CN106089291A - A kind of collaborative extraction is caving the old dead zone of formula and the method for lower coal seam coal bed gas - Google Patents

A kind of collaborative extraction is caving the old dead zone of formula and the method for lower coal seam coal bed gas Download PDF

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CN106089291A
CN106089291A CN201610453385.6A CN201610453385A CN106089291A CN 106089291 A CN106089291 A CN 106089291A CN 201610453385 A CN201610453385 A CN 201610453385A CN 106089291 A CN106089291 A CN 106089291A
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bed gas
extraction
horizontal well
coal
coal bed
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CN106089291B (en
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冯国瑞
李振
张钰亭
高强
杜献杰
白锦文
郭军
张玉江
康立勋
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Taiyuan University of Technology
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    • EFIXED CONSTRUCTIONS
    • E21EARTH 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
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/16Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor using gaseous fluids
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP 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 DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP 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
    • E21B43/12Methods or apparatus for controlling the flow of the obtained fluid to or in wells
    • E21B43/121Lifting well fluids
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP 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
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/164Injecting CO2 or carbonated water
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP 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 DRILLING; MINING
    • E21FSAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F16/00Drainage

Abstract

The invention discloses a kind of collaborative extraction and be caving the old dead zone of formula and the method for lower coal seam coal bed gas.First mine is surveyed by the method, and by ground to old dead zone construction of bottom plates horizontal well, press-in carbon dioxide cleans, and carries out coal bed gas extraction;When coal bed gas unit interval extraction amount drops to Q120% ~ 40%, circulation stops taking out reduction extraction pressure the process of extraction again;When extraction amount drops to Q1Less than 20% time, injecting carbon dioxide displacement again extraction;When extraction amount is re-lowered to Q1Less than 20%, frac water horizontal well and lower coal seam coal rock layer, carry out coal bed gas extraction;When extraction amount drops to Q2Less than 20% time, carry out supercritical carbon dioxide displacement;Extraction is until the Q that drops to of extraction amount again210% time stop taking out.The method achieve collaborative extraction be caving the old dead zone of formula and close on the coal bed gas of girdle, cost-effective and extraction coal bed gas resource to greatest extent.

Description

A kind of collaborative extraction is caving the old dead zone of formula and the method for lower coal seam coal bed gas
Technical field
The present invention relates to a kind of collaborative extraction and be caving the old dead zone of formula and the method for lower coal seam coal bed gas, belong to extraction coal bed gas Technical field.
Background technology
Due to long-term industrialization exploitation, China also exists countless numerous, old dead zone that area is huge.With Shanxi Province it is only Example, ended for the end of the year 2013, and Shanxi Province has more than 4700 place's abandoned mines, and old dead zone area has reached 5000 square kilometres, and these are old Mostly the excavation of dead zone is to use the relatively low old-fashioned blast-winning technology of recovery ratio, its coal mining rate typically 50%~ 60%, even lower, the most above-mentioned old dead zone is composed and is deposited appreciable coal bed gas resource gas reserves, and related data only shows Old dead zone Coal bed gas project about 30 billion cubic meter as a example by Shanxi Province.Gas is a kind of clean energy resource, to old dead zone residual coal The recovery energy of layer gas, can effectively alleviate the situation that China's natural gas is under-supply;Gas is as a kind of harmful gas simultaneously, Being discharged in air produced greenhouse effect is 21 times of carbon dioxide, and therefore the methane drainage and utilization project to this part gas has good Good economic benefit and environmental benefit.
