Research paperEvaluation of source rock potential, matrix effect and applicability of gas oil ratio potential factor in Paleocene-Eocene bituminous shales of Çamalan Formation, Nallıhan - Turkey

•Rock Eval pyrolysis and organic petrography for samples of Çamalan Formation.•Determination of matrix retention effect and Gas-Oil ratio potential factor (GORP).•An excellent oil-prone source rock with an average Tmax and spore color index (SPI) values of about 440 °C and 3, respectively.•Results from GORP factor and visual kerogen studies are in acceptable agreement.

In order to improve the reliability and accuracy of source rock evaluation, a total of 102 shale samples of Çamalan Formation were collected, analyzed and re-characterized with taking matrix retention effect into account. Results from Rock-Eval and visual kerogen analyses indicate: 1. an excellent source rock with an average TOC of 6.39 wt.%. 2. An assemblage of amorphous (i.e., alginite, type I) organic matter as a major organic constituent with an excellent potential for generating oil. 3. Shale samples from Çamalan Formation are in immature/early-intermediate stage of maturity based on Tmax (Avg. ∼440 °C) and spore color index (SCI ∼2.5-4). Also no amount of Çamalan generated oils are migrated out of shale based on S1 vs. TOC plot. (i.e., Transformation ratio (TR ∼0)). Samples of this study show a significant mineral matrix effect. After correction of mineral matrix effect the average hydrogen index (HI) of the Çamalan Formation increased by more than 60 mg HC/g TOC and reached to an average of 811 mg HC/g TOC. Gas oil ratio potential (GORP) factor were used in order to split up the TOC and S2 into oil-prone and gas-prone and also to investigate the level of consistency between the results of GORP factor and those of visual kerogen studies. Based on obtained GORP factor more than 90% of TOC(live) is composed from oil-prone materials which is in acceptable agreement with petrographic assessments.