Accurate evaluation of source rocks in source-reservoir integration: a case study of source rocks in Lucaogou Formation, Jimsar Sag, Junggar Basin

Abstract

In the Middle Permian Lucaogou Formation in the Jimsar Sag of Junggar Basin, source rocks and reservoirs are integrated. Crude oil impregnation is very common in core samples, which leads to the inaccurate determination of source rock evaluation parameters. The impact of migrated hydrocarbon on source rock evaluation was analyzed using chloroform extraction. The hydrocarbon potential of source rocks which were integrated with reservoirs in the Lucaogou Formation was evaluated accurately in view of different lithologies. The higher the content of soluble hydrocarbons in the source rock, the higher the deviation of the measured value of the source rock's total organic carbon, the higher the pyrolysis parameters S1 and S2, the lower the Tmax value, and the higher the hydrogen index. For source rocks integrated with reservoirs, chloroform extraction should be performed first, followed by pyrolysis analysis. For the Lucaogou source rocks in the study area, mudstones have the highest abundance of organic matter and comprise the best source rocks, followed by dolomites, which are good source rocks. Limestones are medium-good source rocks, while siltstones are mainly poor source rocks. The organic matter types of source rocks are mainly type Ⅰ, type Ⅱ1, and type Ⅱ2, with a small amount of type Ⅲ, which has reached the mature oil production stage. The organic carbon content, hydrogen index, and Tmax value of extracted source rocks can be effectively used for the accurate evaluation of the source rocks integrated with reservoirs or impregnated with oil.

Keywords

• source-reservoir integration
• source rock evaluation
• lucaogou formation
• middle permian
• jimsar sag
• junggar basin