MXPA00002672A - Subsea drill fluid pumping and treatment system for deepwater drilling - Google Patents

Abstract

A method is disclosed for offshore drilling in which a bit (44) is driven at a far end of a drill string (34), drilling fluid (32) is injected into the drill string from surface drilling facilities, and drilling fluid flushes the borehole (16) at the bit and entrains drill cuttings (76). The drilling fluid is drawn off near the mudline and is treated through a subsea processing system (22) to remove the cuttings from the drilling fluid. The treated drilling fluid is then returned to the surface with a subsea return pump system (26) and passed to surface drilling facilities for injection and recirculation.

Description

PUMPING SYSTEM AND TREATMENT OF SUBMARINE PERFORATION FLUID FOR MARINE DRILLING IN The present invention relates to a method and system of offshore drilling. More particularly, the present invention is a method and system for handling drilling fluid circulation in offshore drilling operations.

Drilling fluids, also known as slurries, are used to cool the auger, making the cuts flow out of the auger formation interface and then out of the system, and to stabilize the drill hole with a "filter cake" until again cover the perforated sections. The drilling fluid also performs a crucial function for good control and is monitored and adjusted to maintain a pressure with a hydrostatic head in the open sections of the hole that prevents uncontrolled flow of pressurized well fluids into the formation hole. . REF .: 32955 In the conventional drilling fluid offshore, it is circulated down the drilling line and upwards through the annulus between the drilling line and the drilling hole below the mud interface. A duct surrounds the drilling line that starts from the reservoir in the ocean bottom surface to the surface drilling facilities and the drilling fluid return circuit continues from the mud interface to the surface through the annulus in the pipeline / drilling line.

In this conventional system, the relative weight of the drilling fluid on the seawater and the length of the pipeline in offshore applications combine to exert excess hydrostatic pressure at the annulus between the pipeline / drilling line and the annulus between the pierce / 1 ine of drilling.

U.S. Patent 4,813,495 discloses a system for hauling drilling fluid and dragging the angle cuts at the base of the duct and for deploying an underwater pump to facilitate return of the flow through a separate pipe. However, the durability and dependence of a sludge circulation system causes distrust in the offshore environment and particularly in view of the nature of the fluid with the trailing cuts that are handled in the valves and pumps in the return circuit segment. .

Therefore, there is a need for a method and potential system to reduce the excess hydrostatic pressure exerted by the return of the mud column in the annulus between the perforation pipeline or in the annulus between the pipeline / borehole. drilling.

According to one aspect of the invention there is provided a method of drilling an offshore drilling hole in the ground formation, the method comprising drilling the drill hole using a drill line extending into the drill hole; - Pumping a drilling fluid from the surface of the drilling facility through the drilling line, drilling fluid flows from the drilling line into the drilling hole by means of this cuts resulting from the drilling operation crawl in the drilling fluid; - treat the drilling fluid by inducing the drilling fluid to flow into an underwater processing system as well as to remove the drilling fluid cuts; and - returning the treated drilling fluid to the surface by means of a return pumping system.

The system for drilling an offshore drilling hole in the ground formation according to the invention comprises -. a perforation line that extends into the hole; a pump for pumping a drilling fluid from the surface of the drilling facilities through the drilling line and from the drilling line into the hole by means of which the cuts resulting from the drilling operation are dragged into the drilling fluid. drilling; - a subsea processing system to treat the drilling fluid by inducing the drilling fluid to flow into the subsea processing system as well as to remove the drilling fluid cuts; and a return pumping system to return the drilling fluid to the surface.

By treating the drilling fluid in the subsea processing system as well as removing the drilling cuts therefrom, it is achieved that the drilling fluid is substantially free of the cuts before it enters the return pumping system. The durability and ease of the return pump system is greatly improved by this.

Suitably the treated drilling fluid flows from the subsea processing system into a reservoir from which the drilling fluid flows into the return pumping system by means of a suction line. Thus, it is not necessary to ensure the synchronized operation of the pump of the drilling facilities on the surface and the underwater processing system, because the reserve acts as a buffer and allows variations of the level of the drilling fluid inside.

The invention will now be described in more detail and by way of example, with reference to the accompanying drawings in which: FIG. i is a schematic illustration of an embodiment of the subsea pumping system according to the invention; FIG. 2 is a side elevated view of another embodiment of the subsea pumping system according to the invention; FIG. 3 is a transverse sectional view taken longitudinally of the isolation valve of the drilling line of the IG. 2 in a closed position; and FIG. 4 is a transverse sectional view taken longitudinally of the isolation valve of the drilling line of the F1G. 2 in an open position.

