Natural gas exploration of Ordovician Baota Formation in Well Weihan1 of Sichuan Basin and its significance
On November 1,2023,the gas yield from the Ordovician Baota Formation in Well Weihanl was 9.02 × 104m3/d,demon-strating the great exploration potential of Ordovician dolomite karst porous reservoir in Sichuan Basin.Taking this opportunity,based on comprehensively analyzing the sedimentary facies,reservoir lithology and physical properties of the Upper Ordovician Baota Formation in Weiyuan gas field,the study deeply analyzes the natural gas characteristics and distribution characteristics of Baota For-mation.Moreover,the advantageous hydrocarbon accumulation conditions of Baota Formation in Weiyuan area of Sichuan Basin are summarized and analyzed in terms of source,reservoir and cap.Three paleo-uplifts and three stages of tectonic movements controlled the Ordovician sedimentary filling in Sichuan Basin,and large-scale distribution of high energy beaches in Baota Formation around the central uplift of Sichuan Basin.Three types of reservoirs are developed in Baota Formation,i.e.,dolomite karst reservoir,limestone karst reservoir and fault-karst reservoir in weak dolomitization area,among them,Baota Formation in Well Weihan1 is dominated by dolomite karst reservoir.There are two sets of Ordovician accumulation assemblages.Weiyuan area is the upper hydrocarbon accu-mulation block developed on the slope background,and the source rocks are Silurian and Wufeng Formation.The caprocks are ab-sent in Well Weihan1,the source-reservoir-cap assemblage is mainly characterized by"lower generation and upper reservoir",and the gas source is from the Cambrian Qiongzhusi Formation.Baota Formation in Weiyuan area experienced the process of"oil accumu-lation followed by gas enrichment".The peak oil generation occurred in Late Permian,and the peak gas generation was in Early Ju-rassic.Controlled by the peritidal beach body,tectonic setting and strata,the structural-stratigraphic composite gas reservoir in the peritidal beaches of Baota Formation was developed under the background of large anticline structure in Weiyuan gas area.
Sichuan BasinBaota FormationWell Weihan1natural gas explorationcarbonate reservior
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