CN103543475B - A kind of gravity intermediate layer density spectra acquiring method - Google Patents

Abstract

The present invention relates to geophysical exploration gravimetric prospecting data process, be a kind of gravity intermediate layer density spectra acquiring method.Absolute gravity value and the coordinate elevation of each measuring point on survey line is obtained by gravity collection, calculate each point bouguer gravity anomaly value of different densities and the abnormal variation of the most adjacent 2 bouguer gravity anomaly meansigma methodss, form gravity intermediate layer density spectra grid data, color is used from large to small or by being deep to shallow drawing according to gravity intermediate layer density spectra grid data, make minima under each density be transparent to show that, obtain gravity intermediate layer density spectra.The density value that the present invention obtains in hypsography larger area is consistent with the result of density profile method, higher resolution capability is had with density profile method ratio, the density value in the exposure district, stratum with certain area can be identified, and identification to intermediate layer density value is more directly perceived, recognition methods is simpler, and recognition result is more reliable.

Description

A kind of gravity intermediate layer density spectra acquiring method

Technical field

The present invention relates to geophysical exploration technology, belong to gravimetric prospecting data processing method, specifically a kind of Gravity intermediate layer density spectra acquiring method.

Background technology

In seismic prospecting, one of speed most important parameter being by data processing and explanation, normal-moveout spectrum Velocity information is provided for seismic data process.Similarly, in geophysical exploration gravimetric data processing, Intermediate layer density is that gravity data processes parameter the most basic, most important, but in real work, is difficult to obtain Obtain accurate intermediate layer density data.In gravimetric prospecting data processes, calculating bouguer gravity anomaly needs Normal field correction to be carried out, altitude correction, intermediate layer are corrected and topographic correction, and wherein intermediate layer is corrected and ground Shape corrects all relevant with intermediate layer density.Intermediate layer density is chosen inaccurate, will result in bouguer gravity anomaly and deposits At the false abnormality relevant to hypsography, affect the correctness of gravity data geologic interpretation, even result in mistake By mistake.

The method that intermediate layer density is chosen at present is mainly density profile method, i.e. by calculating difference on section The bouguer gravity anomaly of density also contrasts with measuring point elevation, with the Bouguer gravity minimum with measuring point elevation dependency The abnormal density used is as optimal intermediate layer density.Although judgment principle is correct, at hypsography Big area, can find out the dependency of bouguer gravity anomaly and the elevation using different densities, but on ground Other major part position that shape rises and falls relatively small, it is difficult to identify the relation between them, it is impossible to determine conjunction Suitable intermediate layer density, thus cause bouguer gravity anomaly exists the false abnormality relevant to landform.

Yan Liangjun et al. discloses the variable density bearing calibration during a kind of bouguer gravity anomaly is asked for for 2005, The method propose Bouguer anomaly be by each measuring point relative to the gravity difference of total basic point through a series of correction, its Include latitude correction, Bouguer correction and topographical correction.And use the substance and public affairs that gravity data processes Formula: The most i.e. utilize ground rock Statistics of Density data, coordinate geology Figure, makes surface density initial model, then uses spline interpolation and the round and smooth method structure of two-dimensional space function Make surface density distributed model, carry out variable density correction on this basis.It can be seen that the method uses ground Matter outcropping rock sample rate data, coordinates geologic map, the treated surface density information that obtains, field specimen Collecting work amount is big, and reasonability and accuracy that interpolation and the round and smooth parameter of function select are difficult to ensure very well, To the degree of agreement of density model and practical situation correction result will necessarily be produced certain impact.Separately Outward, the important content that the method relates to is to build density model, and its research is ground rock density planes Distribution situation, coordinate is plane coordinates in length and breadth, and model physical parameter is density value, and it is difficult to obtain exactly Intermediate layer density at each measuring point.The method as Given information, is set up density data close by density data Degree model, not by the intermediate layer density value at gravity deflection difference research each point, so can not accurately choose Intermediate layer density value, it is difficult to eliminate the key parameter with landform correlated phenomena.Further, the open country that the method relates to Outer specimen collecting work amount is big, and reasonability and accuracy that interpolation and function parameter select are difficult to ensure that, obtain The degree of agreement of density data and practical situation correction result will necessarily be produced certain impact, in reality Work is difficult to large area industrialization promotion and extensively application.

Chen Chao et al. discloses a kind of method eliminating gravity anomaly and elevation correlated phenomena for 1998, is dividing After having analysed the reason that bouguer gravity anomaly is relevant to elevation, it is proposed that a kind of elimination vacation relevant to hypsography is different Normal method.First the method carries out abnormal calculating with Chang Midu, then inclined to gravity abnormal variation and elevation Difference makees linear statistical, and then calculates remaining density, finally carries out supplementing mid-layer correction, reaches to eliminate gravity The abnormal purpose with elevation correlated phenomena.The method only finally refers to remaining density value in the process of calculating, Can not set up the relation of intermediate layer density and stratum well, intermediate layer density value shows the most directly perceived, it is difficult to accurate Really understand the density feature at each measuring point.