Fig. 1 illustrates schematically one embodiment of a drilling fluid circulation system 10 in accordance with the present invention. The drilling fluid is injected into the drilling line at the drilling rig 12 above the surface of the ocean 14. Drilling fluid is transported down with a drilling line (see Fig. 2), through from the ocean and below hole .16 below the surface of the sludge 18. Near the lower end of the drilling line the drilling fluid passes through a perforation line isolation valve ("DSSOV") 20 and ejects from the drill line through the auger (referred to again in FlG 2). The drilling fluid runs through the bottom of the drilling hole 16, dragging the cuts, and returns to the surface of the sludge 18 inside the annulus 19. Here, near the floor of the ocean, the drilling mud is taken to an underwater processing facility primary 22 where the waste products, see line 24, are separated from the drilling fluid. These waste products include at least coarse cuts entrained in the drilling fluid. With these waste products 24 separated in the facilities 22, the processed drilling fluid proceeds to return with the subsea pump 26 where it is pumped to the surface drilling facilities 14. A second secondary processing facility 28 can be employed to separate the additional gas at low pressure and remove fines from the drilling fluid. The conditioned drilling fluid is supplied to the pumping system on the surface 30 and is ready for recirculation to the perforation line in the drilling equipment 12. This system removes the formation of the hydrostatic head of the mud between the surface and the floor marine and improves the life of the pump and reliability of the submarine return pumping system 26.

The embodiment of FIG. 1 can be used in both drilling operations with or without a drill pipe. In any case, the hydrostatic pressure of the mud back through the water column is isolated from the hydrostatic head under the escape prevention equipment, near the seabed. Of course, with sufficient insulation, the return path of the mud could advance upward in the annulus between the drilling / drilling line. However, it may be convenient to have a separate pipeline for the return of the mud if a drilling pipe is not used otherwise. In addition, even if it is not used as a pipeline back through the water column, it can conveniently have a drill pipe to move the escape prevention equipment and the separation equipment.

FIG. 2 illustrates the underwater components of an embodiment of the drilling fluid circulation system iO, with a drilling pipe that is not used to return the mud through the water column. The drilling fluid or sludge 32 is injected to the perforation line 34 which moves inside the marine drilling pipe 36, through an escape prevention equipment ("BOP stack") 38 near the surface of the sludge 18, through the cover 40, below the open hole 16 towards the bottom hole assembly 42 at the lower end of the perforation line. The bottom hole includes the DSSOV 20 and bit 44.

The flow of the drilling mud 32 through the drill line 34 and out of the auger 44 serves to cool the auger, making the cuts flow from the auger forming interface and to stabilize the open hole with a "filter cake". "until the additional cover line 40 is accommodated in new drilling directions. The drilling mud 32 also performs a crucial well control function by maintaining a pressure with a hydrostatic head in the uncovered sections of the drilling hole 16 which prevents the uncontrolled flow of the pressurized fluids from the well in the drilling hole from the well. training.

However, in this embodiment, the drilling mud is not returned to the surface through the annulus between the marine pipeline / drilling line 46, but is removed from the annulus near the surface of the mud 18, for example, immediately above. of the BOP 38 through the return line of the mud 19. In this illustration, with a drill pipe, the rest of the annulus 46, towards the surface of the ocean, is filled with sea water 48 which is much less dense that the drilling mud. Drilling applications in deep water can exert a hydrostatic head of a thousand meters or more on the base of the marine drilling pipeline 36. However, when this hydrostatic head is of sea water instead of drilling mud in the No. 32, the interior of the marine drill pipe remains substantially at ambient pressure relative to the external conditions of the pipeline at this depth. The same is true for the mud that leaves the hole in the well without the duct. This allows specification of the drilling mud to focus more clearly on the well control substantially from below the surface of the sludge.

The drilling mud 32 is returned to the surface in the drilling fluid circulation system 10 which includes the primary underwater processing system 22, the underwater return pump 26 and a second pipe 50 which serves as the mud return line. of drilling. The primary underwater processing system 22 is illustrated with a first two-component stage 22A contained in the lowermost section of the drill pipe 36 and a subsequent stage 22B in the ocean floor.

