CN104516014A - Fitting landform based wave field reconstruction method - Google Patents

Abstract

The invention discloses a seismic wave field reconstruction method, and provides a fitting landform based wave field reconstruction method. A digital model is established by use of acquisition of exploration data and routine processing and interpretation results of the exploration data, the model is divided into grids, epicenter wavelets are initialized at grid points equivalent to field excitation positions, a seismic wave field is reconstructed at each grid point and at each time point, wave field values are recorded at the grid points equivalent to field detector positions, a reconstructed recording is obtained, the recording is processed and interpreted, a reconstruction data profile is obtained, a comparison is made between the reconstruction data profile and an actual exploration data profile, whether the exploration data processing and interpreting results are correct or not is verified, and the method can be used for evaluating the rationality of an exploration data acquisition observation system. According to the invention, the seismic wave field reconstruction method is suitable for wave field reconstruction of the complex structure of a fluctuating landform, and is high in precision and low in boundary interference, thereby being an effective auxiliary means of petroleum exploration.

Description

A kind of wave field reconstructing method based on matching landform

Technical field

The present invention relates to oil exploration technology, is that one instructs field earthquake data acquisition, and verifies the wave field reconstructing method based on matching landform of survey data process, interpretation results.

Background technology

Signal source and detector, based on the principle of acoustic reflection, are laid in earth's surface by oil seismic exploration, and the fluctuation signal that signal source is launched, through the propagation in underground medium, reflects back into wave detector and goes on record.Geometry Rankine-Hugoniot relations between basis signal source and wave detector, the record received is processed and the anti-spread process such as explanation, finally obtain the physical attributes such as the formation velocity in underground space territory, density, factor of porosity, carry out underground space model reconstruction according to these attribute informations, obtain a mathematical model described with computerese.The present invention is the mathematical model obtained by above technology, the signal source and the detector that re-use exploration process carry out wave field reconstruct, reappear ground observation record, then the data of the record of reconstruct and actual ground observation record are compared, the rationality of verification process, interpretation results, then revises process, interpretation results further, then carries out wave field reconstruct, comparison, iterate, obtain final accurate underground space model.

Seismic wave field reconstruct has great significance for actual exploration data acquisition, structure elucidation.It can describe the evolution process of signal in underground medium is propagated that signal source is launched accurately, very effective for backward tracing tectonic structure.At present, seismic wave field reconstruct usually adopts isotropic elasticity ripple partial differential equation to describe the propagation of signal, and the description signal that this equation can be correct is at the propagation of complicated underground medium and change procedure.

Because the model scope reconstructed for wave field is that size is limited, that is the model of mathematical description has border, artificial reflection interference can be there is when fluctuation signal propagates into the border of model, this interference needs compacting, in order to suppress the reflection interference that Artificial Boundaries causes, generally adopt exponential damping absorbing boundary, this method is outside model, add that one extra has certain thickness border, bound thickness has multiple grid usually, the absorption coefficient numerical value of each grid is (0.0, 1.0) between, when signal spreads into model boundary, energy is decayed gradually along with propagating in border, thus reduce the undesired signal of border reflection.

Above-mentioned exponential damping border is based on following equation:

$p=e^{-\mathrm{\α}\·n^2}---\left(1\right)$

Wherein, p is border attenuation coefficient, and n is the vertical range (counting) of border grid distance model boundary, and α is given decay factor.

When carrying out seismic wave field reconstruct, given model computer capacity is rectangle, the left margin of rectangle, right margin and lower boundary are all straight, the absorption coefficient value of absorbing boundary grid is determined by the distance n on this grid and border, the top boundary of model is if rolling shape, the realization of absorbing boundary be in vertical from earth's surface directly to applying border (Fig. 2 figure below), namely absorbing boundary grid absorption coefficient value by this grid and immediately below it the distance n of border grid determine, when earth's surface exists compared with macrorelief, this border inner can produce sudden change, side interference and diffraction interference is produced when this sudden change can cause signal to be propagated in border, these interference are a kind of illusions in the record of wave field reconstruct, this is a problem that must solve in seismic wave field reconstruct.

CN101290355A patent discloses a kind of method determining carbonate rock hydrocarbon reservoir structure, propose and set up stratigraphic model based on field acquisition the data processed results, carry out wave-field reconstruction, then the result after wave-field reconstruction and field data collection process are obtained superpose and migrated section contrasts, determine the distribution of carbonate rock hydrocarbon reservoir thus, cranny development direction and development degree.This method is practical, but not in wave-field reconstruction process service time territory and spatial domain staggered-mesh High-Order Finite-Difference Method solving equation, the precision which results in wave-field reconstruction is not high, and does not have proposition how to avoid producing the method for artificial reflection interference in the process of process relief surface.

