RU2055277C1 - Method for setting-up geothermal power supply system in shore zone of water basin - Google Patents

Abstract

FIELD: geothermal power supply. SUBSTANCE: method involves selecting optimum location of power supply system on the basis of geothermal survey data and discovered center of subaqueous discharge of thermal waters, launching infiltration of water by gravity from water basin into collecting bed, lifting water through a water-lift well and producing geothermal fluid without pumping it back in operation. EFFECT: higher efficiency. 2 dwg

Description

 The invention relates to methods for extracting and using the deep heat of the Earth and can be applied in a geothermal energy supply system.

 There are methods that allow you to select the geothermal coolant from the bowels of the earth and use it in energy supply systems.

 The known method [1] consisting in the production of geothermal fluid through a well system from an underground reservoir, supplying it to a coolant system and returning the spent fluid to the underground reservoir in an economical mode of operating wells.

 The main disadvantage of this method is the need for significant capital expenditures for drilling and equipping a system of water-lifting and injection wells for the selection and then re-injection of the coolant fluid into the underground reservoir. In the case of the implementation of the geothermal energy supply system at facilities located within the water basin, the volume of capital costs increases with the need to install special drilling platforms.

 This drawback can be attributed to all known methods of geothermal energy supply, including the method of implementation and operation of a geothermal power plant (N. Ram, J. Jahalom. Commercial large-scale binary application. Geother. Res. Soun. Bull. Mau, 1988).

 The aim of the invention is to reduce capital costs, which is achieved by using instead of injection wells communicating with the water area of a permeable layer (discontinuous disturbance) and filling with water from the underground reservoir by gravity without re-injection.

 Figure 1.2 presents a diagram and a graph that implements the proposed method.

 The geothermal energy supply system is selected near the coastline, where an underground reservoir in the form of a subhorizontal permeable layer or discontinuous disturbance extends to the bottom of the water area. The selection of geothermal fluid from the underground reservoir (Fig. 1) through a water-lifting well 1 starts the process of water infiltration from water areas 2 through a water-permeable formation 3 to the level of the depths of the bottom (water sampling) of a water-lifting well 4 in a communicating system: water-water permeable formation is a water-lifting well. Filtered by gravity from the limits of the water during the migration through the reservoir in the infiltration mode is heated to the temperature of the surrounding rocks and by the time it arrives at the water-lifting well, it becomes the heat carrier of deep heat for the power unit of system 5.

 A method of implementing a geothermal power supply system is as follows.

 Within the water area of the water basin (shelf, lake, etc.), geothermal surveys are carried out along the bottom by thermal sensing or continuous infrared thermal profiling (Boykov A.M. Non-stationary methods of marine thermal prospecting. M. Nauka, 1986, p. 135; S. Kornienko; Infrared information-measuring system of continuous thermal profiling and its application areas. Sat Scientific Scientific / Institute of Geometry Problems Dag. FAN USSR, 1987, issue 7, pp. 64-68) and identify and map temperature anomalies associated with foci of subaquatic discharge under emnyh thermal waters. Such foci are usually confined to the arches of hydrogeologically disclosed anticlinal structures (Fig. 1) and the lithological "windows" of permeable formations that extend to the surface of the bottom of water areas from deep land horizons, as well as to discontinuous disturbances, etc. Having thus determined the exit point within the bottom surface the water area of the permeable formation (discontinuous disturbance) with the geothermal fluid 6 filtered in it (Fig. 1), the optimal location and depth of the water-lifting well and power unit g are chosen near the coastline otermalnoy power system (geothermal power). Moreover, the very presence of a hotbed of subaquatic unloading of thermal waters is an indicator of favorable conditions for creating a power supply system for geological and geothermal conditions (elevated temperatures) of occurrence of an underground collector within land. A water-lifting well is drilled with a face or a perforator (water intake) at a depth of the formation that extends into the water area.

The operating mode of the geothermal energy supply system is selected based on the pressure gradient in the permeable formation. Within the entire reservoir, unloading through the bottom of the water area, the hydrodynamic pressure is determined by the expression
H Z + P / γ (1) and the pressure gradient, respectively:
I dH / dZ, (2) where Z is the ordinate of the point where the pressure is determined;
P is the pressure at this point;
γ fluid density. In this case, the water flow in the formation is directed from land to the water basin.

(3) где K_п K (μ/γ) коэффициент проницаемости пласта;
K V/I коэффициент фильтрации пласта;
V Q/F скорость фильтрации в пласте;
F площадь фильтрации;
μ вязкость жидкости;
L длина пути фильтрации.The selection of geothermal fluid from the underground reservoir through a water well in the reservoir creates a lower pressure than the hydrostatic pressure in the exit zone of the permeable formation to the bottom of the water area. Quantitatively, this P value will depend on the thickness of the water layer h above the formation exit zone to the bottom surface (for h 10 m P <2 atm, h 50 m P <6 atm, h 100 m P <11 atm). Then, according to the law of communicating vessels in the system: the water area, the permeable layer, the water-lifting well, the water flow will begin to move in the opposite direction from the water area to the land within the mode of the infiltration process. The pressure drop Δ P required to start the infiltration mode of water movement, with known filtration properties in the system, is found on the basis of economically viable volumes Q of the fluid taken from the well (usually the first tens of liters per second) from the expression (Reference manual hydrogeologist. 1979, v. 1, p. 34):
ΔP

(3) where K _p K (μ / γ) is the permeability coefficient of the formation;
KV / I formation filtration coefficient;
VQ / F formation rate;
F filtration area;
μ fluid viscosity;
L The length of the filtration path.

