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    • 专利摘要:
    The present invention presents a method for evaluating the fracturability of a coal reservoir, comprising the following steps: Step 1: calculation of the fragility index BI of a coal reservoir to be evaluated; Step 2: calculation of the fracture toughness Kc of the coal reservoir under confinement pressure; Step 3: calculation of the thickness Eh of the coal tank to be evaluated; Step 4: calculation of the difference in elastic modulus Ek between the coal reservoir and the surrounding rock; Step 5: calculation of the net pressure coefficient σn of the coal tank to be evaluated; Step 6: Calculation of the degree of humidity Mad of the rocky coal: Step 7: Calculation of the Frac of the coal reservoir for the estimation of the fracturability of the coal; Step 8: evaluation of the fracturability of the coal reservoir. The main advantages of the present invention are as follows: the adopted parameters are easy to obtain, the difficulty in carrying out the evaluation of the fracturing of a coal reservoir is low, the various factors which influence the fracturing of a coal reservoir. coal reservoir are comprehensively considered and fracking can be accurately assessed. It provides important instructions for the further development of coal bed methane, effectively avoids the construction of an invalid well and saves the costs of coal bed methane development.
    公开号:BE1026492B1
    申请号:E20195809
    申请日:2019-11-20
    公开日:2020-12-08
    发明作者:Caifang Wu；Xiuming Jiang；Bo Wang；Xiaojie Fang；Erchao Zhang
    申请人:Univ China Mining；
    IPC主号:
    专利说明:

    METHOD OF EVALUATING THE BE2019 / 5809 FRACTURABILITY OF A COAL TANK
    FIELD OF THE INVENTION The present invention relates to the technical field of the development of coalbed methane and, in particular, to a method for evaluating the fracturability of a coal reservoir.
    PRIOR ART Hydraulic fracturing of a coal reservoir is important for the exploitation of coal bed methane. Consequently, the fracturability of a coal reservoir is a major evaluation parameter in the optimal choice of a favorable zone and of a point of action in the development of coal bed methane. coal. However, in the current process of selecting and evaluating the area to determine the location of a well for coal bed methane, the assessment primarily focuses on the optimal selection of coal bed methane resource factors and physical property parameters, such as the permeability of a coal tank, and no method or technique is applicable to assess the fracturability of a coal tank. Therefore, there are gaps in the choice of area and placement of wells for coal bed methane, and the assessment results are less reliable. During civil engineering works, the special physical properties of a coal tank also place strict demands on the fracturing technique.
    SUMMARY OF THE INVENTION To eliminate the shortcomings of the prior art, the present invention provides a method of evaluating the fracturability of a coal reservoir. The present invention adopts the following technical solution: Method for evaluating the fracturability of a coal tank, comprising the following steps: Step! : calculation of the BI fragility index of a coal tank to be evaluated;
    Step 2: calculation of the fracture toughness Æ, of the confinement pressure coal tank BE2019 / 5808; Step 3: calculation of the thickness Æ, of the carbon tank to be evaluated; Step 4: calculation of the difference in elastic modulus Ex between the coal reservoir and the surrounding rock; Step 5: calculation of the net pressure coefficient 9, of the coal reservoir to be evaluated: Step 6: calculation of the humidity rate Afaa of the coal rock; Step 7: Calculation of the Frac fracturability rating of the 19 coal reservoir; Step &: evaluation of the fracturability of the coal reservoir. In addition, step 1 includes: obtaining the elastic moduli and Poisson ratios of the coal tank, the normalization processing on the elastic moduli and Poisson ratios, and the calculation of the brittleness index 57 of the carbon tank. coal tank to be evaluated:; Egi-Egrmin + Ep = in Fe CD EnImax ”EBImin
    BBI BI gp (2) Bsrmax "EBImin. Ep: + Hs. BI = ELLE 100% (3) where in formula (1), Ep; is a normalized elastic modulus of the coal reservoir to be evaluated, Esmas and Erimn are respectively a maximum elastic modulus and a minimum elastic modulus of the coal tank, and the elastic modulus is expressed in (GPa; in formula (2), #p; 'is a normalized Poisson ratio of the coal tank, Hina © HRImin are respectively a maximum and minimum Poisson ratio of the coal tank, and the Poisson ratio is dimensionless,
