CN112177605A - Method for determining main control factors of favorable gathering area of sea natural gas hydrate - Google Patents
Method for determining main control factors of favorable gathering area of sea natural gas hydrate Download PDFInfo
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Abstract
The invention relates to a method for determining main control factors of a favorable gathering area of sea natural gas hydrate, which comprises the following steps: step 1: determining a plurality of geological parameters which are characterized to influence the aggregation of the natural gas hydrate, and calculating each geological parameter; step 2: selecting a plurality of geological parameters as system characteristics, using the rest geological parameters as system factors, and obtaining a system characteristic sequence and a system factor sequence; and step 3: obtaining a main control factor through gray level correlation analysis between the system characteristic sequence and the system factor sequence; and 4, step 4: and taking the area with superior main factor conditions as the favorable hydrate accumulation area. The method is based on the basic theory of the hydrate accumulation system, and can realize quantitative evaluation of the natural gas hydrate accumulation main control factors under the influence of different structural backgrounds and multiple geological factors through gray level correlation analysis between the system characteristic sequence and the system factor sequence, thereby obtaining the main control factors and scientifically guiding the exploration and drilling of the hydrate area according to the main control factors.
Description
Technical Field
The invention relates to the technical field of natural gas hydrate exploration and development, in particular to a method for determining a main control factor of a favorable gathering area of sea natural gas hydrate.
Background
The existing prediction method of the favorable gathering area is mainly oriented to and suitable for the field of oil and gas (petroleum and natural gas) exploration, and because the principle of the formation of natural gas hydrate and oil and gas, the formation elements, the enrichment rule and the environment are different, the prediction method of the favorable gathering area by means of oil and gas cannot be well applied to the natural gas hydrate. Most of the related prediction methods related to the favorable aggregation area of the natural gas hydrate are based on hydrate exploration or processing technology, such as the aspects of improving seismic data and processing precision, or the prediction of the natural gas hydrate based on a single factor, and the prediction of the favorable aggregation area of the natural gas hydrate is difficult to systematically guide. The existing related prediction method is difficult to be applied to the field of natural gas hydrate exploration, or difficult to carry out systematic prediction and has low prediction precision (success rate), the reservoir forming main control factor is a core element for restricting the distribution of the hydrate favorable accumulation area, the hydrate favorable accumulation area can be obtained by systematic, scientific and efficient prediction according to the main control factor, and the method is favorable for guiding the exploration and drilling of the hydrate area. Therefore, there is a need for a method that can determine the dominant factors in the favorable focal zone of natural gas hydrates, also known as hydrates, and the same applies hereinafter.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for determining the main control factors of the favorable gathering area of the natural gas hydrate in the sea area, which can solve the problem of determining the main control factors of the favorable gathering area of the natural gas hydrate.
The technical scheme for realizing the purpose of the invention is as follows: a method for determining a main control factor of a favorable gathering area of sea natural gas hydrate comprises the following steps:
step 1: determining geological parameters for characterizing and influencing natural gas hydrate aggregation, wherein the geological factors influencing the natural gas hydrate aggregation at least comprise source rock gas production intensity, shallow methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content, hydrate stability region thickness, hydrate geological reserve and hydrate enrichment degree,
(1) strength parameter of gas produced from source rock
The gas production intensity q of the source rock is obtained by the following formula:
q＝qthermal+qmicro
in the formula, qthermalIndicates the strength of gas generation of the thermal cause gas, qmicroThe strength of the produced gas of the biogenesis gas is shown,
(2) superficial methane fluid flux parameter
Superficial methane fluid flux JCH4Obtained by the following formula:
in the formula, D0Represents the diffusion coefficient and is a constant, phi represents the effective porosity of a natural gas hydrate sedimentary deposit,
indicating the sulfate concentration gradient in the region of the shallow methane stream,
(3) gas-containing fluid dredging capacity parameter
Calculating the volume V of the gas-containing fluid dredging channel according to a formula:
V＝α*πr2l------①
wherein r is the radius of the gas chimney or mud pit, l is the height of the gas chimney or mud pit, and alpha is a constant,
(4) BSR Integrated response parameter
BSR Integrated response CBSRCalculating according to a formula II:
CBSR＝a*Hei+b*Amp+c*Con------②
wherein a, b and c are all coefficients and are constants, and a + b + c is 1, HeiDenotes the thickness of the blank reflection band at the upper part of the BSR, AmpRepresenting the amplitude of the BSR, being constant, ConRepresenting the lateral continuity of the BSR, obtained by seismic section reading, HeiCalculated according to the formula (c):
wherein v represents the propagation velocity of seismic waves in the shallow stratum of the seabed, t is the two-way reflection time of the seismic waves corresponding to the blank reflection band,
(5) hydrate stability zone thickness parameter
Hydrate stability zone thickness HstaCalculating by a formula (IV):
in the formula, m and n both represent coefficients which are constants, T represents the formation temperature of the bottom boundary of the hydrate stability region, DWFor depth of sea water, T0Is the seabed temperature, G is the ground temperature gradient,
(6) shallow layer turbid sand content parameter
The content D of the turbid accumulated sand in the shallow layer is calculated by a formula (v):
D＝Hsand/Hsta------⑤
in the formula, HsandThe cumulative thickness of the turbid accumulated sand bodies is shown,
(7) geological reserve factor of hydrate
Hydrate groundMass reserve QhThe calculation is carried out according to the formula:
Qh＝Ah*Zh*φ*Sh*E------⑥
in the formula, AhDenotes the area of the hydrate distribution region, ZhIndicates the effective thickness of hydrate mineral formation zone, ShThe saturation of natural gas hydrate in pores is shown, E represents a gas production factor which is a constant,
(8) hydrate enrichment factor
Enrichment of hydrate QhydCalculated by formula (c):
Qhyd＝φ*Sh------⑦
step 2: taking two geological parameters of hydrate geological reserve and hydrate enrichment as system characteristics, dividing a current region to be predicted into n blocks, calculating each block according to the step 1 to obtain the hydrate geological reserve and the hydrate enrichment corresponding to each block to obtain a series of hydrate geological reserve and hydrate enrichment,
wherein a series of hydrate geological reserves form a hydrate geological reserve system characteristic sequence and are recorded as Y1′，Y1′＝{Y1′(1),Y1′(2),…,Y1′(k),…,Y1′(n)}，Y1' (k) denotes the kth system feature in the sequence of hydrate geological reserve system features,
a series of hydrate enrichment degrees form a hydrate enrichment degree system characteristic sequence marked as Y'2，Y′2＝{Y′2(1),Y′2(2),…,Y′2(k),…,Y′2(n)}，Y′2(k) Represents the kth system characteristic in the characteristic sequence of the enrichment degree system of the hydrate,
