阅读说明：本技术 一种基于井震结合的岩性边界识别方法 (Lithology boundary identification method based on well-seismic combination ) 是由 张晓亮 马玉 贾艳霞 王树芳 朱煜华 杨星 庞萌 于 2019-10-23 设计创作，主要内容包括：本发明涉及石油勘探开发领域,特别是一种基于井震结合的岩性边界识别方法。该方法获取研究区的地震资料和测井资料,根据声波曲线和密度曲线制作合成地震记录,通过合成地震记录标定,开展主力油层地震响应特征分析,并且综合利用地层体切片技术、地震属性分析技术与砂体展布特征研究来识别岩性边界,先通过分析来说明研究区可以开展地震属性刻画的研究,并在主力油层的砂岩平面展布范围内进行地震属性提取,弥补了因砂泥岩速度叠置而无法开展叠后波阻抗反演进行储层预测的不足,提高了岩性边界的预测精度,降低了勘探开发成本。(The invention relates to the field of petroleum exploration and development, in particular to a lithology boundary identification method based on well-seismic combination. The method obtains seismic data and well logging data of a research area, prepares a synthetic seismic record according to an acoustic curve and a density curve, carries out seismic response characteristic analysis of a prime reservoir through the calibration of the synthetic seismic record, and identifies lithologic boundaries by comprehensively utilizing a stratigraphic body slicing technology, a seismic attribute analysis technology and sand body spreading characteristic research.)

1. A lithology boundary identification method based on well-seismic combination is characterized by comprising the following steps:

1) acquiring seismic data and well logging data of a research area, making a synthetic seismic record according to an acoustic curve and a density curve, and calibrating a main reservoir of the research area according to the synthetic seismic record;

2) carrying out stratum comparison on the research area, and combining the comparison result with the calibrated main pay zone to determine an accurate main pay zone;

3) carrying out sand adding and removing tests on the main reservoir with accurate drilled wells, and judging whether positive correlation exists between the amplitude on the time section of the research area and the sand thickness;

4) if the amplitude on the time section of the research area has positive correlation with the sand thickness, extracting seismic attributes in the sandstone plane spread range of any main pay zone of the research area, wherein the seismic attributes comprise root mean square amplitude attributes and instantaneous Q factor attributes, and carrying out seismic attribute analysis to obtain lithologic boundaries of the reservoir, wherein the sandstone plane spread range of the main pay zone in the research area is obtained by means of stratum slicing technology prediction.

2. The method for identifying lithologic boundaries based on well-seismic integration according to claim 1, wherein, if a well with a missing density curve exists in the research area in the step 1), the density curve of the well is obtained by converting the acoustic curve of the well with the missing density curve through a similar gardner formula.

3. The method of claim 2, wherein the Gardner-like equation is derived from seismic data and well log data of the area of interest using least squares fitting.

4. The method for identifying lithologic boundaries based on well-seismic combination according to claim 1, wherein in the step 2), if the comparison result is inconsistent with the calibrated main reservoir, a desanding test is performed on the inconsistent main reservoir, and if a seismic response is found to exist in a peak at the lower part of the main reservoir, the set of peaks is considered to be an accurate main reservoir.

Technical Field

The invention relates to the field of petroleum exploration and development, in particular to a lithology boundary identification method based on well-seismic combination.

Background

Along with the continuous deepening of oil exploration and development, the oil deposit is difficult to be found, and the oil deposit is found by the discovery of a fault-lithology oil deposit. However, for the identification of fault-lithologic traps, not only a fine structural explanation is required, but also corresponding reservoir prediction work is required to be carried out, but for part of old oil zones, due to various reasons, effective electronic version well logging data are uneven, and particularly, a density curve required for accurately calibrating the reservoir is missing, so that corresponding geophysical prospecting analysis work is limited. In addition, the finite electronic version data are subjected to statistical analysis, the overlapping of sand-shale speeds of target intervals of a part of research areas is found, and the boundary of the reservoir is difficult to accurately predict by performing post-stack wave impedance inversion on the overlapped sand-shale speeds. In addition, if the reservoir boundary is predicted only by carrying out a sand body distribution characteristic research, deviation of fault-lithologic trap identification can be caused because the reservoir phase of a part of research areas becomes fast and the accurate description of a single sand body is difficult.

Disclosure of Invention

The invention aims to provide a lithology boundary identification method based on well-seismic combination, which is used for solving the problem that reservoir boundary delineation is inaccurate in the existing sand shale velocity superposition area.

