The application of multi-seismic hydrocarbon detection technology to gas identification in B oilfield

The target field is in the early stage of development with few drilling wells.Unclear boundary of gas reservoir in the target area affects accurate calculation of oil field reserves and well pattern deployment for later development.To solve this problem,the authors analyzed the seismic response characteristics of gas-bearing reservoirs in the target area by spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,and then predicted the boundary of gas-bearing reservoirs in the target area.The result shows that the gas-bearing reservoir in the target area is characterized by "low frequency resonant and high frequency attenuated".That means the increase of low frequency energy and the decrease of high frequency energy due to the attenuation of seismic wave.Through AVO forward analysis of drilled well,it can be determined that the gas-bearing reservoir in the target area belongs to class III AVO anomaly,and its seismic positive amplitude increases with the increase of offset distance.Among the petrophysical parameters,Lame's coefficient,Poisson's ratio and P-S wave velocity ratio are sensitive to gas-bearing sandstone.Besides,Poisson's ratio is the best one for distinguishing gas-bearing sandstone and can reveal the gas-bearing reservoir and predict its plane distribution.Applying spectral decomposition energy attenuation,AVO analysis and pre-stack elastic parameter inversion technology,the authors detected gas-bearing reservoirs. With the application of multi-technology,the prediction precision of gas-bearing reservoir boundary can be improved and this would provide support for accurate calculation of reserves and development of well pattern deployment in the target area.