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Pre-stack fracture density estimation method based on improved ellipse fitting

A technology of crack density and ellipse fitting, applied in measurement devices, instruments, scientific instruments, etc., can solve problems such as the inability to achieve optimal solutions, and achieve the effect of strong anti-noise ability and high fitting accuracy

Active Publication Date: 2021-09-21
DAQING OILFIELD CO LTD +1
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Problems solved by technology

[0005] The current common ellipse fitting algorithm is the least squares method based on the minimum global error. This algorithm establishes an objective function based on the minimum variance between the fitting predicted coordinates and the actual coordinates. The algorithm has the advantages of simple principle and fast calculation efficiency. The least squares method is Linear estimation, the default is a linear relationship, and cannot achieve the optimal solution, so the use has certain limitations

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  • Pre-stack fracture density estimation method based on improved ellipse fitting
  • Pre-stack fracture density estimation method based on improved ellipse fitting
  • Pre-stack fracture density estimation method based on improved ellipse fitting

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[0055] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings, taking the 3D actual seismic work area of ​​Songliao Basin in Daqing Oilfield as an example.

[0056] The pre-stack fracture density estimation method based on improved ellipse fitting of the present invention comprises the following steps:

[0057] (1) Take the data of a time point of the pre-stack gather in the work area, and take the azimuth and amplitude respectively as the coordinates of the ellipse fitting:

[0058] Establish a Cartesian two-dimensional coordinate system with the azimuth as the X axis and the amplitude as the Y axis. Since the coordinates of the ellipse fitting will coincide in the Cartesian coordinate system, the Cartesian coordinate system is transformed into the polar coordinate system. The conversion formula is as follows:

[0059]

[0...

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Abstract

The invention relates to a pre-stack crack density estimation method based on improved ellipse fitting, which comprises the following steps of: taking data of a time point of a pre-stack gather, respectively taking an azimuth angle and an amplitude as coordinates of ellipse fitting, and eliminating abnormal values by utilizing a Pauta rule to obtain a pre-stack crack density estimation result; establishing an objective function of a minimum square difference sum between a forward coordinate point and an actual coordinate point, calculating an ellipse fitting coefficient by utilizing a least square linear fitting algorithm, taking the ellipse fitting coefficient as an initial value of an improved Gauss-Newton optimization iterative algorithm, obtaining an optimal ellipse fitting coefficient by utilizing the iterative algorithm, calculating the fracture density according to the optimal ellipse fitting coefficient. and completing crack density estimation of the whole pre-stack gather. The estimation method has the advantages of being high in calculation efficiency, high in fitting precision, high in noise robustness and the like, and the problems that an existing linear estimation-based least square method cannot achieve an optimal solution and has certain limitation in use are effectively solved.

Description

Technical field: [0001] The invention relates to a pre-stack fracture density estimation method, in particular to a pre-stack fracture density estimation method based on improved ellipse fitting. Background technique: [0002] With the improvement of oil and gas exploration technology, fractured oil and gas reservoirs have become an important new field of exploration. Reservoir fracture identification and accurate description and prediction of fractures are the key to the exploration and development of fractured reservoirs. [0003] At present, fracture prediction techniques can be divided into two categories according to data types, one is post-stack prediction technology, and the other is pre-stack prediction technology. At present, post-stack fracture prediction technologies include coherence analysis technology, image processing technology, curvature analysis technology, dip detection technology, profit analysis technology, etc. They are usually input based on post-stac...

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Application Information

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IPC IPC(8): G01V1/30
CPCG01V1/306G01V2210/512G01V2210/6224
Inventor 何文渊
Owner DAQING OILFIELD CO LTD
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