阅读说明：本技术 一种基于振幅拟合信息提取的地震油气检测方法 (Seismic oil gas detection method based on amplitude fitting information extraction ) 是由 明君 王波 陈瑶 夏同星 刘建辉 李久 刘垒 魏天罡 谢久安 马佳国 于 2019-09-21 设计创作，主要内容包括：本发明属于石油勘探地震油气检测技术领域,公开了一种基于振幅拟合信息提取的地震油气检测方法,按照如下步骤进行：优选已钻井,统计井点处的地震振幅属性、瞬时频率属性、砂体时间厚度和含油饱和度；拟合砂体时间厚度指数因子和瞬时频率属性指数因子；计算油气信息因子,并计算井点处的油气信息因子与已钻井含油饱和度的误差；判断误差是否满足精度要求,若否,则筛选去掉存在异常的已钻井,重复步骤；若是,则利用提取的油气信息因子开展油气检测。本发明认为地震振幅变化受砂岩厚度变化和流体的综合影响,将地震振幅分解为不同厚度砂岩振幅与油气信息因子的乘积,通过拟合不同厚度砂岩的地震振幅,得到油气信息因子,实现高准确度油气检测。(The invention belongs to the technical field of oil exploration seismic oil-gas detection, and discloses a seismic oil-gas detection method based on amplitude fitting information extraction, which is carried out according to the following steps: preferably drilling a well, and counting seismic amplitude attributes, instantaneous frequency attributes, sand time thickness and oil saturation at well points; fitting a sand body time thickness index factor and an instantaneous frequency attribute index factor; calculating an oil gas information factor, and calculating the error between the oil gas information factor at the well point and the oil saturation of the drilled well; judging whether the error meets the precision requirement, if not, screening to remove the drilled well with abnormality, and repeating the steps; and if so, carrying out oil gas detection by using the extracted oil gas information factor. The method considers that the seismic amplitude change is comprehensively influenced by sandstone thickness change and fluid, decomposes the seismic amplitude into products of sandstone amplitudes with different thicknesses and oil-gas information factors, obtains the oil-gas information factors by fitting the seismic amplitudes of the sandstone with different thicknesses, and realizes high-accuracy oil-gas detection.)

1. A seismic oil and gas detection method based on amplitude fitting information extraction is characterized by comprising the following steps:

(1) preferably drilling, and counting the seismic amplitude attribute, the instantaneous frequency attribute, the sand time thickness and the oil saturation at the preferred well drilling point;

(2) and (3) solving a sand body time thickness exponential factor m and an instantaneous frequency attribute exponential factor n by using a fitting method according to the formula (7):

O＝[B^TB]^-1B^TP (7)

wherein the content of the first and second substances,

extracting the value H of the sand time thickness H at the well point_wellInstantaneous frequency property F value at well point F_wellBy the formula B ═ ln H_wellln F_well]B is obtained through calculation;

extracting seismic amplitude attribute A_allValue A at the well point_all-wellSetting constant correction factors epsilon and a, and determining the oil saturation S of the drilled well_oil-wellValue sigma at well point of well as hydrocarbon information factor sigma_wellI.e. sigma_well＝S_oil-wellBy the formula

calculating by the formula (7) to obtain O, namely obtaining a sand body time thickness index factor m and an instantaneous frequency attribute index factor n;

(3) calculating a hydrocarbon information factor sigma using equation (8):

after the oil gas information factor sigma is obtained through calculation, extracting the oil gas information factor sigma 'at the well point from the oil gas information factor sigma'_wellCalculating the oil and gas information factor sigma 'at the well point'_wellWith the oil saturation S of the drilled well_oil-wellError of (2) (erf)_well＝σ′_well-S_oil-wellAnd calculating the average of the errors at all well points erf_avg-wells(ii) a And, given an error threshold erf_threshold；

(4) If erf_avg-wells＞erf_thresholdIf so, the precision requirement is not met; selecting an error erf from the drilled wells that does not exceed a total of 10%_wellRemoving the largest drilled well; repeating the steps (2) to (4) according to the statistical data of the step (1);

if erf_avg-wells≤erf_thresholdThe accuracy requirement is met; using the computed oil-gas information factor sigma as seismic oil-gas information extracted from seismic data, and performing the step (5) by using the extracted oil-gas information factor sigma;

(5) taking the minimum value of the hydrocarbon information factor of the oil reservoir extracted from the drilled well as the threshold value sigma_thresholdMixing oilThe gas information factor sigma is more than or equal to sigma_thresholdThe region is predicted to be a reservoir distribution region, and the oil and gas information factor sigma is less than sigma_thresholdIs predicted as a water layer distribution region.