    Step 2 includes: Step 2.1: Calculation of the compressive strength o, of BE2019 / 5808 coal tank, 5, = (0.0045 + 0.003542) Exec (4) where Va is the shale content of the coal tank , Van = (GR - GR) (GR max - GR) ©) Ex, is a dynamic elastic modulus of the coal tank, Exec = pri Gog - AUS) {vg - vi) (6) Step 2.2: calculation of the resistance uniaxial traction 5; of the coal reservoir, Se = o,. / A (M 18 where in formula (4), / is the shale content of the coal reservoir to be evaluated; in formula (5), GR in APT is a value measured by gamma recording of the coal reservoir to be evaluated, GRmn in API is a natural gamma value measured on a sandstone bed in the well interval, and GR max in APT is a natural gamma value measured on a mudstone bed in the 'well interval; in formula (6), Exec in GPa is a dynamic elastic modulus of the coal tank to be evaluated, 5, in km / s is the longitudinal wave speed of the coal tank to be evaluated, v, in km / s is a transverse wave speed of the coal tank to be evaluated, and p in g / enr ° is the density of the rock; in formula (7), À is a constant; Step 2.3: calculation of the toughness at the fracture Kr of rock under pressure, Ke = 9,0956p, + 0.138358, - 0.0820 (8) to simplify the calculation, the confining pressure p, by a con minimum horizontal main drag in the formula (83: Step 2.4: perform the downstream treatment and the normalization treatment on the fracture toughness of the coal tank to be evaluated,
    that is, downstream processing and standardization. Kc: BE2019 / 5809 Ke = (Koy-Ecmn} (Kgmor-Ecmin} (8} where in formula (9), X. 'is the fracture toughness processed forward, Kg is the fracture toughness of the coal tank to be evaluated, Æcjmi is the minimum fracture toughness of the coal tank to be evaluated and Kom is the maximum fracture toughness of the coal tank to be evaluated; Kai KL (19) SKe where in formula (10) , X. "is the fracture toughness treated in progress ot normalized, Kc 'is the fracture toughness treated in progress, ux. Is an average value of the fracture toughness treated in progress of the coal tank to be evaluated and ox, is a standard deviation of the fracture toughness treated at the advancement of the coal tank to be evaluated. In addition, step 3 includes: Step 3.1: from data relating to the drilling existing and parametric coalbed methane drilling, calculation of the thickness of the coalbed reservoir of a study area using the interpol adjustment constraint linear ation, the thickness of the coal tank being indicated by EZ, in m; Step 3.2: normalization of the thickness of the coal tank: Eng EER Ei (11)
    GEN where in the formula (11), Æ; ' is the normalized thickness of the coal tank, usa is an average value of the thickness of the coal tank to be evaluated and this; is a standard deviation of the thickness of the coal tank to be evaluated. In addition, step 4 includes: Step 4.1: use an elastic modulus ratio Ex between the surrounding rock and the coal tank to represent the difference in elastic modulus between the coal tank and the surrounding rock: _ ErtEn Ey = Ee (12)
    where in formula (12), Æ in GPa is the elastic modulus of the BE2019 / 5809 coal reservoir, Æ; in GPa is the elastic modulus of the roof, and Z in GPa is the elastic modulus of the floor; Step 4.2: normalization of the difference in elastic modulus: Ep HER | 5 Be 13)
    VEK where in formula (13), Ex is the normalized elastic modulus difference, tzt is an average value of the elastic modulus difference of the carbon tank to be evaluated, and ox: is a standard deviation of the elastic modulus difference of the coal tank to be evaluated. In addition, step S comprises: Step 5.1: obtaining a minimum horizontal principal stress Pe, in MPa, of the coal reservoir by hydraulic fracturing. A maximum horizontal principal stress & y of the coal tank: oy = 3P AP AP +} (14) where in formula (14), Pr in MPa is the rupture pressure of the coal tank, P, in MPa is the pressure of the carbon tank and 7 'in MPa is the tensile strength of the carbon tank, the net pressure coefficient &, of the carbon tank is therefore: Pere (15 On pans (15) Step 5.2: normalization of the net pressure coefficient : Fnyy7 #. On L ij FOR (16) Its where in formula (16), it is the normalized elastic modulus difference, Yon is an average value of the net pressure coefficient of the coal tank to be evaluated and om is a standard deviation of the net pressure coefficient of the coal tank to be evaluated.
