Prediction of thin shoal-facies reservoirs in the carbonate platform interior: A case from the Cambrian Xixiangchi Group of the Weiyuan area, Sichuan Basin

Abstract

This paper presents a geological prediction method of thin shoal facies reservoir through the analysis of shoal facies reservoir's genetic mechanism of the Middle-Upper Cambrian Xixiangchi Group in the Weiyuan area, Sichuan Basin. The development of shoal facies reservoirs is controlled by shoal thickness. Both sedimentary rates and scales of the shoal are closely related to microtopographic highs, which can develop inheritably for a long time under a stable tectonic background. So we present a prediction method that depositional microtopographic highs and shoal reservoirs' development probability can be portrayed by the thickness variation of isochronal geological bodies, which mainly composed of grain stone formed in a short time. Based on it, a prediction model was built for thin shoal facies reservoirs of the Middle-Upper Cambrian Xixiangchi Group, where useful geological data are extremely poor. The method was used to predict the distribution of shoal facies reservoirs within the research area. Later drilling showed that the prediction is consistent with the drilling result. This study can provide reference to the exploration of shoal facies reservoirs. Key words: carbonate platform, shoal, thin reservoir, prediction method, Cambrian Xixiangchi Group