JPS6030498A - Operating method of downhole pump for pumping up underground hot water - Google Patents

Abstract

PURPOSE:To have safety operation of a pump by returning part of, or a small amount of, the hot water discharged onto the ground back to the hot water takeout well through a warming piping, thereby keeping the intra-well temp. evenly, and by securing the pump with necessary suction pressure. CONSTITUTION:During operation, part of, or a small amount of, the hot water is returned to the gaseous phase 30 of the well from the portion of discharge pipe 15 located on the ground through a by-pass piping 33 by opening a gate valve 31 upon adjustment of its rate of flow with a flow adjusting valve 32. Because, at said gaseous phase 30 of well, the surrounding soil and rock ground will absorb the heat, the temp. tends to sink to show the saturated steam pressure for the current condition, so that any significant temp. drop will cause too low pressure to lead to disability of a hot water pump 12 with its suction function. In respect thereof, the above-mentioned by-pass piping 33 gives said gaseous phase always a minute amount of hot water at high temp., so that the temp. of the gaseous phase 30, is raised to provide a corresponding pressure. Thus the hot water pump 12 can make safety operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a downhole pump for pumping underground hot water.

When installing a downhole pump to pump underground hot water, the well itself is normally sealed and kept as a sealed tank. However, because heat is dissipated into the atmosphere and bedrock, the temperature in the upper layer of the well, especially in the gas phase, decreases. Due to this temperature drop, the pressure in the gas phase kept at the saturated vapor pressure decreases. Therefore, sufficient pump suction pressure cannot be secured and operation becomes impossible.

The present invention solves the above-mentioned problems in a device that pumps up hot water by equipping a hot water well with a downhole pump, and provides an operation method that can maintain the suction pressure of the downhole pump and stably continue the operation of ground facilities. The purpose is to

The problem with the present invention is that a part (very small amount) of the hot water discharged above the ground is allowed to flow into the hot water extraction well through the warming pipe to maintain a uniform temperature within the well and achieve stable pump operation.

Hot water is not necessarily limited to being taken out from a well, but may be introduced from other hot water or steam sources if there are any.

Embodiments of the present invention will be described below with reference to the drawings. 1 is a production well, and ko is a reduction well. The production well/is a low permeability stratum where the pipe casing reaches the porous stratum 3 where hot water gushes out! The pipe casing is inserted through the pipe, and the area near the ground is hardened with concrete 6, for example. The production well 1 is sealed above ground with a lid 7 so as to withstand the high internal pressure.

The reinjection well has a similar structure, with za being a pipe casing, ji being concrete, and lO being a lid. The reinjection well λ is provided in the porous stratum 3 that is connected to the production well 1, but it is placed in a position that does not affect the amount of hot water springing from the production well and the temperature of the hot water.

A hot water pump 7.2 is submerged in the liquid phase/l of hot water gushing out at the location of the porous stratum 3 of the production well l. There are various types of hot water pumps/2, but they are based on deep well pumps with a motor at the bottom and a pump at the top, and can be operated in high-temperature environments, and are generally considered to be downhole pumps. be done. The hot water pump passes through the lid 7 and
It is suspended and supported by a discharge pipe /j fixed to. A discharge pipe extends from the hot water pump/J to the ground via the check valve/4I! is arranged, and the discharge pipe l! is connected via a gate valve 16 to the primary piping/g on the heat transfer side of a heat exchanger 17 installed on the ground, and the piping 1g passes through the lid 10 from the heat transfer side of the heat exchanger/li to a constrictor, for example. Valve-like pressure holding means/? It leads into the reduced well through the.

The heat receiving side of the heat exchanger/7 is a condenser, and the pipe λ3 from the heat medium pump 22 that sucks up and sends out the liquid of 2/ communicates with its inlet, and the pipe that exits from its outlet. It communicates with the steam inlet, and the steam outlet of the steam turbine 5 communicates with the condenser, 2/ through a piping.

A steam turbine 25 is connected to a generator 27 via a shaft coupling, a cable is used to take out a part of the output of the generator λ, 2ff is a hot water pump/, and a motor and other heat medium pumps incorporated in 2 It communicates with the drive motor λ9.

The discharge pipe l on the upstream side of the gate valve 16! and the gas phase of the production well 30
Gate valve J/ to communicate with.

Bypass piping 33 is provided via three flow rate regulating valves.

Although not shown, to start a power generation plant using underground energy as described above, for example, the hot water pump/J and motor tacho 9 are started using electric power from another commercial power source, and in a steady state, the generator, 2? Power is supplied from the generator a7 to the commercial power supply side, and power is also supplied from the generator a7 to the hot water pump saw, motor, and 2q.

The hot water pumped up by the hot water pump saw is discharged at a pressure equal to or higher than the critical pressure corresponding to the temperature of the hot water.

And the discharge pipe! The heat exchanger 17 is reached by passing through the gate valve 16 used through the pipes and piping.