Extraction currently for old dead zone gas is primarily directed to the extraction of single work surface old dead zone gas, and its method is By ground ground drilling of constructing in the fissure zone of top, old dead zone with extraction old dead zone gas, during this kind of method wellbore construction Difficulty of construction is big, accident rate is high, become porosity low.And a ground pit shaft can only carry out extraction for an old dead zone, The methane output of extraction is low and cost is high.Chinese patent CN105114038A discloses a kind of dependence supercritical CO2Jet pressure The method splitting adjacent old empty interval two old dead zone gas of coal column extraction same level;Chinese patent CN104696006A discloses A kind of method penetrating abandoned coal pillar extraction multilamellar old dead zone, multilamellar old dead zone remnants coal bed gas;Said method is vertical shaft extraction Multiple old dead zones gas is made that important exploration;
But, above-mentioned patent also exists that ground vertical drilling is little with coalbed methane reservoir contact surface, extraction is limited in scope etc. and asks Topic, the most above-mentioned patent retains coal bed gas resource in being the old sky of extraction, the most not by old dead zone coal bed gas be adjacent to mine coal Layer gas resource is planned as a whole to get up, it is considered to work in coordination with extraction.
It is true that coal seam is often composed with multilamellar coal form in a distance and is existed in coalfield, for top in coalfield In the case of being the combination geology that bottom, old dead zone is thinner seam, at present from solid mineral deposit excavation exploitation (tradition excavation is mined) The girdle (0~1.5 meter) that underlying seam thickness fluctuations is bigger is often abandoned and is adopted by angle, abandons the reason adopted and mostly is and adopts Ore deposit is the most infeasible or technically feasible but abandons it from Financial cost angle and adopts, and this has resulted in most coal suitable A large amount of wastes of (coal bed gas) resource.
For this for the problems referred to above, the present invention, from collaborative extraction, the angle of comprehensive exploitation, proposes one and is collapsed on top The method that the while that the method that falls exploitation forming old dead zone coal bed gas and bottom thin coal seam coal bed gas, extraction goes out.
Summary of the invention
Abandoning for above-mentioned coal (coal bed gas) resource and adopt the ample resources wasting phenomenon caused, the present invention proposes one can Collaborative old dead zone, extraction top coal bed gas can reclaim again the coal bed gas pumping method of bottom thin coal seam coal bed gas resource.
For achieving the above object, present invention provide the technical scheme that
The invention provides a kind of collaborative extraction and be caving the old dead zone of formula and the method for lower coal seam coal bed gas, including following step Rapid:
1) according to the existing geology digging data such as coal mine excavation situation, coal seam block diagram and surface-underground contrast plan, simultaneously Use physical prospecting means that the old dead zone excavated carries out on-site land survey, clearly obtain the old dead zone parameter that top has been excavated (including that scope, cavity, coal column distribution situation etc. are excavated in old dead zone), distance D between the old dead zone of underlying seam and top;
2) acquisition is caving the old dead zone of formula by superjacent and excavates the plate destructing depth d caused;
3) if D is d, by ground to the middle rock stratum construction water between top old dead zone base plate and underlying seam top board Horizontal well, open valve II by air injection pipe be pressed in horizontal well 1~2MPa carbon dioxide 30~60 minutes, to horizontal well It is carried out;If during D d, then by ground to top old dead zone plate destructing depth construction level well, open valve II by noting Trachea be pressed in horizontal well 1~2MPa carbon dioxide 30~60 minutes, horizontal well is carried out;
Horizontal well by down-hole extended spot earthward be divided into horizontal well horizontal segment, inclination section, horizontal well vertical section and Horizontal well ground surface end, wherein horizontal well ground surface end is by two branch roads of three reduction of fractions to a common denominators: drainage tube I and air injection pipe, wherein on drainage tube I Being provided with valve I, air injection pipe is provided with valve II, and end near the ground to horizontal well vertical section carries out sealing formation seal section I, and ground sets There is sealing device I;
