The coal mine down-hole drilling hydraulic fracturing stress boundary is determined and removing method
Technical field
The invention belongs to coal mine underground coal bed anti-reflection technical field, relate in particular to a kind of coal mine down-hole drilling hydraulic fracturing stress boundary and determine and removing method.
Background technology
Down-hole drilling hydraulic fracturing is as down-hole coal bed anti-reflection technical measures, has that anti-reflection scope is big, antireflective effect is remarkable, and therefore the characteristics of the extraction efficient of raising coal-bed gas that can be by a relatively large margin, have obtained using comparatively widely at present.
But the restriction that down-hole drilling hydraulic fracturing is subjected to pressure break object (coal seam, rock stratum) character and injects the pressure break liquid measure, existing crack in can not unconfined communication coal rock layer, and, under the effect of water under high pressure, the border of pressure break scope forms the high pressure abnormal belt easily, bring potential safety hazard to digging production, therefore, be necessary that its stress is surveyed and eliminated to the extending stress band scope on pressure break border concentrates scope, make down-hole drilling hydraulic fracturing its drawback that can disappear, obtain higher generalization and use.
Determining of current China down-hole drilling hydraulic fracturing stress boundary can only be by in estimating the pressure break scope, pressure break hole, interval different spacing construction effect inspection hole, and the parameter comparison such as gas natural flow, extraction flow, extraction concentration of investigating the validity check hole increase before determining whether to compare pressure break to some extent, if increase then within the pressure break scope, compare the effective range that not nip territory variation not quite could be determined pressure break up to gas flow, concentration having occurred, and then the stress of definite pressure break is concentrated the border with the boring farthest of pressure break span.The coal seam has inhomogeneity, except the fracturing function influence, itself character of distance coal seam far away is just different, even this has just caused and has not implemented fracturing, it also may exist parameter variation problems greatly such as gas flow, in addition, theoretically will be in construct the respectively boring of different spacing of the different directions of pressure break, but because the digging tunnel deployment constraints of down-hole, often a lot of directions in pressure break all are difficult to construction drill, thereby it is imperfect to have caused the pressure break effective range to divide, divide not science, and then had influence on the division that the pressure break boundary stress is concentrated band, for hidden danger has been buried in safety in production in the future.Simultaneously, concentrate boundary strip, provide corresponding stress and concentrate removing method at stress.
Use in the coal field geology work at home and abroad at present at most, effect ground physical prospecting preferably technology is earthquake and two kinds of transient electromagnetic methods.Though it is comparatively directly perceived, to the control of layer bit depth comparatively accurately, advantage such as can not omit substantially to tomography more than 5 meters and coal seam karst collapse col umn that the time section that seismic wave method has an acquisition is described the seat earth form, but also there is the problem that is difficult to differentiate coal seam roof and floor below 10 meters and coal bed texture, for the property of water-bearing in coal seam and the development condition in crack, more be difficult to now solve.Transient electromagnetic method is though have also that depth of investigation is big, useful signal is strong, speed of application is fast, advantage is better used in the colliery to the low-resistance abnormal response is clear etc., also obtains the checking of Coal Production in production practices really; But, because this technology is to adopt the logarithm Sampling techniques at present, make near (deep) target zone because of the sampling interval excessive (usually tens to rice up to a hundred) can not accurate description target zone locus of living in and geologic body change information.If survey its abnormal ranges in the coal of determining, rock stratum, above-mentioned these two kinds of methods all are difficult to achieve this end.Therefore, have only this sampling interval of CYT less, depth localization is relatively accurate, just possible to the responsive technology of rock stratum attribute reaction.
Utilize nagneto-telluric field to carry out geological exploration, proposed by the scientist of the former Soviet Union the earliest, in 20th century 50, the sixties, China geophysical prospecting equipment research and development technology personnel further investigate; The mid-80 has been developed first model machine of China---CYT-I, test, production application and technological improvement by surplus 20 years, the present instrument of this technology developed the 5th generation product, but restricted by some factor, field verification the verifying results such as oil, underground water, underground heat preferably still the 4th generation product---the CYT-IV.This technical equipment explains that aspect the underground water, water bearing bed position, water yield are all identical substantially with explanation results lacking under the situation of accurate geologic information, and under the situation that has borehole data to demarcate, the degree of agreement of explanation results and drilling data more can reach more than 70%.
CYT belongs to the magnetotelluric method class.It is field source with the natural alternating electromagnetic field, Kelvin effect effect when in the stratum, propagating according to alternating electromagnetic field, utilize the electromagnetic wave of different cycles to have the characteristic of different penetration capacitys, in the ground image data, reflect electrical vertical variation through certain calculating then, infer subterranean strata and attribute change situation thereof with this.