2. The amplitude fitting information extraction-based seismic hydrocarbon detection method of claim 1, wherein the preferred drilled wells in step (1) are drilled wells with well locations in the study area evenly distributed and seismic amplitudes at the well locations not having abnormal values.

3. The amplitude fitting information extraction-based seismic hydrocarbon detection method of claim 1, wherein the fitting in step (2) is as follows:

will be seismic amplitude attribute A_allSeismic amplitude attribute A expressed as sandstone at different thicknesses_sandA product relation with an oil gas information factor sigma, wherein sigma is more than or equal to 0, and epsilon is a constant correction factor;

and (2) realizing different thickness amplitude exponential relation fitting by utilizing the sand time thickness H and the instantaneous frequency attribute F through the statistical data in the step (1):

A_sand＝aH^mFⁿ(2)

in the formula (2), a is a given constant correction factor, m is a sand body time thickness index factor, and n is an instantaneous frequency attribute index factor;

thus:

taking the logarithm of equation (3):

writing equation (4) in matrix form:

equation (5) is simplified to:

P＝B×O (6)

wherein the content of the first and second substances,

solving a target function by using a least square method to obtain a sand body time thickness index factor m and an instantaneous frequency attribute index factor n:

O＝[B^TB]^-1B^TP (7)。

4. the amplitude fitting information extraction-based seismic hydrocarbon detection method of claim 1, wherein the error threshold erf in step (3)_thresholdShould be less than 1/2 of the difference between the average oil saturation of the oil layer and the average oil saturation of the water layer in the study area.

Technical Field

The invention belongs to the technical field of oil exploration seismic oil-gas detection, and particularly relates to a seismic oil-gas detection method based on amplitude fitting.

Background

As early as the 70's of the 20 th century, geophysical workers have used seismic amplitude "bright spots" to find subsurface gas formations and have had many successful examples, but practice has also found that this technique has strong limitations and multiple solutions. In order to more effectively detect oil gas, various methods such as AVO technology, Poisson impedance, LMR technology, frequency dispersion attribute, low-frequency shadow, low-frequency amplitude abnormity and the like are successively provided. However, because the difference of the physical properties of the crude oil of the stratum and the water of the stratum is small, the physical property change of the sand-shale influences the seismic reflection, the seismic data has the influence of a plurality of factors such as noise and the like, and the oil-containing sand body is difficult to identify by using the seismic data and has strong multi-resolution.

In recent years, a large number of earthquake oil-gas detection researches are carried out in Bohai sea oil fields, and the oil-gas detection researches are successfully applied to a plurality of oil fields. According to the practice, the earthquake oil gas detection effect is good under the geological condition that the stratum thickness is relatively stable. However, the requirements of the conditions are strict, the application range is not wide, and the oil-gas detection effect is not good under the condition that the thickness of the sand body which exists widely is greatly changed. The earthquake amplitude after the sand body contains oil and gas has certain response, and the change of the amplitude is not only influenced by the deposition environment, physical properties and fluid of a reservoir, but also influenced by the thickness of the reservoir. Forward modeling studies show that the main factor influencing the single sand body oil and gas detection result is the thickness change of the sand body. Therefore, fluid detection research aiming at a single sand body is carried out, various adverse conditions can be effectively avoided, and the precision and the accuracy of a prediction result are improved.

Disclosure of Invention

The invention aims to solve the technical problem of strong oil-gas multi-resolution by using amplitude direct detection, and provides an amplitude fitting information extraction-based seismic oil-gas detection method.

In order to solve the technical problems, the invention is realized by the following technical scheme:

a seismic oil and gas detection method based on amplitude fitting information extraction is carried out according to the following steps:

(1) preferably drilling, and counting the seismic amplitude attribute, the instantaneous frequency attribute, the sand time thickness and the oil saturation at the preferred well drilling point;

(2) and (3) solving a sand body time thickness exponential factor m and an instantaneous frequency attribute exponential factor n by using a fitting method according to the formula (7):

