CN105182424A - Method and device of reservoir porosity quantitative forecast based on patchy saturation model - Google Patents
Method and device of reservoir porosity quantitative forecast based on patchy saturation model Download PDFInfo
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Abstract
The present invention provides a method and device of reservoir porosity quantitative forecast based on a patchy saturation model. The method of the reservoir porosity quantitative forecast based on the patchy saturation model comprises: acquiring reservoir rock background information; obtaining velocities of longitudinal wave, shear wave velocities and densities with respect to different frequencies; building division frequency PG property crossplot template with respect to different porosities; acquiring pre-stack seismic data of the reservoir; obtaining pre-stack gather data of the division frequency; extracting P and G properties with respect to different porosities; and projecting the P and G properties obtained by inversion onto the division frequency PG property crossplot template, calculating the porosity of the reservoir through employing a template mapping method, and completing the quantitative forecast of the reservoir porosity based on the patchy saturation model. The device of the reservoir porosity quantitative forecast based on the patchy saturation model comprises a reservoir rock background information acquisition unit, a patchy saturation model forward modeling unit, a division frequency PG property crossplot template construction unit, a pre-stack seismic data acquisition unit, a frequency division processing unit, a division frequency PG property acquisition unit and a predicting unit.
Description
Technical field
The present invention relates to a kind of method and apparatus based on patchy saturation quantitative forecast reservoir porosity, belong to field of petroleum geophysical exploration.
Background technology
Along with the continuous intensification of petroleum natural gas exploration degree, the main target of oil-gas exploration changes identification lithologic deposit and subtle reservoir formation into by searching structural deposit gradually, and the fundamental purpose of reservoir prediction develops into quantitative detection from qualitative description gradually.
Along with the raising of real amplitude collection and relative amplitude preserved processing technical merit, the variation characteristic of seismic amplitude energy has become the Main Basis identifying potential hydrocarbon reservoir.The AVO technology that the eighties in last century proposes, base area seismic wave reflection amplitude detects gas sand with the Changing Pattern of offset distance, having become an important application earthquake data before superposition to predict the method for hydrocarbonaceous reservoir, is also the method that the dependence geological data of current most cogency carries out reservoir prediction.
In the process of development, AVO derives from technology goes out multiple property parameters, progressively establishes the relation between underground medium physical parameter and seismic response, substantially increases the precision of reservoir prediction in actual seismic exploration process, reduces the risk of exploration.But the AVO analytical technology of routine is only applicable to carry out Reservoir type identification and fluid detection qualitatively due to the limitation of theory, the physical property infomation for reservoir could not provide effectively quantitative predicting means.The qualitative interpretation of AVO utilizes AVO anomaly classification to determine reservoir whether gassiness, and quantitative forecast then will take into full account the inner link of seismic amplitude response characteristic and reservoir physical parameter, sets up corresponding relation therebetween.Therefore, utilize geophysical method to carry out quantitative forecast to reservoir properties information and become current problem demanding prompt solution.
In recent years, along with going deep into of rock physics theoretical research, scholars generally recognize that seismic event within the scope of different scale and different frequency bands, energy attenuation and velocity dispersion can occur when underground medium is propagated, and the pore fluid caused when causing the main cause of this phenomenon to be seismic wave propagation is relative to the flowing of rock skeleton.