In order to achieve the purpose, the invention provides a lithology boundary identification method based on well-seismic combination, which comprises the following steps:

1) acquiring seismic data and well logging data of a research area, making a synthetic seismic record according to an acoustic curve and a density curve, and calibrating a main reservoir of the research area according to the synthetic seismic record;

2) carrying out stratum comparison on the research area, and combining the comparison result with the calibrated main pay zone to determine an accurate main pay zone;

3) carrying out sand adding and removing tests on the main reservoir with accurate drilled wells, and judging whether positive correlation exists between the amplitude on the time section of the research area and the sand thickness;

4) if the amplitude on the time section of the research area has positive correlation with the sand thickness, extracting seismic attributes in the sandstone plane spread range of any main pay zone of the research area, wherein the seismic attributes comprise root mean square amplitude attributes and instantaneous Q factor attributes, and carrying out seismic attribute analysis to obtain lithologic boundaries of the reservoir, wherein the sandstone plane spread range of the main pay zone in the research area is obtained by means of stratum slicing technology prediction.

The method has the advantages that the lithologic boundary is identified by carrying out seismic response characteristic analysis on the main reservoir through synthetic seismic record calibration and comprehensively utilizing a stratigraphic body slicing technology, a seismic attribute analysis technology and sand body spreading characteristic research, the research that seismic attribute portrayal can be carried out in a research area is explained through analysis, seismic attribute extraction is carried out in the sandstone plane spreading range of the main reservoir, the defect that the reservoir prediction can not be carried out through post-stack wave impedance inversion due to sand shale velocity stacking is overcome, the prediction precision of the lithologic boundary is improved, and the exploration and development cost is reduced.

Further, for effective uneven electronic version logging data, especially density curve missing required for accurately calibrating a reservoir, in order to avoid limitation of corresponding geophysical prospecting analysis work and improve the quality of synthetic seismic records, in step 1), if a well with a missing density curve exists in a research area, the density curve of the well is obtained through conversion by a gardner-like formula according to the acoustic curve of the well with the missing density curve.

Further, in order to accurately obtain the actual density curve, the gardner-like formula is obtained by fitting the seismic data and the well logging data of the research area by using a least square method.

Further, in order to reduce the misjudgment rate of the accurate main reservoir, if the comparison result is inconsistent with the calibrated main reservoir in the step 2), a desanding test is carried out on the inconsistent main reservoir, and if the wave crest at the lower part of the main reservoir is found to have seismic response, the set of wave crest is considered as the accurate main reservoir.

Drawings

FIG. 1 is a slice layer 6 of a stratigraphic body slice of an investigation region of the present invention;

FIG. 2 is a stratigraphic body slice layer 7 view of a study area of the present invention;

FIG. 3 is a stratigraphic body slice layer 8 view of a study area of the present invention;

FIG. 4 is a stratigraphic body slice layer 13 view of a study area of the present invention;

FIG. 5 is a superposition of sandstone contours and formations for a main reservoir of a study area of the present invention;

FIG. 6 is a plot of the RMS amplitude profile of a main force reservoir of an investigation region of the present invention;

FIG. 7 is a plot of the instantaneous Q-factor profile property of the main reservoir of the study area of the present invention;

FIG. 8 is a overlay of the RMS amplitude profile of the key well pay zone along the horizon of the present invention with a sandstone isopachs.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The invention provides a lithology boundary identification method based on well-seismic combination, which comprises the following steps:

1) acquiring seismic data and well logging data of a research area, making a synthetic seismic record according to an acoustic curve and a density curve, and calibrating a main reservoir of the research area according to the synthetic seismic record.

Logging data is collected for wells in the study area, 4 wells have acoustic curves and density curves, 29 wells have acoustic curves only, and 29 wells have gamma curves only with 5 wells.

And if the well with the missing density curve exists in the research area, converting the sound wave curve of the well with the missing density curve through a similar Gardner formula to obtain the density curve of the well.

High quality synthetic seismic records require the use of both sonic and density curves, which in the absence of a density curve are typically converted using the gardner equation in landmark software. However, the gardner formula is not completely suitable for our study area, so that a gardner-like formula is fitted in an area where the number of faults is small, the logging data is complete, and the stratum is relatively flat.

The prototype of the gardner-like formula for the study area is:

ρ＝aV^b

wherein rho is the stratum density of the research area, and V is the stratum speed of the research area.