then, taking the residual geological parameters as system factor parameters, correspondingly obtaining a group of system factor sequences, and respectively recording the system factor sequences of source rock gas production intensity, methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content and hydrate stability region thickness as X'1、X′2、X′3、X′4、X′5、X′6，
The source rock gas production strength system factor sequence is as follows: x'1＝{X′1(1),X′1(2),…,X′1(n)},
Methane fluid flux system factor sequence: x'2＝{X′2(1),X′2(2),…,X′2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x'3＝{X′3(1),X′3(2),…,X′3(n)},
BSR integrated response system factor sequence: x'4＝{X′4(1),X′4(2),…,X′4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x'5＝{X′5(1),X′5(2),…,X′5(n)},
Hydrate stability domain thickness system factor sequence: x'6＝{X′6(1),X′6(2),…,X′6(n)}，
All the system characteristic sequences and the system factor sequences are used as original data, and the original data are subjected to dimensionless and normalization processing to obtain new sequences corresponding to the original data:
characteristic sequence of hydrate geological reserve system: y is1＝{Y1(1),Y1(2),…,Y1(n)}，
Characteristic sequence of hydrate enrichment system: y is2＝{Y2(1),Y2(2),…,Y2(n)},
The source rock gas production strength system factor sequence is as follows: x1＝{X1(1),X1(2),…,X1(n)},
Methane fluid flux system factor sequence: x2＝{X2(1),X2(2),…,X2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x3＝{X3(1),X3(2),…,X3(n)},
BSR integrated response system factor sequence: x4＝{X4(1),X4(2),…,X4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x5＝{X5(1),X5(2),…,X5(n)},
Hydrate stability domain thickness system factor sequence: x6＝{X6(1),X6(2),…,X6(n)}；
And step 3: respectively calculating the correlation coefficient between each system characteristic and each system factor, wherein the jth system characteristic Y in the mth system characteristic sequencem(j) And the jth systematic factor X in the ith systematic factor sequencei(j) Coefficient of correlation between gamma (Y)m(j),Xi(j) Calculated by the formula (v):
where m is 1,2, i is 1,2,3,4,5,6, j is 1,2, …, n, Δmi(j)＝|Ym(j)-Xi(j)|，
P represents a resolution coefficient, and is a constant,
then, the correlation coefficient between the same system factor sequence and the same system characteristic sequence forms a correlation coefficient matrix, and the correlation coefficient matrix between the ith system factor sequence and the mth system characteristic sequence is marked as Rm：
Wherein (gamma)ij)mRepresenting a correlation coefficient between the jth system feature in the mth system feature sequence and the jth system factor in the ith system factor sequence,
then, calculating the correlation degree between each system factor and each system characteristic sequence, wherein the ith system factor sequence and the mth system factor sequenceDegree of association Q between system signature sequencesimCalculated according to the formula ninthly, the following results are obtained:
if it is
Is invariably provided with
Then Q isimCorresponding system factor XiIs the main control factor.
Further, q isthermalObtained by hydrocarbon-generating kinetic or thermal or basin simulationmicroObtained by microorganism enrichment culture or experimental simulation method.
Furthermore, in the step 1, alpha is more than or equal to 0.01 and less than or equal to 0.2.
Further, in the step 1, HsandObtained by the following steps:
identifying sand bodies in the seismic section by seismic facies interpretation, and taking the product of half of the two-way reflection time of the accumulated seismic waves of the sand bodies identified in the seismic section and the propagation velocity of the seismic waves of the shallow stratum on the sea bottom as Hsand。
Further, in the step 1, AhObtained by delineating the BSR distribution area on the plane onto which the seismic profile interpretation results are projected, ZhObtaining or using H from hydrate drilling and logging datastaInstead, phi is obtained by logging while drilling data calculation, ShThe natural gas hydrate pressure-maintaining core sample is obtained by actual measurement of the natural gas hydrate pressure-maintaining core sample or calculation by using logging-while-drilling data.
Further, in step 3, ρ is 0.25, ρ ismax＝0.5。
Further, the step 3 of obtaining the master factor and recording the master factor as the first master factor, and after the step 3 is executed or before the step 1 is executed, the method further includes the following steps:
according to the theory of hydrate reservoir formation system and the actual reservoir formation characteristics of hydrate in the research area, the main control factor of hydrate accumulation in the research area is qualitatively deduced by combining the actual drilling result of hydrate and recorded as a second main control factor,
and if the system factors corresponding to the first main control factor and the second main control factor are consistent, taking the system factor corresponding to the first main control factor or the second main control factor as a final main control factor, otherwise, removing abnormal data from the original data in the step 2 to obtain new original data, and re-executing the step 2 to the step 3 to obtain a new first main control factor, and if the new system factors corresponding to the first main control factor and the second main control factor are not consistent, taking the system factor corresponding to the first main control factor as the final main control factor.
The invention has the beneficial effects that: 1. the method is based on the basic theory of the hydrate accumulation system, breaks through the condition barrier that the traditional oil gas cannot be applied to determining the hydrate main control factors due to different accumulation control factors, and can realize the quantitative evaluation of the natural gas hydrate accumulation main control factors under the influence of different structural backgrounds and multiple geological factors through the gray level correlation analysis between the system characteristic sequence and the system factor sequence, thereby obtaining the main control factors and being beneficial to guiding the exploration and drilling of hydrate regions according to the main control factors.
2. The method has the advantages of low data sample acquisition cost and strong operability;
3. the method combines qualitative analysis to determine the main control factors, realizes the combination and verification of the qualitative evaluation and the quantitative evaluation of the main control factors of the hydrate aggregation, lays a theoretical foundation for subsequently and comprehensively improving the scientificity and the accuracy of the prediction result of the hydrate favorable aggregation area, and provides data support.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic diagram showing the relationship between the distribution and aggregation of hydrates and the mud pit and gas chimney;
fig. 3 is a schematic diagram of BSR and blank band thickness with different amplitudes and different continuity.
Detailed Description
The invention is further described with reference to the accompanying drawings and the specific embodiments.
As shown in fig. 1-3, a method for determining a main control factor of a favorable gathering area of natural gas hydrates in a sea area includes the following steps:
step 1: and determining geological parameters for characterizing and influencing the natural gas hydrate aggregation, wherein the geological factors influencing the hydrate aggregation at least comprise source rock gas production strength, shallow methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content, hydrate stability domain thickness, hydrate geological reserve and hydrate enrichment. The geological parameters are based on a hydrate reservoir forming system, the hydrate reservoir forming system mainly comprises four aspects of gas source conditions, dredging regulation, reservoir conditions and stability domain conditions, and the geological parameters are representative parameters of the four aspects, so that the determined geological parameters can comprehensively and comprehensively reflect the hydrate aggregation degree.