    In addition, step 6 includes: Step 6.1: during the analysis of the correlations between the BE2019 / 5809 moisture content of the coal bed and the logging parameters, perform a multiple regression analysis on the three parameters which are the more closely correlated, and accordingly establish an equation to predict the moisture content of coal bedrock: Mas = 1 4655-0.5827xDEN-2.1115 * xGR + 0.2319x0, (17) where in formula (17), Mad in% is the moisture content of the coal rock in the coal tank to be evaluated, DEN in g / cm is the density of the coal tank to be evaluated, GR in API is a natural gamma value of the coal tank to be evaluated and p, on £ 2-m is the apparent resistivity of the coal tank to be evaluated; Step 6.2: upstream treatment and normalization of the moisture content of the coal rock: Mad ke Mady-Modimin} {M adimax- DM: adjmin} (1 8) where in formula (18), Mag 'is the content of moisture from pre-treated coal rock, Maa; is the moisture content of the coal rock in the coal tank to be evaluated, Mazmin is the minimum moisture content of the coal rock in the coal tank to be evaluated, and Magma is the maximum moisture content of the coal rock in the coal tank to be evaluated, Maa Maa EE (19) Mad where in formula (19), Maa ”is the moisture content of the pre-treated and standardized coal rock, Mag 'is the moisture content of the rock pre-treated coal, gaa is an average value of the moisture content of the pre-processed coal rock in the reservoir to be evaluated, and omg is a standard deviation of the moisture content of the pre-processed coal rock. advance in the tank to be evaluated.
    In addition, step 6 includes: calculating the Frac fracturability rating of the coal reservoir: Frac = 0.3BH0.25K. + 0.05E, + 0.15E; + 0.26, + 0.05Mad "(20 )
    where in formula (20), 57 is the normalized brittleness index, Ae ”is the toughness at BE2019 / 5808 the breakage processed forward and normalized, Ex 'is the normalized thickness of the coal tank, Ex is the ratio of the normalized elastic modulus between the surrounding rock and the coal tank, is the normalized net pressure coefficient of the coal tank and Mg ”is the normalized and forward processed moisture content; and evaluate the fracturability of the coal reservoir according to the score Fm to its fracturability evaluation.
    In addition, step 8 includes: assessment based on Frac LU Fracturability Assessment Score) Fracturability Fame Excellent (in excellent condition, suitable for Fac> 1 fracturing) Very good es ve por Se suitable for { > Furnace 20.5 Good (in good condition, acceptable for 0.5> Frac 20.25 fracture} Fair (modest fracture effect, not 0.25> Fac 20 recommended for fracture) Poor (poor fracturing effect, not Frac <0 recommended for fracturing)
    Compared with the state of the art, the present invention has the following beneficial effects.
    The method uses laboratory data on well test results, recording of experimental parameters and coal samples in a study area; integrates these experimental data and selects six parameters having a significant impact on the fracturability of the coal reservoir, namely the brittleness index, the fracture resistance and the thickness of the reservoir, the elastic modulus between the coal reservoir and the surrounding rock, net pressure coefficient and water content; carries out an evaluation of the weight on these parameters and finally, carries out the evaluation of the fracturability of the reservoir and the optimal selection of coal in the study area.
    DETAILED DESCRIPTION OF THE INVENTION To better understand the present invention, the present invention is described in more detail below with reference to the illustrations and accompanying drawings.
    The representations are used for illustration only, instead of BE2019 / 5809 to limit the scope of protection of the present invention.
    As shown in Figure 1, the present invention adopts the following technical solution: Method for evaluating the fracturability of a coal reservoir, comprising the following steps: Step 1: Calculation of the fragility index BI of a reservoir of coal to be evaluated; Step 2: calculation of the fracture toughness Æ, of the coal tank under confinement pressure; Step 3: calculation of the thickness Es of the coal tank to be evaluated; Step 4: calculation of the difference in elastic modulus Æ between the coal reservoir and the surrounding rock; Step 5: calculation of the net pressure coefficient o, of the coal tank to be evaluated; Step 6: calculation of the moisture content Aa of the coal rock; Step 7: calculation of the evaluation score of the fracturability Fac of the coal reservoir; Step 8: Assessment of the fracturability of the coal reservoir.
