Abstract
Organic-rich shales in between salt rock layers distribute widely in Qianjiang Sag, Jianghan Basin, central China. Due to the complexity of matrix mineral components and their distribution and tight pore structure, Archie’s law cannot be used directly to calculate oil saturation in those shale oil reservoirs. A new oil content model for shale oil reservoirs was introduced. By analyzing the logging and core experimental data from Qianjiang Sag, Jianghan Oilfield, we built the relationship between kerogen and the different well logging porosities including nuclear magnetic resonance (NMR) porosity, neutron porosity, and density porosity. And we used the dual- V sh method to calculate the total organic carbon (TOC). After calculating the volume fraction of the solid organic matters and separating it from the TOC, we acquired the hydrocarbon fluid content in the formations. The calculated oil content results are coherent with the core experimental data, which indicates the efficiency of this model. This model is simple and can be quickly applied. However, this method also shows its weakness in calculation precision when the TOC is not calculated precisely or the quality of the porosity logs is low.
Highlights
Shale oil resources develop vastly in China, which are mainly lacustrine, including the Paleogene shale oil plays in the Bohai Bay Basin, the Triassic shale oil plays in the Ordos Basin, the Eocene shale oil plays in the Pearl River Mouth Basin, the Middle Permian Lucaogou Formation, Jurassic Xishanyao formation shale oil plays in the Junggar Basin, Cretaceous Qingshankou Formation in the southern Songliao Basin, and the intersalt shale oil plays in Qianjiang Formation in the Jianghan Basin [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
The method introduced in the above section was applied in well B and well W located in Qianjiang Sag
Conventional methods for calculating oil content are all based on conductive properties of the pores, which is difficult to realize in shale oil reservoirs
Summary
Shale oil resources develop vastly in China, which are mainly lacustrine, including the Paleogene shale oil plays in the Bohai Bay Basin, the Triassic shale oil plays in the Ordos Basin, the Eocene shale oil plays in the Pearl River Mouth Basin, the Middle Permian Lucaogou Formation, Jurassic Xishanyao formation shale oil plays in the Junggar Basin, Cretaceous Qingshankou Formation in the southern Songliao Basin, and the intersalt shale oil plays in Qianjiang Formation in the Jianghan Basin [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] Those shale oil plays have variable total organic carbon content (TOC) and strong heterogeneity. How to accurately estimate the in-place oil content in oil-bearing shales is a remaining challenge
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