CN113818822A - Drilling fluid recovery system based on no marine riser - Google Patents
Drilling fluid recovery system based on no marine riser Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/001—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor specially adapted for underwater drilling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/10—Valve arrangements in drilling-fluid circulation systems
Abstract
Embodiments of the present description provide a drilling fluid recovery system based on a riser-free system. The system comprises a drilling fluid suction device, a subsea pump module, a return line and a drill pipe valve; the drilling fluid suction device is used for sucking the recovered drilling fluid in the riser into the subsea pump module; the subsea pump module is used for lifting the recovered drilling fluid to a drilling platform through a return line to complete recovery; the return pipeline is connected with the subsea pump module and the drilling platform so as to realize the transmission of the recovered drilling fluid from the subsea pump module to the drilling platform; the drill pipe valve is arranged in the non-marine riser and is in a closed state when the pressure applied to the drill pipe valve is not greater than the opening pressure threshold value; the drill rod valve blocks the drilling fluid in the drill rod from entering a drilling tool below the drill rod in a closed state; the cracking pressure threshold is not less than a pressure differential between hydrostatic pressure within the drill string and hydrostatic pressure at the subsea mudline. The system ensures zero emission to the submarine environment and is beneficial to the effective propulsion of production and development.
Description
Technical Field
The embodiment of the specification relates to the technical field of underwater exploration and development, in particular to a drilling fluid recovery system based on a riser-free pipe.
Background
Compared with the traditional marine drilling technology, the marine riser-free technology is applied to submarine oil gas exploitation, a marine riser is not used during well drilling of a borehole, a drill rod is directly exposed in seawater, drilling fluid is injected through the drill rod and is sprayed out based on a drill bit, mud, rock debris and recovered drilling fluid generated in the drilling process can pass through a borehole annulus return value subsea pump, and the recovered drilling fluid and the recovered rock debris are sent back to a sea surface drilling ship through a pipeline.
Based on the above-mentioned non-riser system, when the pressure at the inlet of the subsea pump is equal to the subsea pressure, the pressure in the drill pipe is not balanced with the pressure in the non-riser annulus, thereby generating a U-tube effect. Under the action of the U-shaped pipe effect, the drilling fluid in the drill rod flows along the drill rod and returns to the annular space through the underground drilling tool and the drill bit, and the drilling fluid recovery process is facilitated. However, when the drilling fluid circulation process is stopped due to the pump stopping check of the subsea pump, the balance state of the U-tube effect is broken, and the drilling fluid in the drilling well may still fall freely under the action of the pressure of the fluid column, so that the downhole condition is disturbed, and the normal operation of the drilling well is affected. Therefore, a method for effectively suppressing the U-tube effect during the pump stop inspection of the subsea pump is needed.
Disclosure of Invention
An object of the embodiments of the present specification is to provide a drilling fluid recovery system based on a non-riser pipe, so as to solve the problem of how to effectively overcome the U-shaped pipe effect during the pump stop inspection of a subsea pump.
In order to solve the technical problem, an embodiment of the present specification provides a drilling fluid recovery system based on a non-riser, including a drilling fluid suction device, a subsea pump module, a return line, and a drill pipe valve; the drilling fluid suction device is used for sucking the recovered drilling fluid in the riser into the subsea pump module; the subsea pump module is used for lifting the recovered drilling fluid to a drilling platform through a return line to complete recovery; the return pipeline is connected with the subsea pump module and the drilling platform so as to realize the transmission of the recovered drilling fluid from the subsea pump module to the drilling platform; the drill pipe valve is arranged in the non-marine riser and is in a closed state when the pressure applied to the drill pipe valve is not greater than the opening pressure threshold value; the drill rod valve blocks the drilling fluid in the drill rod from entering a drilling tool below the drill rod in a closed state; the cracking pressure threshold is not less than a pressure differential between hydrostatic pressure within the drill string and hydrostatic pressure at the subsea mudline.