In research process, geophysicist proposes the multiple equivalent medium mode based on two-phase media theory and is used for describing the propagation condition of seismic event in fluid-satruiated porous medium, wherein comparatively classically comprises: Gassmann equation, Biot are theoretical, injection stream is theoretical and patchy saturation etc.The proposition of equivalent medium mode facilitates people greatly for the understanding of rock physics theory and understanding, help the relation established between seismic reflection characteristic and reservoir properties, for the process of seismic data, inversion and interpretation provide extremely important theories integration, the rock physics masterplate technology simultaneously grown up accordingly has also driven reservoir fluid to detect the development explained to quantification by qualitative description to a certain extent.Rock physics theoretical model is as the EFFECTIVE MEDIUM of actual subsurface reservoir, its primary characteristic is the character that accurately reasonably can reflect subsurface reservoir, describe the Influencing Mechanism between different physical properties of rock, and the response being similar to actual underground medium can be made wherein when seismic event is propagated.Finding when carrying out speed to core sample and fluid saturation is tested in laboratory that measured result is often not quite identical with the result of Biot-Gassmann scheduling theory model prediction, analyzing the problem that reason finds mainly to deposit both ways: one is have ignored pore fluid impact on seimic wave velocity under high frequency condition; Two is the impacts not considering that the uneven spot block distribution of pore fluid is propagated for wave field.Spot block distribution refers to the impact by rock pore structure and fluid saturation, the state of the non-homogeneous spot block distribution of the pore fluid presented in fractional saturation poroelastic medium, spatial being rendered as usually outside is water, the middle spheroid for gas or ellipsoid.White proposes first time in 1975 patchy saturation formed by ball-type hole regular distribution, this model has taken into full account the impact of pore fluid spot block distribution for seismic wave field, accurate description seismic event is unbalance by the patch external and internal pressure caused during fluid section saturated porous media, and the velocity dispersion that caused by it and energy attenuation.1979, Dutta etc. utilized accuracy and the validity of Biot theoretical validation patchy saturation, thus have established the basis of this model in theoretical research and practical application.Ball-type hole in above-mentioned model is generalized to the pore space of gross morphology by Johnson (2001) afterwards.On during the affecting of decay, Carcione etc. (2006) reservoir physical parameter in research cycle layered distribution patchy saturation finds that the impact of factor of porosity on decay is larger, and obtain conclusion, change factor of porosity and these two parameters of gas saturation are carried out AVO forward simulation and are not only contributed to distinguishing fluid type, can also reflect that factor of porosity and gas saturation are on the impact of AVO response characteristic.
The conventional AVO analytical technology based on Zoeppritz equation only considers the elastic information of subsurface interface media of both sides, have ignored velocity dispersion when seismic event is propagated in underground medium and energy attenuation to the impact of reflection amplitude.Actual formation imperfectly elastic media, when being filled with fluid in the crack or hole on stratum, the inelastic nature due to fluid can make actual formation show as viscoelasticity characteristic, and causes seismic wave field generation frequency dispersion and decay in various degree.Now, the AVO response characteristic analyzing stratum should consider that the seismic reflection amplitude energy that this inelastic nature causes is abnormal.Chapman etc. (2003) research thinks that the seismic wave attenuation that hydrocarbonaceous reservoir causes changes making boundary wave resistance difference with the change of frequency, cause reflection coefficient relevant with frequency, that is reflected energy will move to high frequency or low-frequency range, and be correlated with the type of AVO in the direction of movement.For first kind AVO, velocity dispersion causes reflected energy to move to front end, and for the 3rd class AVO, reflected energy will move to low-frequency range.The existence of decay exacerbate utilize AVO anomaly classification to carry out reservoir prediction complicacy with uncertain, also provide a kind of reflected energy that utilizes simultaneously and carry out the potential method of fluid detection with the relation of frequency change.
In recent years along with the development of Time-frequency Decomposition technology, make to utilize low, high-frequency information beyond seismic signal dominant frequency to carry out the focus that reservoir prediction becomes seismic interpretation field.Carry out the earthquake attribute volume relevant with frequency research in conjunction with the existing theory of the rock physics based on viscoelastic medium in a deep going way with AVO inversion technique, will contribute to carrying out reservoir parameter quantitative forecast more accurately and effectively.Meanwhile, although utilize AVO inversion technique effectively to identify for the natural gas pool of China's continental sedimentary basin, how to utilize geophysical method to carry out further quantitative forecast to the physical property infomation of reservoir and be still a problem demanding prompt solution.
Summary of the invention
In order to solve Problems existing in oil-bearing reservoir factor of porosity quantitative forecast, the object of the present invention is to provide a kind of method based on patchy saturation quantitative forecast reservoir porosity and device, be intended to comprehensive utilization patchy saturation and point frequency AVO forward simulation and attribution inversion technology, overcome the restriction at the theoretical Elastic interface of conventional AVO, build a point frequency AVO attribute to cross figure masterplate, to cross the object of the masterplate quantitative forecast reservoir porosity regularity of distribution to apply AVO attribute under realizing frequency constraint, improve the precision of reservoir porosity quantitative forecast.
In order to achieve the above object, the present invention provide firstly a kind of method based on patchy saturation quantitative forecast reservoir porosity, and the method comprises the following steps:
Obtain reservoir rock background information;
In conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density;
Just drilling the physical parameter that obtains calculates point frequency P, G attribute in conjunction with AVO approximate formula according to patchy saturation, setting up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate;
Obtain the earthquake data before superposition of reservoir;
Time-frequency Decomposition process is carried out to described earthquake data before superposition, obtains the prestack road collection data of point frequency;
AVO attribution inversion is carried out to the pre-stack seismic road collection of point frequency, extracts P, G attribute that different frequency is corresponding;
P, G attribute inverting obtained projects to a point frequency PG attribute and crosses on figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of reservoir, completes based on the quantitative forecast of patchy saturation to reservoir porosity.