O＝[B^TB]^-1B^TP (7)

wherein the content of the first and second substances,

B＝[ln H ln F]，

time thickness H of sand body extraction at well pointValue H of_wellInstantaneous frequency property F value at well point F_wellBy the formula B ═ ln H_wellln F_well]B is obtained through calculation;

extracting seismic amplitude attribute A_allValue A at the well point_all-wellSetting constant correction factors epsilon and a, and determining the oil saturation S of the drilled well_oil-wellValue sigma at well point of well as hydrocarbon information factor sigma_wellI.e. sigma_well＝S_oil-wellBy the formula

Calculating to obtain P;

calculating by the formula (7) to obtain O, namely obtaining a sand body time thickness index factor m and an instantaneous frequency attribute index factor n;

(3) calculating a hydrocarbon information factor sigma using equation (8):

after the oil gas information factor sigma is obtained through calculation, extracting the oil gas information factor sigma 'at the well point from the oil gas information factor sigma'_wellCalculating the oil and gas information factor sigma 'at the well point'_wellWith the oil saturation S of the drilled well_oil-wellError of (2) (erf)_well＝σ′_well-S_oil-wellAnd calculating the average of the errors at all well points erf_avg-wells(ii) a And, given an error threshold erf_threshold；

(4) If erf_avg-wells＞erf_thresholdIf so, the precision requirement is not met; selecting an error erf from the drilled wells that does not exceed a total of 10%_wellRemoving the largest drilled well; repeating the steps (2) to (4) according to the statistical data of the step (1);

if erf_avg-wells≤erf_thresholdThe accuracy requirement is met; using the calculated oil-gas information factor sigma as the seismic oil-gas information extracted from the seismic data, and using the extracted oil-gas information factor sigmaA step (5);

(5) taking the minimum value of the hydrocarbon information factor of the oil reservoir extracted from the drilled well as the threshold value sigma_thresholdThe oil gas information factor sigma is more than or equal to sigma_thresholdThe region is predicted to be a reservoir distribution region, and the oil and gas information factor sigma is less than sigma_thresholdIs predicted as a water layer distribution region.

Further, the preferred drilled wells in step (1) are drilled wells in which the locations of the well points in the study area are uniformly distributed and the seismic amplitude at the well points does not have an abnormal value.

Further, the fitting method in step (2) is as follows:

the change of the seismic amplitude is considered to be influenced by the combination of the sandstone thickness change and the fluid, so the seismic amplitude attribute A can be obtained_allSeismic amplitude attribute A expressed as sandstone at different thicknesses_sandA product relation with an oil gas information factor sigma, wherein sigma is more than or equal to 0, and epsilon is a constant correction factor;

and (2) realizing different thickness amplitude exponential relation fitting by utilizing the sand time thickness H and the instantaneous frequency attribute F through the statistical data in the step (1):

A_sand＝aH^mFⁿ(2)

in the formula (2), a is a given constant correction factor, m is a sand body time thickness index factor, and n is an instantaneous frequency attribute index factor;

thus:

taking the logarithm of equation (3):

writing equation (4) in matrix form:

equation (5) is simplified to:

P＝B×O (6)

wherein the content of the first and second substances,B＝[ln H ln F]，

solving a target function by using a least square method to obtain a sand body time thickness index factor m and an instantaneous frequency attribute index factor n:

O＝[B^TB]^-1B^TP (7)。

further, the error threshold erf in step (3)_thresholdShould be less than 1/2 of the difference between the average oil saturation of the oil layer and the average oil saturation of the water layer in the study area.

The invention has the beneficial effects that:

the seismic oil-gas detection method based on amplitude fitting information extraction aims at the interference of sand body thickness change on oil-gas detection, and the change of seismic amplitude is understood as being comprehensively influenced by sandstone thickness change and fluid, so that the seismic amplitude is decomposed into the product of the sand body amplitude with different thicknesses and an oil-gas information factor, the seismic amplitude of sandstone with different thicknesses is obtained by fitting according to the good correlation of frequency, sand body time thickness and the real thickness of a sand body, then the influence caused by the thickness change is eliminated in the actual amplitude, an oil-gas information factor is further obtained, the obtained oil-gas information factor is used as seismic oil-gas information extracted from seismic data, and the information is used for predicting the distribution area of an oil-gas water layer. The method eliminates the influence of the thickness on the seismic amplitude, and can effectively improve the accuracy of single sand body oil gas detection.