According to the technical scheme provided by the embodiment of the specification, the drill rod valve is arranged in the non-marine riser, so that the drilling fluid is prevented from entering a drilling tool below the drill rod when the pressure applied to the non-marine riser is not greater than the opening pressure threshold, and the balance of the drilling fluid in the drill rod is ensured when the non-marine riser stops pumping for inspection. Correspondingly, the drilling fluid suction device is used for sucking the recovered drilling fluid in the non-marine riser into the subsea pump module, the subsea pump module is recycled, and the recovered drilling fluid is lifted to a drilling platform through a backflow pipeline to be recovered, so that the drilling fluid is recycled, the pollution caused by drilling cuttings is avoided, the zero emission of the subsea environment is ensured, meanwhile, the normal work of equipment is also ensured, the normal operation of the drilling process is ensured, and the effective propulsion of production and development is facilitated.
Drawings
In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the specification, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a block diagram of a riser-less drilling fluid recovery system according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram illustrating the application of force to a drill stem valve according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a riser-free structure according to an embodiment of the present disclosure;
FIG. 4A is a schematic illustration of the relationship between operating water depth and subsea pump pressure for different drilling fluid densities in accordance with an embodiment of the present disclosure;
FIG. 4B is a schematic diagram illustrating the relationship between the operating water depth and the lift of the subsea pump at different drilling fluid densities in accordance with an embodiment of the present disclosure;
FIG. 5A is a schematic diagram illustrating the relationship between drilling fluid density and subsea pump pressure at different water depths in accordance with an embodiment of the present disclosure;
FIG. 5B is a schematic diagram illustrating the relationship between the density of drilling fluid and the power of the subsea pump at different water depths according to an embodiment of the present disclosure;
FIG. 6A is a schematic diagram illustrating displacement versus subsea pump pressure for different drilling fluid densities in accordance with an embodiment of the present disclosure;
FIG. 6B is a schematic diagram illustrating displacement versus subsea pump power for different drilling fluid densities, in accordance with an embodiment of the present disclosure;
FIG. 7A is a schematic illustration of the relationship between the internal diameter of the return line and the pump pressure of the subsea pump at different drilling fluid densities in accordance with an embodiment of the present disclosure;
FIG. 7B is a schematic diagram illustrating the relationship between the internal diameter of the return line and the power of the subsea pump at different drilling fluid densities, according to an embodiment of the disclosure.
Detailed Description
The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present specification without any creative effort shall fall within the protection scope of the present specification.
In order to solve the technical problem, an embodiment of the present specification provides a drilling fluid recovery system based on a riser-free pipe. As shown in fig. 1, the riser-less drilling fluid recovery includes a drilling fluid intake device, a subsea pump module, a return line, and a drill pipe valve.
It should be noted that, the drilling fluid recovery system based on a non-riser provided by the present application belongs to a non-riser overall technical architecture, and only focuses on the portion of the non-riser overall technical architecture for recovering the drilling fluid, and in practical applications, the drilling fluid recovery system realizes the recovery of the drilling fluid based on the non-riser.
A riser-less is equipment used when drilling on the seabed. The marine riser-free drilling pipe does not additionally use a marine riser to isolate a drilling part from seawater, but realizes drilling by arranging a pipe in the pipe, drilling fluid is sprayed out from a drill bit based on an inner pipe, the drilling fluid is discharged to a seabed pump based on an annular space without the marine riser after being sprayed out from the drill bit, and the drilling fluid needing to be recovered is conveyed to the ground by the seabed pump to be recovered.
The seabed pump module is a module taking the seabed pump as a core, and the seabed pump is used for applying pressure, so that the recovered drilling fluid can be transmitted to a drilling platform on the ground, the drilling fluid can be recycled after the recovered drilling fluid is processed on the ground, and zero emission of the marine environment is also ensured. Correspondingly, the seabed pump can also reduce the annular pressure of the seabed without the marine riser by generating a certain pressure difference between the outlet and the inlet, so that the double-gradient drilling is realized.
The subsea pump not only plays a role in lifting and recovering drilling fluid, but also can control the pressure at the bottom of a well, so that the subsea pump has important significance for selection. Because the seawater around the subsea pump is corrosive, and the conveyed drilling fluid contains certain rock debris and gas, the overflowing part is abraded, and certain requirements are met on the corrosion resistance and the wear resistance of the subsea pump. In addition, based on the drilling requirements, the water depth and the drilling fluid density may be increased continuously, the lifting height of the subsea pump for the drilling fluid is also increased continuously, and the corresponding requirements for the lift and the power of the subsea pump also need to be met.