In said method of the present invention, preferably, described reservoir rock background information comprises: Rock Matrix bulk modulus, Rock Matrix modulus of shearing, Rock Matrix density, reservoir permeability, pore fluid bulk modulus, pore fluid density, pore fluid glutinousness and pore fluid saturation degree.
In said method of the present invention, preferably, described in conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density, specifically comprise:
In conjunction with reservoir rock, fluid background information, according to by the factor of porosity distribution range that obtains and the frequency band range determined by geological data of logging well, utilize different frequency in the patchy saturation forward simulation respective aperture porosity of layered medium and frequency band range, velocity of longitudinal wave, shear wave velocity and density when different aperture is spent.
According to the specific embodiment of the present invention, the choice criteria of different frequency and different aperture degree is within the scope of seismic band, choose some frequency values and factor of porosity.Such as seismic band scope is 10Hz to 60Hz, the frequency so selected may be 10,20,30,40,50,60Hz.
In said method of the present invention, preferably, in the method after extracting P, G attribute corresponding to different frequency, P, G attribute inverting obtained projects to point frequency PG attribute figure masterplate that crosses and goes forward, and also comprises setting up point frequency PG attribute corresponding to different aperture degree and crossing the step of figure masterplate.
In said method of the present invention, preferably, the cross foundation of figure masterplate of point frequency PG attribute that described different aperture degree is corresponding comprises:
Patchy saturation is just being drilled the physical parameter that obtains in conjunction with AVO approximate formula, forward modelling divides P, G attribute of frequency, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate.
In said method of the present invention, preferably, just drilling the physical parameter that obtains P, G attribute in conjunction with AVO approximate formula forward modelling point frequency according to patchy saturation, setting up a point frequency PG attribute corresponding to the different aperture degree figure masterplate that crosses and comprise the following steps:
In conjunction with cap rock physical property infomation, point frequency compressional wave, shear wave velocity and the density of just drilling the different aperture degree that obtains based on patchy saturation corresponding are updated to Shuey binomial AVO approximate formula, obtain point frequency P corresponding to different aperture degree, G attribute, with P attribute be horizontal ordinate, G attribute is for ordinate, point frequency corresponding for each factor of porosity is just being drilled result to be projected in coordinate system, forms the corresponding point frequency PG attribute of different aperture degree and to cross template.
According to the specific embodiment of the present invention, P and G in template is the function of factor of porosity and frequency, projects in coordinate system during projection by the result of characteristic frequency, and result corresponding to each frequency is the function of factor of porosity.
According to the specific embodiment of the present invention, PG attribute utilizes just to drill and obtains, the process just drilled has multiple variable, comprising factor of porosity and frequency, a factor of porosity is fixed during calculating, calculate P and G that all frequencies of choosing are corresponding, P and G that all frequencies chosen under calculating all factor of porosity are according to this corresponding.Project in coordinate system by P and G obtained after all factor of porosity and all frequencies, the point of same frequency links up, and the point of same factor of porosity links up, and obtains the corresponding point frequency PG attribute of different aperture degree and to cross template.
Present invention also offers a kind of device based on patchy saturation quantitative forecast reservoir porosity, this device comprises:
Reservoir rock background information acquiring unit, for obtaining reservoir rock background information;
Patchy saturation forward simulation unit, for obtaining velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density;
Point frequency PG attribute crosses figure masterplate construction unit, to cross figure masterplate for setting up a point frequency PG attribute corresponding to different aperture degree;
Earthquake data before superposition acquiring unit, for obtaining the earthquake data before superposition in oil-bearing reservoir region;
Scaling down processing unit, for carrying out Time-frequency Decomposition process to earthquake data before superposition, obtains the prestack road collection data that each instantaneous frequency is corresponding;
Dividing frequency P, G attribute acquiring unit, for carrying out AVO attribution inversion to the pre-stack seismic road collection of point frequency, extracting P, G attribute that different instantaneous frequency is corresponding;
Predicting unit, P, G attribute for different frequency inverting obtained projects to a point frequency PG attribute and to cross figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of reservoir.
In said apparatus of the present invention, preferably, described reservoir rock background information acquiring unit, for obtaining Rock Matrix bulk modulus, Rock Matrix modulus of shearing, Rock Matrix density, reservoir permeability, pore fluid bulk modulus, pore fluid density, pore fluid glutinousness and pore fluid saturation degree.
In said apparatus of the present invention, preferably, described patchy saturation forward simulation unit, specifically for according to patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density.
