that returns to the top of a substantially vertical bore outside the production conduit. The fluid mixture may also contain fluid and / or grooves from the subterranean zone.

The flow rate or composition of gas or other fluid supplied downstream of a substantially vertical wellbore may be varied to adjust the pressure of the bottom system to achieve desired drilling conditions, such as vacuum, balanced pressure, or overpressure drilling.

Fig. 5 is a flowchart illustrating an exemplary method of circulating a fluid in a wellbore system according to an embodiment of the present invention. The method begins in step 300 where a substantially vertical borehole is drilled from the surface to the subterranean zone. In particular embodiments, the subterranean zone may contain a thin coal seam or hydrocarbon reserves. In step 302, a segmented wellbore is drilled from the surface to the subterranean zone. A segmental wellbore is drilled using a drill pipe. A segmental wellbore is horizontally offset from a substantially vertical surface wellbore and intersects a substantially vertical wellbore at a node proximate the subterranean zone. The node may be in an enlarged recess.

Step 304 involves drilling a drainage hole from the node to the subterranean zone. In step 306, the drilling fluid is pumped through the drill string as the drainage hole is drilled. The drilling fluid may flow out of the drill string in the vicinity of the drill bit of the drill string. In step 308, the pump column is routed down a substantially vertical wellbore. The pump column has an inlet near the node. In step 310, the fluid mixture is pumped up a substantially vertical bore through the pump column. The liquid mixture flows into the column at the pump inlet. The fluid mixture may contain drilling fluid after the drilling fluid exits the column, the fluid exits the subterranean zone, and / or the recesses exits the subterranean zone.

The rate of pumping the fluid mixture up a substantially vertical bore through the pump column may be varied to adjust the bottom pressure to achieve desired drilling conditions such as vacuum, balanced pressure, or gauge pressure drilling.