CN104678433A - Converted wave extreme attribute hydrocarbon detection method - Google Patents

Abstract

The invention provides a converted wave extreme attribute hydrocarbon detection method, which belongs to the field of hydrocarbon geophysics. The method includes the following steps: (1) a converted wave common conversion point gather is inputted; (2) velocity analysis and dynamic correction are carried out for the common conversion point gather, so that a dynamically corrected gather is formed; (3) longitudinal wave and transverse wave velocity fields are inputted, the angles of converted wave incidence are tracked by a ray, and a converted wave angle gather is formed; (4) the power function y equal to ax<b> plus cx fitting of amplitude versus angle is carried out for a converted wave amplitude sequence at the same time sampling point and different angles of incidence point by point, and an extreme position and extreme amplitude are outputted; (5) a velocity ratio Gamma is obtained by inversion; (6) a transverse wave reflection coefficient Rss0 is inverted; (7) according to a reservoir gas-bearing velocity ratio decrease principle, the gas-bearing property of a reservoir is predicted by means of the velocity ratio Gamma obtained by inversion. The method utilizes high-signal-to-noise-ratio data within an offset range nearby the extreme amplitude, and increases the precision of converted wave AVO (Amplitude Variation with Offset) inversion.

Description

A kind of transformed wave extreme properties gas-oil detecting method

Technical field

The invention belongs to oily vapour geophysics field, be specifically related to a kind of transformed wave extreme properties gas-oil detecting method.

Background technology

In recent years, the relation of seismic reflection amplitude geophone offset change (AVO) has become a focus of geophysical prospecting technology research, along with the development of multicomponent seismic survey technology, and the concern that the research about transformed wave AVO technology causes people larger.Reflection coefficient itself implies the information of elastic parameter with incident angle change, utilizes AVO characteristic can the density of direct inversion rock, velocity of longitudinal wave and shear wave velocity, quantitatively carries out seismic reservoir characterization.Zoeppritz (1919) has derived the Zoeppritz equation of the displacement amplitude relation described between two isotropic medium interphase incident waves, reflection wave, transmitted wave, but due to the non-intuitive in its complicacy mathematically and the physics meaning, never directly applied.Bortfeld (1961), under the condition that hypothesis lithologic interface change of properties is little, gives the formula of reduction that first is distinguished fluid and solid, for people's further studying plane wave-amplitude provides wide thinking with the Changing Pattern of incident angle.Aki & Richards (1980), under the prerequisite that interface two-side elastic Parameters variation is less, is expressed as reflection coefficient the function of elastic parameter rate of change, incident compressional angle and transformed wave reflection angle.Zheng Xiaodong etc. (1991) propose the Uniform Formula of plane elasticity wave reflection and transmission, carried out power series expansion, reflection coefficient is expressed as the odd power function of incident compressional angle sine function to Aki & Richards is approximate.Donati (1998) utilizes binomial expansion to be similar to the angle item relevant with transformed wave in Aki & Richard formula, gives the approximate formula that only and reflection angle mean value incident with compressional wave represents.Gonzalez et al. (2000) adopts the approximation method of Donati, gives linear small angle approximation formula.Xu etc. (1997) obtain the higher approximate formula of precision on the basis retaining the second order terms such as normalization density, speed, but in formula, angle is thought intricate, does not directly show the relation of reflection coefficient and incident angle.Yang Huizhu etc. (1996), with reference to approximation methods such as Mallick, give the approximate formula represented by ray parameter and shear modulus.Li Zhengwen etc. (1996), on the basis that Bortfeld is approximate, propose Section 1 and do not comprise the approximate like formula of velocity ratio.Kelly (2000) etc. gives the linear-apporximation equation represented with normalization density and normalization shear wave velocity.Alvarez (1999) has carried out the comparative study of system to P-SV wave reflection coefficient, gives multi-form approximate formula.Wang Yanghua (1999) is expressed as ray parameter polynomial expression reflection coefficient.Vant etc. (2001) utilize single order power series expansion that is sinusoidal, cosine function to be similar to Zoeppritz equation, give a kind of small angle approximation formula.This is approximate directly carries out small angle approximation to Zoeppritz equation, not by the restriction of weak contrast condition, and replaces ray parameter with incident angle is approximate, simplifies the calculating of complexity, but is only suitable for low-angle AVO and analyzes.Ramos etc. (2001) have directly carried out three rank Taylor expansions to Zoeppritz equation, give the high contrast approximate formula that can be applicable to any lithologic interface, but this approximate formula complex forms, lithologic parameter relation is indefinite, is unfavorable for inversion of lithologic parameters.Sun Peng far waits (2003) etc. to give the approximate formula and the weak contrast approximate formula of second order that utilize different angles item to represent.Sun Peng far waits (2003) to propose transformed wave intercept gradient formula.Sun Peng far waits (2005) with reference to Aki and Richards formula, gives the tangent elastic modulus of similar Mallick approximate formula.Chen Tiansheng etc. (2005), Ma Zhaojun etc. (2007) and Tang Xudong (2008) at large summarize various Converted wave reflection coefficient computing method.

