Quantitative Interpretation of TOC in Complicated Lithology Based on Well Log Data: A Case of Majiagou Formation in the Eastern Ordos Basin, China

Source rock evaluation plays a key role in studies of hydrocarbon accumulation and resource potential. Total organic carbon (TOC) is the basis of source rock evaluation and it is a key parameter that influences petroleum resource assessment. The Majiagou formation in the eastern Ordos Basin has complicated lithology and low abundance of organic matters. There are different opinions over the existence of scale source rocks. Due to inadequate laboratory data of TOC in the Ordos Basin, it is difficult to accurately describe source rocks in the region; thus, log interpretation of TOC is needed. In this study, the neural network model in the artificial intelligence (AI) field was introduced into the TOC logging interpretation. Compared with traditional ΔlogR methods, sample optimization, logging correlation analysis and comparative optimization of computational methods were carried out successively by using measured TOC data and logging data. Results show that the neural network model has good prediction effect in complicated lithologic regions and it can identify variations of TOC in continuous strata accurately regardless of the quick lithologic changes.

Source Rock Evaluation of the Upper Triassic Baluti Formation in Bekhme-1 and Gulak-1 Wells from Akri-Bijeel Block, Kurdistan-Iraq

This study reports on the petroleum potential of the Upper Triassic Baluti Formation in Bekhme-1 and Gulak-1 Wells from Akri¬-Bijeel Block within the Bekhme Anticline area, North of Erbil City. The area is a part of the Zagros Fold and Thrust Belt, and is locally situated within the High Folded Zone. Typically, the Baluti Formation is composed of gray and green shale calcareous dolomite with intercalations of thinly bedded dolomites, dolomitic limestones, and silicified limestones which in places are brecciated. The geochemical indicators obtained from Rock-Eval pyrolysis of Baluti samples gave Total Organic Carbon content (TOC wt. %) average values of 0.15 and 0.18 wt. % and potential hydrocarbon content (S2) average values of 0.78 mg HC/g rock and 0.58 mg HC/g rock for Bekhme-1 and Gulak-1 respectively, suggesting a source rock of poor potential. The type of organic matter is of mixed type II-III and III kerogens with an average Tmax value of 440 °C for both boreholes, exhibiting early to peak stage of thermal maturity. Considering the results of this study, it is concluded that Baluti Formation in the studied area can not be regarded as a potential source rock for hydrocarbon generation.