In normal operation, the solids removal system 54 first brings back the drilling mud 32. This solids removal system 54 is a box arranged with a sticky solid 68 that operates in a drying chamber with ambient pressure filled with gas 72. The hydrostatic head of sludge 32 within annulus 46 leads to the sludge through the sludge return line and into line 74 so that the slits go out to the removal equipment such as a mesh or a slipper with a sticky solid 78 The cuts 76 are also covered when passing through the mesh or through the slide with the sticky solid, detaching from its farthest edge of the iodine tank, and exiting directly to the ocean through the opening at the bottom of the chamber. 72. The sludge, minus the separate cuts, passes through the slide with sticky solid to the sludge tank 80 and flows from the tank 80 via a duct 66 to the sludge tank. 80A Remote maintenance inside the box arranged with sticky solid 68 can be facilitated with a spray-washing system to wash the slide with sticky solid with seawater and a closed loop with television monitor or other electronic data system in the camera. drying The accumulation of the cuts 76 in the well can be prevented by placing a cut-off plate of the cuts 84 under the drying chamber 72 to receive the cuts coming out of the drying chamber. An injection pump 86 injects seawater passing a venturi with a sufficient pressure drop to cause the seawater and any entrained cut to enter the discharge line of the cuts 88 coming from the cut-off plate of the cuts. 84. The cut-off discharge line then transports the cuttings to a sufficiently distant location such that piles of accumulated cuttings will not interfere with well operations.

Another advantage of this mode is that the gas resulting from the control of the well is removed by means of a gas separator 52 and is expelled near the sea floor 18. The operation of the pump in these well operations is critical. In a well control operation where large volumes of gas enter the well, the entire system must handle the gas volumes while creating a low pressure in reservoir 16 by pumping the heavier sludge down to a volume, velocity and enough pressure. Falling below this pressure in a well control operation will result in further reflux of the gas, since increasing the pressure to an excess can fracture the drill hole. The ability to completely recycle the mud with weights suitable for the immediate need is the main control in this critical pressure. However, multiphase flow is a challenge for conventional pumps that are otherwise coupled to the return submarine pump system 26. Thus, only substantially free gas slurry is pumped to the surface through the underwater return pumping system. 26, facilitating the pumping operation during the critical control operation of the well. The additional gas can be removed on the surface at atmospheric pressure with a gas separation system not shown.

The gas separator 52 includes a vertically oriented tank or vessel 58 having an outlet at the top which causes a gas to be vented 60 through an array of an inverted tube 62 and a device for removing the mud 64 near of its base that is connected to the return line 66 downstream of the solids removal system 54.

The subsequent stage of the processing system 22i is another solids removal system, in the form of a second arrangement of a box with sticky solid 68A in a drying chamber at atmospheric pressure filled with gas 72A. the hydrostatic head of the sludge 32 within the tank 80 causes the sludge to pass through a gate 74A so that the sludge comes out and pulls the cuts through closer spaced bars or a slipper with sticky solids with a fine mesh 78A. The separated sludge in the sludge / gas separator can be connected to the tank 80 in this second processing step. A fine degree of cutting is removed and removed with the cut-off discharge plate 84A and the injection pump 86A, as before, with the processed sludge passing to the sludge tank 80A.

It may also be desirable to provide the normal exit position of the tank and a tank volume that allows the accumulation of additional cuts capable of passing through the slide with sticky solid. A discharge valve with activated surface at the bottom of the mud tank can be used to periodically remove the accumulated cuts.

The suction line 94 of the underwater return pump 26 is fixed to the lower base of the sludge tank 80A. A liquid level control 90 in the lower part of the mud tank 8 OA activates the return pump 26. The removal of the sludge cuts greatly improves the operation of the pump in this high pressure pumping operation to return the cuts from the sea floor to the facilities above the surface of the ocean through the return duct 50. The return duct can conveniently be secured at its base to a foundation tai as an anchor pile 98 and supported at its upper end by surface facilities (not shown)H. , however, they are aided by buoyant modules (not shown) arranged along their length at intervals. In this embodiment, the return pump 26 is enclosed in an ambient pressure drying chamber 92 that provides work in the medium and simplifies the design and selection of the pump.

In the operation of the well control, the BOP stack 38 is closed and the gas separator 52 takes the fluid from the subsea shock lines 33 associated with the BOP stack 38. In the well control operation, the gas separator 52 it allows the removal of the gas from the sludge 32 so that the underwater pumping system 2 6 can operate with only one component in a single phase, for example, liquid sludge. The gas separator 52 can be conveniently mounted to the lowermost section of the duct 3 6.

FIG. 3 details the DSSOV 20 shown at the base of the perforation line 34 as part of the assembly at the bottom of the hole 42 in the F1G. 2. The DSSOV is an automatic valve that uses pressures of a cylinder piston / spring balance to close a valve 112 that contains the hydrostatic head of the drilling fluid 32 in the drill line when the assembly is placed on the bottom of the orifice and the normal circulation of the drilling fluid is interrupted, for example, in order to integrate. another section of the drill pipe in the drilling line. In these cases the DSSOV is closed to prevent the drilling fluid from going down and out of the drilling line and going up to ring 46, displacing the much lighter sea water until it reaches equilibrium.

