CN104345336A - Observation system optimizing method based on target area illumination level - Google Patents

Abstract

The invention relates to an observation system optimizing method facing a target layer in the petroleum exploration field. Through analysis on three-dimensional geologic models and earthquake wave illumination, a weak illumination area of a routine observation system at a target area is determined, an amplitude density map of rays spreading from the weak illumination area to the ground surface is utilized to search shot point distribution positions facilitating target area illumination, an expansion observation system is then designed, weight factors of shots are calculated according to the illumination level of each shot at the target area in the expansion observation system, the weight factors are synthesized, the shots capable of improving the illumination effect on the target area are preferably selected, and the method is combined with the routine observation system to optimize the observation system. The optimized observation system satisfies field production requirements, the illumination effect of the target layer shadow area can be improved when the fewest expansion shots are used, so earthquake wave energy of the target layer can be uniformly distributed to a maximum degree, and excellent earthquake data is provided for prestack depth migration processing.

Description

A kind of recording geometry optimization method of based target area illumination degree

Technical field

The present invention relates to the seismic data acquisition recording geometry designing technique of the object-oriented layer of geophysical prospecting for oil, is a kind of optimize big gun based on seismic wave illumination analysis result and examine position, thus obtains recording geometry method that exploration targets layer can be uniformly lighted.

Background technology

Conventional three-dimensional seismic exploration acquisition observation system method for designing builds on horizontal layer hypothesis theory, nowadays seismic prospecting was done all in most of exploratory area, oil gas Some Comments On Geophysical Work person has had priori more or less to underground structure, the target of exploration also turns to high-precision lithology exploration gradually by simple structure exploration, exploration object is no longer simple geologic trap, and the hydrocarbon-bearing pool closed by high-dip structure, overthrust fault, salt dome etc. often.In this case, the contradiction between horizontal layer hypothesis and exploration object complicacy, the common midpoint (CMP) that conventional vision systems Design Mode adopts can not represent the real reflection spot in underground.In this context, recent domestic all starting to attempt designing stereo observing system based on subsurface geology model, is attempted to examine position for the actual reflection spot on buried target layer to the big gun laying ground.

The core of object-oriented layer design view examining system is the wave field information of reflection spot on evaluating objects layer (being also common reflection point CRP).The approach obtaining CRP point wave field information can be summarized as two kinds of modes: one simulates field to blow out process, the ground surface of model excites, receives, then the wave field information of CRP point on evaluating objects layer, can be referred to as the thinking excited based on earth's surface, its core utilizes at present in the seismic wave illumination technology gathering widespread use in design.Another kind is the shot point-acceptance point principle of reciprocity based on seismic wave propagation, CRP point directly on destination layer excites, the ground surface of model receives, and lay real earth's surface big gun, cautious position according to the wave field information of each acceptance point, this can be referred to as the thinking that based target layer excites.

Dong Liangguo (Dong Liangguo etc., inverse seismic wave illumination and the recording geometry optimization covering nappe structure, petroleum exploration, Vol.45, No.1, p40-47,2006) according to wave equation seismic wave illumination result, utilize illumination statistics, the illumination of round trip ripple or one-way wave means of illumination, determine the optimum shot point distribution range in ground for exploration targets layer; Utilize ray tracing and wave equation simulation, analyze each degree of covering of CRP point of specific purpose layer and the distribution situation of irradiation energy; Synthetically descend the different geophone offset seismic trace of destination layer to the degree of covering of each CRP point and contribute energy distribution curve, determine optimum geophone arrangement mode and the spread length of destination layer.Zhao Hu (Zhao Hu etc., the shot point method for designing of based target layer illumination energy, Vol.49, No.5, p478-481,2010) by the numerical simulation result of normal big gun distance, determine illumination energy minimum position, determine that the encryption emplacement of local is put according to the corresponding point of this minimum position on ground.This simple method judging that encryption emplacement is put accurately can not determine that encryption emplacement is put, and the illuminance that fully can not improve destination layer shadow region is closed by final encryption battery.

