Reservoir Characteristics of the Albian Upper Qamchuqa Formation Carbonates, Taq Taq Oilfield, Kurdistan, Iraq

Abstract

The Albian Upper Qamchuqa Formation in NE Iraq is part of an extensive dolomitized carbonate platform developed during the Barremian – Albian over the passive continental margin of NE Arabia. Recent drilling at the Taq Taq oilfield in Kurdistan has renewed interest in this formation as a reservoir unit. In this paper, the reservoir and petrophysical characteristics of the Upper Qamchuqa Formation at Taq Taq are described using data from wireline logs, cores and thin‐sections from four wells. At Taq Taq oilfield, the Qamchuqa Formation can be divided on the basis of lithology into two units: an upper Dolomite Unit and a lower Limestone Unit. The Dolomite Unit is 140–190 m thick and is dominated by massive dolomites and dolomitic limestones. High porosity values (up to 26%, estimated from well logs) were recorded in intervals comprising fine to medium crystalline planar‐e to planar‐s type dolomite which were frequently oil stained. Pore types include microvugs, moulds, fractures, stylolites and intercrystalline porosity. The Limestone Unit is 72–55 m thick and is composed mainly of bioturbated bioclastic limestones with minor dolomites. A wide range of carbonate facies are present and are dominated by foraminiferal wacke‐packstones and rudist packstones. Wireline log data was used to characterize the reservoir quality of the Qamchuqa Formation at Taq Taq. Four porosity units were recognized. The upper porosity units has the best reservoir quality with average porosities of 15 %, compared to the second unit (7.5%), the third unit (7%) and the fourth unit (4%). Different cut‐off values were estimated, and related petrophysical parameters were evaluated and were used to subdivide the reservoir succession into three reservoir units. The uppermost of these units was found to have the best reservoir characteristics and represents the upper part of the Dolomite Unit. It has a thickness of 31–43.5 m with 25–41 m of net pay and 82% oil saturation. Flow in this unit is dual, dominated by fracture flow superimposed on matrix flow.

Petrophysical Properties of the Upper Qamchuqa Carbonate Reservoir through Well Log Evaluation in the Khabbaz Oilfield

“…Increases in gamma ray log and decreases the density and sonic logs have being observed which indicates that the top of the Upper Qamchuqa reservoir is being overlined by the Dukan formation, and an increase in gamma ray log and decreasing sonic, N-D logs in the bottom of the Upper Qamchuqa indicates that it is underlined by the Upper Sarmord Formation. A similar relationship recorded in the Kirkuk Jambour and Khabbaz oilfields (Al-Shdidi et al, 1995;Al-Juboury et al, 2006;Ameen, 2008;Qadir, 2008;Al-Qayim et al, 2010;Al-Qayim and Rashid, 2012).…”

“…The Upper Qamchuqa Formation has being studied by Qadir (2008) and Al-Qayim and Rashid (2012) in the Khabbaz and the Taq Taq oilfields, respectively. The earlier study subdivided the formation into three main units based on lithological variation confirming the upper unit has the best reservoir characteristics, while later divided the Upper Qamchuqa into four units based on porosity variation as follows: The first unit has average porosities of 15 %, the second unit is 7.5%, the third unit is 7%, and the fourth unit is only 4%.…”

Petrophysical Investigation of the Khurmala Formation in Taq Taq Oil Field, Zagros Folded Belt

“…The Khurmala Formation lithologically comprised dolomitic limestone and dolomite rocks, and these lithologies have a potential to hold and transmit hydrocarbons in reservoir rocks. The calculated porosity in the studied wells is high enough to be considered as a productive reservoir rocks, especially the first (Kh-1), third (Kh-3), and fifth (Kh-5) porosity units as the average corrected total porosity is >0.10 (>10%) similar to the matrix porosity in Upper Qamchuqa and Pilaspi reservoir rocks (Al-Qayim and Othman, 2012;Al-Qayim and Rashid, 2012). However, after mud losing while drilling, a formation test flown sulfurous water at 3840 bpd in Tq-1 and saline water in TT-05 and TT-07 (NOC, 1987, Taq Taq Operation Company, 2006.…”

“…1b. The dominant targets in this field were Cretaceous formation including Upper Qamchuqa Formation (Al-Qayim and Rashid, 2012), Kometan Formation (Rashid et al, 2015a), Shiranish Formation (Garland et al, 2010), and Tertiary Pilaspi Formation (Al-Qayim and Othman, 2010; Al-Qayim and Othman, 2012).…”

“…Carbonate rocks are represented the dominant productive reservoir type in the Middle East (Hollis, 2011;Hollis et al, 2017;Jafarian et al, 2017;Adam et al, 2018) and this area holds nearly 15% of the world hydrocarbon reserves (Normi and Standen, 1997). The Iraqi Zagros basin is characterized by extension of different petroleum systems and heterogonous distribution of reservoir types including Triassic (Ryder Scott, 2011), Jurassic (Sherwani and Zangana, 2017), Cretaceous (Al-Qayim and Rashid, 2012;Rashid, 2015;Rashid et al, 2015a and b;Rashid et al, 2017;Ghafur and Hasan, 2017;Rashid et al, 2020), and Tertiary reservoir rocks (Al-Qayim and Othman, 2012;Hussein, 2015;Hussein et al, 2017;and Hussein et al, 2018).…”