(1) Strength parameter of gas produced from source rock
The gas production intensity q of the source rock is obtained by the following formula:
q＝qthermal+qmicro
in the formula, qthermalThe strength of the produced gas of the thermal formation gas can be obtained by a hydrocarbon generation kinetic method, a thermal simulation experiment method, a basin simulation method and the like, qmicroThe expression of the gas production intensity of the biogenic gas can be obtained by microorganism enrichment culture, experimental simulation methods and the like.
(2) Superficial methane fluid flux parameter
The shallow methane fluid flux is the most direct parameter reflecting the activity intensity of the shallow gas-containing fluid at the seabed, and is the surface response of the accumulation of the deep natural gas hydrate. A higher methane fluid flux for a particular geological site generally indicates that the more active the gas-bearing fluid of the underburden, the more readily the gas hydrates in the formation will be enriched. In the area of seabed where shallow methane fluid seepage is active, sulfate reduction-methane Anaerobic Oxidation (AOM) reaction mainly occurs, and then the flux of sulfate ions can be used to approximate the equivalent methane fluid flux, therefore, shallow methaneFluid flux
Obtained by the following formula:
in the formula, D0The diffusion coefficient is expressed as a constant, usually 5.72 x 10-10Phi denotes the effective porosity of the natural gas hydrate deposit layer, is a constant and is usually 0.75,
the gradient of sulfate concentration, which represents the area where the shallow methane stream is located, can be obtained by experimental tests.
(3) Gas-containing fluid dredging capacity parameter
The gas-containing fluid dredging channel is a bridge connecting a gas source and a hydrate stability region, and plays an important role in controlling the gathering of the natural gas hydrate. The gas chimney and the mud pit are the most common and effective gas-containing fluid dredging and conducting and are used as important carriers for the deep gas-containing fluid to migrate to the hydrate stable region. The gas chimney and the mud bottom piece are similar to cylinders in shape, and the deep gas-containing fluid dredging capacity V is quantitatively depicted by calculating the volume of a cylindrical channel according to a formula:
V＝α*πr2l------①
in the formula, r is the radius of the gas chimney or the mud pit, l is the height of the gas chimney or the mud pit, and alpha is a constant which is an empirical value, in the embodiment, alpha is more than or equal to 0.01 and less than or equal to 0.2. The setting alpha is to consider the heterogeneity of the internal structure of the gas chimney and the mud pit and the actual flow guiding capability.
(4) BSR Integrated response parameter
Bottom reflection layer (BSR) on the seismic data. BSR is a particular geophysical response at the interface due to significant differences in seismic reflection characteristics of hydrate layers and underlying free gas layers, the most important, currently applied to sea-based natural gas hydrate explorationDirect geophysical sign. The indicator characterizing the BSR generally has an amplitude A of the BSRmpLateral continuity ConAnd a thickness H of the blank reflection band above the BSRei. Generally, the stronger the amplitude of the BSR, the better the lateral continuity, and the greater the thickness of the blank reflection band, indicating a higher degree of enrichment of hydrates.
Wherein A ismpAfter the BSR in the research area is identified and the statistical analysis of the distribution characteristics is carried out, a plurality of grades can be qualitatively divided, for example, the grades are divided into a strong grade, a middle grade and a poor grade, and each grade is respectively assigned with a value, for example, the grades of the strong grade, the middle grade and the poor grade are respectively assigned with 3,2 and 1. ConCan be directly read in the seismic section. HeiThe method can be obtained by calculation in a mode of reading the two-pass reflection time of seismic waves in a seismic section, and can be specifically obtained by calculation according to a formula II:
in the formula, v is the propagation speed of the seismic wave in the shallow stratum of the seabed, generally 1600m/s, and t is the two-way reflection time of the seismic wave corresponding to the blank reflection band.
Calculate Amp、ConAnd HeiThen, the BSR comprehensive response C can be calculated according to the formula CBSR：
CBSR＝a*Hei+b*Amp+c*Con------③
In the formula, a, b, and c each represent a coefficient and are constant, and a + b + c is equal to 1, preferably, a is equal to 0.4, b is equal to 0.3, and c is equal to 0.3.
(5) Hydrate stability zone thickness parameter
The natural gas hydrate can stably exist only in special low-temperature and high-pressure environments, and the hydrate stability region is a shallow stratum environment below the seabed which theoretically meets the special low-temperature and high-pressure conditions, and the hydrate formation system is the biggest characteristic of being different from the traditional oil and gas formation system. The aggregation and distribution of the traditional oil and gas system are hardly controlled by the temperature and the pressureIn terms of a hydrate accumulation system, the range of a hydrate stability domain controlled by the conditions of temperature and pressure directly restricts whether the hydrate can be accumulated or not and the accumulation scale, so that the accumulation of the hydrate can be reflected by the hydrate stability domain. Hydrate stability zone thickness HstaCan be calculated by the formula (iv):
in the formula, m and n both represent coefficients, which are constants, and values of the constants are constant values obtained according to a hydrate phase equilibrium curve, different regions may have different constant values, and in this embodiment, m and n are 276.23 and 0.1126, respectively. That is, the above formula is a calculation empirical formula established based on a hydrate phase equilibrium curve, and the establishment of the hydrate phase equilibrium curve can be established by computer software (for example, Hydoff). Wherein T represents the formation temperature of the bottom boundary of the hydrate stability region, DWFor depth of sea water, T0Is the temperature of the sea bottom, G is the temperature gradient of the earth, DW、T0And G can be obtained by field actual measurement.
(6) Shallow layer turbid sand content parameter
The shallow layer turbid sand body can provide a high-quality storage condition for the migration of methane gas and the accumulation of natural gas hydrate due to a well-developed pore structure, so that the content of turbid sand bodies in the seabed shallow layer block flow has important significance for controlling the accumulation of hydrate. The content D of the turbid accumulated sand in the shallow layer can be obtained by calculation according to a formula (v):
D＝Hsand/Hsta------⑤
in the formula, HsandRepresenting the cumulative thickness of the turbid accumulated sand bodies, which can be obtained by:
identifying sand bodies in the seismic section by seismic facies interpretation, and taking the product of half of the two-way reflection time of the accumulated seismic waves of the sand bodies identified in the seismic section and the propagation velocity of the seismic waves of the shallow stratum on the sea bottom as Hsand。
(7) Geological reserve factor of hydrate
Hydrate geological reservoirThe amount is an important parameter for measuring the mineralization potential of the hydrate. Only when the geological reserves of the hydrate reach a certain scale, the hydrate deposits really have exploration and development values. Geological reserve Q of hydratehCan be obtained by the calculation of the formula:
Qh＝Ah*Zh*φ*Sh*E------⑥
in the formula, AhThe area of the hydrate distribution area is represented, and the BSR distribution area can be defined on the plane on which the seismic profile interpretation result is projected to obtain, namely the BSR distribution area can be defined on the base map (Basemap) of the interpretation work area, ZhIndicating the effective thickness of the hydrate pay zone, and can be obtained by hydrate drilling and logging information, and can be H if the drilling and logging information is lackedstaApproximately instead. ShThe natural gas hydrate saturation in the pores can be obtained by actually measuring a hydrate pressure-maintaining core sample or calculating by using logging-while-drilling data, and E represents a gas production factor, namely the volume of the natural gas released by the hydrate in unit volume, is a constant value, and the value is usually 164.