In a word, Aki & Richards has made larger contribution to this respect, makes transformed wave AVO inverting become possibility; The computing formula of power series class has form simply, and lithology relation is clear, is easy to intercept-gradient analysis.But approximate or reduced equation only can quite well Zoeppritz solution of equation under low-angle (compressional wave is less than 30 degree, and transformed wave is less than 15 degree) incident condition.Plan intercept under little incident angle condition, plan gradient attribute are difficult to use in oil and gas detection, the transformed wave information of larger incident angle that, energy high for signal to noise ratio (S/N ratio) is strong (20 degree of-50 degree), needs to be described with new attribute and sets up and relation between Oil And Gas Occurrence.

When compressional wave vertical incidence, Converted wave reflection coefficient is zero, and along with the increase of incident angle, reflection coefficient increases, and therefore near migration range (little incident angle) scope internal conversion ripple data signal to noise ratio (S/N ratio) is low, and the precision of AVO inverting is low, poor stability.

Summary of the invention

The object of the invention is to solve the difficult problem existed in above-mentioned prior art, a kind of transformed wave extreme properties gas-oil detecting method is provided, to utilize near extreme value amplitude high s/n ratio data within the scope of offset distance, improve the precision of transformed wave AVO inverting, for multi-wave seismic imaging, reservoir parameter calculates and oil and gas detection provides effective means.

The present invention is achieved by the following technical solutions:

A kind of transformed wave extreme properties gas-oil detecting method, said method comprising the steps of:

(1) transformed wave common-conversion point gather is inputted;

(2) velocity analysis and normal moveout correction are carried out to common-conversion point gather, form normal moveout correction road collection;

(3) input compressional wave and shear wave velocity field, ray tracing transformed wave incident angle, form transformed wave angular-trace gather;

(4) the power function function y=ax of amplitude incident angle is carried out in pointwise to same time-sampling point, different incidence angles transformed wave amplitude sequence ^b+ cx matching, exports extreme value place with extreme value amplitude $R_{\mathrm{ps},\mathrm{ext}}=a{\left(\frac{-c}{\mathrm{ab}}\right)}^{\frac{b}{b-1}}+c{\left(\frac{-c}{\mathrm{ab}}\right)}^{\frac{1}{b-1}};$

(5) inverting obtains velocity ratio γ;

(6) inverting transverse wave reflection coefficients R _ss0;

(7) reduce principle according to reservoir gas-bearing speed ratio, the speed obtained by inverting is than γ predicting reservoir gas-bearing property.