4) open valve I, by drainage tube I, horizontal well is carried out coal bed gas extraction for the first time, record coal in the now unit interval Layer gas extraction amount is Q1
5) when in the unit interval coal bed gas extraction amount drop to Q120%~40% time, close valve I, stop taking out 12~36 Hour, it is again turned on valve I afterwards, reduces extraction pressure simultaneously and proceed coal bed gas extraction;When coal bed gas in the unit interval Extraction amount drops to Q again120%~40% time, be again switched off valve I, stop taking out 12~36 hours, be again turned on valve afterwards Door I, again reduces extraction pressure and carries out coal bed gas extraction;Circulate and above-mentioned stop taking out-the process of blood pressure lowering extraction, until extraction pressure drop As little as force down 80~100kpa than air;
6) when in the unit interval coal bed gas extraction amount drop to Q1Less than 20% time, close valve I, open valve II by Air injection pipe injects the CO of 5~20MPa in horizontal well2Gas 8~36 hours, close valve II on ground afterwards, wait for quietly 12~ 48 hours, it is again turned on valve I afterwards and carries out coal bed gas extraction;
7) when in the unit interval coal bed gas extraction amount again drop to Q1Less than 20% time, dismounting wellhead tee joint and sealing Device I, is transferred staged fracturing equipment by well head, to the interlayer rock stratum between horizontal well horizontal segment and underlying seam and lower coal Layer implements directional fracturing;
8) horizontal well vertical section is carried out vertical extension, until extending at underlying seam base plate 5~20 meters of scopes;
9) being installed relevant mining equipment by horizontal well vertical section, mining equipment is sequentially provided with to above ground portion by down-hole and takes out Oil pump, oil pick-up tube, be provided with sucker rod in oil pick-up tube, the oil pumper that ground is arranged drives oil well pump to hang down horizontal well by sucker rod Water in straight section carries out mining;Horizontal well vertical section ground surface end is divided into three branch roads by four-way: drain pipe, drainage tube II, beam Pipe, drain pipe connects down-hole oil pick-up tube, and ground surface end is provided with valve IV, and drainage tube II ground surface end is connected with valve III, beam pipe ground End is connected with valve V, and the underground part of beam pipe extends in horizontal well horizontal segment, and is positioned at horizontal well horizontal segment and is Mesh section, end near the ground to horizontal well vertical section carries out sealing formation seal section II, and ground is provided with sealing device II;
Open valve III and valve IV, oil pumper drive oil well pump that the water in horizontal well vertical section is entered by sucker rod Row extraction, is carried out coal bed gas extraction by drainage tube II simultaneously, coal bed gas maximum extraction amount Q in the unit interval in record mining2
10) when in the unit interval coal bed gas extraction amount drop to Q2Less than 20% time, close valve III, valve IV, beat Valve opening door V by beam pipe implantation temperature in horizontal well be 32~50 DEG C, pressure be 8~20MPa supercritical CO224~72 Hour, close valve IV, wait for 12~48 hours quietly;
11) it is again turned on valve III, valve IV, mining equipment again carries out drainage and step-down and coal bed gas extraction;
12) when in the unit interval coal bed gas extraction amount drop to Q2Less than 10% time, stop coal bed gas extraction.
Above-mentioned collaborative extraction top is caving the old dead zone of formula and the method for lower coal seam coal bed gas, old dead zone, described top base plate The determination of the formation damage degree of depth, needs to use base plate release depth formula in field measurement, protective coat extracted, based on moulding theory Floor strata maximal destruction depth formula and laboratory values simulation, the mode of analog simulation or five kinds of methods mutually tie Incompatible determine, take minima that said method obtains when determining collapse dept as reference value.
Above-mentioned collaborative extraction top is caving the old dead zone of formula and the method for lower coal seam coal bed gas, described horizontal well vertical section from Passing in the coal column of border, old dead zone, be 10~60 meters with the horizontal range of coal column end, border, horizontal well horizontal segment vertical depth is the end of by Interfloor distance between the old dead zone of plate collapse dept and top and underlying seam is determined, horizontal well inclination section kickoff point (KOP) is chosen Then determined by fixed horizontal segment, vertical section layer position and on-the-spot drilling technology.