(8) Hydrate enrichment factor
The enrichment degree of the hydrate is a key parameter for representing the enrichment degree of the natural gas hydrate, the porosity and the saturation of the hydrate are commonly used for representing the enrichment degree of the hydrate, and the higher the porosity and the saturation are, the better the enrichment degree of the hydrate is. Enrichment of hydrate QhydCan be calculated by formula (c):
Qhyd＝φ*Sh------⑦
through the steps, geological parameters which are used for characterizing and influencing the aggregation of the natural gas hydrate can be determined, and specific numerical values of the geological parameters are calculated.
Step 2: determining the favourable zone of hydrate accumulation generally requires that both of the following conditions be satisfied: the hydrate ore body has larger geological reserve and higher enrichment degree. Therefore, two geological parameters of hydrate geological reserve and hydrate enrichment are used as system characteristics. Dividing a region meeting preset conditions in a current region to be predicted into n blocks, wherein the current region is usually a hydrate potential regionThe method comprises the steps of determining a hydrate favorable accumulation area, namely, determining the hydrate favorable accumulation area only in a hydrate potential accumulation area, wherein the hydrate potential accumulation area generally refers to an area where related exploration work is carried out and a data base with related analysis is located, and the area meeting preset conditions generally refers to an area with certain hydrate exploration and basic geological data, namely, screening a part of area from the current area, dividing n blocks from the screened area, and calculating each block according to the step 1 to obtain the hydrate geological reserve and the hydrate enrichment corresponding to each block, so that a series of hydrate geological reserves and the hydrate enrichment are obtained. Wherein the hydrate geological reserve of the kth block is recorded as Y1' (k) hydrate enrichment of the kth block is noted as Y2' (k), k is more than or equal to 1 and less than or equal to n. Under the condition that the geological reserves of the hydrate are used as system characteristic parameters, a group of system characteristic sequences Y are formed1', i.e. having Y1′＝{Y1′(1),Y1′(2),…,Y1′(k),…,Y1′(n)}，Y1' (k) denotes hydrate geological reserve as the kth system feature in the sequence of system features; similarly, with the hydrate enrichment as the system characteristic parameter, a set of system characteristic sequences Y 'is formed'2I.e. has Y'2＝{Y′2(1),Y′2(2),…,Y′2(k),…,Y′2(n)}，Y′2(k) Indicating the hydrate enrichment as the kth system characteristic in the system characteristic sequence.
And then, taking the residual geological parameters except the hydrate geological reserve and the hydrate enrichment degree as system factor parameters, similarly obtaining the system factor parameters corresponding to the n blocks in the current region, and correspondingly obtaining a group of system factor sequences. Specifically, system factor sequences of source rock gas production intensity, methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content and hydrate stable region thickness are recorded as X'1、X′2、X′3、X′4、X′5、X′6That is to say,
gas production intensity system for source rockFactor sequence: x'1＝{X′1(1),X′1(2),…,X′1(n)},
Methane fluid flux system factor sequence: x'2＝{X′2(1),X′2(2),…,X′2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x'3＝{X′3(1),X′3(2),…,X′3(n)},
BSR integrated response system factor sequence: x'4＝{X′4(1),X′4(2),…,X′4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x'5＝{X′5(1),X′5(2),…,X′5(n)},
Hydrate stability domain thickness system factor sequence: x'6＝{X′6(1),X′6(2),…,X′6(n)}。
After the system characteristic sequence and the system factor sequence are obtained, the composition of the system characteristic sequence and the system factor sequence is used as raw data for predicting a hydrate favorable aggregation area. Since these raw data are unit (dimensional) and not normalized, it is also necessary to subject the raw data to de-dimension and normalization processes. Wherein, the normalization processing means: and dividing each numerical value of the system characteristic sequence or the system factor sequence by the average value of the corresponding system characteristic sequence or the system factor sequence, and taking the numerical value of the calculation result as the numerical value corresponding to the sequence after the unified processing. For example, hydrate geological reserve system signature sequence is noted as Y1＝{Y1(1),Y1(2),…,Y1(n) }, then
ave denotes averaging. And finally, obtaining respective corresponding sequences:
characteristic sequence of hydrate geological reserve system: y is1＝{Y1(1),Y1(2),…,Y1(n)}，
Characteristic sequence of hydrate enrichment system: y is2＝{Y2(1),Y2(2),…,Y2(n)},
The source rock gas production strength system factor sequence is as follows: x1＝{X1(1),X1(2),…,X1(n)},
Methane fluid flux system factor sequence: x2＝{X2(1),X2(2),…,X2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x3＝{X3(1),X3(2),…,X3(n)},
BSR integrated response system factor sequence: x4＝{X4(1),X4(2),…,X4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x5＝{X5(1),X5(2),…,X5(n)},
Hydrate stability domain thickness system factor sequence: x6＝{X6(1),X6(2),…,X6(n)}。
In the above, Ym(k) Representing the kth system feature, X, in the mth system feature sequencei(k) The k-th system factor, m being 1,2, i being 1,2,3,4,5,6, k being 1,2, …, n, represents the i-th system factor sequence. For example, Y1(3) Represents the 3 rd system characteristic, X, in the 1 st system characteristic sequence (namely the hydrate geological reserve system characteristic sequence)2(4) The 4 th system factor representing the 2 nd system factor series (i.e., the methane fluid flux system factor series).
And step 3: respectively calculating the correlation coefficient between each system characteristic and each system factor, wherein the jth system characteristic Y in the mth system characteristic sequencem(j) And the jth systematic factor X in the ith systematic factor sequencei(j) Coefficient of correlation between gamma (Y)m(j),Xi(j) Calculated by the formula (v):
where m is 1,2, i is 1,2,3,4,5,6, j is 1,2, …, n, Δmi(j) Representing the absolute value of the difference between the jth systematic feature of the mth systematic feature sequence and the jth systematic factor of the ith systematic factor sequence, i.e. deltami(j)＝|Ym(j)-Xi(j)|，ΔminAnd ΔmaxRespectively representing the minimum and maximum differences of the two poles, i.e.