Based on the requirements, when the subsea pump is selected, the working environment information corresponding to the subsea pump module can be collected first, the working parameters of the subsea pump are calculated based on the working environment information, and then the subsea pump is selected through the working parameters of the subsea pump.
The working environment information may be an environmental parameter corresponding to a working environment in which the subsea pump is located, or may include a corresponding condition of the subsea pump during a working process. For example, the operating environment information may include at least one of a seawater depth, a seawater density, and a drilling fluid density. The depth and density of seawater can affect the pressure of seawater on the subsea pump, and the density of drilling fluid can also affect the actual working condition of the subsea pump. In practical application, other working environment information can be selected according to requirements to select the subsea pump, which is not limited to the above examples and is not described herein again.
The working parameters of the subsea pump are equipment parameters which the subsea pump needs to have in order to adapt to the working environment information, and are used for overcoming the influence of the working environment information. In some embodiments, the subsea pump is a pump for operationThe number may include the subsea pump head, which refers to the height at which the subsea pump can pump water, and since the subsea pump needs to transfer the recovered drilling fluid to the drilling platform at the sea surface, the subsea pump head is an important factor in selecting the subsea pump. FIG. 3 is a schematic diagram of a non-riser operation structure, wherein H iswThe depth of the sea water corresponding to the position of the sea bottom pump, PinFor the pressure at the inlet of the subsea pump, it can be seen that the subsea pump needs to overcome the corresponding water depth to pump out the recovered drilling fluid.
In some embodiments, when calculating the subsea pump head, the subsea pump head may be calculated by first calculating an inlet pressure corresponding to the subsea pump using the depth of the seawater and the density of the seawater, then calculating an outlet pressure corresponding to the subsea pump using the density of the drilling fluid and the depth of the seawater, and finally calculating the subsea pump head based on the inlet pressure and the outlet pressure.
During operations for recovering drilling fluid without a riser, the subsea pump is generally installed on the seabed, and the inlet pressure P of the subsea pumpinIs generally set to the hydrostatic pressure, and in particular, may utilize the formula Pin＝ρswgHwCalculating the inlet pressure, where PinIs the inlet pressure, pswIs the density of seawater, g is the acceleration of gravity, HwIs the depth of seawater.
Outlet pressure P of subsea pumpoutIs the sum of the drilling fluid clean water pressure in the return line and the friction pressure loss of the return line, and specifically, can utilize the formula Pout＝ρmgHw+ΔPf,rlCalculating the outlet pressure, where PoutIs the outlet pressure, pmFor drilling fluid pressure, Δ Pf,rlPressure loss in the pipeline.
Then according to the above formula, the required lift of the subsea pump can be calculated, specifically, the formula can be used
Calculating the lift of the subsea pump, wherein HSSPIs the pump head, delta P, of the subsea pumpSSPIs the inlet-outlet pressure difference, whereinSSP＝(ρm-ρsw)gHw+ΔPf,rl。
In some embodiments, when calculating the subsea pump power, the subsea pump power may be calculated by first calculating an inlet pressure corresponding to the subsea pump using the seawater depth and the seawater density, then calculating an outlet pressure corresponding to the subsea pump using the drilling fluid density and the seawater depth, and finally calculating the subsea pump power based on the inlet pressure and the outlet pressure.
When the specific calculation process is executed, the formula P may be used firstin＝ρswgHwCalculating the inlet pressure, where PinIs the inlet pressure, pswIs the density of seawater, g is the acceleration of gravity, HwReuse formula P for sea water depthout＝ρmgHw+ΔPf,rlCalculating the outlet pressure, where PoutIs the outlet pressure, pmFor drilling fluid pressure, Δ Pf,rlPressure loss in the pipeline.
After the inlet and outlet pressures are also obtained, the formula can be used
Calculating the power of the subsea pump, wherein WSSPFor subsea pump power, Δ PSSPIs the inlet-outlet pressure difference, whereinSSP＝(ρm-ρsw)gHw+ΔPf,rl，QmAnd eta is the drilling fluid discharge and the lifting efficiency of the subsea pump.
The working parameters of the subsea pump referred to in practical application may not be limited to the above examples, and may specifically be further determined by means of experimental simulation. The importance degree of the working parameters of the subsea pump can be evaluated by analyzing the variation relationship between the corresponding working parameters of the subsea pump and the working environment parameters.