Above-mentioned collaborative extraction is caving the old dead zone of formula and the method for lower coal seam coal bed gas, and described orientation staged fracturing is sleeve pipe One in Limited entry fracturing, multiple-string packer staged fracturing or orientation water-jet staged fracturing technology.
Using technique scheme, the present invention obtains and provides the benefit that:
This invention is from the angle of coal (coal bed gas) resource coordinating exploitation (extraction), and remained old dead zone is big simultaneously Amount coal bed gas resource and employing conventional mining method are abandoned the coal bed gas resource closing on girdle adopted and are taken into account, it is proposed that one Plant the innovative approach of collaborative extraction coal bed gas.The method can effectively solve the old dead zone of vertical drilling extraction, original simple employing ground Time, the difficult problem that extraction drilling well is little with the old dead zone effective contact area of reservoir, extraction is limited in scope;This method avoid ground simultaneously Wellbore construction is high to the drilling failure rate caused above the fissure zone of old dead zone, become the difficult problem that porosity is low, difficulty of construction is big;In extraction By in the coal bed gas resource extraction in the lump closing on girdle while the coal bed gas of old dead zone, solve to abandon and adopt dull coal bed gas money The recovery in source, has accomplished that a well is multiplex, has saved cost greatly;Horizontal well is positioned at more than underlying seam simultaneously, it is to avoid bore When well is directly beaten to coal seam, and the hoistway cave-in accident that occur and hoistway blocking accident the loosest due to coal seam.
Accompanying drawing illustrates:
Fig. 1 is the structural representation of preliminary stage construction level well extraction process of the present invention.
Fig. 2 is that later stage of the present invention sets up the structural representation of extraction process after mining equipment.
In figure 1, drainage tube I, 2, valve I, 3, valve II, 4, air injection pipe, 5, horizontal well vertical section, 6, inclination section, 7, point Section fracturing fracture, 8, staged fracturing spacer, 9, horizontal well horizontal segment, 10, top be caving the old dead zone of formula, 11, staged fracturing section, 12, coal seam floor failure scope, 13, underlying seam, 14, border coal column, 15, horizontal well, 16, seal section I, 17 sealing devices I, 18, drainage tube II, 19, valve III, 20, drain pipe, 21, valve IV, 22, beam pipe, 23, valve V, 24, oil pumper, 25, four Logical, 26, sealing device II, 27, seal section II, 28, oil pick-up tube, 29, sucker rod, 30, oil well pump, 31, threeway.
Detailed description of the invention
Further illustrate the present invention below by embodiment, but be not limited to following example.
Embodiment:
Following example are intended to schematically illustrate the present invention and explain, not delimit the scope of the invention.
In order to technical goal, feature and the effect of the present invention have clearer explanation, take out one is collaborative in conjunction with accompanying drawing The method adopting the old dead zone of the formula of being caving and lower coal seam coal bed gas is described in detail.