ρ represents a resolution coefficient for improving the significance of the difference between the correlation coefficients, and is a constant, in this embodiment, ρ is 0.25, and ρ ismax0.5. For convenience of description, γ (Y) will be mentionedm(j),Xi(j) Simply by (γ)ij)m。
And obtaining the correlation coefficient between any system factor in each system factor sequence and the system characteristic in each system characteristic sequence through a formula, wherein the correlation coefficient between the same system factor sequence and the same system characteristic sequence forms a correlation coefficient matrix. And recording a correlation coefficient matrix between the ith system factor sequence and the mth system characteristic sequence as Rm，RmThe following were used:
wherein (gamma)ij)mAnd representing the correlation coefficient between the jth system characteristic in the mth system characteristic sequence and the jth system factor in the ith system factor sequence. For example, (gamma)42)1Representing the 2 nd systematic feature (i.e. Y) in the 1 st systematic feature sequence (i.e. the hydrate geological reserve systematic feature sequence)1(2) And 2 nd systematic element (i.e., X) in the 4 th systematic element sequence (i.e., BSR integrated response systematic element sequence)4(2) A correlation coefficient γ between) are calculated42. The original data contains 6 system factor sequences, and each system factor sequence contains n data, so that the obtained correlation coefficients have 6 n.
The embodiment comprises a characteristic sequence of a hydrate geological reserve system and hydrate richnessThe characteristic sequence of the system is concentrated, so that there are 2 correlation coefficient matrixes, R respectively1And R2。
After the correlation coefficient matrix is calculated, a plurality of correlation coefficients are included between each system characteristic and each system factor, which are dispersed and inconvenient to compare, for this reason, the correlation degree between each system factor and each system characteristic is taken as the average value of the correlation coefficient sum between all the system factors and the system characteristics in the system factor sequence, namely, the correlation degree Q between the ith system factor sequence and the mth system characteristic sequence can be calculated by a formula ninthly, wherein the correlation degree Q between the ith system factor sequence and the mth system characteristic sequence is not taken as the correlation coefficient sumimCalculated according to the formula ninthly, the following results are obtained:
Qimthe larger the system factor sequence, the more closely the ith system factor sequence and the mth system feature sequence are related to each other, the larger the influence of the system factor sequence on the feature sequence is, and the larger the influence of the corresponding system factor on the system feature sequence is.
According to the formula ninthly, if Qim>QjmI ≠ j, i ≠ 1,2,3,4,5,6, j ═ 1,2,3,4,5,6, then QimCorresponding system factor XiIs superior to QjmCorresponding system factor XjAnd is denoted by Xi>XjTherefore, the maximum correlation (Q) among all the correlationsim)maxThe corresponding system factor is the master factor. That is, if
Is invariably provided with
Then Q isimCorresponding system factor XiIs the main control factor. The master factor is marked as a first master factor.
The main control factors of the favorable accumulation area of the hydrate can be determined through the steps and recorded as the first main control factors, and the main control factors represent that the main control factors have the largest influence on the favorable accumulation area of the hydrate.
Preferably, before step 1 is executed or after step 3 is executed, step 21 is further included: and qualitatively deducing the main control factors of the hydrate accumulation in the research area according to the theory of the hydrate accumulation system and the actual accumulation characteristics of the hydrate in the research area and combining the actual drilling result of the hydrate to obtain second main control factors.
If the system factors corresponding to the first master factor and the second master factor are the same, the system factor corresponding to the first master factor or the second master factor can be used as the final master factor. And if the system factors of the two are not consistent, removing abnormal data from the original data in the step 2 to obtain new original data, and re-executing the step 2 to the step 3 to obtain a new first main control factor. And if the new first main control factor is inconsistent with the system factor corresponding to the second main control factor, taking the system factor corresponding to the first main control factor as the final main control factor.
After the master control factor is obtained, the method further comprises the step 4: the method is characterized in that the main control factors of hydrate mineralization in a research area and the enrichment rule of hydrate ore bodies are determined, and the evaluation and exploration of the hydrate ore bodies are focused on an area with obvious characteristics or outstanding advantages of the main control factors, so that the area is used as the distribution range of the favorable aggregation area of the hydrate, namely the area with superior conditions of the main control factors is used as the favorable aggregation area of the hydrate. According to the favorable accumulation area of the hydrate, the exploration direction of the hydrate in the future and the target area of exploration in the next stage can be indicated.
The following example illustrates how to determine the dominating factors and to determine the advantageous hydrate accumulation zones based on the dominating factors to facilitate understanding of the invention.
For example, hydrate exploration in the southeast basin of Hippocampus and Hippocampus of the south China sea is relatively low. The former people have more sufficient knowledge on geological conditions of the Qiong-southeast basin area, and a hydrate sample is obtained by drilling, but the hydrate enrichment rule and the distribution of favorable aggregation areas are not clear, the main control factor of hydrate mineralization and the control effect of the hydrate formation factor on the hydrate distribution are not clear, and the exploration of the Qiong-southeast basin hydrate is restricted to a certain extent. The determination of the favorable accumulation area of the hydrate in the southeast Qiong basin comprises the following steps:
step 1: the method comprises the following steps of establishing a conceptual model of natural gas hydrate aggregation in the southeast Qiong basin by combining geological background of the southeast Qiong basin and sea natural gas hydrate reservoir formation system theory: gas production from deep gas source rock, gas chimney/mud bottom dredging, accumulation in favorable reservoir, temperature and pressure sealing and formation of ore and hydrate favorable for accumulation.
Determining geological parameters influencing the aggregation of natural gas hydrates in the south-east-Qionghai region according to the conceptual model: the method comprises the steps of source rock gas production intensity, methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow layer turbid sand content and hydrate stability region thickness, and the calculation method of all the parameters is consistent with the method. The following explains how to calculate and obtain each parameter by taking three parameters of the gas-containing fluid dredging capacity, BSR comprehensive response and the thickness of a hydrate stability region as examples.
(1) Gas-containing fluid dredging capacity parameter
The Qiongnan basin is a hydrate resource exploration area, and the development of gas-containing fluid dredging channels such as a mud bottom gate and a gas chimney and the distribution and the collection of hydrates are closely related to the mud bottom gate and the gas chimney, as shown in figure 2. Taking the hydrate exploration area of the southeast Qiong basin as an example, the gas chimney or the mud bottom box is explained in a three-dimensional or two-dimensional seismic profile, the radius r and the height l of the cylinder of the gas chimney or the mud bottom box are directly read, and the dredging capacity of the gas-containing fluid can be obtained by calculation according to the formula (I). Here, the conductivity α of the water hydrate in the southeast penetron basin is taken to be 0.1 in conjunction with the interpretation of the drilling and logging of the hydrate.
