Integrated organic geochemistry with palynofacies analysis of the Chia Gara Formation in the Kirkuk and Hamrin oilfields, North Iraq

S.Y El Beialy,A.Q Mahdi,W Sh El Diasty,A M Al Tarif

doi:10.32894/kujss.2016.124393

Abstract

The idea of the present work was to combine Rock-Eval pyrolysis and palynofacies analysis in an integrated approach to study 51 source rock cores and cuttings samples collected from the middle Tithonian- Berriasian Chia Gara Formation, in well K-109, Kirkuk Oilfield and well Hr-1 drilled in the Hamrin Oilfield, north of Iraq to evaluate quantitatively and qualitatively the nature of sedimentary organic matter, generation potential and assess thermal maturity of the studied formation in both wells. Rock-Eval pyrolysis and palynofacies data indicate that the Chia Gara Formation in well K-109, Kirkuk Oilfield has kerogen type III/II and II/I and the amorphous organic matter AOM is dense and amber brown to very dark brown in color assigned to type C and D which reflects mature to overmature stage (gas-oil prone). On the other hand, the source rock samples of the Chia Gara Formation encountered in well Hr-1, Hamrin Oilfield has kerogen type II/III and II/I and the AOM is dense rounded, yellow to yellowish brown typeD, mature and is oil-gas prone. The regional tectonic movements and thermal history may cause the diversity in kerogen type and the subtle color variation in the AOM from the Chia Gara Formation in the Kirkuk Field in the north to Hamrin Field in the south.

Highlights

‫تتمثل فكرة البحث في دمج طريقة الانحلال الح ارري مع طريقة السحنات البالينولية الدقيقة لأحدى وخمسون عينه‬ ‫صخرية (لباب وفتات)‪,‬لتكوين جياكا ار من حقمي كركوك وحمرين‪,‬شمال الع ارق وذلك لعمل د ارسات كمية ونوعية لطبيعة‬
Fifty-one core and cuttings samples recovered from the Chia Gara Formation in Kirkuk and Hamrin oilfields, northern Iraq, have been subjected to total organic carbon (TOC) and Rock-Eval pyrolysis analyses, which were conducted in StratoChem Laboratory, New Maadi, Cairo, Egypt
The Chia Gara rock samples in the Hr-1 well, Hamrin Oilfield contain 1.01–1.37 % TOC, and yield Rock-Eval S2 values ranging from 2.28 to 3.80 mg HC/g Rock (averaging 3.07 mg/g; Table (1). These data indicate that the petroleum potential of the Chia Gara Formation changes from fair–excellent in well K-109 (Kirkuk Oilfield) to good in well Hr-1 (Hamrin Oilfield; Fig. (3)

Summary

GEOLOGIC BACKGROUND

The study area Fig. (1) is located in the northwestern part of the Zagros fold-thrust belt of the northeast Iraq. The Arabian Shelf in northern Iraq can be divided into Unfolded Area or Stable Shelf and a Folded Zone or Unstable Shelf [4,7,8,9]. [8] and [9] recognized five tectonophysiographic zones: three in the unstable shelf, and two in the stable shelf These tectonic zones include 1) the Thrust Zone, 2) the Folded Zone, 3) the Mesopotamian Basin, 4) The Salman Zone, and 5) The Rutbah-Jezira Zone. Folds generally flatten towards the Mesopotamian Basin where relatively narrow anticlines are separated by wide synclines These structures are open and simple with few thrusts [11]; its geometry suggests that it is a forced fold above the suspected Zagros Foredeep Fault Zone, which is thought to have been reactivated in the Pliocene to Recent [12]. The formation is uniform throughout Iraq, consisting of two basic lithofacies types: thinly bedded limestone and calcareous shale in the lower part of the section, followed upward by marly limestone and marl [6]

Samples and analytical procedures

RESULTS AND DISCUSSION

CONCLUSIONS