Application of seismic waveform inversion in Ess4 beach-bar sandstone in Wangjiagang area, Dongying Depression

Key words:  waveform indication inversion  Bayesian theory  upper part of the fourth member of Shahejie Formation(Es^s₄)  beach-bar sand

Abstract:

The focus of the paper is the upper part of the fourth member of Shahejie Formation (Es^s₄) in Wangjiagang area, Dongying Depression. Based on Bayesian theory, a posterior probability density function of subsurface models was developed by establishing sequence stratigraphy framework, integrating the principles of sedimentology and information from seismic, well logs and geostatistics. The Metropolis-Hastings algorithm was applied to obtain an exhaustive characterization of the posterior probability density to predict the favorable beach-bar sedimentary facies. Results show that in the beach-bar sand development in the lowstand system tract (LST) of the Es^s₄, the bar sand is well developed, relatively thick, has large scale distribution, and less lateral variation in the second order para-sequence. The bar sand is interbedded with beach sand, and the overall thickness of the sand is relatively small in the first and third order para-sequences. The lacustrine transgressive system tracts (TST) and the highstand system tracts (HST) are mainly developed the carbonate beach-bar, and are less developed in sandy beach-bar. The aforementioned method is facies-controlled, which yields results that are more consistent with the geological observations. The proposed method works preferably in the Es^s₄, but may also be applied to other types of reservoirs.