Qin Zhangjian et al. discloses a kind of Digital image technology answering in gravity anomaly topographical correction for 2006 By method, it is proposed that a kind of digital picture application technology, this technology is feelings based on known formation density distribution Carry out under condition calculating, and in real work, true density of earth formations and distribution thereof are unknown quantitys, this technology It is difficult to meet the needs that HIGH-PRECISION GRAVITY DATA processes in actual applications.

In sum, the high-precision gravity and magnetic data processing method used at present is more numerous and diverse, reflection is the most straight See, efficiency low, it is impossible to enough the most effectively eliminate false abnormality relevant to landform in gravity anomaly.

Summary of the invention

Present invention aim at providing one make intermediate layer density intuitive display, reflect sensitive, identify simple, Rational intermediate layer density can be obtained, reduce the weight of false abnormality relevant to landform in bouguer gravity anomaly The acquiring method of power intermediate layer density spectra.

The present invention is realized by following steps:

1) obtained absolute gravity value and the coordinate elevation of each measuring point on survey line by gravity collection, use difference Density calculates bouguer gravity anomaly data；

Calculating described in step 1) includes: calculate normal gravity g according to measuring point plane coordinates₀；According to survey Point height and intermediate layer density calculate Bouguer correction value Δ g_b；Base area graphic data calculates topographic correction value Δ g_TC；Measuring point bouguer gravity anomaly uses formula Δ g=g-g₀+Δg_b+Δg_TCCalculating, in formula, g is for surveying Point absolute gravity value.

Different densities described in step 1), refers to that density span is 1.5g/cm³～3.0g/cm³, value Step-length 0.01g/cm³Or 0.02g/cm³Each density value ρ.

2) each point bouguer gravity anomaly value calculating different densities is put down with the most adjacent 2 bouguer gravity anomalies The abnormal variation of average；

Step 2) described in abnormal variation use $k(i,\mathrm{\ρ})=|\mathrm{\Δg}(i,\mathrm{\ρ})-\frac{\mathrm{\Δg}(i-1,\mathrm{\ρ})+\mathrm{\Δg}(i+1,\mathrm{\ρ})}{2}|$ Calculate, In formula:

K (i, ρ) be the i-th dot density be abnormal variation value during ρ, i is period, and ρ is density value；

△ g (i, ρ), △ g (i-1, ρ) and △ g (i+1, ρ) are respectively i-th, i-1 and i+11 dot density is the Bouguer weight of ρ Power exceptional value；

Step 2) described in different densities refer to each density value ρ of specifying in step 1).

3) the abnormal variation value tried to achieve is carried out gridding, form gravity intermediate layer density spectra grid data；

Gridding described in step 3) use measuring point coordinate or distance as the abscissa of grid data, or with Counting as abscissa, scope is 1 to always counting, and increment takes 1.

Gridding described in step 3) with density value as vertical coordinate, density range and the same step 1) of step-length.

Gravity intermediate layer density spectra grid data file described in step 3) is with measuring point coordinate or period as horizontal stroke Coordinate, to calculate density as vertical coordinate, physical quantity is the gravity deflection difference under respective coordinates and density.Same In the data of one abscissa, minimum density value corresponding to gravity deflection difference is the intermediate layer density value at this.

4) color is used from large to small or by being deep to shallow painting according to gravity intermediate layer density spectra grid data Figure, makes minima under each density be transparent to show that, obtains gravity intermediate layer density spectra image.

The present invention chooses the clear area of oil exploration, and to carry out gravimetric prospecting experiment effect obvious.Fig. 1 a is experiment Geology corridor, district section, owing to rock density data is few, the intermediate layer density value of Bouguer correction chooses existence not Definitiveness, affects the reliability of geological condition.Use conventional method to make density profile, see Fig. 1 b. Visible, there is certain hypsography in survey line east, Midwest hypsography is less.In east, accordingly Shape high-order bit, with density 2.0g/cm³The Bouguer anomaly value calculated is proportionate with landform, with density 3.0g/cm³The Bouguer anomaly value calculated and landform are negative correlation；And correspondence landform lower curtate position, situation is contrary； With density 2.7g/cm³The bouguer gravity anomaly calculated is minimum with landform dependency.According to density profile method Intermediate layer density interpretation method, determines that at this, intermediate layer density should be at 2.7g/cm³Left and right.In survey line Western part, owing to hypsography is little, in density profile, gravity anomaly is indefinite with landform dependency, it is impossible to determine Intermediate layer density.

