JPH0411758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to the initial operation of a downhole pump for pumping underground hot water.

"Problems to be solved by the conventional technology and the invention" In the steady operation of a closed hot water well, the temperature of the liquid phase inside the well is the same as the temperature of the gushing hot water, and is uniform. Since the gas phase is long in the vertical direction, heat is radiated to the surrounding rock, and the average temperature is slightly lower than that of the liquid phase.

In hot water wells that have been shut down for long periods of time, the temperature at the top becomes lower than the bottom temperature due to heat dissipation into the atmosphere and bedrock. Figure 1 is a diagram showing the temperature distribution of a closed hot water well when the pump is stopped.The temperature at that position is taken in the horizontal direction from the vertical coordinate Y-Y, and the diagram shows temperature distribution line 1. O is on the ground. A downhole pump (hereinafter simply referred to as a pump) 4 is installed in the liquid phase portion 3 of the hot water well 2, and the liquid is sent to the ground through a discharge pipe 5 connected to the pump 4.

For example, as shown in the figure, the hot water at bottom 7 is 200℃.
However, the temperature decreases as you go to the upper layer, and in the gas phase 6, the temperature is constant everywhere and may reach 100°C because it is in a saturated vapor state. In such a case, if the pump 4 is operated without considering the above-mentioned temperature difference, the temperature of the hot water sucked into the pump 4 will rise rapidly because the 200° C. hot water at the bottom of the well 7 will rise rapidly. The temperature rise of this hot water is short, lasting only a few minutes. In order for the pump 4 to continue operating, ignoring cavitation, the pressure of the liquid surrounding the suction port of the pump 4 must be higher than the saturated vapor pressure corresponding to the temperature of the hot water sucked into the pump 4. It is. However, unless the sum of the saturated vapor pressure of the gas phase section 6 and the pressure corresponding to the head of the liquid phase section 3 above the pump 4 is greater than the saturated vapor pressure above the temperature of the hot water sucked by the pump 4, However, although the gas phase portion 6 and the upper liquid layer are heated by the hot water passing through the discharge pipe 5, the temperature rises slowly and remains at a low temperature, making it impossible to ensure sufficient pump suction pressure. Due to this, the pump may become inoperable. What kind of temperature change will occur if the pump 4 is operated with what amount of hot water depends on the problems specific to the well, and includes the diameter of the well, the depth of the liquid phase part 3, the temperature of the hot water, the installation depth of the pump 4, The depth of the liquid phase in the upper part of the pump 4, the diameter and length of the water discharge pipe 5, etc. are involved, and it is difficult to predict, although it takes into consideration the amount of spring water in the well 1, the heat exchange load on the ground, etc. Therefore, it is necessary to prepare in advance in case the vehicle becomes inoperable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an operating means that ensures pump suction pressure at the time of starting a downhole pump installed in a hot water well to ensure smooth startup of the pump.

``Means for Solving the Problems'' The first aspect of the present invention is to reduce the amount of hot water discharged to underground equipment during the initial operation of a downhole pump that pumps up underground hot water, thereby increasing the speed at which hot water rises underground. At the same time, some of the hot water discharged from the downhole pump is taken out at or near the ground or guided from another hot water source and introduced into the well, thereby reducing the temperature change of the hot water sucked into the downhole pump. The sum of the saturated vapor pressure corresponding to the temperature of the gas phase and the pressure corresponding to the head of the liquid phase above the pump is greater than the saturated vapor pressure corresponding to the temperature of the hot water sucked into the downhole pump. This is an initial operation method for a downhole pump for pumping up underground hot water, which maintains sufficient pump suction pressure to operate the downhole pump safely.

The second aspect of the present invention is to provide a bypass pipe for initial operation that communicates from the discharge pipe of a downhole pump that pumps up underground hot water from a well to the gas phase part of the well via a flow rate adjustment means, and to adjust the pump discharge amount. This is an initial operating device for a downhole pump for pumping up underground hot water, which is equipped with variable means.

"Embodiments" Examples of the present invention will be described below with reference to the drawings. Figure 2 shows a longitudinal section of a hot water well and also shows a diagram showing the temperature distribution of the hot water well, and the diagram showing the temperature distribution is shown in the same manner as in Figure 1. Y-Y is the vertical coordinate and the origin is 0
indicates the ground.

