Fine modeling on buried anticlines and its application:Examples from the Carboniferous gasfields,eastern Sichuan Basin
Exploration domains on high-steep structures of eastern Sichuan Basin are dominated by anticlinal traps.Limestone exposure to anticlines with poor preservation can result in a little value in the exploration.In contrast,boasting better preservation,burial anticlines grow into favorable belts to accumulate natural gas.The Carboniferous gas reservoirs in eastern basin belong to structural-trapped ones.How to ascertain their trap morphology is very important because of the effect on drilling success.So far,the natural gas in the Carboniferous burial anticlines have entered the stage of potential tapping.But there still exist such anticlines with unconfirmed seismic data or large depth error in logging-seismic interpretation,which need to be further studied.So,based on seismic profiles,surface geology,drilling and logging data,some fine modeling on the burial anticlines was proposed.And such anticlines were divided into 4 categories,including 7 subcategories and 30 classes.Both exploration and development endings were evaluated with regards to the 4 categories.Results show that(ⅰ)model forward and inversion can be conducted,which are beneficial for analyzing complex wavelength,time-domain structural distortion,and high-point migration patterns;(ⅱ)to create a reasonable time-depth conversion and pre-stack depth migration velocity model can improve the reliabil-ity of depth-domain structural morphology;and(ⅲ)for steeply burial anticlines,determining their basic types and morphology based on reflection characteristics of horizontally-stacked time profiles may avoid any pseudo-burial anticlines representing in the depth domain.The proposed fine modeling on this kind of anticlines in eastern Sichuan Basin will play a positive role in the further exploration of the Carbonif-erous gas reservoirs.
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