CN108643878B - High-temperature disturbance strengthened acidizing and fracturing area gas extraction method - Google Patents

High-temperature disturbance strengthened acidizing and fracturing area gas extraction method Download PDF

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CN108643878B
CN108643878B CN201810336463.3A CN201810336463A CN108643878B CN 108643878 B CN108643878 B CN 108643878B CN 201810336463 A CN201810336463 A CN 201810336463A CN 108643878 B CN108643878 B CN 108643878B
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fracturing
acidizing
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temperature
gas
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CN108643878A (en
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倪冠华
解宏超
程卫民
王刚
李钊
董凯
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Shandong University of Science and Technology
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/006Production of coal-bed methane
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25Methods for stimulating production
    • E21B43/26Methods for stimulating production by forming crevices or fractures
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21FSAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F7/00Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose

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Abstract

The invention discloses a gas extraction method of a high-temperature disturbance strengthening acidizing fracturing region, which comprises the steps of firstly, sequentially constructing acidizing fracturing holes and high-temperature disturbance guide holes on a coal seam roadway side of a region to be treated by gas, wherein the acidizing fracturing holes are arranged in a rectangular array with the side length of 2-3 m, the high-temperature disturbance guide holes are arranged at the central positions of diagonal lines of the acidizing fracturing holes, the construction length of the acidizing fracturing holes is twice of that of the high-temperature disturbance guide holes, and the construction aperture of the acidizing fracturing holes is five times of that of the high-temperature disturbance guide holes; the acidizing fracturing equipment mainly comprises a fracturing pump, a liquid storage tank and a control console, and the high-temperature disturbance equipment comprises an electric heating generator and an electric heating control console. Performing acid fracturing on the coal bed through the acid fracturing holes by using acid fracturing equipment, simultaneously starting high-temperature disturbance equipment to heat the coal bed, heating the acidizing fluid through the temperature rise of the coal bed, enhancing the acid corrosion characteristic of the acidizing fluid, and realizing high-temperature disturbance enhanced acid fracturing; by implementing the method for extracting the gas in the acidizing and fracturing area through high-temperature disturbance strengthening, the acidizing and fracturing influence range is enlarged, the extracted gas concentration is improved, the effect is obviously improved compared with the existing common acidizing and fracturing effect, and the requirements of the work of gas treatment and the like in the underground area of the coal mine are met.

