Characteristics of micropores, pore throats, and movable fluids in the tight sandstone oil reservoirs of the Yanchang Formation in the southwestern Ordos Basin, China
| Autor: | Ke Wang, Chunlin Zhang, Kesu Zhong, Fujie Jiang, Zhengfu Zhao |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Field emission scanning electron microscopy
020209 energy Tight oil Energy Engineering and Power Technology Mineralogy Geology 02 engineering and technology Structural basin Permeability (earth sciences) Fuel Technology Geochemistry and Petrology 0202 electrical engineering electronic engineering information engineering Earth and Planetary Sciences (miscellaneous) Porosity Dissolution |
| Zdroj: | AAPG Bulletin. 103:2835-2859 |
| ISSN: | 0149-1423 |
| Popis: | Thin-section analysis, field emission scanning electron microscopy, constant-rate mercury injection (CRMI), x-ray–computed tomography (X-CT), and nuclear magnetic resonance (NMR) were used to investigate pore systems, pore sizes, and pore-throat distributions and determine evaluation criteria for tight oil reservoirs. This research shows that the average porosity of the reservoirs in the Chang 63 to Chang 72 Members of the Yanchang Formation of the Ordos Basin ranges from 4% to 16%, with a corresponding average permeability of 0.1 to 0.4 md. The main pore types in these tight oil reservoirs are dissolution pores and intergranular pores, and the main pore-throat types are laminated throats and control-shaped throats. Based on experimental results, the pore-throat distributions differ among different testing techniques. The results of this study indicate that a combination of CRMI-derived and X-CT–detected pore-throat distributions is most suitable for calibrating NMR-derived pore sizes over the full range of pore sizes. The lower pore-throat radius limit of effective reservoirs is 0.24 μm, and the lower permeability limit for the flow of movable fluid is 0.008 md. Based on a cluster analysis, the studied tight oil reservoirs can be divided into three types. Compared with type III reservoirs (porosity 11% and permeability > 0.15 md) and type II (8% < porosity < 11% and 0.05 md < permeability < 0.15 md) reservoirs are of relatively good quality. |
| Databáze: | OpenAIRE |
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