    Step 1 includes: obtaining the elastic moduli and Poisson ratios of the coal tank, the normalization processing of the elastic moduli and Poisson ratios and the calculation of the brittleness index BI of the coal tank to be evaluated : Egr mn 7 - (3 BIimax Brmin Her '= EEE (2 Bimax BImin _ Esy} Hay 5 BI = 2 2x100% {3}
    where in formula (1), Ep, 'is a normalized elastic modulus of the BE2019 / 5808 coal tank to be evaluated, Erima and Kamin are respectively a maximum elastic modulus and a minimum elastic modulus of the coal tank, and the elastic modulus is expressed in GPa; in formula (2), Ap; is a normalized Poisson ratio of the coal tank, Uamax € BImin are respectively a maximum and minimum Poisson ratio of the coal tank, and the Poisson ratio is dimensionless.
    In addition, step 2 includes: Step 2.1: Calculation of compressive strength 0, of the coal tank, a, = (0.0045 + 0.003542) Exec (4) where Van is the shale content of the coal tank , Van = (GR - GRyin) / (ERymax - GRmin) © Exec is a dynamic elastic modulus of the coal tank, Exec = pv; (34, - vg) (vg - 15) ©) Step 2.2: calculation of the uniaxial tensile strength 5, of the coal tank, Sp = a.
    JAN where in the formula {4}, Vs, is the shale content of the coal reservoir to be evaluated; in formula (5), GR in API is a value measured by gamma recording of the coal reservoir to be evaluated, GR in API is a natural gamma value measured on a sandstone bed in the well interval, and GÆnax in API is a natural gamma value measured on a bed of mudstone in the well interval; in formula (6), Ze. in GPa is a dynamic elastic modulus of the coal tank to be evaluated, 7, in km / s is the longitudinal wave speed of the coal tank to be evaluated, 7, in km / s is a transverse wave speed of the tank of charcoal to be evaluated, and p on g / cm is the density of the rock; in formula (7), A is a constant 36; Step 2.3: calculation of the fracture toughness Æ, of rock under pressure,
    Kr = 0.0956p, + 0.13835, - 0.0820 (8) BE2019 / 5809 to simplify the calculation, the confining pressure p, by a minimum horizontal principal stress in the formula (83; Step 2.4: carry out the downstream processing and the processing standardization on the fracture toughness of the coal tank to be evaluated, that is to say the downstream processing and standardization Æ ,: Ke {Kog Kgmin} (Keimax-Kejmin) (9) where in the formula ( 9), X. 'is the fracture toughness processed forward, Æoy is the fracture toughness of the coal tank to be evaluated, Komi is the minimum fracture toughness 160 of the coal tank to be evaluated and max is the maximum fracture toughness of the charcoal reservoir to be evaluated; K € Keij TÜRE (10) Re; where in formula (10), A. ”is the normalized, processed fracture toughness, Kc 'is the fracture toughness treated during advancement, (x. is an average value of the fracture toughness treated during advancement of the tank of cha rbon to evaluate and ax. is a standard deviation of the fracture toughness treated at the advancement of the coal tank to be evaluated.
    Step 3 includes: Step 3.1: from data relating to existing boreholes and parametric coalbed methane boreholes, calculation of the thickness of the coalbed reservoir of a study area by the interpolation adjustment constraint Linear, the thickness of the coal tank being indicated by Æz in m; Step 3.2: normalization of the thickness of the coal tank: En; HER E, ALL TEh where in formula (11), Ex is the normalized thickness of the coal tank, (zh BE2019 / 5808 is an average value of the thickness of the coal tank to be evaluated and dan is a standard deviation of the thickness of the coal tank to be evaluated Step 4 includes: Step 4.1: use an elastic modulus ratio Æ; between the surrounding rock and the coal tank to represent the difference in elastic modulus between the coal tank and the surrounding rock: _ ErtEn> Ez = FE (12) where in formula (12), Æ in GPa is the elastic modulus of the charban reservoir, Æ; in GPa is the elastic modulus of the roof, and Æ in GPa is the modulus 16 elastic of the floor; Step 4.2: normalization of the difference in elastic modulus: In HER E = 03)
    TER where in formula (13), Et is the normalized elastic modulus difference, zt is an average value of the elastic modulus difference of the carbon tank to be evaluated, and oet ost is a standard deviation of the elastic modulus difference of the tank of coal to be evaluated. Step 5 comprises: Step 5.1: obtaining a minimum horizontal principal stress P., in MPa, of the coal reservoir by hydraulic fracturing. A maximum horizontal principal stress o; of the coal tank: dp = 3P-P # P, T (14) where in formula (14), Pr in MPa is the rupture pressure of the coal tank, P, in MPa is the pressure of the coal tank and J'in MPa is the tensile strength of the coal tank, the net pressure coefficient o, of the coal tank is therefore:
    pp BE2019 / 5809 2E (15) TH Pr Step 5.2: normalization of the net pressure coefficient: On Ban 4 - 6; Ln (16) Its where in formula (16), & 'is the normalized elastic modulus difference, Zen is an average value of the net pressure coefficient of the coal tank to be evaluated and om is a standard deviation of the net pressure coefficient of the coal tank to be evaluated.