In said apparatus of the present invention, preferably, described point of frequency PG attribute crosses figure masterplate construction unit, calculate P, G attribute of point frequency for the frequency varied property parameter just drilled according to patchy saturation in conjunction with AVO approximate formula, set up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate.
In said apparatus of the present invention, preferably, described point of frequency PG attribute crosses figure masterplate construction unit, specifically in conjunction with cap rock physical property infomation, p-and s-wave velocity corresponding to the frequency field different aperture degree that obtains will be just being drilled and density is updated to Shuey binomial AVO approximate formula based on patchy saturation, calculate P, G attribute of point frequency, set up PG attribute corresponding to different aperture degree under frequency constraint and to cross figure masterplate.
Method based on patchy saturation quantitative forecast reservoir porosity of the present invention and device, p-and s-wave velocity and density that different aperture degree under the patchy saturation forward simulation frequency constraint of layered medium is corresponding is utilized in conjunction with reservoir rock background information, then establish PG attribute corresponding to different aperture degree under frequency constraint in conjunction with AVO forward simulation to cross figure masterplate, a point frequency prestack AVO attribution inversion is utilized to obtain P corresponding to different frequency, G attribute, finally by the different frequency P of masterplate reflection method by practical inversion, G attribute projects to the effect reaching reservoir porosity regularity of distribution quantitative forecast in the figure masterplate that crosses, overcome the limitation of conventional AVO technology on quantitative forecast reservoir properties, research for oil-bearing reservoir factor of porosity distribution quantitative forecast and reservoir oil-gas possibility has great directive significance, improve the precision of quantitative reservoir prediction.
Accompanying drawing explanation
Fig. 1 is a kind of method flow diagram based on patchy saturation quantitative forecast reservoir porosity that the present invention proposes;
Fig. 2 is a kind of device block diagram based on patchy saturation quantitative forecast reservoir porosity that the present invention proposes;
Fig. 3 a is the graph of a relation that under the frequency constraint obtained based on patchy saturation in the present embodiment, factor of porosity and AVO analyze P attribute;
Fig. 3 b is the graph of a relation that under the frequency constraint obtained based on patchy saturation in embodiment, factor of porosity and AVO analyze G attribute;
Fig. 4 is just drilling PG attribute corresponding to different aperture degree under the frequency constraint obtained based on patchy saturation in embodiment to cross figure masterplate;
Fig. 5 a is according to the objective interval factor of porosity diagrammatic cross-section that masterplate reflection method calculates in embodiment;
To be the porosity prediction result that calculates according to masterplate reflection method in embodiment to cut into slices schematic diagram along zone of interest Fig. 5 b.
Embodiment
In order to there be understanding clearly to technical characteristic of the present invention, object and beneficial effect, existing following detailed description is carried out to technical scheme of the present invention, but can not be interpreted as to of the present invention can the restriction of practical range.
When processing the problem of oil-bearing reservoir factor of porosity quantitative forecast, the embodiment of the present invention is based on some researchs of forefathers, introduce patchy saturation, the PG attribute setting up different aperture degree under frequency constraint corresponding based on Shuey binomial AVO approximate formula crosses figure masterplate to carry out the quantitative forecast of factor of porosity, and then improves the precision of reservoir properties information quantitative forecast.
Fig. 1 is a kind of method flow diagram based on patchy saturation quantitative forecast reservoir porosity of the present invention, and the described method based on patchy saturation quantitative forecast reservoir porosity comprises:
Step 101: obtain reservoir rock background information;
Step 102: in conjunction with patchy saturation and reservoir rock background information, carries out point frequency forward simulation of different aperture degree, obtains velocity of longitudinal wave corresponding to different instantaneous frequency, shear wave velocity and density;
Step 103: just drilling the physical parameter that obtains calculates point frequency P, G attribute in conjunction with AVO approximate formula according to patchy saturation, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate;
Step 104: the earthquake data before superposition obtaining oil-bearing reservoir;
Step 105: carry out Time-frequency Decomposition process to earthquake data before superposition, obtains the prestack road collection data that different frequency is corresponding;
Step 106: carry out AVO attribution inversion to the pre-stack seismic road collection of point frequency, extracts P, G attribute that different frequency is corresponding;
Step 107: P, G attribute inverting obtained projects to a point frequency PG attribute and crosses on figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of target reservoir.
Described acquisition reservoir rock background information, comprising: obtain the information such as Rock Matrix bulk modulus, modulus of shearing, density, reservoir permeability and pore fluid bulk modulus, fluid density, glutinousness and saturation degree.
