RU2521255C1 - Method of underground gasification - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: proposed method comprises well drilling from surface into processed interval in underground sea, placing the electrodes in the wells, application of voltage to said electrodes and heating of the seam of Joule heat. Voltage sufficient for producing of partial discharges and treeing is applied to electrodes to make the channel of electric-heat disruption of the seam, its formation being used for conclusion about decreased in electrode dap resistance. Then, current is passed via said channel of electric-heat disruption of the seam.

EFFECT: lower labour input and costs.

1 dwg

Description

The invention relates to mining, in particular to methods of underground gasification of solid fossil fuels, and can be used to obtain a gaseous energy carrier (combustible gas) from coal or shale at the site of occurrence.

A known method of underground gasification, including drilling wells, their failure, ignition, supply of blast and removal of productive gas [RF Patent No. 2385412, IPC E21B43 / 295, publ. 03/27/2010].

The disadvantage of this method is the low energy intensity (calorific value) of the produced commercial gas due to the presence in it of a large amount of ballast gas resulting from the burning of part of the organic mass in the chamber of the underground gas generator.

A known method of processing an underground formation containing a solid organic substance, comprising providing at least one well extending into the processing interval in the underground formation, creating at least one fracture from at least one well that intersects at least at least one well, placing the conductive material in the gap, contacting the two electrodes with the conductive material, applying voltage to the two electrodes to pass an electric current through the gap Thus, an electric current passes through at least a portion of the electrically conductive material and sufficient heat is generated by electrical resistivity in the portion of the electrically conductive material to pyrolyze at least a portion of the solid organic matter into recoverable hydrocarbons [RF Patent No. 2349745, IPC E21B43 / 24, publ. 03/20/2009]. The specified method is selected for the prototype.

The disadvantage of the prototype is the complexity of the method associated with the presence of additional technological operations, the possible toxicity of the electrically conductive material.

The objective of the invention is the creation of an effective, environmentally friendly method of underground gasification.

The technical result achieved by using the invention is to reduce the complexity of the gasification method, lower economic costs in the preparation of gasification by creating a channel for electrical thermal breakdown in the reservoir.

The specified technical result is achieved by the fact that in the method of underground gasification, which includes, like the prototype, drilling wells from the earth’s surface in the processed interval in the underground formation, placing electrodes in the wells, applying voltage to the electrodes, transmitting electric current and heating the formation, unlike of the prototype, a sufficient voltage is applied to the electrodes for the occurrence of partial discharges and tringing until the formation of an electric thermal breakdown channel in the formation, the formation moment of which is judged by reduced The resistance of the interelectrode space is then passed through a channel of electrical thermal breakdown in the formation and the formation is heated by Joule heat.

The invention is illustrated by the illustration of figure 1, which shows a functional diagram of the implementation of the method of underground gasification.

The method of underground gasification involves drilling two wells 1 from the soil surface, passing into the processed interval in the underground layer 2 of solid fossil fuels and placing electrodes 3 inside them, connected by cables to a ground current source 4 (Fig. 1). Gasification is carried out by heating the formation to a gas temperature of solid fuel (300-500 ° C). The rock is heated by passing current through an electrothermal breakdown channel due to Joule heat.

The electrical resistance of solid fuels is high (10 ⁸ ÷ 10 ¹² Ohm · cm), therefore, the Joule heat in the rock at technically possible voltage values will be small. The application of a high alternating voltage to the interelectrode gap of the formation causes the appearance of partial discharges that form electrically conductive sections at the site of the discharge in the bulk of the solid fuel rock. The action of the next discharge lengthens the conductive section. The resulting discharge structure, called dendrite, has a tree shape and propagates from the electrodes in the direction of the electrode of a different polarity. This process, called triing, continues until a through channel is formed between the electrodes. The voltage applied to the electrodes at this stage should be sufficient to form partial discharges. This voltage depends on the distance between the electrodes and the type of rock. The voltage value is determined experimentally on rock samples extracted to the surface. In this case, the presence of partial discharges is established visually, and the formation of a conducting channel is determined by reducing the interelectrode resistance. The voltage should be approximately 1-10 kV / m. It is necessary to use alternating voltage, voltage of industrial frequency can be used. When dendrites growing from bipolar electrodes are closed, forming a through conductive channel between the electrodes, the linear resistance of the interelectrode gap becomes low (10-100 Ohm / cm). To determine the moment of formation of the channel, control the voltage at the electrodes and the current between them. In this case, Joule heat in the formed conductive channel is possible. At this stage, a high-current source of direct or alternating voltage is connected to the electrodes. Then carry out heating due to the Joule heat in the conductive channel. The source voltage in this mode can be 10-100 V / m, and the current is limited by the power of the source and can be 10-100 A.

Example 1

A laboratory test of the method was carried out in an experimental chamber on a sample of oil shale with an electrode spacing of 50 cm. The preliminary measured ohmic resistance of the interelectrode distance was ~ 250 kOhm. At the initial stage, a sinusoidal voltage of 50 Hz and an amplitude of 5 kV was applied to the electrodes. This voltage is sufficient for the occurrence of partial discharges, the presence of which is established visually. A power of ~ 300 W was consumed from the source. This mode lasted for 30 minutes. After this time, a through conductive channel is formed. The ohmic resistance of the interelectrode distance became ~ 800 Ohms. Then, a current of 50 Hz from a regulated voltage source was passed through the interelectrode gap, and heating was performed due to Joule heat in the formed low-resistance channel. The voltage at first was hundreds of volts, as the channel was heated, its resistance decreased to ~ 10 Ohms, the voltage was reduced to 100 V to maintain a power of ~ 1 kW.

Example 2

A laboratory test of the method was carried out in an experimental chamber on a brown coal sample with a distance between the electrodes of 45 cm. The preliminary measured ohmic resistance of the interelectrode distance was ~ 150 kOhm. At the initial stage, a sinusoidal voltage of 50 Hz and an amplitude of 8 kV was applied to the electrodes. This voltage is sufficient for the occurrence of partial discharges, the presence of which is established visually. A power of ~ 600 W was consumed from the source. This regimen lasted for 15 minutes. After this time, a through conductive channel is formed. The ohmic resistance of the interelectrode distance began to be ~ 300 Ohms. Then, a current of 50 Hz from a regulated voltage source was passed through the interelectrode gap, and heating was performed due to Joule heat in the formed low-resistance channel. The voltage at first was hundreds of volts, as the channel was heated, its resistance decreased to ~ 3-5 Ohms, the voltage was reduced to 60 V to maintain a power of ~ 1 kW.

Thus, the claimed method allows to reduce the number of preparatory work, to exclude hydraulic fracturing and the use of toxic conductive materials and to increase the efficiency of the process.

Claims (1)

An underground gasification method, including drilling wells from the surface of the earth in an interval to be processed in an underground formation, placing electrodes in the wells, applying voltage to the electrodes, transmitting electric current and heating the formation due to Joule heat, characterized in that sufficient voltage is applied to the electrodes partial discharges and tiring until the formation of an electric thermal breakdown channel in the formation, the moment of formation of which is judged by the decrease in the resistance of the interelectrode space, for it passes a current through the electrothermal breakdown channel in the formation.