Granite buried hill cave body prediction method and device

Abstract

The invention discloses a granite buried hill cave body prediction method and device. The granite buried hill cave body prediction method comprises the following steps: obtaining an omni-directional common inclination angle gather based on an underground local angle domain omni-directional migration imaging method; mirror energy data and scattering energy data are separated from the omnibearing common-inclination-angle gather; according to well logging and well drilling data, the development position of the granite buried hill cave body on the well is determined; superposing the mirror image energy data and the scattering energy data according to the common dip angle gather energy characteristics corresponding to the development position of the ground granite buried hill cave body to generate a scattering imaging seismic data body; according to the scattering imaging seismic data volume, performing spectral analysis on a seismic channel where the granite buried hill cave body development well is located, and determining a target frequency range of the granite buried hill cave body; energy spectrum data corresponding to the target frequency range is extracted from the scattering imaging seismic data body, the distribution range of the granite buried hill cave body is predicted, and the prediction accuracy of the granite buried hill cave body is effectively improved.

Description

technical field [0001] The invention relates to the technical field of seismic reservoir prediction for petroleum geophysical exploration, in particular to a method and device for predicting a granite buried hill cave. Background technique [0002] Among the crystalline bedrock oil and gas reservoirs that have been discovered in the world, granite bedrock oil and gas reservoirs account for about 40%, and the reserves account for 75%. Exploration practice shows that granite bedrock reservoirs have strong heterogeneity, generally do not develop matrix pores, and mainly rely on effective fractures and caves to form productivity. Accurately predicting the distribution of cave bodies is of great significance for improving the productivity of granite bedrock buried hills. [0003] At present, the main cave prediction research methods are all for carbonate cave-type reservoirs. The wave impedance of carbonate caves filled with fluids is very different from that of surrounding car...

AI Technical Summary

Problems solved by technology

[0004] Under the action of multi-stage regional structural uplift in the granite bedrock buried hill, granite intrusions have been exposed to the surface for a long time. Affected by tectonic movement and weathering and leaching, the weathered crust and other dominant reservoir rocks are broken, loose, and fractures are developed. The difference in wave impedance between dissolved caves and surrounding rock formed by the intrusion of atmospheric precipitation and groundwater along the fracture network in the fracture-cavity development zone is small, resulting in weak reflection characteristics of cave bodies on conventional post-stack seismic sections, and it is difficult to form a “string of beads” like carbonate caves. Therefore, the cave body prediction technology for carbonate cave-type reservoirs is not suitable for the identification and prediction of small-scale weak reflection cave bodies in granite buried hills.

In addition, the continuous strong reflection interface of the weathering crust on the top also has a certain interference effect on the identification of weak reflection features such as caves in the fracture-cavity development zone

As a result, caves in buried hill reservoirs in granite bedrock have no obvious seismic response, which increases the difficulty of using seismic data to identify and predict caves in buried hills in granite bedrock

[0005] For the above problems, no effective solutions have been proposed so far

Images