    Step 6 includes: Step 6.1: When analyzing the correlations between the moisture content of the coal bedrock and the logging parameters, perform multiple regression analysis on the three parameters that are most closely correlated, and establish consequently an equation to predict the moisture content of coal rock: Mad = 1 4655-0.5827 <DEN-2.1115 * GR + 0.2319xp, (17) where in formula (17), Mag in% is the moisture content of coal in the coal tank to be evaluated, DEN in g / en is the density of the coal tank to be evaluated, GR in API is a natural gamma value of the coal tank to be evaluated and js in £ 2-m is the apparent resistivity of the coal tank to be evaluated; Step 6.2: upstream treatment and normalization of the moisture content of the coal rock: Mad = {Maay-M. adjmin} / (M adimas- DM, admin} {1 &) where in formula (18), Maa 'is the moisture content of the pre-treated coal rock, Maag is the moisture content of the coal rock in the coal tank to be evaluated, Madymi is the minimum moisture content of the coal rock in the coal tank to be evaluated, and Madimax is the maximum moisture content of the coal rock in the coal tank to be evaluated,
    van Hear has 19) BE2019 / 5809 Mad where in formula (19), Mad ”is the moisture content of the pre-treated and normalized coal rock, Mag 'is the moisture content of the pre-treated and normalized coal rock. 'advance, Haa is an average value of the moisture content of the pre-treated coal rock in the reservoir to be evaluated, and mag is a standard deviation of the moisture content of the pre-processed coal rock in the tank to be evaluated. Step 7 includes: the calculation of the evaluation score of the fracturability Fu of the coal reservoir: Fra 3BH025K. "O, 05E; # G.15E £ + 0 Zon + 0.05Mad" (20) where in the formula (20), B7 is the normalized brittleness index, Ae ”is the tensile strength at break forward treated and normalized, Ex 'is the normalized thickness of the carbon tank, Ex is the ratio of the normalized elastic modulus between surrounding rock and coal tank, this is the normalized net pressure coefficient of the coal tank and Mad "is the normalized and forward treated moisture content; and evaluate the fracturability of the coal tank according to the Frac note to its fracturability assessment.
    Step 8 includes: assessment based on the Frac Fracturability Assessment Score: LU Fracturability I Pre Excellent (in excellent condition, suitable for fracturing) Frae> 1 Very good (in very good condition, suitable for fracturing) 1> Frac 20.5 Good (in good condition, acceptable for fracture) 0.5> Frac 20.25 Fair (modest Fracture effect, not recommended for 0.25> Frac 20 fracture) Poor (poor fracturing effect , not recommended for Frac <0 fracturing) The above descriptions are only exemplary embodiments of the present invention, and the present invention is not limited thereto. Based on the above embodiments, those of ordinary skill in the art can easily understand the spirit of the present invention, and make modifications and changes without departing from the spirit of the present invention.
    All these modifications and changes BE2019 / 5809 fall within the scope of the protection of the present invention.
    权利要求:
    Claims (9)
    [1]
    1. Method for evaluating the fracturability of a coal reservoir, comprising the following steps: Step 1: calculation of the brittleness index BZ of a coal reservoir to be evaluated; Step 2: calculation of the fracture toughness Kc of the coal reservoir under confinement pressure; Step 3: calculation of the thickness Ea of the coal tank to be evaluated; Step 4: calculation of the difference in elastic modulus E between the coal reservoir and the surrounding rock; Step 5: calculation of the net pressure coefficient on of the coal tank to be evaluated; Step 6: Calculation of the Maa moisture content of the coal rock; Step 7: Calculation of the Frac fracturability rating of the coal reservoir; Step 8: Assessment of the fracturability of the coal reservoir.