The analysis process is described below using a specific example. Firstly, the whole working environment is introduced, the water depth corresponding to the testing environment can be 500-3000m, and the drilling fluid density is 1.2-2.0g/cm3The discharge amount of the drilling fluid is 700 and 1200gal/min, and the inner diameter of the return line is 4 '-8'.
Firstly, the influence of the operating water depth on the working parameters is described, wherein the discharge capacity is set to be 900gal/min, and the inner diameter of the return pipeline is 108.6 mm. Fig. 4A is a schematic diagram illustrating the correspondence between the operating water depth and the pumping pressure of the subsea pump at different drilling fluid densities. Accordingly, as shown in fig. 4B, the corresponding relationship between the operation water depth and the power of the subsea pump under different drilling fluid densities is schematically illustrated. From the above schematic diagram, it can be seen that the deeper the water depth, the higher the pumping pressure and power requirements of the subsea pump.
The effect of drilling fluid density on the operating parameters is then described, wherein a displacement of 900gal/min and an internal diameter of the return line of 108.6mm is set. FIG. 5A shows the relationship between drilling fluid density and subsea pump pressure at different water depths; accordingly, as shown in fig. 5B, the relationship between the drilling fluid density and the lift of the subsea pump at different water depths is shown. Based on the above schematic, it can be determined that the greater the drilling fluid density, the higher the power requirements for the subsea pump.
The influence of the drilling fluid displacement and the operating parameters will be described below, wherein the water depth is set to 1500m and the internal diameter of the return line is 108.6 mm. As shown in fig. 6A, the relationship between the drilling fluid displacement and the pumping pressure of the subsea pump is shown schematically under different drilling fluid density conditions. Correspondingly, as shown in fig. 6B, the corresponding relationship between the drilling fluid displacement and the power of the subsea pump under different drilling fluid density conditions is shown schematically. It can be seen from the above schematic that the greater the drilling fluid displacement, the higher the power demand on the subsea pump.
Finally, the influence of the internal diameter of the return line on the operating parameters was described, wherein the water depth was set at 1500m and the internal diameter of the return line was 108.6 mm. FIG. 7A is a schematic representation of the relationship between return line internal diameter and subsea pump pressure at different drilling fluid densities; FIG. 7B is a graphical representation of the relationship between return line internal diameter and subsea pump power at different drilling fluid densities. Based on the results presented in the above schematic, the return line size has a large impact on the pumping pressure and the pumping power.For example: the mud density is 1.5g/cm at the water depth of 1500m3Under the condition of 900gal/min of discharge capacity, if a backflow pipeline with 4' inner diameter is adopted, the required pumping pressure is 36.9MPa, and the required pumping power is 1233kW (without considering factors such as pumping efficiency, safety factor and the like of a subsea pump); if a backflow pipeline with the inner diameter of 6' is adopted, the required pumping pressure is 24.5MPa, and the required pumping power is 562 kW. However, based on the variation trend of the curve in the graph, the influence degree on the pumping pressure and the pumping power is correspondingly reduced along with the further expansion of the inner diameter, so that the requirement on the capacity of the subsea lifting pump can be effectively reduced by selecting the return pipeline with the larger inner diameter under the condition of considering the variation trend.
The selected working parameters and the analysis process of the working parameters are only described in an exemplary application process, and in practical application, other standards can be provided for the selection of the subsea pump, for example, the requirement on the conveying medium is low, so that the subsea pump can treat a certain content of rock debris and gas; the volume is small, the modularized installation is convenient, and ROV friendly operation can be realized; the device is suitable for underwater working environment, and has the standards of corrosion resistance, reliable performance, long service life and the like. In practical application, no limitation is made on the selection process of the working parameters and the subsea pump.
After determining the operating parameters corresponding to the subsea pump, the selection of the subsea pump may be achieved with reference to the operating parameters. In some embodiments, the subsea pump may comprise at least one of a centrifugal pump, a diaphragm pump, a jet pump, and a disc pump.
The subsea pumps are classified into a positive displacement pump and a power pump according to the working principle, wherein the diaphragm pump, the plunger pump, the screw pump, and the like belong to the positive displacement pump, and the centrifugal pump, the jet pump, the disc pump, and the like belong to the power pump.