(2) BSR Integrated response parameter
The overall response characteristics of the Johnson basin BSR are closely related to the underlying gas-containing fluid activity, typically manifested as the amplitude A of the Upper BSR when the underlying gas chimney (mudpot) or gas charge is relatively adequatempThe stronger the lateral continuity ConThe better, the thickness H of the blank reflection bandeiThe larger the number, the higher the enrichment of hydrate indicated, as shown in fig. 3.
AmpCan be qualitatively marked out by carrying out statistical analysis on the BSR distribution characteristics in a research area,The middle and weak evaluation grades are respectively assigned as 3,2 and 1;
Concan be obtained by direct reading (for continuous BSR) or segmented reading accumulation (for discontinuous BSR) in a three-dimensional or two-dimensional seismic profile;
Heithe two-pass reflection time t of the seismic waves can be read in the seismic section and calculated according to the formula II, wherein v is generally 1600 m/s.
Obtaining BSR comprehensive response C of research area by calculation according to formula CBSR。
(3) Hydrate stability zone thickness parameter
According to actually measured hydrate gas component data of the Qiongnan basin, simulating and generating a hydrate phase equilibrium curve by using Hydoff software to form an actual hydrate phase equilibrium equation of the Qiongnan basin: hsta＝268.42e0.1231T-DW. Substituting the actually measured seabed temperature and geothermal gradient data of the hydrate implementation station into a formula T ═ T0+G*HstaAnd forming a geothermal gradient curve, and forming an equation set by the two formulas to solve in parallel so as to obtain the thickness of the hydrate stability region.
Step 2: and collecting parameter information of hydrate aggregation influencing factors of the Qiongnan basin to form a system factor sequence and a system characteristic sequence sample. Wherein, the geological reserves and the enrichment degree of the hydrate are taken as system characteristics, and the respective system characteristic sequences are respectively recorded as Y1' and Y2'the rest 6 parameters are taken as system factors, namely, the system factor sequences of the gas production intensity of the source rock, the flux of the methane fluid, the dredging capacity of the gas-containing fluid, the BSR comprehensive response, the content of shallow turbid sand and the thickness of a hydrate stability region are respectively marked as X'1、X′2、X′3、X′4、X′5、X′6. Preferably, 6 research blocks which have been developed for hydrate exploration and have data bases in the southeast Qiongensis basin are used as sample blocks, and the geological factor parameters corresponding to the blocks are calculated according to the step 1, wherein the method specifically comprises the following steps:
Y′1＝(3300,3280,5700,6300,8600,2500)，Y′2＝(0.13,0.26,0.17,0.36,0.09,0.25)，
X′1＝(0.15,0.5,0.37,0.46,0.6,0.48)，X′2＝(32,58,16,47,25,39)，
X′3＝(306,405,503,718,976,825)，X′4＝(3.26,1.58,4.39,2.87,1.69,7.88)，
X′5＝(0.18,0.06,0.15,0.19,0.08,0.12)，X′6＝(195,267,188,235,278,302)。
then dividing each data in each sequence by the average value of the sum of all data of the corresponding sequence to obtain a new dimensionless and normalized data sequence, which is specifically as follows:
Y1＝(0.6671,0.6631,1.1523,1.2736,1.7385,0.5054)
Y2＝(0.6190,1.2381,0.8095,1.7143,0.4286,1.1905)
X1＝(0.3516,1.1719,0.8672,1.0781,1.14063,1.1250)
X2＝(0.8848,1.6037，0.4424,1.2995,0.6912,1.0783)
X3＝(0.4918,0.6510,0.8085,1.1540,1.5687,1.3260)
X4＝(0.9026,0.4375,1.2155,0.7946,0.4679,2.1818)
X5＝(1.3846,0.4615,1.1538,1.4615,0.6154,0.9231)
X6＝(0.7986,1.0935,0.7700,0.9625,1.1386,1.2369)。
calculating according to the formula to obtain the correlation coefficient between the system factor sequence and the system characteristic sequence, thereby obtaining a correlation coefficient matrix between each system factor sequence and the hydrate geological reserve as the system characteristic sequence as follows:
similarly, the correlation coefficient matrix between the obtained system factor sequences and the obtained hydrate enrichment as the system characteristic sequences is as follows:
for the above preferred 6 hydrate exploration sample blocks, each system factor sequence has 6 data, so each system factor sequence corresponds to 6 correlation coefficients, for example, the correlation coefficient between the system factor sequence corresponding to the gas production intensity of the source rock and the hydrate geological reserve as the system characteristic sequence is:
(0.6827,0.5405,0.7122,0.816,0.6675,0.4828)
the two correlation coefficient matrixes are not convenient to compare due to dispersion, the average value of the correlation coefficient sum of each system factor sequence is taken as the correlation degree of the corresponding system factor, the larger the value of the correlation degree is, the closer the relationship between the system factor and the system characteristic sequence is, and the larger the influence of the system factor on hydrate aggregation is. And averaging the correlation coefficients of each system factor sequence according to the two correlation coefficient matrixes, namely obtaining two correlation degree matrixes according to a formula ninthly. The row matrix of the correlation degree between the system factor sequences and the hydrate geological reserves as system characteristics is as follows:
(0.6503 0.5958 0.8085 0.6130 0.6987 0.6236)
for example, 0.6503 ═ (0.6827+0.5405+0.7122+0.816+0.6675+ 0.4828)/6. Similarly, the row matrix of the association degree between the factor sequences and the hydrate enrichment degree of each system as the system characteristics is as follows:
(1.0275 0.8899 0.9462 0.7368 0.7742 1.0478)
and step 3: combining the two relevance row matrixes to obtain a gray relevance matrix R', which is as follows:
from the grey correlation matrix R', γ can be known13＝0.8085>γ15＝0.6987>γ11＝0.6503>γ16＝0.6236>γ14＝0.6130>γ12From para-hydrate (0.5958)From the viewpoint of the degree of influence of the mass reserve, X is present3>X5>X1>X6>X4>X2Namely, the dredging capacity of the gas-containing fluid is the most main influence factor of the geological reserves of the hydrate, and then the shallow turbid accumulated sand content, the gas production intensity of the source rock, the thickness of the stable region of the hydrate, the BSR comprehensive response and finally the shallow methane fluid flux are sequentially carried out.