On the heat receiving side of the heat exchanger 17, a heat medium pump 2- sends the heat medium sucked from the condenser and 2/ to the secondary side of the heat exchanger 17, and is heated by hot water passing through the secondary side. be done. Hot water whose temperature has decreased is a means of maintaining pressure/? The pressure decreases to match the pressure inside the reinjection well and enters the reinjection well. By means of the pressure holding means 19, the hot water from the discharge side of the hot water pump/2 to the pressure holding means/9 is kept above the critical pressure, and since vaporization does not occur, calcium carbonate, etc. contained in the hot water is Since minerals do not precipitate, clogging of piping is prevented.

From the pressure holding means 19 to the reinjection well, the temperature decreases and the hot water becomes a liquid phase, and the critical pressure is maintained by the internal pressure of the reinjection well 2. It is desirable that the reduction well does not exhibit a gas phase, and it is desirable that the injection pressure is such that the hot water to be reduced is maintained at a critical pressure or higher. The hot water whose temperature has been reduced and which has been reduced into the reinjection well a is reduced into the porous stratum 3 against the ejection pressure of the reinjection well a.

The heat medium sent out by the heat medium pump here and turned into superheated steam in the heat exchanger 17 is supplied to the steam turbine 5 through the pipe 2'1, and the heat and pressure energy held by the steam turbine λS are converted into power and steam is generated. Turbine λ! The steam turbine generator 5 rotates the generator and generates electricity.

The heat medium leaving the steam turbine 23 passes through a piping roller, is liquefied in a condenser 1 equipped with a heat medium cooling means (not shown), and is sucked into a heat medium pump and circulated.

As mentioned above, in geothermal power generation, in the closed Rankine heat engine cycle in which hot water is guided from the production well 1 to the return well through a heat exchange relationship, the primary side equipment through which the hot water passes maintains the hot water in a liquid phase by the pressure holding means 19. This is how the pressure is maintained.

During operation, the gas phase 30 of the well generates a suction pressure in the hot water pump 12, so it is necessary to maintain stable pressure. Then, the gate valve 31 is opened, the flow rate is adjusted by the flow rate regulating valve 32, and a portion of the hot water is returned to the gas phase 30 of the well from the above ground portion of the discharge pipe 13 through the bypass pipe 33. Well gas phase 3Q
Since heat is being taken away by the surrounding soil, bedrock, etc., the temperature tends to decrease and the saturated steam pressure is reached at that time, so if the temperature decreases significantly, the pressure will decrease and the hot water pump will no longer be able to suck in the steam. .

However, since a very small portion of high-temperature hot water is constantly supplied to the gas phase 30 from the bypass pipe 33, the temperature of the gas phase Jθ rises and a corresponding pressure is exhibited, so that the hot water pump operates stably. be able to.

Although the bypass piping 33 in the embodiment returns the gas to the gas phase 30 of the well, it is also effective to return the gas to a relatively upper part of the liquid phase // of the well, and the temperature of the liquid phase // in contact with the gas phase 30 increases. Gas phase 3
It has the effect of raising the temperature of 0.

In the embodiment, the hot water returned to the production well I is made into own hot water and obtained from the discharge pipe /&, but the hot water added to this production well / may be hot water that comes from another production well. good. In some cases, the hot water taken out from before the pressure holding means has a temperature of about 130° C., and in such a case, the hot water may be introduced after the work of heat exchange in the heat exchanger/7.

As described above, the present invention allows a very small amount of hot water to be injected into the production well compared to the amount of hot water discharged, so the temperature inside the well is kept uniform, ensuring stable pump suction pressure, and the pump can be operated safely. made it possible to do so.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of an embodiment of the present invention. L... Production well Co... Reduction well 3... Porous stratum D...
・Pipe casing left・・Low permeability stratum 6・・Concrete 7・・Lid g・・Pipe casing ta・・
Concrete/g...(-next) Piping 19...Pressure holding means, 2...Condenser, 22...Heating medium pump 3
, 2'l--Piping 25 fists, steam turbine 2t...Piping λri...generator, 2g...cable, 29...motor, 30--gas phase 31...gate valve, ? K...Flow rate adjustment valve 33...Piping. Patent applicant Ebara Corporation Agent Arai -be

Claims (1)

[Claims] l In the operation of a downhole pump that pumps up underground hot water, an amount of heat that is extremely smaller than the discharge amount of the downhole pump is generated in the well where the downhole pump is installed. A method of operating a downhole pump for pumping up underground hot water, in which water is supplied from a hot water source to a well through piping to the well, uniformly increasing the gas phase temperature within the well and maintaining pump suction pressure. A method for operating a downhole pump for pumping up underground hot water according to claim 1, wherein the opening position in the well of the piping from the hot water source to the well is a space in the well where the gas phase exists. The method of operating a downhole pump for pumping up underground hot water according to claim 1, wherein the opening position in the well of the piping from the hot water source to the well is a space in the well where the liquid phase exists. H The hot water source is hot water pumped from a private well,
A method for operating a downhole pump for pumping up underground hot water according to any one of claims 1 to 3, wherein one side of the piping from the hot water source to the well communicates with an above-ground discharge pipe. ! A method for operating a downhole pump for pumping up underground hot water according to any one of claims 1 to 3, wherein the hot water source is external hot water.