Lithofacies and Diagenetic Controls on Tight Silty and Sandy Upper Triassic Reservoirs of the Heshui Oil Field (Ordos Basin, North China)
Hu, Chenlin (School of Geology and Mining Engineering and Xinjiang Key Laboratory of Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University) | Han, Changcheng (School of Geology and Mining Engineering and Xinjiang Key Laboratory of Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University (Corresponding author)) | Tian, Jijun (School of Geology and Mining Engineering and Xinjiang Key Laboratory of Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University (Corresponding author)) | Fu, Zhiqiang (School of Geology and Mining Engineering and Xinjiang Key Laboratory of Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University (Corresponding author)) | Ma, Jinghui (School of Geology and Mining Engineering and Xinjiang Key Laboratory of Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University (Corresponding author)) | Algeo, Thomas J. (Department of Geology, University of Cincinnati)
Summary Tight oil, present in reservoirs of low porosity and permeability, can be regarded as a kind of unconventional resource. The tightening process in this kind of reservoir is controlled by the lithology and diagenetic history of the host formation. Upper Triassic Yanchang Formation siltstones and sandstones are the main reservoirs for hydrocarbon accumulation in the Heshui Oil Field (HOF), southwestern Ordos Basin. The reservoirs exhibit low porosity, low permeability, and strong heterogeneity. In recent years, numerous drillcores have been recovered from these units, but the porosity-permeability characteristics and burial history of these silty and sandy reservoirs have not yet been reported in detail. In this study, an integrated analysis of the lithofacies, diagenesis, and reservoir characteristics of the siltstones and sandstones was achieved using a combination of core and thin section, grain size, scanning electron microscopy (SEM), X-ray diffraction (XRD), δC and δO, mercury intrusion capillary pressure (MICP), and porosity and permeability data. Our primary goals were to quantify the porosity-permeability characteristics of these silty and sandy reservoirs, restore their diagenetic histories, and examine the paragenetic relationship of reservoir tightness to hydrocarbon accumulation. The silty and sandy reservoirs represent braided river delta facies consisting of compositionally and texturally immature sediments. In the burial environment, they underwent complex diagenetic processes that reduced porosity from an initial average of ~38% to the present ~8%. Porosity-destructive processes included compaction (~ –12.5%) and cementation (~ –21%), with increases in porosity related to grain dissolution (~ +2.2%) and tectonic fractures (~ +1.1%). The reservoirs underwent four diagenetic stages: (1) Penesyngenetic and Eogenetic A Stage (Late Triassic-Early Jurassic); (2) Eogenetic B Stage (Late Jurassic); (3) Early Mesogenetic A Stage (Early Cretaceous); and (4) Late Mesogenetic A Stage (Late Cretaceous to recent). Hydrocarbon charging of these reservoirs occurred in three pulses. Existing pore space was partly filled by hydrocarbons during the Eogenetic B Stage. A second hydrocarbon charging event occurred during the Early Mesogenetic A Stage, when residual primary intergranular pores and secondary dissolution pores were filled. A third hydrocarbon charging event occurred during the Late Mesogenetic A Stage, when the reservoirs were tight. Siltstone beds deposited in delta front environments are the main future exploration targets in the Chang 6 to 8 members. The results of this study provide a useful reference framework for future exploration of hydrocarbon resources in the Upper Triassic Yanchang Formation of the HOF, as well as potential insights into the evolution of similarly tight reservoirs in other basins.
SPE-214289-PA
SPE Reservoir Evaluation & Engineering
January, 2023
OnePetro PDF doi: 10.2118/214289-PA
- Country:
- Asia
- China
- Gansu Province (0.86)
- Shaanxi Province (0.86)
- Shanxi Province (0.73)
- Middle East > Israel
- Southern District (0.24)
- China
- North America > United States
- Montana (0.68)
- Asia
- Genre:
- Research Report > New Finding (0.86)
- Geologic Time:
- Phanerozoic > Mesozoic
- Cretaceous (1.00)
- Triassic > Upper Triassic (1.00)
- Phanerozoic > Mesozoic
- Geology:
- Geology
- Rock Type > Sedimentary Rock
- Clastic Rock > Mudrock (1.00)
- Sedimentary Geology (1.00)
- Rock Type > Sedimentary Rock
- Geology
- Geophysics:
- Geophysics (0.46)
- Oilfield Places:
- Africa > Middle East
- Egypt > Gulf of Suez > Gulf of Suez Basin > October Field (0.99)
- Asia
- China
- Jiangsu > Subei Basin (0.99)
- Qinghai > Qaidam Basin (0.99)
- Shanxi > Ordos Basin
- Changqing Field (0.99)
- Shaanxi > Ordos Basin
- Changqing Field (0.99)
- Inner Mongolia > Ordos Basin
- Changqing Field (0.99)
- Daniudi Field (0.99)
- Sichuan > Sichuan Basin (0.99)
- Ningxia > Ordos Basin
- Changqing Field (0.99)
- Northeast China > Songliao Basin
- Quantou Formation (0.99)
- Gansu > Ordos Basin
- Changqing Field (0.99)
- Middle East
- Iran > Khuzestan
- Zagros Basin > Ramshir Field > Bangestan Formation (0.99)
- Iraq > Kurdistan
- Zagros Basin > Kometan Formation (0.99)
- Iran > Khuzestan
- China
- Europe > Germany
- Saxony Basin (0.99)
- North America
- Canada > Alberta
- United States
- North Dakota > Williston Basin
- Bakken Shale Formation (0.99)
- Wyoming
- DJ (Denver-Julesburg) Basin > Codell Formation (0.93)
- Laramie Basin > Niobrara Formation (0.99)
- Colorado
- DJ (Denver-Julesburg) Basin > Codell Formation (0.93)
- Laramie Basin > Niobrara Formation (0.99)
- Piceance Basin > Williams Fork Formation (0.99)
- Montana > Williston Basin
- Bakken Shale Formation (0.99)
- New Mexico > Orogrande Basin (0.99)
- Kansas > Laramie Basin
- Niobrara Formation (0.99)
- Texas
- Nebraska > Laramie Basin
- Niobrara Formation (0.99)
- South Dakota > Williston Basin
- Bakken Shale Formation (0.99)
- North Dakota > Williston Basin
- Oceania > Australia
- Victoria > Bass Strait > Gippsland Basin (0.97)
- South America
- Africa > Middle East