CN104422957A - Optimizing design method of observing system - Google Patents

Abstract

The invention relates to an optimizing design method of an observing system for geophysical exploration. The optimizing design method comprises the following steps of when the imaging travel of a target body is tracked by rays, converting a speed model to obtain a root mean square speed field, simulating shooting for a primarily proposed observing system, ensuring a full-coverage area to cover all target bodies, performing the integral pre-stack time migration on a shot-geophone pair in the root mean square speed field, obtaining the effective coverage spectrum of the target bodies, and selecting the proposed observing system with high coverage times, so as to complete the optimizing design of the observing system. The optimizing design method has the advantage that the illumination intensity of the observing system on underground complicated mediums is quickly and accurately calculated, so the qualities of different observing systems are evaluated, and the effect is good.

Description

A kind of recording geometry Optimization Design

Technical field

The present invention relates to geophysical exploration method, is effectively cover by analyzing different recording geometry migration before stack a kind of recording geometry Optimization Design that spectrum differentiates recording geometry quality.

Background technology

Geophysical prospecting for oil is based on geophysics and oil geology theory, adopt corresponding geophysical instrument and be equipped in earth surface (comprising land and ocean), or, record subsurface information in well aloft, and physical property (elasticity, electrical, magnetic, density, radioactivity) and the structure of subsurface formations is obtained by corresponding data process and interpretation, find the method for the petroleum and natural gas hidden in the earth formation.

Seismic prospecting is the means that geophysical survey is conventional, need shot point and acceptance point to form the arrangement sheet of Continuous Observation according to certain way when implementing seismic prospecting, complete this combination and recording geometry design, it directly determines the final quality gathering achievement.Mainly see that whether degree of covering is even in current recording geometry analysis.

It is set out recording geometry according to the acquisition parameter cloth of design that current recording geometry analyzes concrete steps, selects full areal coverage to calculate degree of covering, checks that within the scope of this, whether degree of covering is even.Conventional degree of covering refers to the number of mid point in bin, and the height of its degree of covering has nothing to do with subsurface model, does not also have direct relation with imaging effect, so can not the high-quality imaging effect of seismic exploration corresponsively.The method of mid point degree of covering is also not suitable for the design evaluatio of complex area recording geometry.

Summary of the invention

The object of the invention is to provide a kind of migration before stack effectively to cover spectrum and adopts imaging point degree of covering, can the recording geometry Optimization Design of direct response imaging effect.

The present invention adopts following steps to realize:

1) objective body undetermined in rate pattern is determined;

Rate pattern described in step 1) is the geological data coming from seismic acquisition, treated, explain after the explanation section that obtains.

Objective body described in step 1) refers to the target that in rate pattern, user determines, is single-point, aspect or whole model.

2) ray tracing is utilized to calculate the imaging whilst on tour of objective body;

Described imaging whilst on tour be objective body along normal direction divergent-ray, ray arrives time of experiencing of ground.

3) rate pattern is changed by Dix formula, obtain mean-square-root velocity field;

Dix formula described in step 3) is:

$v_n=\left(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{V_i}^2{t}_i}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{t}_i}\right)---\left(1\right)$

In formula, v _nfor the root-mean-square velocity of n-th layer, V _ithe interval velocity of i-th layer, t _iit is the vertical two-way time of i-th layer.

4) the recording geometry simulation tentatively drafted is blown out, guarantee that full overlay area covers all objective bodies;

The described recording geometry tentatively drafted is before recording geometry is evaluated, the alternative recording geometry drafted or candidate's recording geometry;

5) examine doing integral method pre-stack time migration in mean-square-root velocity field a big gun of the recording geometry tentatively drafted, if the difference of the imaging moment of objective body and imaging whilst on tour is less than 1/4 dominant frequency cycle, then the effective imaging of this objective body once;

Dominant frequency cycle value described in step 5) equals the inverse of objective body dominant frequency.

6) repeat step 5), until all big gun inspections of the recording geometry drafted are to deadline skew, obtain effective covering spectrum of objective body;

7) according to effective covering spectrum of objective body, select the recording geometry drafted that degree of covering is high, complete recording geometry optimal design.

The present invention can calculate the illumination intensity of a certain recording geometry to underground complex dielectrics fast and accurately, thus evaluates the quality of different recording geometry; The present invention is applied to the evaluation analysis of actual stereo observing system, achieves reasonable effect.

Accompanying drawing explanation

The rate pattern that Fig. 1 uses for ray tracing can be layered medium, also can be arbitrary velocity distribution.

Fig. 2 is that user carries out the objective body that migration before stack effectively covers analysis of spectrum at needing of selecting, and can be loose point, aspect or whole model.

Fig. 3 is the objective body imaging whilst on tour utilizing three-dimensional ray tracing method to calculate, and color represents the imaging time tracking out and.

Fig. 4 is recording geometry to be evaluated, blue expression acceptance point, red expression shot point.

The migration before stack of the orthogonal recording geometry in Fig. 5 18 line 6 big gun 120 road effectively covers spectrum;

Track pitch 50 meters, big gun, apart from 50 meters, receives line-spacing 300 meters, and when excitation line is apart from 300 meters, the migration before stack calculated effectively covers spectrum, and color represents degree of covering.