In July, 2005 " petroleum exploration " Pei Zhenglin discloses a kind of method of Three-Dimensional Isotropic dielectric resilient wave equation staggering grid high-order finite-difference, this article is the basic algorithm of solutions of the motion equations, the finite difference of carrying out any even-order precision of staggered-mesh solves, and utilize PML method to carry out absorbing boundary process, under flatly surface condition, well can absorb process to the border of model.This method does not consider the problem of relief surface, but actual conditions are, the model set up based on field result of seismic explosion is all relief surface.Formula (14) formula in literary composition and ⊥ and the II component described by (15) formula only with space derivative, relevant perpendicular to the space derivative of y and z in the plane in x direction, have nothing to do with surface configuration, carry out wave-field reconstruction according to this absorbing boundary processing mode, artificial reflection interference certainly will be caused in relief surface situation.

In the method for wave field reconstruct, absorbing boundary condition is a difficult problem for puzzlement industry always, the PML method that Pei Zhenglin proposes in paper can use the implementation procedure of most of wave field reconstruct, also be applicable to the wave field restructuring procedure that above-mentioned patent adopts, but the combination of method both this still effectively can not eliminate the artificial reflection interference in wave field reconstruct mesorelief earth's surface.

Summary of the invention

The object of the invention is to provide a kind of wave field reconstructing method based on matching landform effectively suppressing the artificial reflection interference in wave field reconstruct mesorelief earth's surface.

The present invention is realized by following steps:

1) known seismic data treatment and decryption is utilized to set up tectonic model;

2) utilize the geological property of known oil-gas pool distribution attributive character determination tectonic model, obtain discrete attribute model;

Described geological property comprises p-and s-wave velocity and rock density.

3) based on field layout and step 2) attribute model, utilize staggered-mesh High-Order Finite-Difference Method to solve isotropic elasticity ripple partial differential equation in time domain and spatial domain;

Described High-Order Finite-Difference Method adopts 2 rank difference accuracy in time domain, adopts 8 rank difference accuracy to calculate in spatial domain.

4) wave field reconstruct is carried out at any one time, ventional absorption boundary treatment is carried out along model horizontal direction respectively on the left and right border of model scope, the lower boundary of model scope carries out ventional absorption boundary treatment along the vertical direction of model, the boundary treatment of matching landform is carried out in the coboundary of model scope relief surface, apply the absorbing boundary consistent with surface configuration, the direction of its attenuation by absorption is along earth's surface normal direction, instead of along the vertical direction of model;

5) using the wave field reconstruct record of each moment wave detector position wave field as this moment, the record obtained is carried out conventional processing, obtains the superposition after wave field reconstruct and migrated section;

6) wave field is reconstructed that the superposition obtained and migrated section and field data collection carry out that conventional processing obtains superpose and migrated section contrasts, the achievement of the process of checking survey data, explanation.

The present invention can carry out accurate wave field reconstruct in arbitrary complex geological structure.Have computational accuracy high, the feature of top boundary prosthetic reflection interference, the method can use in each link of the collection of oil seismic exploration, process, explanation.

Accompanying drawing explanation

Fig. 1 precision is the difference gridding schematic diagram on time 2 rank, rank, space 8, wherein, and P-τ _xx, Q-τ _zz, G-τ _xz, Vx-v _x, Vz-v _z;

Fig. 2 matching of the present invention landform boundary processing method implementation procedure (upper figure), conventional boundary processing method implementation procedure (figure below);

Fig. 3 matching of the present invention landform boundary treatment (upper figure), conventional boundary treatment (figure below);

The relief surface rate pattern that Fig. 4 example of the present invention adopts;

Fig. 5 the present invention is along the absorption factor (upper figure) of the border reflection loss of normal direction, and routine is along the absorption factor (figure below) of the border reflection loss of model vertical direction;

Fig. 6 (a) 0.5 second moment wave field record of the present invention; The wave field record of (b) 0.5 second moment conventional method; (c) 2.0 second moment wave field record of the present invention; The wave field record of (d) 2.0 second moment conventional method;

Fig. 7 composite traces of the present invention (left figure); The composite traces (right figure) of conventional method.

Embodiment

The present invention carries out seismic wave field reconstruct by solving isotropic elasticity ripple partial differential equation, obtains the seismologic record reconstructed.First, the physical location of given shot point and wave detector, simulation is from zero moment, a time sampled point in office calculates the wave field value of each space physics point, in wave field computation process, wave field attenuation processing is carried out to model boundary, ventional absorption boundary treatment is carried out along model horizontal direction respectively on the left and right border of model scope, the lower boundary of model scope carries out ventional absorption boundary treatment along the vertical direction of model, carries out the boundary treatment of matching landform in the coboundary of model scope relief surface.Order carries out the wave field reconstruction calculations in all moment, and namely obtains the composite traces of seismic wave field reconstruct at the wave field of each moment output detector position.