    [2]
    The method of evaluating the fracturability of a coal tank according to claim 1, wherein step 1 comprises: obtaining elastic moduli and Poisson ratios of the coal tank, performing the normalization processing on the modules. elastics and Poisson ratios and the calculation of the brittleness index BZ of the coal tank to be evaluated: Ep: —EBrmin Er = (1 BI Fatman Erm) Ver! - TESTEN (2) BImax HBImin BI = “era 100% (3)
    where in formula (1), Fp; is a normalized elastic modulus of the BE2019 / 5809 coal tank to be evaluated, E3 / max and EB / min are respectively a maximum elastic modulus and a minimum elastic modulus of the coal tank, and the elastic modulus is expressed in GPa; in formula (2), Up; is a normalized Poisson ratio of the coal pool, / Bimax and Bimin are a maximum and minimum Poisson ratio of the coal pool, respectively, and the Poisson ratio is dimensionless.
    [3]
    3. Method of evaluating the fracturability for a coal tank according to claim 1, wherein step 2 comprises: Step 2.1: calculation of the compressive strength 9, of the coal tank, a, = (0.0045 + 0.0035V ,,) Ere (4) where V ,, is the shale content of the coal tank, Vin = (GR - GRmin) / (GRmax - GRmin) ©) Exc is a dynamic elastic modulus of the coal tank, Exec = pv (3vp - 4v5) / (V5 - v5) (6) Step 2.2: calculation of the uniaxial tensile strength S, of the coal tank, Se = 0c / A (7) where in formula (4), Vsa is the clay shale content of the coal reservoir to be evaluated; in formula (5), GR in API is a value measured by gamma recording of the coal tank to be evaluated, GRmin in API is a natural gamma value measured on a bed of sandstone in the well interval, and GRmax in API is a natural gamma value measured on a bed of mudstone in the well interval; in formula (6), Ex- in GPa is a dynamic elastic modulus of the coal tank to be evaluated, v in km / s is the longitudinal wave speed of the coal tank to be evaluated, v, in km / s is a transverse wave velocity of the coal tank to be evaluated, and p in g / cm 'is the density of the rock; in formula (7), A is a constant; Step 2.3: calculation of the fracture toughness Kc of rock under pressure,
    Kc = 0.0956p, + 013835, - 0.0820 (8) BE2019 / 5809 to simplify the calculation, the confining pressure py by a minimum horizontal principal stress in formula (8); Step 2.4: Perform the downstream treatment and the normalization treatment on the fracture toughness of the coal tank to be evaluated, that is to say the downstream treatment and the Kc normalization: Ke = (Koij-Kejmin) / (Kejmax-Kejmin) (9) where in formula (9), Kc! is the fracture toughness processed forward, Ki; is the fracture toughness of the coal tank to be evaluated, Kejmin is the minimum fracture toughness of the coal tank to be evaluated and Kejmax is the maximum fracture toughness of the coal tank to be evaluated; Kn Keine (10) OKc where in formula (10), Ke "is the fracture toughness treated in progress and normalized, Kc 'is the fracture toughness treated in progress, uxc is an average value of the fracture toughness treated at the advancement of the coal tank to be evaluated and oxc is a standard deviation of the fracture toughness treated at the advancement of the coal tank to be evaluated.
    [4]
    4. A method of evaluating the fracturability for a coal reservoir according to claim 1, wherein step 3 comprises: Step 3.1: from data relating to existing boreholes and parametric coal bed methane boreholes, calculation of the l 'thickness of the coal reservoir of a study area by the linear interpolation adjustment constraint, the thickness of the coal reservoir being indicated by E, enm; Step 3.2: normalization of the thickness of the coal tank: E il En hij TER (11) Eh where in formula (11), Ex 'is the normalized thickness of the coal tank, UE: BE2019 / 5809 is a value mean of the thickness of the coal tank to be evaluated and "oz" is a standard deviation of the thickness of the coal tank to be evaluated.
    [5]
    The method of evaluating fracturability for a coal tank according to claim 1, wherein step 4 comprises: Step 4.1: using an elastic modulus ratio Ex between the surrounding rock and the coal tank to represent the difference. elastic modulus between the coal tank and the surrounding rock: _ EttEp Ex = "22 (12) where in formula (12), Æc in GPa is the elastic modulus of the coal tank, Æ; in GPa is the elastic modulus of the roof, and E "in GPa is the elastic modulus of the floor; Step 4.2: normalization of the difference in elastic modulus: Erik Er = (13) Ek where in formula (13), Æ is the difference in normalized elastic modulus, ME: is an average value of the difference in elastic modulus of the charcoal tank to be evaluated, and ox is a standard deviation of the difference in elastic modulus of the charcoal tank to be evaluated.
