Integrated Formation Evaluation for Cretaceous Carbonate Khasib II of AD Oilfield, Iraq
- Limin Zhao (PetroChina Co. Ltd) | He Liu (Research Inst. Petr. Expl/Dev) | Rui Guo (China Natl. Petroleum Corp.) | Mingsheng Feng (China Natl. Petroleum Corp.) | Zhaowu Zhang (PetroChina Co. Ltd.) | Yaowen Zhang (CNPC) | Jun Wang (RIPED, PetroChina)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 22-24 October, Perth, Australia
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 5.5.2 Core Analysis, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.1.5 Geologic Modeling, 5.1.1 Exploration, Development, Structural Geology, 5.6.2 Core Analysis, 1.14 Casing and Cementing, 5.1.8 Seismic Modelling, 5.8.7 Carbonate Reservoir, 5.6.1 Open hole/cased hole log analysis, 1.6.9 Coring, Fishing, 5.1 Reservoir Characterisation, 1.6 Drilling Operations, 1.2.3 Rock properties
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AD oilfield is located in the southeast of Iraq and structurally it is a long axis gentle anticline in Mesoptamian foredeep. This oilfield is in the development planning stage. The accurate formation evaluation plays an important role in making development strategy. In this paper, integrated evaluations of major target formation, Cretaceous carbonate Khasib II were introduced with the combinations of available data.
Khasib II was mainly deposited within marine carbonate platform shoals and distributed stably in the full field with an average thickness of 40m. Based on the core data, four rock types are defined. Upwards lithology varies from planktonic foram micritc wackestone through green algae packstone to bioclastic and calcarenite grainstone. The porosities are almost same, about 25% while permeability varies in a large range for different lithology. Lower Khasib II planktonic foram limestone has no more than 1mD in permeability and no higher than 1ohm.m in resistivity while Upper Khasib II limestones have 10mD in average permeability and high resistivity. Reservoir spaces are mainly pores and vugs while fractures are not developed. Pore types are mainly intragranular pores, intergranular pores and intercrystal pores. Two throat types, the tubular throat and the lamellar throat are identified which are the major control factors for leading to the difference of permeability in lower and upper Khasib II. Test results show that lower planktonic foram limestone is dry and upper limestones produce oil which can be inferred that the low resistivity for lower Khasib II is resulted from the lithology rather than water. Reservoir distribution, petrophysical properties and fluid distribution for upper Khasib II are analyzed.
AD oilfield is located between Nomina Town and Kut Town of Wasit Province, 180km southeast away from Baghdad. Structurally it is a long axis gentle anticline in Mesoptamian foredeep basin. There are three crests in AD oilfield, namely east dome, middle dome and west dome. It was discovered to be oil-bearing in Cretaceous Carbonate Khasib formation by the first well AD-1 in late 1980's. Since then 7 exploration wells have been drilled to preliminarily delineate the structure and formation. The field activity was suspended since 1990 and re-started up since 2010. 3D seismic aquisition and coring actions were executed. Testing and core analysis were carried out for three domes. The accurate formation evaluation plays an important role in making the field development strategy. In combination of all available data Cretaceous carbonate Khasib II were evaluated. Lithology changes vertically in Khasib II, from planktonic foram limestone through algae limestone upper to bioclastic and calcarenite limestone, which was resulted from the sedimentary facies change. Although the porosity for Lower and Upper Khasib II is almost same while the permeability is very different. Throat sizes play an important role in formation permeability. Combined with core data and test data, the Lower Khasib II is determined as dry layer and the Upper is oil-bearing. Reservoir distribution, petrophysical properties and fluid distribution for upper Khasib II are analyzed.
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