Prediction Of Coal Seam Fracture Development Zone Based On OVT Data

The area and direction of coal seam fracture development is an important factor to control the permeability of coal reservoir and influence the development of CBM.It is also a characterization of stress field distribution and direction in a certain range.Coalbed methane development can not only make up for the shortage of conventional oil and gas resources,but also reduce coal mine gas outburst accidents,reduce greenhouse gas emissions and improve the atmospheric environment.Therefore,it is particularly important to carry out fracture prediction in coal reservoirs.At present,the main methods of fracture prediction in geophysical reservoirs are logging data prediction and geophysical data analysis.Most of the conventional fracture prediction methods are based on the conventional processing methods without anisotropic information.In order to delineate the fracture development area of the target coal seam in the study area more accurately,based on the wide azimuth seismic exploration data of Pangbi block,this paper obtains multi-azimuth data volume containing anisotropic information through OVT domain processing,and extracts multi-azimuth data volume attributes.According to the geological structure characteristics of the study area,the fracture development area of 2# coal seam in the study area is predicted.The results show that:1.Wide-azimuth seismic data formed by wide-azimuth seismic exploration can be processed in OVT domain,which can obtain more azimuth and offset information than conventional processing,improve formation imaging accuracy,have good consistency ofOVT gathers,retain original acquisition characteristics,have the same near,medium and long-range energy after OVT migration,have good amplitude fidelity,and can retain azimuth information,which is beneficial to all directions of coal reservoirs.Heterogeneity study and fracture prediction.2.In the prediction of fracture development area in coal reservoir,because of the great variation of azimuthal anisotropy of seismic attributes and insufficient coverage times in the middle azimuth,the sensitive attributes of conventional post-stack fracture prediction are not necessarily applicable to coal reservoir,and many common fracture prediction attributes of each azimuth need to be extracted.Based on HTI medium theory,the root mean square vibration is screened out in this study.Amplitude,coherence and minimum negative curvature are sensitive attributes of fracture prediction in the study area,and the sensitive attributes are fused to reduce the multi-solution of single attributes,improve the prediction accuracy,and predict the fracture development area of 2# coal seam in the study area more accurately.3.By calculating and analyzing the azimuth seismic attributes and combining with the geological structure law of the study area,the fracture development area of 2# coal seam in the study area is predicted.In the northern part of the study area,the fracture development of 2# coal seam is mainly in the north-south and north-west positions.In the central part of the study area,the fracture development is mainly in the north-east direction.In the southern part of the study area,the fracture development is mainly in the north-south and east-west directions,which conforms to the law of regional geological structure and achieves good results.