Described step (5) is achieved in that

Adopt formula (6) inversion speed than γ:

$\mathrm{\&gamma;}=\frac{36-{54x}_{\mathrm{ext}}^2+\sqrt{{({54x}_{\mathrm{ext}}^2-36)}^2+840x_{\mathrm{ext}}^2}}{{310x}_{\mathrm{ext}}^2}---\left(6\right).$

Described step (6) is achieved in that

Adopt formula (7) inverting transverse wave reflection coefficients R _ss0:

$R_{\mathrm{ss}0}=\frac{{5R}_{\mathrm{ps},\mathrm{ext}}}{\frac{(70\mathrm{\&gamma;}+46)(1+18\mathrm{\&gamma;})}{105\mathrm{\&gamma;}+54}\sqrt{\frac{2(1+18\mathrm{\&gamma;})}{{105\mathrm{\&gamma;}}^2+54\mathrm{\&gamma;}}}}---\left(7\right).$

Reservoir gas-bearing speed in described step (7) refers to than reducing principle: after reservoir gas-bearing, velocity of longitudinal wave reduces, and shear wave velocity is constant, and P-S wave velocity ratio reduces.

Compared with prior art, the invention has the beneficial effects as follows:

(1) transformed wave extreme properties to take full advantage of near extreme value amplitude high s/n ratio data within the scope of offset distance, improves the precision of transformed wave AVO inverting.

(2) extreme value place is the function of velocity ratio, can by transformed wave extreme properties direct inversion reservoir velocities ratio and Poisson ratio parameter, extreme value place and the joint inversion of extreme value amplitude can obtain transverse wave reflection coefficient (being embodied in formula (6) and (7)), under known shear wave velocity and density relationship condition, shear wave velocity can be obtained.Transformed wave conventional stacking amplitude is the mean value of certain deviation apart from amplitude in scope, there is no clear and definite physical significance, transformed wave extreme value amplitude and have clear and definite physical significance by the transverse wave reflection coefficient of its inverting, is more conducive to geologic structure interpretation and transformed wave horizon calibration than conventional transformed wave superposition amplitude.

(3) the transformed wave AVO curve third power Function Fitting that the present invention uses both had contained the impact of high-order term, turn avoid the jitter of equation of higher degree matching by noise effect, improve AVO curve precision, obtain more accurate transformed wave AVO extreme properties.

Accompanying drawing explanation

Fig. 1 is the schematic diagram that Converted wave reflection coefficient changes with incident angle.

Fig. 2 is transformed wave extreme value place attribute and velocity ratio graph of a relation.

Fig. 3 is transformed wave extreme value amplitude and transverse wave reflection coefficient and velocity ratio graph of a relation.

Fig. 4 is transformed wave AVO power function fitting.

Fig. 5 is a certain actual converted radio frequency channel collection in embodiment.

Tu6Shi Tu5 road collection transformed wave amplitude power function fitting result, t=3100ms.

Tu7Shi Tu5 road collection power function fitting result.

Fig. 8 (a) is the conventional stacking sectional view of real data in embodiment.

Fig. 8 (b) is transformed wave extreme value sectional view in embodiment.

Fig. 9 is that real data velocity ratio predicts the outcome.

Figure 10 is the step block diagram of the inventive method.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

In the domestic literature retrieved, transformed wave AVO approximate formula only has degree of precision near migration range (little incident angle) scope, in large offseting distance (large incident angle) scope, transformed wave AVO approximate error is larger, amplitude variation with Offset rule can not be described, because the accuracy rating of transformed wave AVO approximate formula limits, transformed wave AVO inverting needs restriction transformed wave data in small angle range.Different with P-wave AVO feature, when compressional wave vertical incidence, Converted wave reflection coefficient is zero, and along with the increase of incident angle, reflection coefficient increases; When incident angle reaches a certain special angle (medium incident angle), Converted wave reflection coefficient reaches extreme value; Then along with the increase of incident angle, Converted wave reflection coefficient reflection coefficient increases with incident angle and reduces.Less at low-angle internal conversion wave-amplitude, ground roll and noise are comparatively strong, and seismic data poor signal to noise, transformed wave reflects axle in the same way and is buried in noise, and transformed wave AVO inversion error is larger.

Under larger incident angle condition, there is extreme value in transformed wave amplitude, and, energy high in the transformed wave data signal to noise ratio (S/N ratio) of Near The Extreme Point be strong, it is clear to reflect axle in the same way.In order to make full use of high s/n ratio transformed wave data in medium ranges of incidence angles, the present invention proposes transformed wave extreme properties, the relation between derivation transformed wave extreme properties and reservoir velocities ratio, Poisson ratio, and then for oil and gas detection.