Solving for linear relationship rho ═ aV for wells in work area^bThe calculation process is as follows:

the first step is as follows: from rho to aV^bThe formula Ln (ρ) ═ Ln (a) + b × Ln (v) can be derived;

the second step is that: establishing a linear equation of the formula in the previous step, and solving the processes of Ln (a) and b;

the third step: by applying a least square principle, taking the minimum value of the square sum of the deviations of the measured values and the calculated values of Ln (rho) as an 'optimization criterion', namely determining Ln (a) and b;

the fourth step: by using a LINEST function in EXCEL, the slope (b) and intercept Ln (a) of a linear equation with (Ln (V) and Ln (rho)) as variables can be obtained;

the fifth step: according to the LN (v) and LN (ρ) arrays, a least square method is applied, and a LINEST function is used to calculate that b is 0.0792 and a is 1.1626.

Finally, the gardner-like formula is as follows:

ρ＝1.1626V^0.0792。

2) and carrying out stratum comparison on the research area, and combining the comparison result with the calibrated main pay zone to determine an accurate main pay zone.

6 skeleton sections covering the whole research area are established, and stratum comparison and stratification work is carried out on the whole area according to the skeleton sections.

And if the comparison result is inconsistent with the calibrated main force reservoir, performing a desanding test on the inconsistent main force reservoir, and if the lower wave crest of the main force reservoir shows seismic response, determining that the inconsistent main force reservoir is the accurate main force reservoir. In this embodiment, through the desanding test of the main reservoir, it is found that the lower set of wave peaks has seismic response, and therefore, the set of wave peaks can be traced and depicted.

3) And carrying out sand adding and sand removing tests on the accurate main oil layer calibrated by the drilled well, and judging that the positive correlation exists between the amplitude on the time section of the research area and the sand thickness.

In the embodiment, through the sand adding and sand removing tests of the key well (namely the drilled well with the main reservoir calibrated accurately), the amplitude of the same-phase axis where the main reservoir is located is enhanced to some extent after the sand is added, and the phase relation is unchanged; after sand removal, the amplitude of the in-phase axis where the main force oil layer is located is weakened to some extent, and the phase relation is unchanged. Therefore, analysis shows that the amplitude on the time section of the research area has a positive correlation with the sand thickness, and the river sand in the work area can be described by extracting the amplitude attribute.

4) And predicting the sandstone plane spread range of the main reservoir in the research area by using a stratigraphic slicing technology, extracting seismic attributes in the sandstone plane spread range of any main reservoir in the research area, and carrying out seismic attribute analysis to obtain the lithologic boundary of the reservoir.

And establishing an interval model of a target interval according to an accurate main force oil layer of a research area, and extracting 15 root-mean-square amplitude attribute slices from the stratum clamped between the target interval and the target interval in a top-bottom balanced slicing mode under the control of a sequence interface. As shown in fig. 1-4, it can be seen that slice of the stratigraphic bodies of layers 6, 7, 8 and 13 in the interval characterize and evolve different sand body planes in the interval. The 7 th stratum slice better depicts the spreading characteristics of the source, the spreading direction is integrally shown as spreading from north to south, and branch sand bodies in east and west directions are formed, wherein the sand body in the research area is mainly controlled by the north-east source (figure 5).

And acquiring the sandstone plane spread range of a main reservoir in the research area, and carrying out seismic attribute analysis to predict the lithologic boundary of the reservoir on the basis.

Seismic attribute analysis includes profile attribute analysis and planar attribute analysis.

Profile property analysis: as shown in fig. 6 and 7, through the analysis of the seismic profile by the root mean square amplitude attribute and the instantaneous Q factor attribute, it is found that the main pay zone of the key well gradually appears an attribute change to a high position, and it is presumed that there may be a lithological change, which is basically consistent with the analysis result of the well-tie profile.

Analyzing the plane property: and (3) extracting root mean square amplitude attributes of the accurate main stress oil layer obtained by comparing the synthetic seismic record with the stratum by a single-layer bit attribute extraction mode by respectively opening 2ms time windows along the upper and lower layers. As shown in fig. 8, it can be seen that the root mean square amplitude attribute of the main force oil layer along the layer depicts the sand bodies in the area clearly, the boundary is obvious, and the main force oil layer is basically consistent with the sand bodies spreading from north to south.

Comprehensive analysis shows that fault-lithologic traps are easily formed by the reservoir and the northeast fault configuration in the research area.

The present invention has been described in relation to particular embodiments thereof, but the invention is not limited to the described embodiments. In the thought given by the present invention, the technical means in the above embodiments are changed, replaced, modified in a manner that is easily imaginable to those skilled in the art, and the functions are basically the same as the corresponding technical means in the present invention, and the purpose of the invention is basically the same, so that the technical scheme formed by fine tuning the above embodiments still falls into the protection scope of the present invention.