The high-altitude is radiated the plasma jet of the earth, speed and earth magnetosphere top, magnetosphere and ionosphere with 8~14 pulses of per second collide, excite in each instability boundary to produce various types of plasma waves, comprise that spread speed is that 25~90 kilometer per seconds, frequency are 10
-4~10
6The low frequency Alfven waves and the electromagnetic wave of hertz, these low-frequency electromagnetic waves can both obtain reflected back ground in each degree of depth.Ground is a strong reflection face, and low-frequency electromagnetic wave is decayed slower in the stratum, thereby has set up the past interflection between rock stratum and ground, has formed stable (repeatedly) resonant electromagnetic ripple (as shown in Figure 1), has become the field source of mt class methods such as CYT.
Theoretically, derive from the electromagnetic field of space, can be considered the plane wave of vertical earth surface incident.Suppose that earth medium is made up of level, homogeneous layered material, medium electrical parameter of the same race only is the function of the degree of depth, promptly becomes one-dimensional medium model (as shown in Figure 2).
The frequency (f) of the antiradiation pulse electromagnetic field (En, Hn) that produces at the interface of horizontal N layer uniform dielectric is relevant with rock stratum interface buried depth (h) with the resistivity (R) of overlying rock.Because the earth has low pass " window " characteristic to electromagnetic wave propagation.It is almost undamped when the relative pulsed electromagnetic fields (En or Hn) that the interface, underlying stratum produces is propagated in " window ".
The low-frequency electromagnetic wave of releasing according to auspicious (Burrel) is in vain propagated the medium and low frequency window by frequency f n design formulas in even horizontal N layer medium:
In the formula: fn--frequency (hertz)
K-constant, K=9.4 * 105
ρ-resistivity (ohm meter)
H-degree of depth (rice)
Know cut-off frequency fn and h thus
2Be inversely proportional to, both along with the increase of h, fn reduced, and promptly dark more bed boundary pulse electromagnetic wave reflection frequency is low more; In addition, cut-off frequency fn is directly proportional with resistivity (ρ), and promptly formation resistivity is high more, and its corresponding cut-off frequency (fn) also will be high more.
Layer depth h=2000 rice hypothetically, resistivity increment d ρ=0.1 ohm meter, by following formula:
Conversely, if known depth and frequency increment also just can be calculated the resistivity increment.If there are differences between resistivity that obtains by different frequency test and calculated value, indicating that this test data is comprising some rock stratum and other information.CYT gathers subterranean strata and reflexes to the energy of electromagnetic field that ground changes with small frequency (degree of depth), that is:
, can realize understanding and resolution to underground different depth rock stratum attribute.This just released full CYT on the face of land by the implication of test electromagnetic field.
As everyone knows, the wave field of certain frequency has certain penetration capacity, and electromagnetic wave is also like this: a little less than the penetration capacity of electromagnetic field of high frequency, the average effect coverage is also little; The low frequency electromagnetic field penetrating capacity is strong, and the average effect coverage is also big, and promptly penetration depth is big.CYT utilizes be frequency in 0.001~1000Hz long wave part, according to the skin depth theory, the degree of depth and resistivity and frequency (cycle) have following relation:
In the formula: the H--degree of depth, km; K-constant; R--resistivity, ohm meter;
The T--cycle, second; F-frequency, hertz.
Electromagnetic methods such as Here it is CYT survey underground electrically and the physical basis of depth relationship.
Because the minimum sampling interval of CYT technology is 0.5 meter at present, the maximum probe degree of depth is ten thousand metres, can satisfy the test job needs that the down-hole drilling hydraulic fracturing stress boundary is concentrated band fully.
Summary of the invention
The present invention provides a kind of coal mine down-hole drilling hydraulic fracturing stress boundary safe, efficient, credible, that engineering quantity is little to determine and removing method in order to solve weak point of the prior art.
For solving the problems of the technologies described above, the present invention adopts following technical scheme: the coal mine down-hole drilling hydraulic fracturing stress boundary is determined and removing method, may further comprise the steps,
⑴. choose the pairing on the ground reference point in underground fracture zone;
⑵. to carrying out the layout and the test of CYT measuring point before the pressure break in the corresponding scope of fracture zone location face;
⑶. CYT measuring point information before the pressure break is carried out data acquisition, arrangement, processing and analysis;
⑷. carry out the down-hole drilling hydraulic fracturing operation;
⑸. to carrying out the layout and the test of CYT measuring point after the pressure break in the corresponding scope of fracture zone location face;
⑹. CYT measuring point information after the pressure break is carried out data acquisition, arrangement, processing and analysis;
⑺. the difference of CYT measuring point data information before and after the comparative analysis pressure break, determine the pressure break scope;
⑻. eliminate the down-hole drilling hydraulic fracturing extending stress band.