The extreme properties (extreme value amplitude and extreme value place) of transformed wave AVO has very important using value.Extreme value place is the function of velocity ratio, and reduces with the increase of velocity ratio.When velocity ratio is constant, extreme value amplitude is the monotonous descending function of transverse wave reflection coefficient.When transverse wave reflection coefficient is normal number, the increase of extreme value amplitude velocity ratio and increasing; When transverse wave reflection coefficient is negative constant, the increase of extreme value amplitude velocity ratio and reducing.Can inversion speed and transverse wave reflection coefficient easily from extreme point position and extreme value amplitude, then obtain other reservoir elastic parameter.

1) transformed wave extreme properties

During compressional wave vertical incidence, Converted wave reflection coefficient is zero, and along with incident angle increases, Converted wave reflection coefficient absolute value increases gradually, reaches maximum value in a certain angle, then reduces along with the increase of incident angle (as shown in Figure 1).Within the scope of the contiguous offset distance of very big transformed wave amplitude, axle is clear and signal to noise ratio (S/N ratio) is high by force, in the same way for transformed wave seismologic record reflected energy.According to the variation characteristic of transformed wave reflection amplitude with offset distance, the present invention proposes transformed wave extreme properties first: extreme value amplitude, extreme value place and extreme value curvature.Conventional transformed wave is intended intercept and intended gradient attribute is near migration range transformed wave amplitude matching gained, but near migration range transformed wave amplitude is less, and noise effect is large, and AVO error of fitting is large, unstable.

When stratum, both sides, interface elastic parameter rate of change is very little, Converted wave reflection coefficient can be expressed as:

According to Gardner (1974) relational expression, above formula is reduced to:

$R_{\mathrm{ps}}\left(x\right)=[-\frac{1}{5}\frac{x}{\sqrt{1-{\left(\mathrm{\&gamma;x}\right)}^2}}+\frac{18}{5}\frac{{\mathrm{\&gamma;}}^3{x}^3}{\sqrt{1-{\left(\mathrm{\&gamma;x}\right)}^2}}-\frac{18}{5}\mathrm{\&gamma;x}\sqrt{1-x^2}]R_{\mathrm{ss}0}---\left(2\right)$

Wherein R _ss0=0.5 (Δ ρ/ρ+Δ v _s/ v _s), x=sin θ and γ=v _s/ v _p.

The accurate expression of extreme value place and velocity ratio can be obtained by extreme value of a function theory:

$\frac{-1+54{\mathrm{\&gamma;}}^2{x}^2}{\sqrt{1-{\left(\mathrm{rx}\right)}^2}}+\frac{{18\mathrm{\&gamma;}}^4{x}^4-{\mathrm{\&gamma;}}^2{x}^2}{\sqrt{{[1-{\left(\mathrm{rx}\right)}^2]}^3}}+\frac{{18\mathrm{\&gamma;x}}^2}{\sqrt{1-x^2}}-18\mathrm{\&gamma;}\sqrt{1-x^2}=0---\left(3\right)$

(1-(γ x) ²) ^-1/2(1-x ²) ^1/2carry out Taylor expansion, only remain into the cube of x, extreme value place x can be tried to achieve _extwith extreme value amplitude R _{ps, ext}be respectively:

$x_{\mathrm{ext}}=\sqrt{\frac{2(1+18\mathrm{\&gamma;})}{{105\mathrm{\&gamma;}}^2+54\mathrm{\&gamma;}}}---\left(4\right)$

$R_{\mathrm{ps},\mathrm{ext}}=-\frac{R_{\mathrm{ss}0}}{5}\left[\frac{(70\mathrm{\&gamma;}+46)(1+18\mathrm{\&gamma;})}{105\mathrm{\&gamma;}+54}\sqrt{\frac{2(1+18\mathrm{\&gamma;})}{{105\mathrm{\&gamma;}}^2+54\mathrm{\&gamma;}}}\right]---\left(5\right)$