FIGS. 3 and 4 illustrate the DSSOV 20 in the closed and open positions respectively. The DSSOV has a main body 120 and can be conveniently provided with connectors such as a threaded box 122 and a tip 124 at the other end to be integrated into the perforation line in the lower region of the hole assembly. The body 120 has a cylinder 128 that receives a piston 116 having a first pressure face 114 and a second pressure face 130. The first pressure face 114 is present on the face of the piston and moves inside a cylinder upwards of the DSSOV 20 through channel 132 passing through the piston. The channel 132 can conveniently be fixed with a lid for waste 134.

The second pressure face 130 is at the rear of the piston 116 and moves within a cylinder down from the DSSOV 20. In addition, the first and second faces of the piston 116 are insulated by w0"136 sealing rings. Sliding between the piston and the cylinder.

The body 120 also has a main flow path 140 interrupted by the valve 112, but is interconnected with the flow channels of the drilling mud 126. A plurality of "O" shaped rings 142 between the valve 112 and the body 120 it assulates the fluid from the sludge-drilling flow channels 126 except through the holes 118 of the valve 112.

The DSSOV is used to maintain a positive pressure in the drill pipe on the surface all the time. When the surface mud pumping system 30 (see FIG. 1) is isolated, for example, to add a section of drill pipe 34 while drilling is in progress, a spring tension of the isolating valve isolates the valve 112 to a closed position wherein the holes of the valve 118 are integrated with an alignment with the flow channels of the drilling mud 126 in the body 120. The spring 110, the surface area of the first pressure face 114, and the surface area of the second pressure face 130 of the piston 116 are balanced in the design of the valve being closed 112 to maintain the marginal pressure created by the difference in density between seawater 48 and the mud. 32 above the distance between the surface of water 14 and the ocean floor 18. Thus the excess positive pressure in drill pipe 34 is kept dissipating by moving the drilling mud towards the bottom of the pipe. e the drill pipe and up the annulus 46, which isolates the excess pressure from the drill hole 16.

After the new drillpipe section is engaged or the drilling is otherwise ready to proceed, the surface pumping system 30 (FIG.1) is used to increase the pressure in the valve 112 until the the face 114 of the piston 116 overcomes the influence of the spring 110, opening the valve 112 and continuing the circulation. See FIG.4.

The DSSOV 20 also provides a method to determine the required weight of the sludge in the operation of the well control. With the DSSOV closed, the pump pressure increases slightly while the leakage signs are monitored carefully, which is observed as an interruption of the pressure build-up despite the fact that the pump operation continues. These flow signals have been established and the pressure is recorded as the opening pressure of the DSSOV. The pumping system on the surface 30 is introduced with a reduced speed of the pump used to circulate the fluids out of the well while carefully monitoring the pressure to prevent further entry into the formation. The opening pressure, the reduced speed of the pump and the circulating pressure are each recorded periodically or when a significant adjustment of the mud weight has been made.

With this information, the pressure at the bottom of the hole can be determined by the well control operation occurring. After an isolated flow is detected the pumping system on the surface 30 will close the DSSOV 20. The excess pressure causes the event, that is, the unbalanced pressure of the formation, will be added to the pressure needed to open the valve 112. The valve pressure is then applied again and slowly increased, monitoring a leak signaling the resumption of flow. The difference in pressure between the pre-registered opening pressure and the pressure after the flow is the sub-balanced pressure that must be compensated by adjustments in mud density 32. The dead weight of the iodine is then calculated and drilled and make the adjustments according to the mud formulation.

In the illustrated embodiment, some of the components of the submarine primary processing system 22 are provided in the marine drilling rig36 and others are placed directly on the ocean floor 18. The components that are placed on the ocean floor may be useful. to deploy a minimum standard or at least guide posts and receiving funnels interconnected with the key components placed in subsea packages at secured, relatively prearranged positions. These facilities make the connections between the components placed as separate submarine packages with vehicles operated by remote control ("ROV"). These connections include power lines, gas supply lines, mud transport lines, and cut lines. A system of gas supply lines (not shown) each supplied with drying chambers 72, 72A, and 92 with gas to compensate for the volumetric understanding of the gas in the drying chambers opened at the bottom when air is trapped Atmospheric pressure on the surface is submerged at great depths. Other combinations of the submarine primary processing components and their placements are possible. In addition, some components may be deployed in the return duct 50 analogous to that deployed in the marine drilling duct 36.