The discharge pipe 5 of the pump 4 is hermetically inserted through the cover 8 of the well 2 above ground. It is connected to the ground facility side via a gate valve 9 that can also adjust the flow rate.

On the ground facility side, hot water supplied from a hot water well (hereinafter referred to as well) 2 is guided to a heat exchanger, the heat medium is used as superheated steam, the superheated steam drives a steam turbine, and the steam turbine drives a generator. The primary hot water that exits the heat exchanger is sent to the reinjection well.

Bypass piping 11 for initial operation that communicates between the upstream side of the gate valve 9 of the discharge pipe 5 and the gas phase part 6 of the well 2
The bypass piping 11 is equipped with a thermometer 12 that measures the temperature of the liquid in the bypass piping 11, a gate valve 14 that opens at the beginning of operation after startup, and a bypass piping 11.
A flow rate adjustment valve 13 is interposed to adjust the flow rate of liquid flowing through the tube. Note that the bypass pipe 11 may communicate with the well 2 from another heat source, for example, another hot water well.

At startup, the gate valve 14 is opened and the gate valve 9 is throttled. Then, when the pump 4 is energized, a portion of the hot water is returned to the gas phase section 6 of the well 2 through the bypass pipe 11 that sends the hot water to the above-ground facility through the discharge pipe 5.

Let Q be the amount of hot water discharged from the pump 4 to the inland equipment side, and let q be the amount of hot water returned from the bypass piping 11 for initial operation into the well 2. In this case, the flow rate discharged from pump 4 is Q+
q, and the amount of hot water Q' rising from the bottom 7 may be treated as equal to the amount of hot water Q discharged to the ground equipment side. That is, the well has a depth of several thousand meters to several hundred meters, and the liquid level fluctuation in the liquid phase portion 3 is small compared to the total head of the pump 4.

At the beginning of the operation of the pump 4, the amount of hot water Q discharged to the ground equipment side is throttled by the gate valve 9, and by reducing Q', the rise of the hot water from the bottom 7 is made gradual. As a result, pump 4
The amount of hot water sucked into the pump 4 is smaller than the discharge amount of the pump 4 during steady operation, and the temperature of the hot water sucked in increases slowly.

Also, at this time, the above-mentioned bypass piping 1 for initial operation
A portion q of the hot water discharged from 1 is returned to well 2.
At this time, by making q as large as possible, the temperature in the well above the pump 4 can be made nearly uniform. In this way, immediately after the pump 4 is started, the difference in temperature between the temperature of the hot water sucked into the pump 4 and the gas phase part 6 is small, and if the temperature of the hot water sucked into the pump 4 is slightly higher than the temperature of the hot water sucked into the well 1 Return to.
That is, Q may be made extremely small. As a result, the temperatures of the upper portions of the gas phase portion 6 and the liquid phase portion 3 both rise while the temperature difference between the temperature of the liquid sucked into the pump 4 remains small.

Therefore, by reducing Q' (=Q) and increasing q, the temperature change caused by the hot water rising from the bottom of the shaft 7 can be made gradual, and the temperature near the pump 4 and above it can be made uniform. It is possible to maintain sufficient suction pressure of the pump 4 in a similar state and safely operate the pump 4.