Make intermediate layer density spectra according to the present invention, see Fig. 1 c.It can be seen that in section east, Bright spot is concentrated mainly on 2.7g/cm³Left and right, geologic information shows main exposure Triassic Sandstone and ash at this Rock, density value corresponding to bright spot is consistent with the sentence read result of density profile method；In the middle part of section, bright spot is distributed At 2.2g/cm³Left and right, earth's surface is the 4th to be deposition here, and the 4th is that the density value of deposition typically exists 2.2g/cm³Left and right.Finally, according to exposure Paleozoic group stratum main in district, its density value is at 2.7g/cm³ The situation of left and right, determines that this district uses 2.7g/cm³Intermediate layer density carry out bouguer gravity anomaly calculating, Obtain reliable Bouguer map.

Above-mentioned it is demonstrated experimentally that in the relatively large area of hypsography, density value that the present invention obtains and density The result of profile method is consistent；In the area that middle part hypsography is less, the present invention can preferably obtain density Information, and density profile method is difficult to judge intermediate layer density.Visible, specific density profile method of the present invention has more High resolution capability, can be identified the density value in the exposure district, stratum with certain area, Er Qiemi Degree spectrum is more directly perceived to the identification of intermediate layer density value, and recognition methods is simpler, and recognition result is more reliable.

Accompanying drawing explanation

Fig. 1 density profile method and density spectra comparison diagram；

A is geology corridor section, and black line is density profile position；B is density profile, and c is density spectra.

Detailed description of the invention

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

The invention provides the acquiring method of a kind of gravity intermediate layer density spectra.

Gravity intermediate layer density spectra, i.e. calculates each point Bouguer weight along certain section with different intermediate layer density respectively Power exceptional value and the difference (referred to herein as " deviation ") of left and right consecutive points bouguer gravity anomaly value meansigma methods, work as meter When the intermediate layer density of calculation employing is consistent with actual density, deviation value will minimize value.So " surveying Point-density " on plane graph, less deviation value is shown with the form of bright spot, just constitute similarly The gravity intermediate layer density spectra of shake normal-moveout spectrum.

Bouguer gravity anomaly includes subsurface structure gravimetric response and earth's surface gravimetric response, and subsurface structure gravity rings Should be primarily referred to as the gravimetric response that underground density interface rises and falls, earth's surface gravimetric response is primarily referred to as intermediate layer and ground Shape gravimetric response.Owing to point is away from generally less than subsurface structure buried depth, therefore, the subsurface structure gravity of consecutive points Response is linearly, the most unrelated with intermediate layer density.And top layer gravimetric response rises and falls with measuring point elevation and middle Layer density value is closely related.When the intermediate layer density calculated and top layer rock density are suitable, top layer gravity Linearly, at this moment deviation is the least in response；When the intermediate layer density calculated is the biggest with top layer rock density variation, The linearity of top layer gravimetric response is the poorest, and deviation is the biggest.Therefore, (typically take in certain density range 1.5g/cm³～3.0g/cm³), (the desirable 0.01g/cm with certain density increment as step-length³～0.02g/cm³), Calculate each point and use the bouguer gravity anomaly of different densities, then ask for and left and right consecutive points bouguer gravity anomaly The difference (deviation) of meansigma methods, then, in the density corresponding to the bouguer gravity anomaly that certain some upper deviation is minimum It is exactly the surface rock density at this.

The specific embodiment of the invention is as follows:

1) obtained by gravity collection and survey absolute gravity value and the coordinate elevation of each measuring point in district, then select Take an East and West direction survey line in the middle part of work area, use different densities to calculate bouguer gravity anomaly data；

Calculating described in step 1) includes: calculate normal gravity g according to measuring point plane coordinates₀；According to survey Point height and intermediate layer density calculate Bouguer correction value Δ g_b；Base area graphic data calculates topographic correction value Δ g_TC；Measuring point bouguer gravity anomaly uses formula Δ g=g-g₀+Δg_b+Δg_TCCalculating, in formula, g is real Survey measuring point absolute gravity value.

Different densities described in step 1), refers to that density span is 1.5g/cm³～3.0g/cm³, value Step-length 0.02g/cm³Each density value ρ.

2) each point bouguer gravity anomaly value calculating different densities is put down with the most adjacent 2 bouguer gravity anomalies The abnormal variation of average；

Step 2) described in abnormal variation use $k(i,\mathrm{\ρ})=|\mathrm{\Δg}(i,\mathrm{\ρ})-\frac{\mathrm{\Δg}(i-1,\mathrm{\ρ})+\mathrm{\Δg}(i+1,\mathrm{\ρ})}{2}|$ Calculate, In formula:

K (i, ρ) be the i-th dot density be abnormal variation value during ρ, i is period, and ρ is density value；

△ g (i, ρ), △ g (i-1, ρ) and △ g (i+1, ρ) are respectively i-th, i-1 and i1 dot density is the Bouguer weight of ρ Power exceptional value；

Step 2) described in different densities refer to each density value ρ of specifying in step 1).