Described in conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different instantaneous frequency, shear wave velocity and density, comprising:
According to reservoir rock and fluid background information, in conjunction with layered medium patchy saturation forward simulation different frequency, different aperture is spent time velocity of longitudinal wave, shear wave velocity and density.
The described basis physical parameter of just drilling calculates P, G attribute of point frequency in conjunction with AVO approximate formula, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate, comprising:
In conjunction with cap rock physical property infomation, p-and s-wave velocity corresponding to the frequency field different aperture degree that obtains will be just being drilled and density is updated to Shuey binomial AVO approximate formula based on patchy saturation, calculate P, G attribute of point frequency, set up PG attribute corresponding to different aperture degree under frequency constraint and to cross figure masterplate.
Fig. 2 is a kind of device based on patchy saturation quantitative forecast reservoir porosity that the present invention proposes, and described device comprises:
Reservoir rock background information acquiring unit 201, for obtaining reservoir rock background information;
Patchy saturation forward simulation unit 202, in conjunction with patchy saturation and reservoir background information, a point frequency of carrying out different aperture degree is just drilled, and obtains velocity of longitudinal wave corresponding to different instantaneous frequency, shear wave velocity and density;
Point frequency PG attribute crosses figure masterplate construction unit 203, to calculate P, G attribute of point frequency for just drilling the reservoir physical parameter that obtains according to patchy saturation in conjunction with AVO approximate formula, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate;
Earthquake data before superposition acquiring unit 204, for obtaining the earthquake data before superposition of oil-bearing reservoir;
Scaling down processing unit 205, for carrying out Time-frequency Decomposition process to earthquake data before superposition, obtains the prestack road collection data of point frequency;
Dividing frequency P, G attribute acquiring unit 206, for carrying out AVO attribution inversion to the pre-stack seismic road collection of point frequency, extracting P, G attribute that different frequency is corresponding;
Predicting unit 207, point frequency PG attribute that P, G attribute for inverting being obtained projects to foundation crosses figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of target reservoir.
In an embodiment of the present invention, described rock background information comprises: the information such as Rock Matrix bulk modulus, modulus of shearing, density, reservoir permeability and pore fluid bulk modulus, fluid density, glutinousness and saturation degree.
In an embodiment of the present invention, described in conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different instantaneous frequency, shear wave velocity and density, comprise: in conjunction with reservoir rock background information, according to the patchy saturation forward simulation different frequency of layered medium, different aperture is spent time velocity of longitudinal wave, shear wave velocity and density.
In an embodiment of the present invention, describedly just drilling the physical parameter that obtains calculates point frequency P, G attribute in conjunction with AVO approximate formula according to patchy saturation, set up a point frequency PG attribute corresponding to different aperture degree to cross figure masterplate, comprise: p-and s-wave velocity corresponding for the frequency field different aperture degree obtained based on patchy saturation and density are updated to Shuey binomial AVO approximate formula, obtain P, G attribute of point frequency, the PG attribute set up under frequency constraint crosses figure masterplate.
Embodiment
In the method flow diagram based on patchy saturation quantitative forecast reservoir porosity shown in Fig. 1, in step 101, reservoir background information relates to geologic report, logging trace, core data etc., needs the information therefrom understood to comprise: lithology, mineralogical composition and content, factor of porosity distribution range, fluid saturation, pore fluid type etc.
In step 102, required model parameter relates to reservoir solid matrix, pore fluid, factor of porosity, saturation degree four aspects.Solid matrix parameter comprises matrix bulk modulus K
g, matrix modulus of shearing μ
g, density of matrix ρ
g, matrix permeability κ.Pore fluid parameter comprises hydro carbons bulk modulus K
f, hydro carbons density p
f, hydro carbons coefficient of viscosity η
f, water volume modulus K
w, water-mass density ρ
w, water coefficient of viscosity η
w.Factor of porosity parameter relates to macroscopical distribution range of reservoir porosity, obtains based on well logging information.
In step 102, reservoir rock skeleton bulk modulus adopts Krief formulae discovery, and the matrix modulus of known rock and factor of porosity, utilize Krief formula to provide the modulus of rock skeleton.
Krief formula is as follows:
K
m＝K
g(1-φ)
4/(1-φ),μ
m＝K
mμ
g/K
g(1)
Wherein, K
gand μ
gbe bulk modulus and the modulus of shearing of Rock Matrix respectively, φ is factor of porosity, K
mand μ
mbulk modulus and the modulus of shearing of rock skeleton respectively.