Drawings

FIG. 1 is a flow chart of a seismic hydrocarbon testing method based on amplitude fitting information extraction provided by the present invention;

FIG. 2 is a graph of hydrocarbon information factor versus log oil saturation at the well site drilled in example 1;

FIG. 3 is an effect diagram of the extracted hydrocarbon information factor of example 1;

FIG. 4 is a graph of the oil-containing area of example 1;

FIG. 5 is the minimum amplitude attribute extracted from seismic data of example 2;

FIG. 6 is the effect diagram of the extracted hydrocarbon information factor of example 2.

Detailed Description

As shown in FIG. 1, the invention provides a seismic hydrocarbon detection method based on amplitude fitting information extraction, comprising the following steps:

(1) and selecting the drilled wells with well points uniformly distributed in the research area and seismic amplitude without abnormal values at the well points, and counting the seismic amplitude attribute, the instantaneous frequency attribute, the sand body time thickness and the oil saturation of the drilled wells of the seismic data at the drilled wells.

(2) And fitting a sand body time thickness index factor m and an instantaneous frequency attribute index factor n, wherein the specific fitting method comprises the following steps:

the change of the seismic amplitude is considered to be influenced by the combination of the sandstone thickness change and the fluid, so the seismic amplitude attribute A can be obtained_allExpressed as seismic amplitude attribute A of the sand body to be researched under different thicknesses_sandAnd the product relation of the oil gas information factor sigma, wherein sigma is more than or equal to 0, and epsilon is a constant correction factor. When the sand body contains water, sigma is close to 0; when the sand body contains oil, σ should be more than 0.

And (2) realizing different thickness amplitude exponential relation fitting by utilizing the sand time thickness H and the instantaneous frequency attribute F through the statistical data in the step (1):

A_sand＝aH^mFⁿ(2)

in the formula (2), a is a given constant correction factor, m is a sand body time thickness exponential factor, and n is an instantaneous frequency attribute exponential factor.

Thus:

taking the logarithm of equation (3):

writing equation (4) in matrix form:

further simplification is as follows:

P＝B×O (6)

wherein the content of the first and second substances,

B＝[ln H ln F]，

and solving a target function by using a least square method to obtain a sand body time thickness index factor m and an instantaneous frequency attribute index factor n.

O＝[B^TB]^-1B^TP (7)

Extracting the value H of the sand time thickness H at the well point_wellInstantaneous frequency property F value at well point F_wellBy the formula B ═ ln H_wellln F_well]B is obtained through calculation; extracting seismic amplitude attribute A_allValue A at the well point_all-wellSetting constant correction factors epsilon and a, and determining the oil saturation S of the drilled well_oil-wellValue sigma at well point of well as hydrocarbon information factor sigma_wellI.e. sigma_well＝S_oil-wellBy the formula

Calculating to obtain P; and (4) calculating by the formula (7) to obtain O, namely obtaining a sand body time thickness index factor m and an instantaneous frequency attribute index factor n.

(3) Calculating hydrocarbon information factor using equation (8):

and after obtaining the oil gas information factor sigma, extracting the oil gas information factor sigma 'at the well point from the oil gas information factor sigma'_wellCalculating the oil and gas information factor sigma 'at the well point'_wellWith the oil saturation S of the drilled well_oil-wellError of (2) (erf)_well＝σ′_well-S_oil-wellAnd calculating the average of the errors at all well points erf_avg-wells. And, given an error threshold erf_thresholdError threshold erf_thresholdShould be less than 1/2 of the difference between the average oil saturation of the oil layer and the average oil saturation of the water layer in the study area.

(4) If erf_avg-wells＞erf_thresholdIf so, the precision requirement is not met; selecting an error erf from the drilled wells that does not exceed a total of 10%_wellThe largest drilled well, and this portion of the drilled well is removed. And (4) repeating the steps (2) to (4) according to the statistical data of the step (1).

If erf_avg-wells≤erf_thresholdThe accuracy requirement is met; and (5) taking the oil gas information factor sigma obtained by calculation as seismic oil gas information extracted from seismic data, and performing the step.

(5) Carrying out oil gas detection research by using the extracted oil gas information factor sigma: taking the minimum value of the hydrocarbon information factor of the oil reservoir extracted from the drilled well as the threshold value sigma_thresholdThe oil gas information factor sigma is more than or equal to sigma_thresholdThe region is regarded as a predicted reservoir distribution region, and the oil and gas information factor sigma < sigma_thresholdIs considered to be a predicted water layer distribution region.

The present invention will be described in further detail by way of examples. The following examples are presented to enable those skilled in the art to more fully understand the present invention and are not intended to limit the invention in any way.