Below as a example by the work surface of Jin Mei group Yue Cheng ore deposit, this inventive method is described: Yue Cheng ore deposit is seated Qinshui coalfield, This coalfield is one of abundant important coalfield of China's coal bed gas resource, and in the range of coalfield, in field with "nine squares", minable coal seam is the 3 of Shanxi group Number coal seam and No. 9 of Taiyuan Forma-tion, No. 15 coal seams.The reasons such as the backwardness due to history and recovery method, main mining coal seam 3 in coalfield Number coal recovery ratio is low, is retained in a large amount of coal in down-hole, and old dead zone Coal bed gas project is the abundantest.With 3 coal seam floor average headways it is No. 9 coals of the girdle of 46 meters, thick 1 meter of its average coal, this coal seam is not yet exploited.If this girdle well work in traditional mining mode is opened Adopt the most with high costs, value can be adopted not quite, but this part resource is hesitated to discard.For satisfactorily resolve top be caving the old dead zone of formula with And the collaborative exploitation of lower coal seam coal bed gas resource, the present invention provide inventive method particularly as follows:
For solving the collaborative exploitation of coal (coal bed gas) resource, this invention provides method particularly includes:
1, have geology digging data according to coal mine excavation situation, coal seam block diagram and surface-underground contrast plan etc. and combine The means such as three-dimensional laser scanner, transient electromagnetic method determine that top, down-hole is caving the old dead zone of formula (10) parameter and underlying seam And top is caving the distance D=47 rice between the old dead zone of formula (10) (13);Described old dead zone parameter includes the scope in post exploiting field, number Mesh and coal column number, size, distribution general location;
2, acquisition is caving the old dead zone of formula by superjacent and excavates the plate destructing depth d caused: about plate destructing depth And the determination of width, need to use base plate release depth formula in field measurement, protective coat extracted, based on moulding theory herein Floor strata maximal destruction depth formula and laboratory values simulation, the mode of analog simulation or five kinds of methods mutually tie Incompatible determine, take minima that said method obtains when determining collapse dept as reference value;Present example have employed protection Layer exploitation correlation theory and floor strata maximal destruction depth formula based on moulding theory are theoretical:
Obtain according to above-mentioned geology and physical prospecting means: according to geological condition of coal mine and exploitation situation Yue Cheng colliery work Make face parameter as follows: No. 3 coal seams (protective layer) averagely thick 6.19 meters of coal, average 3 degree of buried depth 400m seam inclination, these work surfaces 3 The average working thickness 4 meters of coal (protective layer), work surface tendency face length 125 meters, across pitch work surface face length 400 meters, this coal seam is adopted Coal method uses and moves towards longwall, and roof controlling method is whole caving method.
A. theoretical by protective coat extracted, determine plate destructing depth h according to " preventing and treating coal and gas prominent regulation "0:
Protected lower limits can be calculated relative to protection according to release angle, bottom (taking 60 degree) and interlamellar spacing (47 meters) In layer work surface, wrong distance is: L1=H*ctg60=26m, L2=H*ctg60=26m;
Wherein L1The width cannot protected relative to protection work surface open-off cut side for protected seam;
L2For stopping adopting the width that line side cannot be protected relative to protection work surface for protected seam;
Interlayer maximum effective protection aquiclude spacing: S after No. 3 seam miningsOn=S'Onβ1β2
Tabling look-up according to " preventing and treating coal and gas prominent specifies ", it is theoretical the most maximum vertical away from S' to obtain up-protective layer exploitationOn= 66m, protective layer is adopted rear 4m, is taken β1=1, β2=1, so maximum effective protection aquiclude interval SOnIt is 66 meters, herein, maximum effectively guarantor Sheath spacing is the plate destructing depth h theoretical based on protective coat extracted0, i.e. h0=SOn=66m.
B. by moulding theory analysis floor rock maximal destruction degree of depth h1For:
In above formula, xaFor yield region, coal seam length,Internal friction angle for floor rock;
Herein, yield region, coal seam length xaDetermination can by field measurement or according to A.H.Wilson propose yield limit Formula, takes into account coal seam and the roof and floor lithologic impact on coal seam floor failure, if coal strength is less than roof and floor rock mass strength, then:
If coal strength is close to when determining floor rock intensity:
Wherein:
To should operating mode, by correlation report, No. 3 seam mining m=4m, internal friction angle 30 degree, base plate volume-weighted average is 2.5t/m3, buried depth H=400 rice, the average internal friction angle of floor rock takes 45 degree, and coal mass strength is less than roof and floor intensity, therefore K1= 3;F=2.55;
So yield region, coal seam length
Floor rock maximal destruction degree of depth h will be brought into1For:
So, based on moulding theory analysis floor rock maximal destruction degree of depth h1=21.56m;
To sum up, determine that plate destructing depth takes h in above-mentioned two methods0And h1Minima i.e. d=min (h0,h1)=21m,
It should be noted that the determination of plate destructing depth herein can be combined with field measurement data or laboratory Interior analog simulation or numerical simulation result, take the minima in applied method as collapse dept d during value.