Utilize the principle of patchy saturation calculating different aperture degree sandstone reservoir point frequency velocity of longitudinal wave, shear wave velocity and density as follows in step 102:
Cycle stratiform patchy saturation is made up of fluid-saturated porous media 1 and 2, and density is respectively ρ
1and ρ
2, thickness is respectively d
1and d
2, the elastic modulus expression formula that compressional wave is propagated in a model is:
In formula, E
0expression formula as follows:
P represents the saturation degree of often kind of pore fluid, and its expression formula is:
p
i＝d
i/(d
1+d
2),i＝1,2(4)
For each pore fluid, the computing formula of its compressional wave elastic modulus is as follows:
In formula, K
gfor Gassmamm bulk modulus, μ
mfor the modulus of shearing of rock skeleton, K
gexpression formula be:
K
G＝K
m+b
2M(6)
In formula, b is Biot coefficient, and M is pore fluid elastic modulus, and expression formula is:
In formula, K
mfor rock skeleton bulk modulus, K
gfor solid matrix bulk modulus, K
ffor hole fluid-mixing bulk modulus, can be obtained by Wood formula:
In formula, K
f1and K
f2represent the bulk modulus of two kinds of pore fluids respectively.
On layer border, the mobility due to fluid causes all producing a STRESS VARIATION in every one deck medium, and the medium total stress that this change can be caused by fluid characterizes with the ratio of perpendicular stress when not having fluid to flow:
The expression formula of the Slow P-wave impedance I of every one deck medium is:
In above formula, k is the complex wave number of Slow P-wave, and its expression formula is:
In formula, ω is angular frequency, and η is fluid viscous coefficient, and κ is permeability, μ
mfor the modulus of shearing of rock skeleton.
Then the expression formula of the velocity of longitudinal wave of cycle stratiform patchy saturation, shear wave velocity and density is:
In above formula, velocity of longitudinal wave, shear wave velocity are the function of frequency, factor of porosity respectively, and density is the function of factor of porosity.
Utilize Shuey binomial approximate formula combination interface media of both sides physical parameter to calculate P, G attribute of point frequency in step 103, the expression formula of Shuey approximate formula is:
R in above formula
0for normal-incidence reflection coefficient, be P value,
for gradient terms.Wherein σ is the Poisson ratio of medium, A
0expression formula be:
In formula, Δ v
pfor the velocity of longitudinal wave of upper and lower two layer medium is poor, v
pfor the average velocity of longitudinal wave of upper and lower two layer medium, Δ ρ is the density difference of upper and lower two layer medium, and ρ is the average density of upper and lower two layer medium.
Point frequency P utilizing Shuey approximate formula to calculate, the G attribute PG attribute built under frequency constraint crosses masterplate.
Step 104 obtains the earthquake data before superposition of oil-bearing reservoir.
Step 105, for carrying out Time-frequency Decomposition process to earthquake data before superposition, obtains the prestack road collection data of point frequency.Time-frequency Decomposition adopts the method for generalized S-transform, and its principle is as follows:
Wherein f is frequency, and x (t) is original seismic signal, and S (τ, f) is corresponding time-frequency domain seismic signal, λ
afor regulatory factor, when after selected p value, if λ
awhen >1 then accelerates, window width is with the speed of frequency change, otherwise, if λ
a<1 has then slowed down this speed.The span of p is 1/2 to 3/2.Through generalized S-transform, original time domain geological data changes time-frequency domain seismic signal into, chooses specific instantaneous frequency values, can obtain the pre-stack seismic road collection that this frequency is corresponding.Frequency values selected when carrying out Time-frequency Decomposition to prestack road collection in the present embodiment is 5,10,20,30,40,50,70,90Hz, and obtain the single-frequency section of respective frequencies.
Carry out AVO attribution inversion to the prestack road collection of point frequency in step 106, extract P attribute and the G attribute of corresponding frequencies, the theoretical foundation of its foundation is Shuey binomial AVO approximate formula, and as shown in formula (13), specific works flow process is as follows:
First, the basis of study area reservoir rock physical analysis is just drilled in conjunction with prestack AVO, determine reservoir AVO response characteristic, a point angular stack is carried out to pre stack data, the present invention chooses three angle-data bodies (5-13 °, 14-24 °, 25-33 °) and carries out overlap-add procedure, then carries out to a point frequency-portions superposition of data body P, G attribute volume that AVO attribution inversion extracts point frequency.
Point frequency P in zone of interest region inverting obtained in step 107, G attribute project to point frequency PG attribute that step 103 sets up and cross on masterplate, adopt masterplate reflection method to calculate the factor of porosity of target reservoir, the determining hole porosity regularity of distribution.