Likewise, there is γ26＝1.0478>γ21＝1.0275>γ23＝0.9462>γ22＝0.8899>γ25＝0.7742>γ24From the point of view of the degree of influence on hydrate enrichment, X is 0.73686>X1>X3>X2>X5>X4Namely, the thickness of a hydrate stability region is the most main influence factor of the enrichment degree of the hydrate, and then the gas production intensity of source rocks, the dredging capacity of gas-containing fluid, the flux of shallow methane fluid, the content of shallow turbid sand, and finally the BSR comprehensive response are sequentially carried out.
However, from the view of the overall influence on the favorable hydrate accumulation area, the comprehensive influence on the hydrate geological reserve and the hydrate enrichment degree needs to be considered at the same time, and the comprehensive influence on the hydrate geological reserve and the hydrate enrichment degree by the same system factor in the gray correlation matrix needs to be compared, so that the comparison includes:
thus, from the overall effect of favourable aggregation of the hydrate, there is X3>X1>X6>X2>X5>X4Namely, the gas-containing fluid dredging capacity is the most main factor influencing the distribution of the favorable accumulation area of the natural gas hydrate in the Yandong south basin, and is sequentially followed by the gas production intensity of source rocks, the hydrate stability area, the shallow methane fluid flux, the shallow turbid sand content and finally the BSR comprehensive response. Therefore, the system factor sequence X3The corresponding system factor is taken as the first main control factor, namely the dredging capacity of the gas-containing fluid is taken as the first main control factor.Namely, the main control factor influencing hydrate aggregation in the southeast Qionry basin determined by using gray level correlation analysis is the gas-containing fluid dredging capacity.
Then, combining geological background of the qiong-southeast basin area and a hydrate drilling result, qualitatively judging main control factors influencing hydrate aggregation, and naturally, the step can be processed before the step 1 in the embodiment: the overpressure effect of the deep stratum development overpressure system of the southeast Qin basin causes wide distribution of basin gas chimneys and mud bottom bodies. The exploration practice of oil gas and hydrate in the early period shows that the formation and distribution of hydrate reservoir are closely related to the deep overpressure, and the gas chimney and the mud pit are the important expression form of the deep overpressure function. Hydrate drilling results also indicate: drilling stations of underburden development gas chimneys such as W09 and W08 wells to obtain high-saturation blocky hydrate samples; drilling sites with insignificant underburden gas chimney development characteristics, such as wells W03, W20, have either no hydrates or only dispersed hydrates with very low saturation. The combination of the hydrate formation system of the southeast Qiong basin and the drilling result of the hydrate can be qualitatively deduced: the development of channels indicating higher gas-containing fluid channeling capacity, such as gas chimneys, mud traps, etc., may be an important factor in controlling hydrate enrichment in the southeast Qiong basin. Therefore, the gas-containing fluid channeling capacity is taken as a second main control factor.
The hydrate gathering main control factors qualitatively predicted according to the geologic background of the Qiongnan basin region and the hydrate drilling result are consistent, the correctness of geological understanding is explained again, and meanwhile, the scientificity of the gray level correlation analysis method and the reliability of the prediction result are also verified. In conclusion, the gas-containing fluid dredging capacity is used as a final main control factor for influencing the distribution of the advantageous accumulation area of the hydrate in the southeast Qiongpan.
And 4, step 4: according to the steps, the leading control factor of favorable aggregation of the hydrate in the southeast basin of the Qiongong is the dredging capacity of the gas-containing fluid. The gas chimney and the mud pit concentrated development area with superior dredging conditions of the gas-containing fluid are used as the favorable hydrate accumulation area, and the prediction of the favorable hydrate accumulation area is completed.
The embodiments disclosed in this description are only an exemplification of the single-sided characteristics of the invention, and the scope of protection of the invention is not limited to these embodiments, and any other functionally equivalent embodiments fall within the scope of protection of the invention. Various other changes and modifications to the above-described embodiments and concepts will become apparent to those skilled in the art from the above description, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.
Claims (7)
1. A method for determining the main control factors of the favorable gathering area of the sea natural gas hydrate is characterized by comprising the following steps:
step 1: determining geological parameters for characterizing and influencing natural gas hydrate aggregation, wherein the geological factors influencing the natural gas hydrate aggregation at least comprise source rock gas production intensity, shallow methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content, hydrate stability region thickness, hydrate geological reserve and hydrate enrichment degree,
(1) strength parameter of gas produced from source rock
The gas production intensity q of the source rock is obtained by the following formula:
q＝qthermal+qmicro
in the formula, qthermalIndicates the strength of gas generation of the thermal cause gas, qmicroThe strength of the produced gas of the biogenesis gas is shown,
(2) superficial methane fluid flux parameter
Superficial methane fluid flux
Obtained by the following formula:
in the formula, D0Represents the diffusion coefficient and is a constant, phi represents the effective porosity of a natural gas hydrate sedimentary deposit,
indicating the sulfate concentration gradient in the region of the shallow methane stream,
(3) gas-containing fluid dredging capacity parameter
Calculating the volume V of the gas-containing fluid dredging channel according to a formula:
V＝α*πr2l------①
wherein r is the radius of the gas chimney or mud pit, l is the height of the gas chimney or mud pit, and alpha is a constant,
(4) BSR Integrated response parameter
BSR Integrated response CBSRCalculating according to a formula II:
CBSR＝a*Hei+b*Amp+c*Con------②
wherein a, b and c are all coefficients and are constants, and a + b + c is 1, HeiDenotes the thickness of the blank reflection band at the upper part of the BSR, AmpRepresenting the amplitude of the BSR, being constant, ConRepresenting the lateral continuity of the BSR, obtained by seismic section reading, HeiCalculated according to the formula (c):
wherein v represents the propagation velocity of seismic waves in the shallow stratum of the seabed, t is the two-way reflection time of the seismic waves corresponding to the blank reflection band,
(5) hydrate stability zone thickness parameter
Hydrate stability zone thickness HstaCalculating by a formula (IV):
in the formula, m and n both represent coefficients which are constants, T represents the formation temperature of the bottom boundary of the hydrate stability region, DWFor depth of sea water, T0Is the seabed temperature, G is the ground temperature gradient,
(6) shallow layer turbid sand content parameter
The content D of the turbid accumulated sand in the shallow layer is calculated by a formula (v):
D＝Hsand/Hsta------⑤
in the formula, HsandThe cumulative thickness of the turbid accumulated sand bodies is shown,
(7) geological reserve factor of hydrate