3) the abnormal variation value tried to achieve is carried out gridding, form gravity intermediate layer density spectra grid data；

The gridding described in the step 3) abscissa with the abscissa of measuring point as grid data.

Gridding described in step 3) with density value as vertical coordinate, density range and the same step 1) of step-length.

Gravity intermediate layer density spectra grid data file described in step 3) is with period or measuring point coordinate as horizontal stroke Coordinate, to calculate density as vertical coordinate, value data is the gravity deflection difference under respective coordinates and density.? In the data of same abscissa, minimum density value corresponding to gravity deflection difference is the intermediate layer density at this Value.

4) according to gravity intermediate layer density spectra grid data use from large to small color by dark blue, light blue, green, The order of change yellow, red is drawn, then by adjusting the color of abnormal variation value, makes most abnormal variation K (i, ρ) minima presents red to yellow, and other deviation value presents dark blue to green, so that different on each point Often deviation minima is significantly shown, i.e. obtains gravity intermediate layer density spectra image.See Fig. 1 c.

After obtaining gravity intermediate layer density spectra, contrasted with geology corridor section (Fig. 1 a), Between coordinate 17410000 to 17460000, bright spot is substantially distributed in 2.7g/cm³Up and down, this and density The consistent in density of profile method interpretation；Between coordinate 17360000 to 17410000, bright spot is substantially distributed in 2.2g/cm³Up and down, geology corridor section is the 4th be deposition at this, 2.2g/cm³Density value be the 4th It is the typical density value of sedimentary, but goes out the density value at this at the upper None-identified of density profile (Fig. 1 b)； Between coordinate 17320000 to 17360000, between consecutive points, landform relative relief is the least, and intermediate layer is close Degree spectrum and density profile method all None-identified intermediate layer density, this is owing to both approaches is all based on passing through Analyze gravity and relatively change the relation that change relative with landform to study the method for intermediate layer density in landform phase To the common issue existed when rising and falling the least.

From the density spectra of intermediate layer, (Fig. 1 c) is it can also be seen that intermediate layer density value intuitive display, reflection Sensitive, identify simple, possess general Professional knowledge and just can show that intermediate layer is close by reading average density value Angle value, and on density profile, do not possess the professional knowledge of comparison be difficult to out correct intermediate layer density Value, this explanation uses intermediate layer density spectra to obtain reliable bouguer gravity anomaly data ratio and uses density profile method There is bigger advantage.

Claims (3)

1. an acquiring method for gravity intermediate layer density spectra, feature is through the following steps that realize:

1) obtained absolute gravity value and the coordinate elevation of each measuring point on survey line by gravity collection, use different densities meter Calculate bouguer gravity anomaly data；

Described different densities, refers to that density span is 1.5g/cm³～3.0g/cm³, value step-length 0.01g/cm³ Or 0.02g/cm³Each density value ρ；

Calculating in this step includes: calculate normal gravity g according to measuring point plane coordinates₀；According to measuring point elevation and in Interbed density calculates Bouguer correction value Δ g_b；Base area graphic data calculates topographic correction value Δ g_TC；Measuring point Bouguer gravity is different Frequently with formula Δ g=g-g₀+Δg_b+Δg_TCCalculating, in formula, g is measuring point absolute gravity value；

2) each point bouguer gravity anomaly value calculating described different densities is average with the most adjacent 2 bouguer gravity anomalies The abnormal variation of value, described abnormal variation usesCalculate, in formula:

K (i, ρ) be the i-th dot density be abnormal variation value during ρ, i is period, and ρ is density value；

Δ g (i, ρ), Δ g (i-1, ρ) and Δ g (i+1, ρ) are respectively i-th, i-1 and i+1 dot density is the bouguer gravity anomaly of ρ Value；

3) the abnormal variation value tried to achieve is carried out gridding, form gravity intermediate layer density spectra grid data；

Described gravity intermediate layer density spectra grid data is with measuring point coordinate or period as abscissa, calculating density is Vertical coordinate, physical quantity is the gravity deflection difference under respective coordinates and density；

4) use color from large to small or by being deep to shallow drawing according to gravity intermediate layer density spectra grid data, make Under each density, minima is transparent to show that, obtains gravity intermediate layer density spectra.

Method the most according to claim 1, feature is: step 3) described in gridding to count as abscissa, Scope is 1 to always counting, and increment takes 1.

Method the most according to claim 1, feature is: step 3) described in gridding sit with density value for vertical Mark, density range and step-length and step 1) identical.