The centrifugal pump has the advantages that the centrifugal pump has no vibration in the liquid discharging process, the switch of a valve is not needed in the operation process of the pump, and the discharge capacity can be continuously adjusted by controlling the rotating speed of the impeller; the drilling fluid containing the rock debris is an abrasive medium, so that the drilling fluid has the defects of serious abrasion to flow parts of a conventional centrifugal pump and a positive displacement pump, poor dynamic sealing performance and greatly shortened service life.
The diaphragm pump has the advantages that the rated power and the mechanical efficiency of the pump are higher, and high-density liquid or liquid containing solids can be processed; the disadvantage is that the valve needs to be controlled to open and close during the action process, and meanwhile, in order to reduce the abrasion of the diaphragm and prolong the service life of the pump, the selection of the diaphragm material faces great difficulty.
The jet pump has the advantages that the jet pump lifts return liquid containing rock debris, the lifting capacity of the jet pump is determined by the pressure of power liquid, a lifting power source can be arranged on the sea surface or the sea bottom, and the lifting is easy to achieve theoretically, but the jet pump has high requirements on the pressure of working liquid, the pressure loss of a throat is high, the jet pump is small in structural size, the pump is easy to stop due to blockage failure, and the implementation difficulty is high.
The disc pump is a new type pump which is researched and popularized abroad in recent years, is applied to the countries such as the United states, Russia and the like, has the greatest advantage that the friction failure of structural parts of the pump caused by the contact of a conveyed medium and a flow passage part can be avoided to the greatest extent, and can be used for conveying fluid with higher viscosity and higher particle impurity concentration. The outer circle disc pump is simple in structure, convenient to maintain and simple to machine and manufacture compared with a conventional centrifugal pump and a positive displacement pump, and therefore, the outer circle disc pump is most suitable for a drilling fluid lifting drilling system without a marine riser.
As an example for the selection of the subsea pump, the deepwater surface well bore is usually drilled with seawater at a water depth of 1500m and a drilling fluid density of 1.08g/cm3The discharge capacity is 55L/s; the working condition of the shallow pneumatic control well is considered, and the density of the control well fluid is designed to be 1.2g/cm3. The subsea pump pumping pressure and power requirements were simulated using different sized drill pipes as return lines, and the results are shown in table 1 below.
TABLE 1
Drill rods with different sizes are used as backflow pipelines to simulate the pumping pressure and power requirements of a subsea pump, and the results show that the influence of the inner diameter on the power requirements of the pump is obvious. With the principle of minimizing pump power requirements, 5-1/2 "drill pipe is initially preferred as the return line, and the internal diameter will be further optimized based on the anchoring scheme and strength check results.
The single-stage power of the disc pump is 300kW, the maximum allowable solid phase size is 2.5', the allowable free gas content is 10%, and the lifting capacity can be improved by adopting a multi-stage pump group. The pump efficiency, the safety coefficient and the requirements of the shallow air-pressure well are comprehensively considered, a 3-grade disc pump is recommended to be selected, the total power is 900kW, and the requirement of lifting drilling fluid without a marine riser in 1500m water depth can be met.
The above process is only for describing the process of selecting the subsea pump by using the working parameters, and the actual application is not limited to selecting the disc pump, and further description of other selecting processes is not provided herein.
The drilling fluid suction device is used for sucking the recovered drilling fluid in the annular space without the marine riser into the subsea pump module, so that the subsea pump module can convey the recovered drilling fluid to a drilling platform on the ground. The drilling fluid suction device is generally arranged at the upper part of a low-pressure wellhead of the seabed, and when the drilling fluid in front of a drill bit returns to an annular space, the drilling fluid suction device is used for changing the advancing direction of the drilling fluid to enable the drilling fluid to enter a drilling fluid recovery system, so that an interface is provided for a drilling mud and rock debris return pipeline, and meanwhile, the function of righting a drilling tool to be put in is also achieved. The drilling fluid suction device can also be provided with a pressure sensor, an illumination camera device and the like, so that the operation quality in practical application is further improved.