    [6]
    6. A method of evaluating the fracturability for a coal reservoir according to claim 1, wherein step 5 comprises: Step 5.1: obtaining a minimum horizontal principal stress Pc, in MPa, of the coal reservoir by hydraulic fracturing; A maximum horizontal principal stress oy of the coal tank: Oy = 3P.-P + Po + T (14)
    where in formula (14), Pr in MPa is the burst pressure of the BE2019 / 5809 coal tank, P, in MPa is the pressure of the coal tank and 7 in MPa is the tensile strength of the coal tank, the net pressure coefficient 9 "of the coal tank is therefore: _Po-Pe rn (15) Step 5.2: normalization of the net pressure coefficient: oP (16) Jon where in formula (16), o„ 'is the difference of normalized elastic modulus, Lon is an average value of the net pressure coefficient of the coal tank to be evaluated and om is a standard deviation of the net pressure coefficient of the coal tank to be evaluated.
    [7]
    7. A method of evaluating the fracturability for a coal reservoir according to claim 1, wherein step 6 comprises: Step 6.1: during the analysis of the correlations between the moisture content of the coal rock and the parameters of logging, perform a multiple regression analysis on the three parameters which are most closely correlated, and establish an equation accordingly to predict the moisture content of coal bedrock: Mad = 1.4655-0.5827xDEN-2.1115xGR + 0.2319xp; (17) where in formula (17), Maa in% is the moisture content of the coal rock in the coal tank to be evaluated, DEN in g / cm is the density of the coal tank to be evaluated, GR in API is a natural gamma value of the coal tank to be evaluated and ps in Q-m is the apparent resistivity of the coal tank to be evaluated; Step 6.2: upstream treatment and normalization of the moisture content of the coal rock: Maa = (Mady-Madjmin) / (Madimax-Madjmin) (1 8)
    where in formula (18), Mag 'is the moisture content of the coal rock treated BE2019 / 5809 in advance, Maa is the moisture content of the coal rock in the coal reservoir to be evaluated, Madjmin is the content in the minimum moisture content of the coal rock in the coal tank to be evaluated, and Maajmax is the maximum moisture content of the coal rock in the coal tank to be evaluated, M _,., - May "IM (19) OMad where in the formula (19), Mad "is the moisture content of the pre-treated and normalized coal rock, M'ad is the moisture content of the pre-processed coal rock, mad is an average value of the content in the moisture content of the pre-treated coal rock in the reservoir to be evaluated, and Omad is a standard deviation of the moisture content of the pre-processed coal rock in the reservoir to be evaluated.
    [8]
    The method of evaluating the fracturability for a coal tank according to claim 1, wherein step 7 comprises: calculating the Frac fracturability evaluation score of the coal tank: Frac = 0.3BH + 0.25K. " + 0.05E, + 0.15E # + 0.20, + 0.05M2a "(20) where in formula (20), BZ is the normalized brittleness index, Ke" is the toughness at break processed forward and normalized , E; ' is the normalized thickness of the coal tank, Et 'is the ratio of the normalized elastic modulus between the surrounding rock and the coal tank, on' is the normalized net pressure coefficient of the coal tank and Maa "is the moisture content standardized and processed forward; and evaluate the fracturability of the coal reservoir according to the Fra note to its fracturability evaluation.
    [9]
    The method of evaluating fracturability for a coal tank according to claim 1, wherein step 8 comprises: evaluating based on the Frac fracturability evaluation score.
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    同族专利:
    公开号 | 公开日
    WO2020103414A1|2020-05-28|
    ZA202000093B|2021-08-25|
    LU101489B1|2020-05-22|
    CN109558663A|2019-04-02|
    CN109558663B|2020-04-03|
    BE1026492A1|2020-02-18|
    NL1043472A|2020-06-03|
    NL1043472B1|2020-09-04|
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    法律状态:
    2021-02-03| FG| Patent granted|Effective date: 20201208 |
    优先权:
    申请号 | 申请日 | 专利标题
    CN201811398934.XA|CN109558663B|2018-11-22|2018-11-22|Coal reservoir fracturing property evaluation method|
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