3, in present example, D d (47m > 21m), so being caving below the old dead zone of formula (10) base plate by ground to top Construction level well (15) at 21m, open valve II (3) and are pressed into the carbon dioxide of 1MPa by air injection pipe (4) in horizontal well (15) Gas 30 minutes, is carried out horizontal well;
Horizontal well (15) is divided into horizontal well horizontal segment (9), inclination section (6), horizontal well by down-hole extended spot earthward Vertical section (5) and horizontal well ground surface end, wherein horizontal well ground surface end is by threeway (31) point two branch roads: drainage tube I (1) and Air injection pipe (4), wherein drainage tube I (1) is provided with valve I (2), and air injection pipe (4) is provided with valve II (3), vertical to horizontal well Section (5) end near the ground carries out sealing formation seal section I (16), and ground is provided with sealing device I (17);
4, opening valve I (2), by drainage tube I (1), horizontal well (15) is carried out coal bed gas extraction for the first time, record is now single In bit time, coal bed gas extraction amount is Q1
5, when in the unit interval coal bed gas extraction amount drop to Q126% time, close valve I (2), stop taking out 12 hours, it After be again turned on valve I (2), reduce extraction pressure simultaneously and proceed coal bed gas extraction;When coal bed gas extraction in the unit interval Amount drops to Q again126% time, be again switched off valve I (2), stop taking out 12 hours, be again turned on valve I (2) afterwards, again Reduce extraction pressure and carry out coal bed gas extraction;Circulate and above-mentioned stop taking out-the process of blood pressure lowering extraction, until extraction pressure drop as little as ratio is greatly The low 80kpa of air pressure;
6, when in the unit interval coal bed gas extraction amount drop to Q1Less than 20% time, close valve I (2), open valve II (3) CO being injected 10MPa by air injection pipe (4) in horizontal well (15)2Gas 36 hours, closes valve II on ground afterwards (3), wait for quietly 48 hours, be again turned on valve I (2) afterwards and carry out coal bed gas extraction;
7, when in the unit interval coal bed gas extraction amount again drop to Q1Less than 20% time, dismounting wellhead tee joint (31) and Sealing device I (17), is transferred staged fracturing equipment by well head, to the layer between horizontal well horizontal segment (9) and underlying seam (13) Between rock stratum and underlying seam (13) implement directional fracturing;
8, horizontal well vertical section (5) is carried out vertical extension, until extending at 10 meters of scopes of underlying seam (13) base plate;
9, being installed relevant mining equipment by horizontal well vertical section (5), mining equipment is set to above ground portion successively by down-hole Having oil well pump (30), oil pick-up tube (28), be provided with sucker rod (29) in oil pick-up tube (28), the oil pumper (24) that ground is arranged is by taking out Beam hanger (29) drives oil well pump (30) that the water in horizontal well vertical section (5) is carried out mining;Horizontal well vertical section (5) ground surface end by Four-way (25) is divided into three branch roads: drain pipe (20), drainage tube II (18), beam pipe (22), drain pipe (20) connects down-hole and takes out Oil pipe (28), ground surface end is provided with valve IV (21), and drainage tube II (18) ground surface end is connected with valve III (19), beam pipe (22) ground End is connected with valve V (23), and the underground part of beam pipe (22) extends in horizontal well horizontal segment (9), and is positioned at horizontal well Being mesh section in horizontal segment (9), carry out horizontal well vertical section (5) end near the ground sealing formation seal section II (27), ground sets There is sealing device II (26);
Open valve III (19) and valve IV (21), oil pumper (24) drive oil well pump (30) right by sucker rod (29) Water in horizontal well vertical section (5) carries out extraction, is carried out coal bed gas extraction, unit in record mining by drainage tube II (18) simultaneously Coal bed gas maximum extraction amount Q in time2
10, when in the unit interval coal bed gas extraction amount drop to Q2Less than 20% time, close valve III (19), valve IV (21), open valve V (21) by beam pipe (22) implantation temperature in horizontal well (15) be 38 DEG C, pressure be that the super of 15MPa faces Boundary CO224 hours, close valve IV (21), wait for 12 hours quietly;
11, it is again turned on valve III (19), valve IV (21), mining equipment again carries out drainage and step-down and coal bed gas Extraction;
12, when in the unit interval coal bed gas extraction amount drop to Q2Less than 10% time, stop coal bed gas extraction.