The specific embodiment of the present invention is:

1) conventional processing is carried out to the data of field acquisition, obtain the superposition and the migrated section that describe this area's underground structure, carry out opening up painting based on conventional processing result section, obtain the tectonic model of this area, architectonic fundamental described by tectonic model comprises the position of geologic horizon, the p-and s-wave velocity of geologic horizon, rock density;

2) tectonic model utilizing step 1) to obtain carries out discretize, and set up discrete geology attribute model (Fig. 4), the geological property mentioned here comprises p-and s-wave velocity and rock density;

3) in step 2) the relevant position setting steps 1 of discrete geology attribute model that obtains) adopt field layout (major parameter comprises: excite spacing, track pitch, excite count, number of channels, sampling interval, record length).Based on the isotropic elasticity ripple partial differential equation of routine, Fig. 1 is the room and time relative position of each component of High-Order Finite-Difference Method, each moment solves the wave field value of each discrete grid block point, involved wavefield component divides and comprises Vx, Vz, P, Q, G, the respectively v of corresponding isotropic elasticity ripple partial differential equation _x, v _z, τ _xx, τ _zz, τ _xzcomponent.Wave field border attenuation processing is carried out according to the absorbing boundary condition described by formula (1) in each moment, on a left side for model scope, right margin carries out ventional absorption boundary treatment along model horizontal direction respectively, the lower boundary of model scope carries out ventional absorption boundary treatment along the vertical direction of model, the boundary treatment of matching surface configuration is carried out in the coboundary of model scope relief surface, apply the absorbing boundary (Fig. 5) consistent with surface configuration, obtain space wave field reconstructed results (Fig. 6) in each moment, and the wave field in each moment is recorded in wave detector position, obtain final wave field reconstruct record (Fig. 7).

Described isotropic elasticity ripple partial differential equation is as follows:

$\begin{array}{c}\mathrm{\ρ}\frac{{\∂v}_x}{\∂t}=\frac{\∂{\mathrm{\τ}}_{\mathrm{xx}}}{\∂x}+\frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂z}\\ \mathrm{\ρ}\frac{{\∂v}_z}{\∂t}=\frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂x}+\frac{{\∂\mathrm{\τ}}_{\mathrm{zz}}}{\∂z}\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{xx}}}{\∂t}=c_{11}\frac{{\∂v}_x}{\∂x}+c_{13}\frac{{\∂v}_x}{\∂z}\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{zz}}}{\∂t}=c_{13}\frac{{\∂v}_x}{\∂x}+c_{33}\frac{{\∂v}_z}{\∂z}\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂t}=c_{44}\frac{{\∂v}_z}{\∂x}+c_{44}\frac{{\∂v}_x}{\∂z}\end{array}---\left(2\right)$

Wherein, v _xfor particle x direction speed component, v _zfor particle z direction speed component, τ _xxfor x direction normal stress, τ _zzfor z direction normal stress, τ _xzfor shear stress, ρ is density, c _ijfor the elastic constant of medium.

When the boundary treatment of matching surface configuration is carried out in the coboundary of model scope relief surface, the account form of employing formula (1), wherein, α is that a scope is (0,1) constant, in border, the corresponding size of each point is the integer of n, and it represents the normal distance of the some distance relief surface in border, as shown in the upper figure of Fig. 2, concrete border implementation procedure is:

A) along relief surface normal direction to external expansion 1 layer of border, in this one deck attenuation coefficient be a little $p=e^{-\mathrm{\α}\·1^2};$

B) along existing 1st layer of boundary normal direction again to external expansion 1 layer of border, obtain the 2nd layer of border, in this one deck border point attenuation coefficient be

C) successively extrapolate, until the outermost layer border specified by arriving, suppose always to have k layer border, so the attenuation coefficient on outermost layer border is

4) seismic wave field reconstruct record step 3) obtained carries out conventional processing, explanation, obtains superposition or the migrated section of wave field reconstruct;

Described conventional processing comprises the general step of Seismic Exploration Data Processing, comprises the general procedure means such as Noise Elimination, deconvolution, static correction, velocity analysis, superposition and skew;

5) superposition step 4) obtained or migrated section with after field data collection conventional processing superpose and migrated section contrasts, evaluate the rationality of exploration data acquisition recording geometry, or the process of checking survey data, interpretation results correctness.

Claims (1)

1., based on a wave field reconstructing method for matching landform, feature is realized by following steps:

1) known seismic data treatment and decryption is utilized to set up tectonic model;

2) utilize the geological property of known oil-gas pool distribution attributive character determination tectonic model, obtain discrete attribute model;

3) based on field layout and step 2) attribute model, utilize staggered-mesh High-Order Finite-Difference Method to solve isotropic elasticity ripple partial differential equation in time domain and spatial domain;

4) wave field reconstruct is carried out at any one time, ventional absorption boundary treatment is carried out along model horizontal direction respectively on the left and right border of model scope, the lower boundary of model scope carries out ventional absorption boundary treatment along the vertical direction of model, the boundary treatment of matching landform is carried out in the coboundary of model scope relief surface, apply the absorbing boundary consistent with surface configuration, the direction of its attenuation by absorption is along earth's surface normal direction, instead of along the vertical direction of model;

5) using the wave field reconstruct record of each moment wave detector position wave field as this moment, the record obtained is carried out conventional processing, obtains the superposition after wave field reconstruct and migrated section;

6) wave field is reconstructed that the superposition obtained and migrated section and field data collection carry out that conventional processing obtains superpose and migrated section contrasts, the achievement of the process of checking survey data, explanation.