The concrete steps of described step ⑴ are by checking coal mine excavation engineering plan view, to read the geodetic coordinates and the record of underground fracture boring position of opening and whole hole site; Seek corresponding geodetic datum on ground according to pressure break boring coordinate, as having geodetic datum in the fracture zone, then determine the coordinate of tapping point and whole hole point by the geodetic datum that exists, if there is not geodetic datum in the fracture zone, can use GPS or other location instrument to introduce corresponding geodetic datum and determine pressure break boring, and write down this point at the ground sign-posting in the position of opening and the whole hole site on ground from the existing nearest corresponding earthward fracture zone of geodetic datum.
The concrete steps of described step ⑵ are, according to boring length and the pre-pressure break boundary stress band range accuracy size that requires, determine the arrangement form and the cloth point range of pressure break drilling hole stress scope CYT measuring point, layout and to cover the pressure break scope that whole boring is estimated, and uniformly-spaced layout, the form of layouting is rectangle or ellipse.
The concrete steps of described step ⑶ are, be each measuring point numbering, and write down the geodetic datum of each measuring point, use CYT-IV type instrument to carry out data acquisition, the degree of depth of data acquisition determines that according to pressure break boring buried depth the degree of depth is greater than fractured layer position buried depth 20 ~ 30 m; Data preparation comprises zero correction and two contents of gain-adjusted; It is to calculate similar with potential logging to resistivity logging " class apparent resistivity " and " class natural potential " curve by certain design formulas by computer that data are handled; Data analysis is based upon data preparation and handles on the basis, comprises the demarcation of layer position and unusual identification.
Among the described step ⑸ position of the method for the layout of CYT measuring point and test and CYT measuring point with pressure break before the layout of CYT measuring point, promptly identical with step ⑵.
The concrete steps of described step ⑹ are, number and write down the geodetic datum of each measuring point for each measuring point, use CYT-IV type instrument to carry out data acquisition, the degree of depth of data acquisition determines that according to pressure break boring buried depth the degree of depth is greater than fractured layer position buried depth 20 ~ 30 m; Data preparation comprises zero correction and two contents of gain-adjusted; It is to calculate similar with potential logging to resistivity logging " class apparent resistivity " and " class natural potential " curve by certain design formulas by computer that data are handled; Data analysis is based upon data preparation and handles on the basis, comprises the demarcation of layer position and unusual identification.
The concrete steps of described step ⑺ are, read the difference of information according to CYT-IV type instrument before and after the pressure break, determine the fracturing scope, if the pressure break abnormity point appears between two test points, at this moment the stress of pressure break concentrates the border to be difficult to determine, can determine by the method that increases test point between latter two test point of pressure break.
The concrete steps of described step ⑻ are that spacing is not more than the boring of 5m at the bottom of construction hole, the place of each 20 m about stress boundary, carries out extraction then, concentrates band to eliminate stress.
The concrete steps of described step ⑻ are that on the basis of determining the pressure break radius, contiguous first second pressure break hole of construction, pressure break hole makes overlapping 20 m that are no less than of its pressure break radius carry out extinction.
Adopt technique scheme, the present invention utilizes existing advanced technology, provided definite method of coal mine down-hole drilling hydraulic fracturing anti-reflection mash gas extraction stress boundary, provide corresponding stress boundary removing method simultaneously, not only can go out the pressure break effective range by Validity Test, can mark off simultaneously in the pressure break implementation process because the stress that pressure break produces is concentrated scope, and compare down-hole construction effect inspection hole and have the characteristics safe, efficient, credible, that engineering quantity is little.
Description of drawings
Fig. 1 is repeatedly electromagnetic schematic diagram;
Fig. 2 is the layer-cake model schematic diagram;
Fig. 3 is boring tapping point and the definite schematic diagram of whole hole point geographical coordinates in the middle of the present invention;
Fig. 4 is the layout of CYT measuring point in the middle of the present invention and the schematic diagram of test.
The specific embodiment
Coal mine down-hole drilling hydraulic fracturing stress boundary of the present invention is determined and removing method, may further comprise the steps,
⑴. choose the pairing on the ground reference point in underground fracture zone;
As shown in Figure 3, by checking coal mine excavation engineering plan view, read the geodetic coordinates and the record of underground fracture boring position of opening and whole hole site; Seek corresponding geodetic datum 1 on ground according to pressure break boring coordinate, as having geodetic datum 1 in the fracture zone, then determine the coordinate of tapping point 2 and whole hole point 3 by the geodetic datum 1 that exists, if there is not geodetic datum 1 in the fracture zone, can use GPS or other location instrument 4 to introduce corresponding geodetic datum and determine pressure break boring, and write down this point at the ground sign-posting in the position of opening and the whole hole site on ground from the existing nearest corresponding earthward fracture zone of geodetic datum 5.