The actual process of blowing out of the thinking excited based on earth's surface and field is very similar, and more intuitively, but for the tectonic structure of some complexity, this mode likely produces specular dead, can not carry out effective imaging to complex geologic body; And for complex structure, analyze wave field characteristics sometimes very difficult.Therefore, the thinking excited based on earth's surface is not best scheme to have document to think, and the principle of reciprocity of big gun-cautious should be utilized, shot point is directly placed on destination layer, namely the direct common reflection point at destination layer (CRP) excites, investigation wave field propagates into the distribution situation behind earth's surface, is exactly lay big gun, cautious position in the region that ground wave field energy is strong.

Chih-Ping J.Lu(Chih-Ping J.Lu etc., Flower Plot:a new tool for smart survey design, Ann.Internat Mtg. in 2002, Soc.Expl.Geophys, Expanded Abstracts, p45-47) a kind of new instrument is proposed---floral diagram (Flower Plot), determine the earth's surface big gun in the accurate illumination target region of energy, cautious position by the ray excited on buried target layer.Liu Shouwei (Liu Shouwei etc., Controlled illumination and seismic acquisition geometry for target-oriented imaging, Applied Geophysics, Vol.2, No.4, p230-234, 2005) from the thought controlling illumination, propose a kind of seismic observation system method for designing of object-oriented imaging, namely focus is placed on destination layer and seismic event is upwards propagated, the wavefield energy distribution received on earth's surface can reflect the big gun required by target imaging, cautious position: shot point or geophone station should be positioned over the strongest region of wavefield energy.

Based target layer excite the target of thinking design view examining system be try hard to make all common reflection surfaces on destination layer illumination energy, degree of covering, position angle and geophone offset be uniformly distributed, but in fact, after underground is even, must cause the uneven of earth's surface big gun inspection relation, such recording geometry cannot be used for actual field and produce.

In sum, thinking and based target layer is excited to excite thinking respectively to have the relative merits of oneself based on earth's surface.The former and field actual production process are similar, but effectively can not solve the lighting problem of complex structure specular dead; The latter directly can determine that position examined by the big gun of illumination target layer CRP point, but the recording geometry how obtaining meeting field production requirement, adapt to field production run is the large problem that it exists.

Summary of the invention

The object of the invention is to provide a kind of illumination of effective solution complex structure specular dead and meets the recording geometry optimization method of based target area illumination degree of field production requirement.

The present invention is achieved through the following technical solutions:

1) set up three-dimensional geological model according to the known earthquake in work area, geologic information, require according to surveying tasks and seismic acquisition parameter laying conventional vision systems;

Represent this conventional vision systems set with Q, use Q _irepresent shot point and the arrangement of corresponding geophone station of wherein the i-th big gun, then conventional vision systems can be expressed as:

Q={Q ₁,Q ₂,Q ₃,…,Q _r}

Three-dimensional geological model calculates the illuminance of conventional vision systems in formation at target locations, the closed polygon in the weak district that determines to throw light on; The illuminance of a jth bin in this polygon is designated as I _j, calculate all bin illuminance I in this polygon _jmean square deviation e.

I in step _jsubscript j represent bin sequence number in illumination weak district closed polygon, i.e. j=1,2,3,4 ... m.

I in step _jmean square deviation e adopt following formula calculate, namely

$e=\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{(I_j-\stackrel{\‾}{I})}^2$

Wherein $\stackrel{\‾}{I}=\frac{\underset{j=1}{\overset{m}{\mathrm{\Σ}}}{I}_j}{m}.$

2) in destination layer throws light on weak district polygon according to the mode uniform stationing of lateral separation Δ x, longitudinal separation Δ y, on each point according to horizontal direction and vertical direction scope to earth's surface divergent-ray, calculate the eye point position (x of every root ray i on earth's surface _i, y _i) and ray amplitude A _i;

According to lateral separation Δ a, longitudinal separation Δ b horizontal division grid on three-dimensional geological model earth's surface, to add up the emergent ray in each grid at the eye point position coordinates on earth's surface according to ray, with the amplitude density p of formula (1) computing grid j _j, obtain the outgoing amplitude density figure on earth's surface;

$p_j=\frac{\underset{i=1}{\overset{k}{\mathrm{\Σ}}}\mathrm{Ai}}{\mathrm{\Δa}\·\mathrm{\Δb}}---\left(1\right)$

Wherein k represents there is k root emergent ray in the grid j on model earth's surface;

Transverse direction described in step refers to X-direction, towards the direction in due east on surface level; Longitudinally refer to Y-direction, towards the direction in positive north on surface level.