Fig. 3 a is the graph of a relation that under the frequency constraint obtained based on patchy saturation in the present embodiment, factor of porosity and AVO analyze P attribute, Fig. 3 b is the graph of a relation that under the frequency constraint obtained based on patchy saturation in embodiment, factor of porosity and AVO analyze G attribute, and its specific implementation step is:
Step 1: input the bulk modulus of the bulk modulus of target reservoir section Rock Matrix, modulus of shearing, density, permeability and pore fluid, the coefficient of viscosity and density, setting gas saturation according to well logging interpretation conclusion is 30%, the variation range of factor of porosity is 0 to 50%, calculates the velocity of longitudinal wave of point frequency, shear wave velocity and density respectively according to patchy saturation.
Step 2: according to well logging interpretation information and Rock physical analysis result, input study area regional cap rock velocity of longitudinal wave, shear wave velocity and density information, cap rock and reservoir properties information are updated to Shuey binomial AVO approximate formula, obtain P, G property value that different aperture degree under frequency constraint is corresponding.
Fig. 4 is that PG attribute that under the frequency constraint obtained based on patchy saturation in the present embodiment, different aperture degree is corresponding crosses figure, it realizes principle: given gas saturation is 30%, factor of porosity distribution range is 0-50%, comprehensive patchy saturation and Shuey binomial AVO approximate formula calculate P attribute corresponding to each factor of porosity, frequency and G property value, are then projected to and cross on figure.In figure, horizontal ordinate is P attribute, and ordinate is G attribute, and black arrow indicates the direction that factor of porosity increases, and factor of porosity isoline from right to left variation range is 0 to 50%, and frequency isoline from top to bottom variation range is 5Hz to 90Hz.As shown in Figure 4, the solid black lines of band mark represents equi-frequency contour, black dotted lines represents isoporosity separatrix, porosity value is labeled in below isoline, there is notable difference in P, G property value that as can be seen from the figure different frequency is corresponding, and P, G property distribution feature presents obvious regularity when different aperture is spent, namely low-porosity is distributed on the right side of the figure that crosses, high porosity is distributed on the left of the figure that crosses.In this example, projected to by P, G attribute that prestack weighted band_wise is obtained and cross in masterplate, effectively achieve the quantitative forecast of factor of porosity.
In this example, choose a continental sedimentary basin and carry out oil-bearing reservoir factor of porosity quantitative forecast, according to above-mentioned techniqueflow, first Time-frequency Decomposition and AVO inverting are carried out to earthquake data before superposition, obtain P, G attribute of point frequency, then point frequency variable orifice porosity PG attribute set up in conjunction with forward simulation crosses masterplate (Fig. 4 shown), carries out reservoir porosity quantitative forecast.As shown in Figure 5 a, for the objective interval hole calculated according to masterplate reflection method in embodiment spends well profile, in figure, white represents factor of porosity high level, black represents factor of porosity low value, and the logging trace of display is the porosity curve utilizing Using Conventional Logs to explain, the lvalue of curve is high porosity, r value is low-porosity, and can see predicts the outcome has the very high goodness of fit with result of log interpretation.Fig. 5 b is the porosity prediction result that calculates according to masterplate reflection method in the present embodiment section display figure along zone of interest, the position, well point of drilling well is shown in figure, predict the outcome consistent to the well testing result of relevant 4 mouthfuls of wells, confirm the validity of the method for the present embodiment.
Above embodiment explanation, method and apparatus based on patchy saturation quantitative forecast reservoir porosity of the present invention, by introducing patchy saturation, on the basis of AVO forward simulation and back analysis, the lower PG attribute of a kind of new applying frequency constraint the provided masterplate that crosses carries out the method for oil-bearing reservoir factor of porosity quantitative forecast, improves the precision of reservoir properties quantitative forecast.
Claims (10)
1., based on a method for patchy saturation quantitative forecast reservoir porosity, the method comprises the following steps:
Obtain reservoir rock background information;
In conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density;
Just drilling the physical parameter that obtains calculates point frequency P, G attribute in conjunction with AVO approximate formula according to patchy saturation, setting up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate;
Obtain the earthquake data before superposition of reservoir;
Time-frequency Decomposition process is carried out to described earthquake data before superposition, obtains the prestack road collection data of point frequency;
AVO attribution inversion is carried out to the pre-stack seismic road collection of point frequency, extracts P, G attribute that different frequency is corresponding;
P, G attribute inverting obtained projects to a point frequency PG attribute and crosses on figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of reservoir, completes based on the quantitative forecast of patchy saturation to reservoir porosity.