Description

High-temperature disturbance strengthened acidizing and fracturing area gas extraction method
Technical Field
The invention relates to a high-temperature disturbance strengthening acidizing and fracturing region gas extraction method, belongs to the field of coal mine underground region coal seam permeability-increasing gas extraction, and is particularly suitable for gas coal seam operation with high adsorption, difficult desorption and low gas permeability.
Background
China is one of the most serious countries in the world with gas disasters. More than twenty coal mine accidents with more than one hundred deaths occur since the country is built, and 20 of the coal mine accidents are gas accidents. The annual average increase of the coal mining depth is more than 15m, and the annual average increase of the gas pressure of a coal mining layer is 0.15-0.3 MPa. Along with the increase of mining intensity and depth, the increase of gas pressure and gas content, geological structure complexity deepens, will lead to coal mine gas calamity to become serious day by day. And coal seam gas extraction is a main measure for reducing gas hidden danger and gas disasters.
The acid fracturing is a very complex fluid-solid coupling process containing a chemical process, and the evolution rule of crack propagation and extension and the development length of cracks determine the development direction and trend of an anti-reflection range, so that the acid fracturing is an important index for measuring the anti-reflection range. But the effect of the acid fracturing is not obvious enough when the acid fracturing is simply applied to the coal bed with high adsorption, difficult desorption and low air permeability at present. Therefore, in order to overcome the defects of the existing acid fracturing technology, a novel fracturing method is urgently needed to meet the requirements of work such as gas control in an underground coal mine field area. The advantages of the existing acid fracturing are combined and absorbed, and the characteristic of high-temperature reinforced acid corrosion is utilized to form a set of high-temperature disturbance reinforced acid fracturing area gas extraction method.
Disclosure of Invention
The technical problem is as follows: the invention aims to provide a high-temperature disturbance strengthening acidizing and fracturing area gas extraction method which is large in gas extraction concentration, wide in fracturing influence range and remarkably increased in effect compared with the existing common acidizing and fracturing technology, aiming at the limitations of the existing gas extraction technology for promoting gas extraction of a gas coal seam with high adsorption, difficult desorption and low air permeability.
The technical scheme is as follows: the invention discloses a gas extraction method for a high-temperature disturbance strengthened acidizing and fracturing area, which is characterized by comprising the following steps of:
a. firstly, sequentially constructing acidizing fracturing holes and high-temperature disturbing guide holes on the coal seam roadway side of an area to be treated by gas, wherein the acidizing fracturing holes are arranged in a rectangular array with the side length of 3-5 m, the high-temperature disturbing guide holes are arranged at the diagonal center positions of the acidizing fracturing holes, and the construction length of the acidizing fracturing holes is twice that of the high-temperature disturbing guide holes;
b. the method comprises the following steps that acidizing and fracturing equipment is connected to an orifice of an acidizing and fracturing hole, the acidizing and fracturing equipment consists of an acid corrosion resistant high-pressure rubber pipe, an acidizing and fracturing pipe and an acidizing and fracturing pump device, each section of the acid corrosion resistant high-pressure rubber pipe is connected through a tee joint, one end of an outlet of the tee joint is connected with the acidizing and fracturing pipe, and each section of the acid corrosion resistant high-pressure rubber pipe is provided with a one-way throttle valve;
c. the high-temperature disturbance guide hole is connected with high-temperature disturbance equipment, and the high-temperature disturbance equipment consists of a high-temperature disturbance transmitting head and a high-temperature disturbance controller;
d. sequentially carrying out conventional drilling and sealing on the acidizing fracturing hole and the high-temperature disturbance guide hole;
e. starting high-temperature disturbance equipment, adjusting the temperature of a high-temperature disturbance emitter by using a high-temperature disturbance controller to heat the pre-extracted gas coal bed, setting the heating temperature to be 120 ℃, and keeping the temperature constant after the temperature reaches the set temperature;
f. opening a switch, simultaneously starting an acid fracturing pump device, and performing acid fracturing on the pre-extracted gas coal bed, wherein the acid fracturing liquid is in a high-temperature state due to the heating of the high-temperature disturbance device on the coal bed, so that the acid etching characteristic of the acid fracturing liquid is enhanced, and the high-temperature disturbance reinforced acid fracturing is realized;
g. setting different operation time according to different coal qualities, stopping high-temperature disturbance strengthening acidizing and fracturing operation after the set time is reached, dismantling equipment, and connecting the acidizing and fracturing holes and the high-temperature disturbance guide holes into a gas extraction pipe network for gas extraction.
The acidizing fracturing holes are arranged in a rectangular array with the side length of 3-5 m, and the construction aperture of the acidizing fracturing holes is five times that of the high-temperature disturbance guide holes.
The acidizing fracturing fluid consists of 10% hydrochloric acid, 5% hydrofluoric acid and 5% sodium dodecyl sulfate solution.