Therefore transformed wave extreme value place is the monotonic quantity of P-S wave velocity ratio, thereupon velocity ratio increase and increase (as shown in Figure 2).Transformed wave extreme value amplitude is the function (as shown in Figure 3) of velocity ratio and S-wave impedance.Both transformed wave extreme value place and extreme value amplitude can be analyzed intuitively by reservoir parameter, again can from the amplitude extreme properties inverting reservoir velocities ratio of actual converted ripple seismologic record, Poisson ratio and transverse wave reflection coefficient etc.That is:

Velocity ratio: $\mathrm{\&gamma;}=\frac{36-{54x}_{\mathrm{ext}}^2+\sqrt{{({54x}_{\mathrm{ext}}^2-36)}^2+840x_{\mathrm{ext}}^2}}{{310x}_{\mathrm{ext}}^2}---\left(6\right)$

Transverse wave reflection coefficient: $R_{\mathrm{ss}0}=\frac{{5R}_{\mathrm{ps},\mathrm{ext}}}{\frac{(70\mathrm{\&gamma;}+46)(1+18\mathrm{\&gamma;})}{105\mathrm{\&gamma;}+54}\sqrt{\frac{2(1+18\mathrm{\&gamma;})}{{105\mathrm{\&gamma;}}^2+54\mathrm{\&gamma;}}}}---\left(7\right)$

Converted wave reflection coefficient can be similar to the odd power series that Taylor expansion is incident angle sine function, and the normalization Converted wave reflection coefficient in existing document only retains the third power of sine function.Use cubic polynomial y=ax ³+ cx matching (with linear fit after normalized) have ignored the impact of high-order term abridged, can not best-fit vibration amplitude with off-set distance variation characteristic (as Fig. 4).The present invention is generalized to power function fitting y=ax the change of amplitude incident angle ^b+ cx.Power function fitting had both considered the impact of high-order term, turn avoid the instability of equation of higher degree matching by noise effect, at full migration apart from can best-fit vibration amplitude with off-set distance variation characteristic in scope, improve AVO curve precision (as Fig. 4).Obtain high-precision transformed wave extreme value amplitude and extreme value place.

Simultaneous extreme value place and extreme value amplitude equation, can solve reservoir velocities than γ, Poisson ratio, transverse wave reflection coefficients R _ss0with other reservoir parameters.

2), transformed wave extreme properties petroleum-gas prediction

As shown in Figure 10, transformed wave extreme properties petroleum-gas prediction treatment scheme is as follows:

(1) transformed wave common-conversion point gather is inputted;

(2) velocity analysis and normal moveout correction are carried out to common-conversion point gather, form normal moveout correction road collection;

(3) input compressional wave and shear wave velocity field, ray tracing transformed wave incident angle, form transformed wave angular-trace gather;

(4) the power function function y=ax of amplitude incident angle is carried out in pointwise to same time-sampling point, different incidence angles transformed wave amplitude sequence (obtaining from transformed wave angle road) ^b+ cx matching, exports extreme value place extreme value amplitude (extreme value place is used for the inversion speed ratio of step (5));

(5) γ is compared by formula (6) inversion speed;

(6) by formula (7) inverting transverse wave reflection coefficients R _ss0

(7) according to after reservoir gas-bearing, velocity of longitudinal wave reduces, and shear wave velocity is constant, and P-S wave velocity ratio reduces principle, by inversion speed than γ predicting reservoir gas-bearing property.Namely low velocity is than representing gas-bearing property.