In said method, described top is caving the determination of the old dead zone of formula (10) floor strata collapse dept, needs to use now Actual measurement, base plate release depth formula in protective coat extracted, floor strata maximal destruction depth formula based on moulding theory with And laboratory values simulation, the mode of analog simulation or five kinds of methods combine and determine, take above-mentioned when determining collapse dept The minima that method obtains is as reference value;
In said method, described horizontal well vertical section (5) passes from border, old dead zone coal column (14), with border coal column (14) horizontal range of end is 40 meters, and horizontal well inclination section (6) kickoff point (KOP) is chosen then by fixed horizontal well horizontal segment (9), horizontal well vertical section (5) layer position and on-the-spot drilling technology determine.
In said method, have employed orientation water-jet staged fracturing technology.

Claims (4)

1. a collaborative extraction is caving the old dead zone of formula and the method for lower coal seam coal bed gas, it is characterised in that: comprise the following steps:
1) according to the existing geology digging data such as coal mine excavation situation, coal seam block diagram and surface-underground contrast plan, use simultaneously Physical prospecting means carry out on-site land survey to the old dead zone excavated, and clearly obtain the old dead zone parameter that top has been excavated, bottom Distance D between the old dead zone in coal seam and top, old dead zone parameter includes that scope, cavity, coal column distribution situation are excavated in old dead zone;
2) acquisition is caving the old dead zone of formula by superjacent and excavates the plate destructing depth d caused;
3) if D is d, by ground to the middle rock stratum construction level well between top old dead zone base plate and underlying seam top board, Open valve II in horizontal well, be pressed into the carbon dioxide 30 ~ 60 minutes of 1 ~ 2MPa by air injection pipe, horizontal well is carried out clearly Wash;If during D d, then by ground to top old dead zone plate destructing depth construction level well, open valve II by air injection pipe to In horizontal well, the carbon dioxide of press-in 1 ~ 2MPa 30 ~ 60 minutes, are carried out horizontal well;
Horizontal well is divided into horizontal well horizontal segment, inclination section, horizontal well vertical section and level by down-hole extended spot earthward Well ground surface end, wherein horizontal well ground surface end passes through two branch roads of three reduction of fractions to a common denominators: drainage tube I and air injection pipe, wherein drainage tube I is provided with Valve I, air injection pipe is provided with valve II, and end near the ground to horizontal well vertical section carries out sealing formation seal section I, and ground is provided with close Seal apparatus I;
4) open valve I, by drainage tube I, horizontal well is carried out coal bed gas extraction for the first time, record coal bed gas in the now unit interval Extraction amount is Q1
5) when in the unit interval coal bed gas extraction amount drop to Q120% ~ 40% time, close valve I, stop taking out 12 ~ 36 hours, afterwards It is again turned on valve I, reduces extraction pressure simultaneously and proceed coal bed gas extraction;When in the unit interval, coal bed gas extraction amount is again Drop to Q120% ~ 40% time, be again switched off valve I, stop taking out 12 ~ 36 hours, be again turned on valve I afterwards, again reduce and take out Adopt pressure and carry out coal bed gas extraction;Circulate and above-mentioned stop taking out-the process of blood pressure lowering extraction, until extraction pressure drop is as little as forced down than air 80~100kpa;
6) when in the unit interval coal bed gas extraction amount drop to Q1Less than 20% time, close valve I, open valve II by air injection pipe The CO of 5 ~ 20MPa is injected in horizontal well2Gas 8 ~ 36 hours, closes valve II on ground afterwards, waits for quietly 12 ~ 48 hours, it After be again turned on valve I and carry out coal bed gas extraction;