The different operation time is determined according to the permeability coefficient of the coal bed
Figure GDA0002281881160000021
And lambda is the permeability coefficient of the coal bed.
Has the advantages that: the method solves the limitation of the existing technology for promoting the gas in the coal bed by using the gas coal bed with high adsorption and difficult desorption, the acidizing and fracturing equipment is used for acidizing and fracturing the coal bed through the acidizing and fracturing holes, meanwhile, the high-temperature disturbance equipment is started to heat the coal bed, the acidizing fluid is heated through the temperature rise of the coal bed, the acid corrosion characteristic of the acidizing fluid is enhanced, and the high-temperature disturbance enhanced acidizing and fracturing is realized; by implementing the method for extracting the gas in the acidizing and fracturing area through high-temperature disturbance strengthening, the acidizing and fracturing influence range is enlarged, the extracted gas concentration is improved, the effect is obviously improved compared with the existing common acidizing and fracturing effect, and the requirements of work such as gas treatment in the underground area of a coal mine are met.
Drawings
FIG. 1 is a drilling layout diagram of the gas extraction method in the high-temperature disturbance strengthening acidizing and fracturing area.
FIG. 2 is a schematic diagram of a gas extraction method in a high-temperature disturbance strengthening acidizing and fracturing area.
In the figure: the method comprises the following steps of 1-roadway side, 2-coal bed, 3-acidizing fracturing hole, 4-high-temperature disturbance guide hole, 5-high-temperature disturbance emitter head, 6-high-temperature disturbance controller, 7-acid corrosion prevention high-pressure rubber pipe, 8-acidizing fracturing pipe, 9-hole sealing material, 10-tee joint, 11-one-way throttle valve, 12-acidizing fracturing pump device, 13-switch, 14-acid storage liquid tank and 15-crack.
The specific implementation method comprises the following steps:
embodiments of the invention are further described below with reference to the following drawings:
in fig. 1 and 2, a high-temperature disturbance strengthening acidizing and fracturing area gas extraction method is characterized in that firstly, acidizing and fracturing holes 3 and high-temperature disturbance guide holes 4 are sequentially constructed on a roadway side 1 of a coal seam 2 of an area to be treated by gas, the acidizing and fracturing holes 3 are arranged in a rectangular array, the high-temperature disturbance guide holes 4 are arranged at the diagonal center positions of the acidizing and fracturing holes 3, and the construction length of the acidizing and fracturing holes 3 is twice that of the high-temperature disturbance guide holes 4; the orifice of the acidizing and fracturing hole 3 is connected with acidizing and fracturing equipment, the acidizing and fracturing equipment consists of an acid corrosion resistant high-pressure rubber pipe 7, an acidizing and fracturing pipe 8 and an acidizing and fracturing pump device 12, each section of the acid corrosion resistant high-pressure rubber pipe 7 is connected by a tee joint 10, one end of the outlet of the tee joint 10 is connected with the acidizing and fracturing pipe 8, and each section of the acid corrosion resistant high-pressure rubber pipe 7 is provided with a one-way throttle valve 11; the high-temperature disturbance guide hole 4 is connected with high-temperature disturbance equipment which is subjected to high-temperature disturbanceThe shooting head 5 and the high-temperature disturbance controller 6; sequentially carrying out conventional drilling and sealing on the acidizing fracturing hole 3 and the high-temperature disturbance guide hole 4; starting high-temperature disturbance equipment, adjusting the temperature of a high-temperature disturbance emitter 5 by using a high-temperature disturbance controller 6 to heat the pre-extracted gas coal seam 2, setting the heating temperature to be 120 ℃, and keeping the temperature constant after the set temperature is reached; the switch 13 is turned on, the acidizing and fracturing pump device 12 is turned on at the same time, acidizing and fracturing are carried out on the coal seam 2 of the gas to be extracted, and the acidizing and fracturing liquid is in a high-temperature state due to the fact that the high-temperature disturbance device heats the coal seam 2, so that the acid corrosion characteristic of the acidizing liquid is enhanced, and high-temperature disturbance strengthening acidizing and fracturing is achieved; setting different operation time according to different coal qualities, stopping high-temperature disturbance strengthening acidizing and fracturing operation after the set time is reached, dismantling equipment, and connecting the acidizing and fracturing holes 3 and the high-temperature disturbance guide holes 4 into a gas extraction pipe network through a gas extraction pipe to extract gas. The acidizing fracturing holes 3 are arranged in a rectangular array with the side length of 3-5 m, and the construction aperture of the acidizing fracturing holes is five times that of the high-temperature disturbance guide holes; the acidizing fracturing fluid consists of 10% hydrochloric acid, 5% hydrofluoric acid and 5% sodium dodecyl sulfate solution. The different operation time is determined according to the permeability coefficient of the coal bed
Figure GDA0002281881160000031
And lambda is the permeability coefficient of the coal bed. By implementing the method for extracting the gas in the acidizing and fracturing area through high-temperature disturbance strengthening, the acidizing and fracturing influence range is enlarged, the extracted gas concentration is improved, the effect is obviously improved compared with the existing common acidizing and fracturing effect, and the requirements of work such as gas treatment in the underground area of a coal mine are met.