In some embodiments, the drilling fluid intake device is further configured to adjust the subsea pump speed based on a drilling fluid level inside the drilling fluid intake device to vary a drilling fluid pumping rate to prevent drilling fluid within the drilling fluid intake device from spilling out of the intake module. Due to the fact that the amount of recovered drilling fluid which can be buffered by the suction device is limited, when the amount of drilling fluid introduced into the annular space is too large, the drilling fluid can overflow the suction module. Therefore, the pressure monitoring device and the liquid level monitoring device are arranged in the drilling fluid suction device, the rotating speed of the subsea pump can be effectively adjusted, the mass of the drilling fluid in the drilling fluid suction device is controlled, the drilling fluid can be timely sucked into the side outlet of the lower part of the device, enters the subsea pump through a subsea drilling fluid conveying pipeline, is lifted to a drilling ship and is recycled after being processed.
The return line is used for connecting the subsea pump module and a drilling platform on the sea surface, and the subsea pump can transmit the recovered drilling fluid from the subsea pump module to the drilling platform through the return line so as to realize the transportation of the recovered drilling fluid.
The drill pipe valve is arranged in a riser-free pipe, in particular typically installed in a subsea drilling tool. The drilling platform is provided with a sea surface pump which conveys the drilling fluid to the subsea string through a drill rod, so that the drilling fluid can drill on the seabed after rushing out of a drill bit at a certain speed and returns to the annulus. The annulus outlet has a height differential compared to the drilling fluid in the drill pipe, thereby creating a U-tube effect that can provide horsepower to assist the drill pump in propelling the drilling fluid through the drill pipe, downhole drilling tool, and drill bit. However, in the case of circulation stoppage, such as connection or pump stop inspection, the balance of the U-tube effect is broken, so that the drilling fluid in the drill pipe sinks, thereby affecting the effective drilling. The drill stem valve is used for solving the problems.
The valve core of the drill pipe valve is generally of a spring structure and is usually connected to the upper part of a drill pipe bottom drilling assembly. The drilling fluid passes through the drill pipe valve and then enters the shaft annulus after reaching the drill bit. As shown in fig. 2, which is a schematic diagram of the stress of the drill pipe valve, when the surface pump on the drilling platform is in a closed state, the drill pipe valve is in a closed state when the pressure applied to the drill pipe valve is not greater than the opening pressure threshold, so that the drilling fluid in the drill pipe is prevented from entering the drilling tool below the drill pipe, and the balance in the drill pipe is not affected. When the sea surface pump operates, the pressure applied to the drilling fluid is larger than the opening pressure threshold value of the drill rod valve, so that the valve core in the drill rod valve is pushed to move downwards, the nozzle on the valve core extends out of the closed area of the valve seat, the drill rod valve is in an open state, and the drilling fluid can enter the lower part of the drill rod through the drill rod valve. When the pressure of the lower part of the drill stem valve is greater than the pressure of the upper part of the drill stem valve, the compressed spring drives the valve core to gradually reset until the drill stem valve is completely closed.
Aiming at the opening pressure threshold of the drill rod valve, the pressure is larger than the hydrostatic pressure difference between the hydrostatic water of the mud in the drill string and the hydrostatic water of the seawater at the mud line, and a certain amount of water is addedPressure margin to allow for an increase in mud weight. Thus, formula P can be utilizeddov＝(ρm-ρsw)gHw+ΔPsfCalculating an opening pressure threshold value, wherein PdovTo turn on the pressure threshold, ρmAs drilling fluid pressure, pswIs the density of seawater, g is the acceleration of gravity, HwIs the depth of sea, Δ PsfThe pressure allowance of the drill rod valve is obtained.
It can be seen that the greater the water depth, the greater the drilling fluid density and the consequent increase in the opening pressure set by the drill pipe valve. Therefore, in the case of different drilling fluid densities used in different well sections, the spring spool of the drill pipe valve needs to be replaced to adjust the opening pressure of the drill pipe valve.
In addition, the drill rod valve can also have different installation positions, and the different installation positions have different opening degrees and correspondingly have different local resistance losses. In some embodiments, the installation location includes at least one of a downhole, an upper collar, a lower blowout preventer, and an upper blowout preventer.