Horizontal direction described in step refers to 0 ° ~ 360 °; Vertical direction refers to 0 ° ~ 90 °.

3) be positioned at emergent ray amplitude density figure high level region according to shot point and lay expansion recording geometry, adopt conventional illuminance computing method (as rays method illumination, Gaussian beam illumination, wave equation illumination etc., these are public algorithm) calculate the every illuminance of big gun on formation at target locations bin in expansion recording geometry, determine the bin position at every big gun illuminance maximal value place, then illuminance maximal value place bin is arranged in the battery one-tenth set U of illumination weak district polygon.

U={U ₁,U ₂,U ₃,…,U _n}

4) from set U, the big gun that can strengthen target area illuminating effect is optimized:

Described is preferably:

First, according to the position (x of illuminance minimum value place bin in illumination weak district closed polygon _min, y _min), the i-th big gun illuminance maximal value E in set U _iand bin position, place (x _imax, y _imax), the weight factor λ of this big gun is calculated according to formula (2) _i;

${\mathrm{\λ}}_i=\frac{E_i}{\sqrt{{(x_{i\max }-x_{\min })}^2+{(y_{i\max }-y_{\min })}^2}}---\left(2\right)$

Secondly, from set U, weight factor λ is taken out _imaximum big gun, is added to the illuminance of every big gun in illumination weak district polygon bin illuminance respectively, and adopt the method for exhaustion to find out bin illuminance mean square deviation in illumination weak district polygon can be made to reduce and the minimum big gun of mean square deviation, this big gun is just preferred big gun;

Then, the illuminance of preferred big gun is added on illumination weak district polygon bin, recalculates the weight factor λ remaining big gun in set U _i, again with the big gun that the algorithm that above-mentioned step 4) describes preferably makes new advances;

Finally, when can not preferably make new advances big gun time, stop preferred process.

Described weight factor λ _imaximum big gun is 5 to 15.

5) big gun optimized from set U and conventional vision systems are combined, the recording geometry be optimized.

The present invention optimizes big gun and examines position on conventional vision systems basis, make use of and excite thinking and based target layer to excite the advantage of thinking based on earth's surface, the recording geometry simultaneously optimizing generation can meet again the requirement of field production, the illuminating effect of destination layer shadow region effectively can be improved when using minimum expansion big gun, the seismic wave energy of destination layer is uniformly distributed as far as possible, thus provides good geological data for pre-stack depth migration process.

Accompanying drawing explanation

Accompanying drawing of the present invention is described as follows:

The three-dimensional salt dome geologic model of Fig. 1;

Fig. 2 conventional vision systems, (a) receives arrangement template, the sp location of (b) conventional vision systems;

The light chart of Fig. 3 conventional vision systems on destination layer

Fig. 4 is from the weak district of illumination to earth's surface divergent-ray schematic diagram

Fig. 5 outgoing amplitude density figure

Fig. 6 expands recording geometry

Fig. 7 expands the light chart of a big gun in recording geometry

Expansion recording geometry after Fig. 8 optimizes

Fig. 9 optimizes recording geometry

Figure 10 optimizes the light chart of recording geometry on destination layer

Embodiment

The present invention is described in detail below in conjunction with accompanying drawing.

The present invention is first by three-dimensional geological model and seismic wave illumination analytical technology, determine that conventional vision systems is in the weak district of the illumination of target area, by certain interval uniform stationing in the weak district of illumination, from each point to earth's surface divergent-ray, emergent ray amplitude in each grid in statistics earth's surface, thus obtain outgoing amplitude density figure.According to the principle design expansion recording geometry of placing shot point in outgoing amplitude density figure intensity values region, calculate the every illuminance of big gun in target area in expansion recording geometry, then optimize the big gun that can strengthen target area illuminating effect, these big guns and conventional vision systems combine and be just optimized after recording geometry.

The technology of the invention provides comprise determine conventional vision systems throw light on weak district, calculate outgoing amplitude density figure, calculate illuminance in target area of every big gun in expansion recording geometry and preferably can strengthen target area illuminating effect big gun four part.