7) when in the unit interval coal bed gas extraction amount again drop to Q1Less than 20% time, dismounting wellhead tee joint and sealing device I, Transferred staged fracturing equipment by well head, the interlayer rock stratum between horizontal well horizontal segment and underlying seam and underlying seam are implemented Directional fracturing;
8) horizontal well vertical section is carried out vertical extension, until extending at 5 ~ 20 meters of scopes of underlying seam base plate;
9) being installed relevant mining equipment by horizontal well vertical section, mining equipment is sequentially provided with oil pumping by down-hole to above ground portion Pump, oil pick-up tube, be provided with sucker rod in oil pick-up tube, the oil pumper that ground is arranged drives oil well pump vertical to horizontal well by sucker rod Water in Duan carries out mining;Horizontal well vertical section ground surface end is divided into three branch roads by four-way: drain pipe, drainage tube II, beam pipe, Drain pipe connects down-hole oil pick-up tube, and ground surface end is provided with valve IV, and drainage tube II ground surface end is connected with valve III, and beam pipe ground surface end is even There are valve V, the underground part of beam pipe to extend in horizontal well horizontal segment, and to be positioned at horizontal well horizontal segment be mesh Section, end near the ground to horizontal well vertical section carries out sealing formation seal section II, and ground is provided with sealing device II;
Open valve III and valve IV, oil pumper drive oil well pump that the water in horizontal well vertical section is taken out by sucker rod Adopt, carried out coal bed gas extraction by drainage tube II simultaneously, coal bed gas maximum extraction amount Q in the unit interval in record mining2
10) when in the unit interval coal bed gas extraction amount drop to Q2Less than 20% time, close valve III, valve IV, open valve V by beam pipe implantation temperature in horizontal well be 32 ~ 50 DEG C, pressure be the supercritical CO of 8 ~ 20MPa2 24 ~ 72 hours, close Valve IV, waits for 12 ~ 48 hours quietly;
11) it is again turned on valve III, valve IV, mining equipment again carries out drainage and step-down and coal bed gas extraction;
12) when in the unit interval coal bed gas extraction amount drop to Q2Less than 10% time, stop coal bed gas extraction.
2. being caving the old dead zone of formula and the method for lower coal seam coal bed gas according to the collaborative extraction described in claims 1, its feature exists In: the determination of old dead zone, top floor strata collapse dept, need to use the base plate release degree of depth in field measurement, protective coat extracted Formula, floor strata maximal destruction depth formula based on moulding theory and laboratory values simulation, the mode of analog simulation Or five kinds of methods combine and determine, take the minima of said method acquisition when determining collapse dept as reference value.
Collaborative extraction the most according to claim 1 is caving the old dead zone of formula and the method for lower coal seam coal bed gas, it is characterised in that: Described horizontal well vertical section passes from the coal column of border, old dead zone, is 10 ~ 60 meters with the horizontal range of coal column end, border, level Well horizontal segment vertical depth is determined by the interfloor distance between the old dead zone of plate destructing depth and top and underlying seam, horizontal well Inclination section kickoff point (KOP) is chosen and is determined by fixed horizontal well horizontal segment, horizontal well vertical section layer position and on-the-spot drilling technology.
Collaborative extraction the most according to claim 1 is caving the old dead zone of formula and the method for lower coal seam coal bed gas, it is characterised in that: Described orientation staged fracturing is in sleeve pipe Limited entry fracturing, multiple-string packer staged fracturing or orientation water-jet staged fracturing technology One.
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