Specifically, formula F can be utilizedspring＝Ftop-Fbottom＝Av[Pp+(ρm-ρw)gH-ΔPdphv-ΔPchv]Calculating the pressure, wherein FspringIs a pressure difference, FtopFor the pressure at the top of the drill pipe valve, FbottomThe pressure at the bottom of the drill pipe valve, AvIs a coefficient, PpFor pumping pressure, pmIs the drilling fluid density, pwIs the density of seawater, H ═ min { H ═ min }w，HvIn which HwTo the depth of water, HvFor drill pipe valve installation depth, Δ PdphvFor the pressure loss, Δ P, in the drill string above the drill pipe valvechvThe pressure loss in the annulus at the upper part of the drill rod valve. Accordingly, the relationship between the installation position of the drill pipe valve and the opening degree can be calculated as shown in the following table 2.
TABLE 2
| Drill pipe valve position | Spring pressure MPa | Opening degree% |
| Downhole | 3.71 | 21 |
| Upper part of drill collar | 3.75 | 23 |
| Lower part of blowout preventer | 3.91 | 32 |
| Upper part of blowout preventer | 4.02 | 38.3 |
It can be seen that the higher the installation position of the drill stem valve, the higher the Δ PdphvAnd Δ PchvThe smaller the opening of the valve, the smaller the local friction loss at the drill pipe valve. But when the drill pipe valve is installed higher than the blowout preventer, (ρ)m-ρw) The gH decreases and the degree of opening of the valve decreases instead. Therefore, analysis has determined that it is most reasonable to have the drill stem valve mounted near the upper portion of the blowout preventer.
The opening pressure threshold of the drill rod valve can be adjusted by replacing spring valve cores with different stiffness. Correspondingly, according to the drilling tool combination used in the drilling process, different types of drill rod valves need to be designed to meet the size requirements of drill rods in different drilling tool combinations.
Through the introduction of the above embodiment, it can be seen that the drilling fluid recovery system prevents the drilling fluid from entering the drilling tool below the drill pipe when the pressure applied to the drilling fluid recovery system is not greater than the opening pressure threshold value by arranging the drill pipe valve in the non-riser pipe, and ensures the balance of the drilling fluid in the drill pipe when the pump is stopped for inspection. Correspondingly, the drilling fluid suction device is used for sucking the recovered drilling fluid in the non-marine riser into the subsea pump module, the subsea pump module is recycled, and the recovered drilling fluid is lifted to a drilling platform through a backflow pipeline to be recovered, so that the drilling fluid is recycled, the pollution caused by drilling cuttings is avoided, the zero emission of the subsea environment is ensured, meanwhile, the normal work of equipment is also ensured, the normal operation of the drilling process is ensured, and the effective propulsion of production and development is facilitated.
While the process flows described above include operations that occur in a particular order, it should be appreciated that the processes may include more or less operations that are performed sequentially or in parallel (e.g., using parallel processors or a multi-threaded environment).
While the process flows described above include operations that occur in a particular order, it should be appreciated that the processes may include more or less operations that are performed sequentially or in parallel (e.g., using parallel processors or a multi-threaded environment).
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the specification. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium.
Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
As will be appreciated by one skilled in the art, embodiments of the present description may be provided as a method, system, or computer program product. Accordingly, embodiments of the present description may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, embodiments of the present description may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein.
The embodiments of this specification may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The described embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment. In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of an embodiment of the specification. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A drilling fluid recovery system based on a riser-free pipe is characterized by comprising a drilling fluid suction device, a subsea pump module, a return line and a drill pipe valve;
the drilling fluid suction device is used for sucking the recovered drilling fluid in the riser into the subsea pump module;
the subsea pump module is used for lifting the recovered drilling fluid to a drilling platform through a return line to complete recovery;
the return pipeline is connected with the subsea pump module and the drilling platform so as to realize the transmission of the recovered drilling fluid from the subsea pump module to the drilling platform;
the drill pipe valve is arranged in the non-marine riser and is in a closed state when the pressure applied to the drill pipe valve is not greater than the opening pressure threshold value; the drill rod valve blocks the drilling fluid in the drill rod from entering a drilling tool below the drill rod in a closed state; the cracking pressure threshold is not less than a pressure differential between hydrostatic pressure within the drill string and hydrostatic pressure at the subsea mudline.