The present invention is utilized to process a certain actual converted radio frequency channel collection, its road collection as shown in Figure 5, road collection transformed wave amplitude power function fitting result as shown in Figure 6, road collection power function fitting result as shown in Figure 7, its conventional stacking is as shown in Fig. 8 (a), the transformed wave extreme value section utilizing the inventive method to obtain is as shown in Fig. 8 (b), and comparing two figure can find out, extreme value section is more clear than stacked section imaging.The real data velocity ratio utilizing the inventive method to obtain predicts the outcome as shown in Figure 9, and as can be seen from Figure 9, velocity ratio predicts the outcome better with the actual well drilled oil and gas indication goodness of fit.Dark expression low velocity ratio in figure, white represents high speed ratio.Fg21, fg23, cf563, cf175 are gas-producing wells, and (dark color) coincide better with predicting the outcome.Fg22 is dry-well, and (white) is consistent with predicting the outcome.

The invention belongs to reservoir geophysics technical field, propose transformed wave extreme properties first, derive the relation of transformed wave extreme properties and reservoir parameter, establish the method utilizing this generic attribute to carry out oil and gas detection.This invention is multi-wave seismic imaging, reservoir parameter calculates and oil and gas detection provides effective means.Under multi-component seismic data acquisition condition, multi-wave seismic information can be effectively utilized to carry out layer description and fluid prediction, in seismic monitoring in the oil and gas discovery of new prospecting area, the remaining oil description in exploitation old liberated area and developing of reservoirs, there is high industrial utility value and popularizing application prospect.

Technique scheme is one embodiment of the present invention, for those skilled in the art, on the basis that the invention discloses application process and principle, be easy to make various types of improvement or distortion, and the method be not limited only to described by the above-mentioned embodiment of the present invention, therefore previously described mode is just preferred, and does not have restrictive meaning.

Claims (4)

1. a transformed wave extreme properties gas-oil detecting method, is characterized in that: said method comprising the steps of:

(1) transformed wave common-conversion point gather is inputted;

(2) velocity analysis and normal moveout correction are carried out to common-conversion point gather, form normal moveout correction road collection;

(3) input compressional wave and shear wave velocity field, ray tracing transformed wave incident angle, form transformed wave angular-trace gather;

(4) the power function function y=ax of amplitude incident angle is carried out in pointwise to same time-sampling point, different incidence angles transformed wave amplitude sequence ^b+ cx matching, exports extreme value place with extreme value amplitude $R_{\mathrm{ps},\mathrm{ext}}=a{\left(\frac{-c}{\mathrm{ab}}\right)}^{\frac{b}{b-1}}+c{\left(\frac{-c}{\mathrm{ab}}\right)}^{\frac{1}{b-1}};$

(5) inverting obtains velocity ratio γ;

(6) inverting transverse wave reflection coefficients R _ss0;

(7) reduce principle according to reservoir gas-bearing speed ratio, the speed obtained by inverting is than γ predicting reservoir gas-bearing property.

2. transformed wave extreme properties gas-oil detecting method according to claim 1, is characterized in that: described step (5) is achieved in that

Described step (5) is achieved in that

Adopt formula (6) inversion speed than γ:

$\mathrm{\&gamma;}=\frac{36-{54x}_{\mathrm{ext}}^2+\sqrt{{({54x}_{\mathrm{ext}}^2-36)}^2+840x_{\mathrm{ext}}^2}}{{310x}_{\mathrm{ext}}^2}---\left(6\right).$

3. transformed wave extreme properties gas-oil detecting method according to claim 2, is characterized in that: described step (6) is achieved in that

Described step (6) is achieved in that

Adopt formula (7) inverting transverse wave reflection coefficients R _ss0:

$R_{\mathrm{ss}0}=\frac{{5R}_{\mathrm{ps},\mathrm{ext}}}{\frac{(70\mathrm{\&gamma;}+46)(1+18\mathrm{\&gamma;})}{105\mathrm{\&gamma;}+54}\sqrt{\frac{2(1+18\mathrm{\&gamma;})}{{105\mathrm{\&gamma;}}^2+54\mathrm{\&gamma;}}}}---\left(7\right).$

4. transformed wave extreme properties gas-oil detecting method according to claim 3, it is characterized in that: the reservoir gas-bearing speed in described step (7) refers to than reducing principle: after reservoir gas-bearing, velocity of longitudinal wave reduces, and shear wave velocity is constant, and P-S wave velocity ratio reduces.