1, set up three-dimensional geological model according to work area earthquake, geologic information, prove result cloth according to surveying tasks requirement and seismic acquisition parameter and set out conventional vision systems.

Be illustrated in figure 1 a three-dimensional salt dome geologic model, long 13000m, wide 10000m, high 7000m, is topmost earth's surface, respectively has the stratal surface of a set of fluctuating at salt dome up and down, the speed of salt dome is the constant speed of 4500m/s, around country rock is the variable velocity media from 2000m/s to 3500m/s, and the stratum chosen below salt dome is destination layer, and its speed is the constant speed of 5000m/s.

Fig. 2 is the conventional vision systems set up, and has 1620 big guns, 27 big gun lines, perpendicular offset 480 meters, shotpoint spacing 160 meters, and every big gun adopts 8 middle shooting arrangements receiving line, has 244 and receives line, receive line-spacing 40 meters, geophone interval 40 meters.

Three-dimensional geological model calculates the illuminance of conventional vision systems in formation at target locations by rays method lighting engineering, and then man-machine interactively is determined to throw light on the closed polygon in weak district.

Fig. 3 is the illuminance distribution plan that conventional vision systems destination layer is used rays method lighting calculation below salt dome, from figure, due to blocking of high speed salt dome, thereunder defines one piece of weak district of illumination.Black line in figure is the illumination weak district closed polygon that man-machine interactively is determined.

2, throwing light in weak district polygon according to certain intervals uniform stationing, on each point according to horizontal direction (0 ° ~ 360 °), vertical direction (0 ° ~ 90 °) scope to earth's surface divergent-ray, calculate every root ray at the eye point position on earth's surface and ray amplitude.Emergent ray amplitude in the grid of statistics three-dimensional geological model earth's surface, obtains outgoing amplitude density figure.

As shown in Figure 4, according to the mode uniform stationing of lateral separation 100m, longitudinal separation 100m in illumination weak district polygon, according to horizontal direction (0 ° ~ 360 °) scope, 5 °, interval on each point, vertical direction (0 ° ~ 90 °) scope, 1 °, interval, to earth's surface divergent-ray, calculate every root ray at the eye point position on earth's surface and ray amplitude.

According to lateral separation 120m, longitudinal separation 120m grid division on three-dimensional geological model earth's surface, to add up the emergent ray in each grid at the eye point position coordinates on earth's surface according to ray, with the ray amplitude density in formula (1) computing grid, thus obtain the earth's surface outgoing amplitude density figure shown in Fig. 5, the high level region of amplitude density has been marked in figure with black line.

3, the principle laying expansion recording geometry in emergent ray amplitude density figure high level region is positioned at according to shot point, calculate the illuminance of every big gun on formation at target locations bin, determine the bin position at every big gun illuminance maximal value place, then illuminance maximal value place bin is arranged in the battery one-tenth set U of illumination weak district polygon.

Use the reception arrangement template identical with conventional vision systems, adopt shotpoint spacing 160m, perpendicular offset 40m, in the expansion recording geometry shown in emergent ray amplitude density high level region artwork 6, have 1545 big guns, 135 big gun lines, on every bar big gun line, big gun number is not etc., minimum 1 big gun, maximum 22 big guns.

The every illuminance of big gun on destination layer in expansion recording geometry is calculated by rays method lighting engineering, Fig. 7 illustrates shot point and is positioned at (6800m, 6460m) the destination layer illuminance distribution of place one big gun, from figure, its illuminance maximal value place bin is positioned at illumination weak district polygon, so this big gun is put into set U.

4, from set U, optimize the big gun that can strengthen target area illuminating effect, method is as follows:

First, according to the position (x of illuminance minimum value place bin in illumination weak district closed polygon _min, y _min), the i-th big gun illuminance maximal value E in set U _iand bin position, place (x _imax, y _imax), the weight factor λ of this big gun is calculated according to formula (2) _i;

Secondly, from set U, weight factor λ is taken out _i10 maximum big guns, are added to the illuminance of every big gun in illumination weak district polygon bin illuminance respectively, and then adopt the method for exhaustion to find out bin illuminance mean square deviation in illumination weak district polygon can be made to reduce and the minimum big gun of mean square deviation, this big gun is just preferred big gun;

Then, the illuminance of preferred big gun is added on illumination weak district polygon bin, recalculates the weight factor λ remaining big gun in set U _i, again with the big gun that above-mentioned identical algorithm preferably makes new advances;

Finally, when can not preferably make new advances big gun time, just stop preferred process.