2. The system of claim 1, wherein the cracking pressure threshold is obtained by:
using the formula Pdov＝(ρm-ρsw)gHw+ΔPsfCalculating an opening pressure threshold value, wherein PdovTo turn on the pressure threshold, ρmAs drilling fluid pressure, pswIs the density of seawater, g is the acceleration of gravity, HwIs the depth of sea, Δ PsfThe pressure allowance of the drill rod valve is obtained.
3. The system of claim 1, wherein the drill pipe valve corresponds to an installation location comprising at least one of a downhole, an upper collar, a lower blowout preventer, and an upper blowout preventer; different installation positions correspond to different drill rod valve openings.
4. The system of claim 1, wherein the drilling fluid intake device is further configured to adjust a subsea pump speed based on a drilling fluid level within the drilling fluid intake device to vary a drilling fluid suction rate to prevent drilling fluid within the drilling fluid intake device from spilling over the intake module.
5. The system of claim 1, wherein the subsea pump module comprises a subsea pump; the subsea pump is selected in the following manner:
collecting working environment information corresponding to a subsea pump module; the working environment information comprises at least one of seawater depth, seawater density and drilling fluid density;
calculating the working parameters of the subsea pump based on the working environment information;
and selecting the subsea pump according to the subsea pump working parameters.
6. The system of claim 5, wherein the subsea pump operating parameter comprises a subsea pump head; the calculating of the subsea pump working parameters based on the working environment information comprises:
calculating an inlet pressure corresponding to the subsea pump using the depth of the seawater and the density of the seawater;
calculating the outlet pressure corresponding to the subsea pump by using the drilling fluid density and the seawater depth;
and calculating the sea bottom pump head based on the inlet pressure and the outlet pressure.
7. The system of claim 6, wherein the calculating an inlet pressure corresponding to a subsea pump using seawater depth and seawater density comprises:
using the formula Pin＝ρswgHwCalculating the inlet pressure, where PinIs the inlet pressure, pswIs the density of seawater, g is the acceleration of gravity, HwIs the depth of seawater;
the calculating of the outlet pressure corresponding to the subsea pump using the drilling fluid density and the seawater depth comprises:
using the formula Pout＝ρmgHw+ΔPf,rlCalculating the outlet pressure, where PoutIs the outlet pressure, pmFor drilling fluid pressure, Δ Pf,rlPressure loss in the pipeline;
the calculating of the subsea pump head based on the inlet pressure, the outlet pressure comprises:
using formulas
Calculating the lift of the subsea pump, wherein HSSPIs the pump head, delta P, of the subsea pumpSSPIs the inlet-outlet pressure difference, whereinSSP＝(ρm-ρsw)gHw+ΔPf,rl。
8. The system of claim 5, wherein the subsea pump operating parameters comprise subsea pump power; the calculating of the subsea pump working parameters based on the working environment information comprises:
calculating an inlet pressure corresponding to the subsea pump using the depth of the seawater and the density of the seawater;
calculating the outlet pressure corresponding to the subsea pump by using the drilling fluid density and the seawater depth;
calculating the subsea pump power based on the inlet pressure and the outlet pressure.
9. The system of claim 8, wherein the calculating an inlet pressure corresponding to a subsea pump using seawater depth and seawater density comprises:
using the formula Pin＝ρswgHwCalculating the inlet pressure, where PinIs the inlet pressure, pswIs the density of seawater, g is the acceleration of gravity, HwIs the depth of seawater;
the calculating of the outlet pressure corresponding to the subsea pump using the drilling fluid density and the seawater depth comprises:
using the formula Pout＝ρmgHw+ΔPf,rlCalculating the outlet pressure, where PoutIs the outlet pressure, pmFor drilling fluid pressure, Δ Pf,rlPressure loss in the pipeline;
the calculating subsea pump power based on the inlet pressure, outlet pressure, comprising:
using formulas
Calculating the power of the subsea pump, wherein WSSPFor subsea pump power, Δ PSSPIs the inlet-outlet pressure difference, whereinSSP＝(ρm-ρsw)gHw+ΔPf,rl，QmAnd eta is the drilling fluid discharge and the lifting efficiency of the subsea pump.
10. The system of claim 1, wherein the subsea pump in the subsea pump module comprises at least one of a centrifugal pump, a diaphragm pump, a jet pump, and a disc pump.
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