Abstract
Thirty rock samples were selected from the well Tq-1 that penetrated the Jurassic beds in the Taq Taq Oilfield to be studied the source rock potentiality of the Sargelu Formation. The formation is characterized by three types of microfacies, namely, foraminiferal packstone, grainstone microfacies, fossiliferous packstone microfacies, and foraminiferal wackestone which were deposited in an environment extending from middle to outer carbonate ramp. An average of 3.03 wt.% of total organic carbon was obtained from a Rock Eval pyrolysis analysis carried out on 24 selected rock samples. The petrographic analysis for such organic matters revealed that they are of kerogen types III and IV and they are currently in a post-mature state. Pyrolysis parameters showed that limited generation potential was remained for these sources to expel generated hydrocarbons. The palynological study showed that Amorphous Organic Matter forms the highest percentage of organic matter components with more than 70%, followed by phytoclasts with 10 – 25 % and palynomorphs of less than 10%. The organic matters within the Sargelu Formation are deposited at the distal part of the basin under suboxic to anoxic condition. The color of the organic matter components, examined under transmitted light, showed Thermal Alteration Index values between 3+ and 4-. Such values may indicate that these organic matters are thermally at the end of the liquid oil generation zone and beginning of condensate-wet gas generation zone. The thermal maturity of the Sargelu Formation depending on the calculated VRo% revealed that the formation in the studied oilfield is currently at the peak of the oil generation zone. The Sargelu Formation in the studied field is considered as an effective source rock, as it has already generated and expelled hydrocarbons.
Highlights
Taq Taq Oilfield is located in Zagros Oil Province in the Kurdistan Region of Iraq, about 61 Km northeast of Kirkuk City and about 120 Km northwest of Sulaimani City (Fig.1)
This microfacies is mainly observed in the upper most and lower parts of the Sargelu Formation. This microfacies consists of black organic rich limestone and dolomitic limestone. It is characterized by the abundance of skeletal grains of benthic foraminifera including Siphovalvulina variabilis, Epistomina sp., Bosniella oenensis, Siphovalvulina sp., Lenticulina muensteri. (Figs. 5A-E respectively), Meandrovoluta asiagoensis, Pseudocyclammina sp., Ophthalmidium strumosum, Remondoedis lugeoni (Figs. 5G-L respectively), Orbitopsella primaeva (Fig. 6A), Haghimashella arcuata, Praepeneroplis senoniensis, Quinqueloculina sp. (Figs. 6C-E respectively)
Three main types of microfacies were identified in the Sargelu Formation
Summary
Taq Taq Oilfield is located in Zagros Oil Province in the Kurdistan Region of Iraq, about 61 Km northeast of Kirkuk City and about 120 Km northwest of Sulaimani City (Fig.1) This field is located within the Zagros Fold Belt Zone, the northeast unit of the Foot Hill Zone (ButmahChemchemal Subzone) (Jassim and Goff, 2006). There is a broad agreement that most of the accumulated oil in the Iraqi oilfield reservoirs is generated by the middle and upper Jurassic formations of Sargelu, Naokelekan, Barsarin, and Chia Gara. The properties of these formations as source rocks vary from place to place in the Iraqi territory. Different tools are used in the evaluation process and the results compared with work previously done on the same formation in nearby areas (Ahmed, 2001; Pitman et al, 2004; Al-Ahmed, 2006; Al-Ameri et al, 2014; Abdula, 2015; English et al, 2015; Fatah and Mohialdeen, 2016; Najaf, 2018, Hakimi et al, 2018; Kobraei et al, 2019; Mamaseni, 2020)
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