Abstract
In recent years, new oil reservoirs have been discovered in the middle Jurassic tight mixed rocks of the Turpan–Hami Basin. However, the generation potential of the J2q2 source rocks remains poorly understood. Petrographic, petrological, and geochemical analyses were carried out to assess the quality of the J2q2 source and reservoir rocks. The hydrocarbon generation potential method was utilized to evaluate the hydrocarbon generation and expulsion potentials. The results indicated that the rocks can be classified as high-quality source rocks with a relative lower degree of maturity. The hydrocarbon bearing zones are classified as tight reservoirs (average porosity of 5.90% and permeability of 0.18 mD) with an average pore throat radius >150 nm, which is higher than the cut-off pore-throat radius. The source rocks start to expel hydrocarbons when Ro% is 0.56%. Bulk hydrocarbon generation and expulsion intensities in the center of the study area were calculated with the values of 900 × 104 t/km2 and 400 × 104 t/km2, while the weights of these hydrocarbons were 48.8 × 108 t and 27.3 × 108 t, respectively. The tight oil reservoir-forming conditions are superior, and the hydrocarbon generation and expulsion intensities are more remarkable in controlling the tight oil distribution. This study provides an important example for the Jurassic source rocks in Western China, and indicates that middle Jurassic lacustrine source rocks deserve attention in future exploration.
Highlights
The qualities of source rocks are the material factors that control petroleum generation and accumulation; they are prerequisites in hydrocarbon exploration and prospect appraisal, especially for unconventional resources (Hu et al, 2018; Jia et al, 2016)
More than 90% of the world’s recoverable hydrocarbon reserves are produced from six sets of source rocks, including Jurassic source rocks which account for about 25% of the total source rocks in the whole geological period, and Jurassic tight oil reserves account for 31.0% of the total tight oil resources (Klemmeetal, 1991; Ma et al, 2014; Wang 2016; Zou et al, 2015)
These data indicate that the source rocks have high hydrocarbon generation potential
Summary
The qualities of source rocks are the material factors that control petroleum generation and accumulation; they are prerequisites in hydrocarbon exploration and prospect appraisal, especially for unconventional resources (Hu et al, 2018; Jia et al, 2016). The Jurassic source rocks in Qaidam Basin, Yabrai basin (The estimated resource of tight oil is 0.92 Â 108 t) are of high quality and have potential for tight oil exploration (Fu et al, 2013; Gao et al, 2017; Liu et al, 2008). These examples showed that there are considerable tight oils in Jurassic stratum. The study on the quality of source rocks and tight oil resource potential of the second member of Qiketai formation will provide an important research example, which will be helpful to promote the exploration and research of tight oil in the Jurassic system
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