In an alternate mode, the first and second stages of the processing system and the gas separator are mounted in a selected section of the duct. This selected section needs to be adequate in size to move through the aqueous body of the surface drilling facilities, preferably having a horizontal cutting section no larger than the external contour of the BOP stack. The components of this system, for example, a pair of boxes with sticky solid and a pair of gas / mud horizontal separators, are placed on a structure secured in the selected section of the duct. Also, cut-off plates, injection pumps, and cut-off lines can be placed in this section. This allows the connection between these components and the annulus inside the marine drilling duct and the BOP stack to assemble them in a modular manner on the surface before integrating the drilling pipe with the subsea well.

Other modifications, changes and substitutions are also attempted in the discussion of the procedure. In addition, in some cases, some features of the present invention will be employed without a corresponding use of other features described in these illustrative embodiments.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (10)

1. A method for drilling an offshore drilling hole in a land formation, the method comprises: drilling the drilling hole using a drill line that extends into the drill hole; - pumping a drilling fluid from the drilling facility on the surface through the drilling line, the drilling fluid flows from the drilling line into the drilling hole by means of these cuts resulting from the operation of drilling. perforation creep into the drilling fluid; - treat the drilling fluid by inducing the drilling fluid to flow into an underwater processing system as well as to remove the drilling fluid cuts; Y returning the treated drilling fluid to the surface by means of a return pumping system, wherein the drilling fluid flows into the subsea processing system by means of an outlet opening provided in a drilling duct, characterized in that the The drilling hole is provided with a cover and an escape prevention equipment (BOP) placed between the cover and the exit opening of the drill pipe, and the fluid flows through the drilling pipe through the lining and the BOP.

2. The method of claim 1, characterized in that the treated drilling fluid flows from the subsea processing system to a reservoir through which the drilling fluid flows into the return pumping system by means of a suction line thereof.

3. The method according to claim 1 or 2, characterized in that it also comprises passing the drilling fluid returning to the drilling facilities on the surface for its reinjection.

4. The method according to any of claim 1-3, characterized in that the step of treating the drilling fluid comprises passing the drilling fluid in a gas chamber at ambient pressure near the sea floor through a gate, separating the cuts in railings with sticky solid and pass the drilling fluid towards the collection pool, and transport the cuts away from the underwater processing system for disposal.

5. The method according to claim 4, characterized in that the transportation of the coasts away from the underwater processing system for the arrangement comprises the cuts at the end of the railing with sticky solid by means of an opening at the bottom of the ocean. the gas chamber at ambient pressure, the collection of the cuts in a discharge plate under the opening in the bottom of the gas chamber at ambient pressure, and bring the cuts of the discharge plate with an injection pump and boost cut them to a disposal site away from the underwater processing system through a cut-off line.

6. The method according to any of claims 1-5, characterized in that the step of treating the drilling fluid comprises separating any gas that enters the drilling fluid from the ground formation during a well operation upstream of the pumping system of return.

7. The method according to any of claims 1-6, characterized in that it further comprises treating the drilling fluid after returning to the surface in a secondary processing system to remove the gas and fine particles from the cut.

8. The method according to any of claims 1-7, characterized in that it further comprises selectively isolating the hydrostatic head of the drilling fluid in the drilling line from the relatively smaller fluid pressure in the drilling hole by means of an isolation valve. in the line of perforation activated by pressure placed in the line of perforation, when the circulation of the drilling fluid is interrupted.

9. A system for drilling an offshore drilling hole in a land formation, the system comprises - a drilling line that extends into the drilling hole; a pump for pumping a drilling fluid from the drilling facility on the surface through the drilling line and from the drilling line into the drilling hole by means of this the cuts resulting from the drilling operation are dragged in the drilling fluid; - an underwater processing system to treat the drilling fluid by inducing the drilling fluid to flow into an underwater processing system as well as to remove the drilling fluid cuts; and a return pumping system for returning the treated drilling fluid to the surface, the system further comprising a drilling duct provided with an exit opening for the drilling fluid to flow to the subsea processing system, characterized in that the bore The drilling rig is provided with a cover and an escape prevention equipment (BOP) placed between the cover and the exit opening of the drill pipe.

10. The system of claim 9, characterized in that it also comprises an isolation valve in the line of perforation activated by pressure placed in the line of perforation, this valve closes with a difference of pressure through the valve due to the interruption of circulation of fluid through the perforation line in order to prevent the outflow of drilling fluid from the perforation line into the drilling hole.