Major factors affecting the closure of marine carbonate caprock and their quantitative evaluation: A case study of Ordovician rocks on the northern slope of the Tazhong uplift in the Tarim Basin, western China
| Autor: | Hongfeng Yu, Zhongkai Bai, Yafang Wang, Xiuxiang Lü |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
020209 energy
Stratigraphy 02 engineering and technology 010502 geochemistry & geophysics Oceanography 01 natural sciences chemistry.chemical_compound Caprock 0202 electrical engineering electronic engineering information engineering Petrology Geomorphology 0105 earth and related environmental sciences Cement business.industry Fossil fuel Drilling Geology Diagenesis Geophysics chemistry Ordovician Carbonate Carbonate rock Economic Geology business |
| Zdroj: | Marine and Petroleum Geology. 83:231-245 |
| ISSN: | 0264-8172 |
| DOI: | 10.1016/j.marpetgeo.2017.03.006 |
| Popis: | There are many examples of oil and gas reservoirs throughout the world that have tight carbonate rock as the caprock. These oil and gas reservoirs are often vertically overlapped (with multiple oil and gas sections) and laterally connected (to many oil and gas reservoirs). The closure of carbonate caprock is affected by many factors, such as the clay content, differential diagenesis and layer thickness. As evaluation parameters, the clay content can be determined by a gamma ray well-logging curve; the differential diagenesis is reflected in filling effects, rupture effects, cement composition and content and can be measured through the displacement pressure; the layer thickness can be obtained from drilling and well-logging data. In different regions or different members, the factors and parameters to be considered or evaluated for the closure are dependent on actual geological conditions. In this study, the clay content, displacement pressure and layer thickness were analysed, determined, calculated and normalized to generate an overall closure evaluation index (λ) for the caprock in wells on Ordovician Liang 3–5 mud-bearing limestone members on the northern slope of the Tazhong uplift. On the plane distribution map, the area with λ ≥ 1 was effectively sealed. The tight carbonate in the inner Yingshan Formation (with high-resistivity, referred to as a high-resistivity layer) was also effectively caprock. Regardless of whether it can seal oil and gas, the sealing capacity mainly depends on the displacement pressure difference between the high-resistivity layer and the underlying carbonate reservoir. Based on drilling results and the comparison of the displacement pressure difference between the two layers (by actual measurements and calculations), we observed that when the pressure difference is more than 1.95 MPa, it is an effective caprock. |
| Databáze: | OpenAIRE |
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