Quantitative prediction of seismic rock physics of hybrid tight oil reservoirs of the Permian Lucaogou Formation, Junggar Basin, Northwest China

Abstract

Abstract Tight oil exploration and development in the Jimusar Sag of southeastern Junggar Basin of Northwest China has led to development of two reservoir segments in the Lucaogou Formation. The upper segment is mostly carbonate rocks, while the lower segment consists mainly of fine-grained clastic rocks. Both segments are mixed with clay, sand, and dolomite, which makes it difficult to identify the lithology and predict the porosity using a traditional seismic rock physics template (RPT). We analyzed the trends of ultrasonic P-wave impedance and Vp/Vs of laboratory data changing with lithology, porosity, and total organic carbon (TOC) content. Our data provide parametric sensitivity regarding porosity and TOC content by use of a bi-material-matrix–double-inclusion concentration model. We propose a modified RPT of P-wave impedance versus Vp/Vs with three end members (sandstone, dolostone, and mudstone) to predict porosity and lithology of reservoirs. We also present a new RPT of density versus Poisson ratio with the same three end members to predict TOC content and lithology of source rocks. These were validated by comparisons with laboratory measurements and log data. We inverted the porosity, TOC content, and thickness of the upper reservoir segment in the Lucaogou Formation of the J17 work area of Jimusar Sag by using the new RPT quantitative prediction method. The inversion results were identical to oil testing results, supporting the viability and effectiveness of the new RPTs.