2. method according to claim 1, wherein, described reservoir rock background information comprises: Rock Matrix bulk modulus, Rock Matrix modulus of shearing, Rock Matrix density, reservoir permeability, pore fluid bulk modulus, pore fluid density, pore fluid glutinousness and pore fluid saturation degree.
3. method according to claim 1, wherein, described in conjunction with patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density, specifically comprise:
In conjunction with reservoir rock, fluid background information, according to by the factor of porosity distribution range that obtains and the frequency band range determined by geological data of logging well, utilize different frequency in the patchy saturation forward simulation respective aperture porosity of layered medium and frequency band range, velocity of longitudinal wave, shear wave velocity and density when different aperture is spent.
4. method according to claim 1, wherein, in the method after extracting P, G attribute corresponding to different frequency, P, G attribute inverting obtained projects to point frequency PG attribute figure masterplate that crosses and goes forward, and also comprises setting up point frequency PG attribute corresponding to different aperture degree and crossing the step of figure masterplate.
5. method according to claim 4, wherein, the cross foundation of figure masterplate of point frequency PG attribute that described different aperture degree is corresponding comprises:
Patchy saturation is just being drilled the physical parameter that obtains in conjunction with AVO approximate formula, forward modelling divides P, G attribute of frequency, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate.
6. method according to claim 5, wherein, just drilling the physical parameter that obtains according to patchy saturation in conjunction with AVO approximate formula, forward modelling divides P, G attribute of frequency, set up a point frequency PG attribute corresponding to different aperture degree to cross figure masterplate, concrete steps are:
In conjunction with cap rock physical property infomation, point frequency compressional wave, shear wave velocity and the density of just drilling the different aperture degree that obtains based on patchy saturation corresponding are updated to Shuey binomial AVO approximate formula, obtain point frequency P corresponding to different aperture degree, G attribute, then with P attribute be horizontal ordinate, G attribute is for ordinate, point frequency corresponding during each factor of porosity is just being drilled result to be projected in coordinate system, forms the corresponding point frequency PG attribute of different aperture degree and to cross masterplate.
7., based on a device for patchy saturation quantitative forecast reservoir porosity, this device comprises:
Reservoir rock background information acquiring unit, for obtaining reservoir rock background information;
Patchy saturation forward simulation unit, for obtaining velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density;
Point frequency PG attribute crosses figure masterplate construction unit, to cross figure masterplate for setting up a point frequency PG attribute corresponding to different aperture degree;
Earthquake data before superposition acquiring unit, for obtaining the earthquake data before superposition in oil-bearing reservoir region;
Scaling down processing unit, for carrying out Time-frequency Decomposition process to earthquake data before superposition, obtains the prestack road collection data that each instantaneous frequency is corresponding;
Dividing frequency P, G attribute acquiring unit, for carrying out AVO attribution inversion to the pre-stack seismic road collection of point frequency, extracting P, G attribute that different instantaneous frequency is corresponding;
Predicting unit, P, G attribute for different frequency inverting obtained projects to a point frequency PG attribute and to cross figure masterplate, adopts masterplate reflection method to calculate the factor of porosity of reservoir.
8. device according to claim 7, wherein, described reservoir rock background information acquiring unit, for obtaining Rock Matrix bulk modulus, Rock Matrix modulus of shearing, Rock Matrix density, reservoir permeability, pore fluid bulk modulus, pore fluid density, pore fluid glutinousness and pore fluid saturation degree.
9. device according to claim 7, wherein, described patchy saturation forward simulation unit, specifically for according to patchy saturation and reservoir rock background information, carry out point frequency forward simulation of different aperture degree, obtain velocity of longitudinal wave corresponding to different frequency, shear wave velocity and density;
Described point of frequency PG attribute crosses figure masterplate construction unit, calculates P, G attribute of point frequency for the frequency varied property parameter just drilled according to patchy saturation in conjunction with AVO approximate formula, sets up a point frequency PG attribute corresponding to different aperture degree and to cross figure masterplate.
10. device according to claim 7, wherein, described point of frequency PG attribute crosses figure masterplate construction unit, specifically in conjunction with cap rock physical property infomation, p-and s-wave velocity corresponding to the frequency field different aperture degree that obtains will be just being drilled and density is updated to Shuey binomial AVO approximate formula based on patchy saturation, calculate P, G attribute of point frequency, set up PG attribute corresponding to different aperture degree under frequency constraint and to cross figure masterplate.
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