Now, the pump 4 according to the initial operation of the pump 4
Let's find the temperature tp at the inlet of the suction port. When pump 4 is started and operated for a certain period of time, pump 4 will be pumped from underground 7.
The hot water in well 2 rises up to the bottom, and the hot water in well 7 rises to position 15, and the hot water in well 2 rises to position 15 from bottom well 7.
Until then, the temperature is constant T°, and the temperature of the increased hot water becomes T at the position of the pump 4 where the temperature distribution line 1 in FIG. 1 is overlapped with the position 15 as a reference. On the other hand, the flow rate of a part of the hot water returned from the bypass pipe 11 to the gas phase section 6 is q, and as shown by the line 17, the saturation temperature t' of the gas phase section 6 (gas phase section 6) and reaches the liquid level in the liquid phase section 3. Then, it liquefies at the liquid level 16 and the temperature gradually increases.
From t' to t, it is sucked into the pump 4. Since the suction liquid is a mixture of hot water rising from the bottom 7 side and hot water returning through the gas phase section 6, the temperature tp at the inlet of the suction port of the pump 4 is tp=QT+qt/Q+q. T, t, and tp increase with time, but when starting the pump 4, either throttle the gate valve 9 or, if the pump is a variable discharge type pump, reduce the discharge volume of the pump 4 to send liquid to the ground facility. By reducing the amount Q and increasing the return amount q, the change in T is reduced and the temperature difference between T, t, and tp is reduced. In this way, the pressure in the gas phase section 6 is increased, and the suction pressure of the pump 4 can be ensured. As shown by the dotted line 18, the hot water sucked in by the pump 4 gradually loses heat in the discharge pipe 5 by the gas in the gas phase 6, and when it reaches the temperature t' on the ground, it is balanced. There is also a liquid phase section 3 at the top, and the suction of the pump 4 is continued by its head. However, as the suction of the pump 4 continues, the liquid phase portion 3 rises, the temperature T rises, and the temperatures t, tp, T
As both become higher and closer together, the temperature of the hot water discharged to the ground is slightly higher than the temperature of the gas phase part 6, and the gas phase part 6 collects the returned hot water and the discharge pipe 5.
Due to the heat dissipation of the hot water, which rises at a slow rate, the temperature of the hot water is gradually raised without becoming large in temperature difference from the temperature of the hot water sucked by the pump 4. Thus, if this operation is continued, the gas phase portion 6 and liquid phase portion 3 will have a uniform temperature T°.

〔Effect of the invention〕

The present invention is designed to adjust the flow rate and return a portion of the hot water discharged from the discharge pipe into the well from a bypass pipe or other hot water source into the well during operation of a downhole pump in an initial operation state where the temperature inside the well is uneven. In the early stages of operation, the amount of hot water sent to the ground equipment is reduced, and temperature changes due to hot water rising from the bottom of the well are moderated. By returning the hot water discharged into the well from the bypass piping or sending hot water into the well from another hot water source, the temperature change of the hot water sucked into the pump is minimized, and at the same time sufficient pump suction pressure is maintained. This enabled safe initial operation of the pump.

Therefore, according to the present invention, it is possible to change from a stopped state with a large temperature difference in the well to a steady state (state where the temperature in the well is constant).
The pump can be operated safely up to

[Brief explanation of drawings]

FIG. 1 is a diagram showing the temperature distribution when the well pump is stopped, and FIG. 2 is a longitudinal sectional view of an embodiment of the present invention. 1...Temperature distribution line, 2...Hot water well, 3...Liquid phase section, 4...Pump, 5...Discharge pipe, 6...Gas phase section, 7...Bottom hole, 8...Lid, 9...Gate valve, 11
...Bypass piping for initial operation, 12...Thermometer,
13...Flow rate adjustment valve, 14...Gate valve, 15...
position.

Claims (1)

[Scope of Claims] 1. In the initial operation of a downhole pump that pumps up underground hot water, the amount of hot water discharged to above-ground equipment is reduced to slow down the speed at which underground hot water rises, and at the same time the downhole pump is discharged. By extracting some of the hot water above ground or near the ground, or guiding it from another hot water source and introducing it into the well, the temperature change of the hot water sucked into the downhole pump is reduced, and the temperature change of the hot water sucked into the downhole pump is reduced. A pump that is sufficient to maintain the sum of the saturated vapor pressure corresponding to the temperature of the gas phase and the pressure corresponding to the head of the liquid phase above the pump is greater than the saturated vapor pressure corresponding to the temperature of the hot water. An initial operating method for a downhole pump for pumping up underground hot water to secure suction pressure and operate the downhole pump safely. 2. Provide bypass piping for initial operation that communicates from the discharge pipe of the downhole pump that pumps underground hot water from the well to the gas phase part of the well via a flow rate adjustment means, and also includes means for making the pump discharge rate variable. Initial operation equipment for a downhole pump for pumping up underground hot water.