Keeping the indicated pressure in the underground reservoir by continuous selection of geothermal fluid, in the operating mode of the power supply system, a heat carrier is obtained for the power unit with the renewal of its selected volumes in the reservoir due to the infiltration of the water flow from the water area. The flow is heated to the temperature of the surrounding rock mass during the migration of water to the bottom of a water well. In this case, the necessary balance between the volumes of selection and flow of fluid coolant into the underground reservoir is controlled by the water level in the well and is approximately calculated on the basis of the known ratio for pressurized water (Reference book of a hydrogeologist. L. Nauka, 1979, v. 1, p. 293);
S _m [0,366 · Q · log (2 d / r)] / K · μ (4) where S _{m is the} decrease in water level in the well;
Q well flow rate;
d distance from the well to the water edge in the pond;
r well radius;
μ power underground collector.

 The application of the proposed method allows to reduce capital costs during the implementation and operation of the geothermal energy supply system due to the absence of the need for drilling and arrangement of special injection wells and the implementation of the reverse injection of waste fluid into the underground reservoir.

PRI me R. An example of an object for the implementation of the proposed method can serve as exploration area Duzlak in the territory of Primorsky Dagestan (Dagestan ASSR). A geological section of the area is shown in figure 2. The oil and gas bearing anticlinal uplift along its major semiaxis is parallel to the coastline, complicated by a discontinuous break, discovered by the parametric well N 100 at a depth of 2700. The width of the fault reaches 150 m. The lithological section of the area is made mainly by permeable sandstones. The temperature of the rocks, measured in the well at a depth of 2700 m in the fault zone, is 100 ^about C, a pressure of 400 kgf / cm ² . The fault across the strike extends from the arched part of the structure in the northeast to the bottom surface of the Caspian Sea, where the thickness of the water layer reaches 10 m. The hydrostatic pressure at the bottom is 2 atm, respectively.

At Duzlak Square, the proposed methods and arrangement of a geothermal power supply system (geothermal power station) can be implemented. Geothermal survey in the water area showed the presence of a temperature anomaly indicator over the fault of the indicator of the source of subaqueous unloading of groundwater. The deep hole N 100 can be used as a water well, and a discontinuous disruption instead of an injection well. After the start and stabilization of the infiltration process in the fault in accordance with the description of the proposed method of the coolant will serve as sea water entering the reservoir until a depth of 2700 m from the water area. Then the water-coolant is pumped to the surface by a pump through a water well N 100 and enters the power unit. The coolant will thus be at a temperature ^of intake hole 100 C. In order to maintain the process water by gravity infiltration of outside water area to a depth of fault intake water-lifting wellbore at that depth necessary to create in relation to the surface of the seabed pressure drop which can be approximately determined from the formula (3 ) The parameters required for the calculation for the Duzlak area are known: fluid viscosity μ taking into account the temperature dependence is 0.6 cps; the length of the filtration path along the fault L 4.4 · 10 ⁵ cm; the filtration area F based on the fault width of 150 m and a kilometer stretch along its strike in the vicinity of well N 100 will be 15 · 10 ⁸ cm ² ; the permeability coefficient Kp within the area can be estimated as 0.055 darsi. Taking as a cost-effective value of the selection of the coolant from a water well Q 20 · 10 ³ cm ³ / s (approximately 20 l / s) according to formula (3), the required pressure drop Δ P 60 kgf / cm ^{2 is} obtained. Such a pressure differential with respect to hydrostatic pressure at the bottom of the sea (2 atm) and reservoir pressure at a depth of 2700 m (400 kgf / cm ² ) can be created by pumping fluid from a water well with a pump with an energy consumption of about 100 kW. Since the length of the seawater filtration path along the fault is 4.4 km, the effect of annual temperature fluctuations at the bottom of the sea at the depth level of the well’s intake will not be visible and the heat transfer medium will take the rock temperature near the intake, i.e. 100 ^about S.

 Thus, the implementation of the method and device of the geothermal power supply system (geothermal power plant) at the Duzlak facility will reduce capital costs due to the absence of the need for drilling and the construction of an injection well with a depth of 2700 m and the implementation of the reverse injection of fluid into the reservoir.

Claims (1)

 A METHOD FOR IMPLEMENTING A GEOTHERMAL POWER SUPPLY SYSTEM IN THE COASTAL AREA OF THE AQUATORIA, which consists in selecting a geothermal fluid from an underground reservoir through a water-lifting well and supplying fluid to a reservoir, characterized in that the water is carried out in a geothermal way to reduce water costs unloading of underground thermal waters, determine the optimal location of the geothermal energy supply system, drill or use a ready-made water-lifting well with a bottom or water intake at a depth of this formation with the formation of the aforementioned reservoir, selection of geothermal fluid, create pressure in the reservoir that provides fluid to it from the water area, maintain the created pressure in the operating mode of the geothermal system.

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