Claims (4)

1. A gas extraction method in a high-temperature disturbance strengthened acidizing and fracturing area is characterized by comprising the following steps:
a. firstly, sequentially constructing an acidizing fracturing hole (3) and a high-temperature disturbance guide hole (4) on a roadway side (1) of a pre-extraction gas coal seam (2), wherein the acidizing fracturing hole (3) is arranged in a rectangular array, the high-temperature disturbance guide hole (4) is arranged at the center of the diagonal line of the acidizing fracturing hole (3), the construction length of the acidizing fracturing hole (3) is twice that of the high-temperature disturbance guide hole (4),
b. the method is characterized in that an orifice of an acidizing and fracturing hole (3) is connected with acidizing and fracturing equipment, the acidizing and fracturing equipment consists of an acid corrosion resistant high-pressure rubber pipe (7), an acidizing and fracturing pipe (8) and an acidizing and fracturing pump device (12), each section of the acid corrosion resistant high-pressure rubber pipe (7) is connected with a tee joint (10), one end of an outlet of the tee joint (10) is connected with the acidizing and fracturing pipe (8), and each section of the acid corrosion resistant high-pressure rubber pipe (7) is provided with a one-way throttle valve (11);
c. the high-temperature disturbance guide hole (4) is connected with high-temperature disturbance equipment, and the high-temperature disturbance equipment consists of a high-temperature disturbance emitter (5) and a high-temperature disturbance controller (6);
d. sequentially carrying out conventional drilling and sealing on the acidizing fracturing hole (3) and the high-temperature disturbance guide hole (4);
e. starting high-temperature disturbance equipment, adjusting the temperature of a high-temperature disturbance emitter (5) by using a high-temperature disturbance controller (6) to heat the pre-extracted gas coal seam (2), setting the heating temperature to be 120 ℃, and keeping the temperature constant after the temperature reaches the set temperature;
f. the switch (13) is turned on, the acidizing and fracturing pump device (12) is turned on at the same time, acidizing and fracturing are carried out on the pre-extracted gas coal seam (2), and the acidizing and fracturing liquid is in a high-temperature state due to the fact that the high-temperature disturbance equipment heats the pre-extracted gas coal seam (2), so that the acid corrosion characteristic of the acidizing liquid is enhanced, and high-temperature disturbance enhanced acidizing and fracturing is achieved;
g. setting different operation time according to different coal qualities, stopping high-temperature disturbance strengthening acidizing and fracturing operation after the set time is reached, dismantling equipment, and connecting the acidizing and fracturing holes (3) and the high-temperature disturbance guide holes (4) into a gas extraction pipe network through a gas extraction pipe to extract gas.
2. The method for extracting gas from the high-temperature disturbance reinforced acid fracturing area according to claim 1, wherein the acid fracturing holes (3) are arranged in a rectangular array with the side length of 3-5 m, and the construction aperture of the acid fracturing holes (3) is five times that of the high-temperature disturbance guide hole (4).
3. The method for extracting gas from the high-temperature disturbance-enhanced acidized fractured region according to claim 1, wherein the acidizing fracturing fluid is composed of 10% hydrochloric acid, 5% hydrofluoric acid and 5% sodium dodecyl sulfate solution.
4. The method for extracting gas from the high-temperature disturbance-enhanced acid fracturing region according to claim 1, wherein the different operation times are determined according to the permeability coefficient of the coal seam
Figure FDA0002333815770000011
And lambda is the permeability coefficient of the coal bed.
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CN110130866B (en) * 2019-07-02 2021-07-30 湖南科技大学 Coal seam permeability increasing method with cooperation of hydraulic slotting and acidification demineralization
CN111119982B (en) * 2019-12-27 2021-01-08 中国矿业大学 High-gas coal seam in-situ pyrolysis gas fluidization mining method
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101353958A (en) * 2007-07-25 2009-01-28 中国石油天然气股份有限公司 Acid fracturing process of oil gas well mining temperature control various mucic acid
WO2014158427A1 (en) * 2013-03-14 2014-10-02 Halliburton Energy Services, Inc. Controlling Net Treating Pressure in a Subterranean Region
CN104179488A (en) * 2013-05-27 2014-12-03 中国石油化工股份有限公司 Method for improving low-permeability carbonate rock heavy oil reservoir development effect
CN105114116A (en) * 2015-07-30 2015-12-02 山东科技大学 Method for strengthening regional gas extraction through hydro-thermal coupling fracturing
CN106437824A (en) * 2016-11-28 2017-02-22 田成林 Gas-containing-coal multistage permeability increasing method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101353958A (en) * 2007-07-25 2009-01-28 中国石油天然气股份有限公司 Acid fracturing process of oil gas well mining temperature control various mucic acid
WO2014158427A1 (en) * 2013-03-14 2014-10-02 Halliburton Energy Services, Inc. Controlling Net Treating Pressure in a Subterranean Region
CN104179488A (en) * 2013-05-27 2014-12-03 中国石油化工股份有限公司 Method for improving low-permeability carbonate rock heavy oil reservoir development effect
CN105114116A (en) * 2015-07-30 2015-12-02 山东科技大学 Method for strengthening regional gas extraction through hydro-thermal coupling fracturing
CN106437824A (en) * 2016-11-28 2017-02-22 田成林 Gas-containing-coal multistage permeability increasing method

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
提高煤岩渗透性的酸化处理室内研究;李瑞等;《煤炭学报》;20140531;第39卷(第5期);全文 *
酸化工艺的煤层增透新技术;张迎新等;《黑龙江科技大学学报》;20140331;第24卷(第2期);全文 *

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