Fig. 8 illustrates the big gun that optimizes from set U, has 315 big guns, 70 big gun lines, and on every bar big gun line, big gun number is not etc., minimum 1 big gun, maximum 9 big guns.

5, the big gun optimized from set U and conventional vision systems are combined, just obtain the last recording geometry optimized.

Fig. 9 illustrates the optimization recording geometry finally obtained, its below salt dome on destination layer illuminance distribution as shown in Figure 10, from figure, the illuminating effect originally in illumination weak district polygonal region obtains reinforcement.

Claims (6)

1. a recording geometry optimization method for based target area illumination degree, is characterized in that being realized by following steps:

1) three-dimensional geological model is set up according to the known earthquake in work area, geologic information, require according to surveying tasks and seismic acquisition parameter laying conventional vision systems, three-dimensional geological model calculates the illuminance of conventional vision systems in formation at target locations, the closed polygon in the weak district that determines to throw light on;

2) in destination layer throws light on weak district polygon according to the mode uniform stationing of lateral separation Δ x, longitudinal separation Δ y, on each point according to horizontal direction and vertical direction scope to earth's surface divergent-ray, calculate the eye point position (x of every root ray i on earth's surface _i, y _i) and ray amplitude A _i;

According to lateral separation Δ a, longitudinal separation Δ b horizontal division grid on three-dimensional geological model earth's surface, to add up the emergent ray in each grid at the eye point position coordinates on earth's surface according to ray, the amplitude density p of computing grid j _j, obtain the outgoing amplitude density figure on earth's surface;

3) the principle laying expansion recording geometry in emergent ray amplitude density figure high level region is positioned at according to shot point, calculate the every illuminance of big gun on formation at target locations bin in expansion recording geometry, determine the bin position at every big gun illuminance maximal value place, then illuminance maximal value place bin is arranged in the battery one-tenth set U of illumination weak district polygon;

4) from set U, the big gun that can strengthen target area illuminating effect is optimized;

5) big gun optimized from set U and conventional vision systems are combined, the recording geometry be optimized.

2. method according to claim 1, feature is step 2) described in transverse direction refer to X-direction, towards the direction in due east on surface level; Longitudinally refer to Y-direction, towards the direction in positive north on surface level.

3. method according to claim 1, feature is step 2) described in horizontal direction refer to 0 ° ~ 360 °; Vertical direction refers to 0 ° ~ 90 °.

4. method according to claim 1, feature is step 2) the amplitude density p of computing grid j _jadopt following formula:

$p_j=\frac{\underset{i=1}{\overset{k}{\mathrm{\Σ}}}\mathrm{Ai}}{\mathrm{\Δa}\·\mathrm{\Δb}}---\left(1\right)$

Wherein k represents there is k root emergent ray in the grid j on model earth's surface.

5. method according to claim 1, feature is being preferably described in step 4):

First, according to the position (x of illuminance minimum value place bin in illumination weak district closed polygon _min, y _min), the i-th big gun illuminance maximal value E in set U _iand bin position, place (x _imax, y _imax), the weight factor λ of this big gun is calculated according to formula (2) _i;

${\mathrm{\λ}}_i=\frac{E_i}{\sqrt{{(x_{i\max }-x_{\min })}^2+{(y_{i\max }-y_{\min })}^2}}---\left(2\right)$

Secondly, from set U, weight factor λ is taken out _imaximum big gun, is added to the illuminance of every big gun in illumination weak district polygon bin illuminance respectively, and adopt the method for exhaustion to find out bin illuminance mean square deviation in illumination weak district polygon can be made to reduce and the minimum big gun of mean square deviation, this big gun is just preferred big gun;

Then, the illuminance of preferred big gun is added on illumination weak district polygon bin, recalculates the weight factor λ remaining big gun in set U _i, again by the big gun that step 4) preferably makes new advances; Finally, when can not preferably make new advances big gun time, stop preferred process.

6. method according to claim 4, feature is described weight factor λ _imaximum big gun is 5 to 15.