The migration before stack of the orthogonal recording geometry in Fig. 6 16 line 6 big gun 112 road effectively covers spectrum;

Track pitch 50 meters, big gun, apart from 50 meters, receives line-spacing 300 meters, and when excitation line is apart from 300 meters, the migration before stack calculated effectively covers spectrum, and color represents degree of covering.

Embodiment

Describe in detail below in conjunction with example and accompanying drawing.

The 2 cover recording geometrys tentatively drafted are:

Recording geometry 1:16 line 6 big gun 112 road is orthogonal, track pitch 50 meters, and big gun, apart from 50 meters, receives line-spacing 300 meters, and excitation line is apart from 300 meters;

Recording geometry 2:18 line 6 big gun 120 road is orthogonal, track pitch 50 meters, and big gun, apart from 50 meters, receives line-spacing 300 meters, and excitation line is apart from 300 meters.

1) according to existing explanation section, set up corresponding rate pattern, Fig. 1 is the three bed interface rate patterns set up;

In conjunction with geological tasks, in Confirming model, third layer interface is objective body to be analyzed, and Fig. 2 is grabgraf when only showing third layer interface.

2) from third layer interface along normal direction divergent-ray, calculate the time that ray arrival ground experiences, save as imaging whilst on tour.Fig. 3 is the imaging whilst on tour calculated, and different colours represents the length of time.

3) rate pattern of Fig. 1 is changed by Dix formula, obtain mean-square-root velocity field, for the pre-stack time migration of the 5th step provides speed data; Described Dix formula is:

$v_n=\left(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{V_i}^2{t}_i}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{t}_i}\right)---\left(1\right)$

In formula, v _nfor the root-mean-square velocity of n-th layer, V _ithe interval velocity of i-th layer, t _iit is the vertical two-way time of i-th layer.

4) carry out simulation to recording geometry 1 to blow out, Fig. 4 is the 18 orthogonal recording geometrys in line 6 big gun 120 road obtained;

The region that recording geometry is blown out is changeable, but at least will guarantee that full overlay area covers all objective bodies.

5) do integral method pre-stack time migration to certain big gun inspection of recording geometry 1 in the mean-square-root velocity field that step 3) obtains, if the difference of the imaging moment of objective body and imaging whilst on tour is less than 1/4 dominant frequency cycle, then the effective imaging of this objective body once.

6) repeat step 5), until all big gun inspection of recording geometry 1 is to after completing pre-stack time migration, effective coverings obtaining the recording geometry 1 shown in Fig. 5 is composed.

7) step 4), 5 is repeated to recording geometry 2), 6), obtain the effective covering spectrum of the recording geometry 2 shown in Fig. 6.

Comparison diagram 5 and Fig. 6, as can be seen from degree of covering, the numerical value of recording geometry 1 is 12229, and the numerical value of recording geometry 2 is 10081, and numerical value is larger, and imaging effect is better, so select the recording geometry 1 that degree of covering is higher, completes recording geometry optimal design.

Final three-dimensional imaging effect is consistent with analysis result, confirms that the orthogonal recording geometry in employing 18 line 6 big gun 120 road greatly improves the image quality of image data.

Claims (6)

1. a recording geometry Optimization Design, feature adopts following steps to realize:

1) objective body undetermined in rate pattern is determined; Described rate pattern is the geological data coming from seismic acquisition, treated, explain after the explanation section that obtains;

2) ray tracing is utilized to calculate the imaging whilst on tour of objective body;

3) rate pattern is changed by Dix formula, obtain mean-square-root velocity field;

4) the recording geometry simulation tentatively drafted is blown out, guarantee that full overlay area covers all objective bodies;

5) examine doing integral method pre-stack time migration in mean-square-root velocity field a big gun of the recording geometry tentatively drafted, if the difference of the imaging moment of objective body and imaging whilst on tour is less than 1/4 dominant frequency cycle, then the effective imaging of this objective body once;

6) repeat step 5), until all big gun inspections of the recording geometry drafted are to deadline skew, obtain effective covering spectrum of objective body;

7) according to effective covering spectrum of objective body, select the recording geometry drafted that degree of covering is high, complete recording geometry optimal design.

2. method according to claim 1, feature is the target that the objective body described in step 1) refers to that in rate pattern, user determines, is single-point, aspect or whole model.

3. method according to claim 1, feature is step 2) described in imaging whilst on tour be objective body along normal direction divergent-ray, ray arrives the time that ground experiences.

4. method according to claim 1, to be the Dix formula described in step 3) be feature:

$v_n=\left(\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{V_i}^2{t}_i}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{t}_i}\right)---\left(1\right)$

In formula, v _nfor the root-mean-square velocity of n-th layer, V _ithe interval velocity of i-th layer, t _iit is the vertical two-way time of i-th layer.

5. method according to claim 1, feature is the recording geometry tentatively drafted described in step 4) is before recording geometry is evaluated, the alternative recording geometry drafted or candidate's recording geometry.

6. method according to claim 1, feature is the inverse dominant frequency cycle value described in step 5) equaling objective body dominant frequency.