⑵. to carrying out the layout and the test of CYT measuring point before the pressure break in the corresponding scope of fracture zone location face;
As shown in Figure 4, according to boring length (distance between tapping point 2 and the whole hole point 3) and the pre-pressure break boundary stress band range accuracy size that requires, arrangement form and the cloth point range of determining pressure break drilling hole stress scope CYT measuring point 6 will cover the pressure break scope that whole boring is estimated, and uniformly-spaced layout, the form of layouting is rectangle or ellipse.Layout for rectangle shown in Fig. 2, the distance L between its measuring point is 10 m, can mini-frac the scope of each 40 m of boring both sides, certainly, layout what can determine according to the pressure break scope of preliminary injected water volume and expectation, also can after pressure break, mend survey.
⑶. CYT measuring point information before the pressure break is carried out data acquisition, arrangement, processing and analysis;
Be each measuring point numbering, and write down the geodetic datum of each measuring point, use CYT-IV type instrument to carry out data acquisition, the degree of depth of data acquisition is determined according to pressure break boring buried depth, the degree of depth is greater than fractured layer position buried depth 20 ~ 30 m, so that more effectively determine pressure break scope and stress boundary thereof; Data preparation comprises zero correction and two contents of gain-adjusted, this is a groundwork before the indoor analysis, it mainly is the influence that change is drifted about and the field intensity variation brings when subduing test data because of the space electromagnetic field, test data is adjusted near the same number axis, and with the profile amplitude adjusting within the specific limits, so that the contrast of data; It is to calculate similar with potential logging to resistivity logging " class apparent resistivity " and " class natural potential " curve by certain design formulas by computer that data are handled, to help our analysis to test data; Data analysis is based upon data preparation and handles on the basis, comprises the demarcation of layer position and unusual identification.
⑷. carry out the down-hole drilling hydraulic fracturing operation; The concrete steps of fracturing operation are prior art, do not repeat them here.
⑸. to carrying out the layout and the test of CYT measuring point after the pressure break in the corresponding scope of fracture zone location face;
In this step the position of the method for the layout of CYT measuring point and test and CYT measuring point with pressure break before the layout of CYT measuring point, promptly identical with step ⑵.
⑹. CYT measuring point information after the pressure break is carried out data acquisition, arrangement, processing and analysis;
This step is identical with step ⑶, be each measuring point numbering, and write down the geodetic datum of each measuring point, use CYT-IV type instrument to carry out data acquisition, the degree of depth of data acquisition is determined according to pressure break boring buried depth, the degree of depth is greater than fractured layer position buried depth 20 ~ 30 m, so that more effectively determine pressure break scope and stress boundary thereof; Data preparation comprises zero correction and two contents of gain-adjusted, this is a groundwork before the indoor analysis, it mainly is the influence that change is drifted about and the field intensity variation brings when subduing test data because of the space electromagnetic field, test data is adjusted near the same number axis, and with the profile amplitude adjusting within the specific limits, so that the contrast of data; It is to calculate similar with potential logging to resistivity logging " class apparent resistivity " and " class natural potential " curve by certain design formulas by computer that data are handled, to help our analysis to test data; Data analysis is based upon data preparation and handles on the basis, comprises the demarcation of layer position and unusual identification.
⑺. the difference of CYT measuring point data information before and after the comparative analysis pressure break, determine the pressure break scope;
Read the difference of information according to CYT-IV type instrument before and after the pressure break, determine the fracturing scope, if the pressure break abnormity point appears between two test points, at this moment the stress of pressure break concentrates the border to be difficult to determine, can determine by the method that increases test point between latter two test point of pressure break.
⑻. eliminate the down-hole drilling hydraulic fracturing extending stress band.
Although fracturing technology is anti-reflection and improve and to have better action aspect the gas pumping efficient in the coal seam, but after the fracturing, its degree of danger of stress zone that produces is not second to implementing before the pressure break, is necessary that therefore the counter stress border determines, simultaneously it eliminated.
The fracturing extending stress band can adopt following two kinds of methods to eliminate after determining:
1.. spacing is not more than the boring of 5m at the bottom of construction hole, the place of each 20 m about stress boundary, carries out extraction then, concentrates band to eliminate stress.
2.. on the basis of determining the pressure break radius, contiguous first second pressure break hole of construction, pressure break hole makes overlapping 20 m that are no less than of its pressure break radius carry out extinction.Such as, surveying the pressure break radius according to CYT is 50 m, after first pressure break drilling construction is finished, second pressure break of constructing apart from first 80 m places that hole holed and carried out pressure break, like this, the lap of two borings has 20 m, and it is concentrated effectively to eliminate stress.