Geological reserve Q of hydratehThe calculation is carried out according to the formula:
Qh＝Ah*Zh*φ*Sh*E------⑥
in the formula, AhDenotes the area of the hydrate distribution region, ZhIndicates the effective thickness of hydrate mineral formation zone, ShThe saturation of natural gas hydrate in pores is shown, E represents a gas production factor which is a constant,
(8) hydrate enrichment factor
Enrichment of hydrate QhydCalculated by formula (c):
Qhyd＝φ*Sh------⑦
step 2: taking two geological parameters of hydrate geological reserve and hydrate enrichment as system characteristics, dividing a current region to be predicted into n blocks, calculating each block according to the step 1 to obtain the hydrate geological reserve and the hydrate enrichment corresponding to each block to obtain a series of hydrate geological reserve and hydrate enrichment,
wherein a series of hydrate geological reserves form a hydrate geological reserve system characteristic sequence and are recorded as Y1′，Y1′＝{Y1′(1),Y1′(2),…,Y1′(k),…,Y1′(n)}，Y1' (k) denotes the kth system feature in the sequence of hydrate geological reserve system features,
a series of hydrate enrichment degrees form a hydrate enrichment degree system characteristic sequence marked as Y'2，Y′2＝{Y′2(1),Y′2(2),…,Y′2(k),…,Y′2(n)}，Y′2(k) Represents the kth system characteristic in the characteristic sequence of the enrichment degree system of the hydrate,
then, taking the residual geological parameters as system factor parameters, correspondingly obtaining a group of system factor sequences, and respectively recording the system factor sequences of source rock gas production intensity, methane fluid flux, gas-containing fluid dredging capacity, BSR comprehensive response, shallow turbid sand content and hydrate stability region thickness as X'1、X′2、X′3、X′4、X′5、X′6，
The source rock gas production strength system factor sequence is as follows: x'1＝{X′1(1),X′1(2),…,X′1(n)},
Methane fluid flux system factor sequence: x'2＝{X′2(1),X′2(2),…,X′2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x'3＝{X′3(1),X′3(2),…,X′3(n)},
BSR integrated response system factor sequence: x'4＝{X′4(1),X′4(2),…,X′4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x'5＝{X′5(1),X′5(2),…,X′5(n)},
Hydrate stability domain thickness system factor sequence: x'6＝{X′6(1),X′6(2),…,X′6(n)}，
All the system characteristic sequences and the system factor sequences are used as original data, and the original data are subjected to dimensionless and normalization processing to obtain new sequences corresponding to the original data:
characteristic sequence of hydrate geological reserve system: y is1＝{Y1(1),Y1(2),…,Y1(n)}，
Characteristic sequence of hydrate enrichment system: y is2＝{Y2(1),Y2(2),…,Y2(n)},
The source rock gas production strength system factor sequence is as follows: x1＝{X1(1),X1(2),…,X1(n)},
Methane fluid fluxSequence of system factors: x2＝{X2(1),X2(2),…,X2(n)},
The aerated fluid dredging capacity system factor sequence is as follows: x3＝{X3(1),X3(2),…,X3(n)},
BSR integrated response system factor sequence: x4＝{X4(1),X4(2),…,X4(n)},
The shallow layer turbid accumulated sand content system factor sequence is as follows: x5＝{X5(1),X5(2),…,X5(n)},
Hydrate stability domain thickness system factor sequence: x6＝{X6(1),X6(2),…,X6(n)}；
And step 3: respectively calculating the correlation coefficient between each system characteristic and each system factor, wherein the jth system characteristic Y in the mth system characteristic sequencem(j) And the jth systematic factor X in the ith systematic factor sequencei(j) Coefficient of correlation between gamma (Y)m(j),Xi(j) Calculated by the formula (v):
where m is 1,2, i is 1,2,3,4,5,6, j is 1,2, …, n, Δmi(j)＝|Ym(j)-Xi(j)|，
P represents a resolution coefficient, and is a constant,
then, the correlation coefficient between the same system factor sequence and the same system characteristic sequence forms a correlation coefficient matrix, and the correlation coefficient matrix between the ith system factor sequence and the mth system characteristic sequence is marked as Rm：
Wherein (gamma)ij)mRepresenting a correlation coefficient between the jth system feature in the mth system feature sequence and the jth system factor in the ith system factor sequence,
then, calculating the correlation degree between each system factor and each system characteristic sequence, wherein the correlation degree Q between the ith system factor sequence and the mth system characteristic sequenceimCalculated according to the formula ninthly, the following results are obtained:
if it is
Is invariably provided with
Then Q isimCorresponding system factor XiIs the main control factor.
2. The method for determining the key control factors of the favorable gathering area of the sea natural gas hydrates as claimed in claim 1, wherein in the step 1, q isthermalObtained by hydrocarbon-generating kinetic or thermal or basin simulationmicroObtained by microorganism enrichment culture or experimental simulation method.
3. The method for determining the key control factors of the favorable gathering area of the sea natural gas hydrates as claimed in claim 1, wherein in the step 1, the alpha is more than or equal to 0.01 and less than or equal to 0.2.
4. The method for determining the key control factors of the favorable gathering area of the sea natural gas hydrates as claimed in claim 1, wherein in the step 1, HsandObtained by the following steps:
identifying sand bodies in the seismic section by seismic facies interpretation, and connecting the seismic sectionTaking the product of half of the two-way reflection time of the accumulated seismic waves of the identified sand bodies and the propagation velocity of the seismic waves of the shallow seabed stratum as Hsand。
5. The method for determining the key control factors of the favorable gathering area of the sea natural gas hydrates as claimed in claim 1, wherein in the step 1, AhObtained by delineating the BSR distribution area on the plane onto which the seismic profile interpretation results are projected, ZhObtaining or using H from hydrate drilling and logging datastaInstead, phi is obtained by logging while drilling data calculation, ShThe natural gas hydrate pressure-maintaining core sample is obtained by actual measurement of the natural gas hydrate pressure-maintaining core sample or calculation by using logging-while-drilling data.
6. The method for determining the key control factors of the favorable sea area natural gas hydrate gathering area according to claim 1, wherein in the step 3, p is 0.25, and p ismax＝0.5。
7. The method for determining the key factors of the favorable sea area natural gas hydrate gathering area according to claim 1, wherein the key factors obtained in the step 3 are recorded as first key factors, and after the step 3 is executed or before the step 1 is executed, the method further comprises the following steps:
according to the theory of hydrate reservoir formation system and the actual reservoir formation characteristics of hydrate in the research area, the main control factor of hydrate accumulation in the research area is qualitatively deduced by combining the actual drilling result of hydrate and recorded as a second main control factor,
and if the system factors corresponding to the first main control factor and the second main control factor are consistent, taking the system factor corresponding to the first main control factor or the second main control factor as a final main control factor, otherwise, removing abnormal data from the original data in the step 2 to obtain new original data, and re-executing the step 2 to the step 3 to obtain a new first main control factor, and if the new system factors corresponding to the first main control factor and the second main control factor are not consistent, taking the system factor corresponding to the first main control factor as the final main control factor.
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