| Autor: |
Lai, Jie, Guo, Jianchun, Ma, Yingxian, Zhou, Hangyu, Wang, Shibin, Liu, Yuxuan |
| Předmět: |
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| Zdroj: |
Rock Mechanics & Rock Engineering; Jan2022, Vol. 55 Issue 1, p35-49, 15p |
| Abstrakt: |
Acid treatment is widely used for exploiting tight limestone reservoirs, and how acid affects the microstructure and mechanical property of tight limestone needs deeper understanding. Tight limestone cores from Middle Ordovician Yijianfang Formation in Tarim Basin, China, were collected to conduct acid coreflooding tests, simulating acid–rock reaction process between tight limestone and gelled acid or crosslinked acid. After that, surface indentation tests were conducted to characterize the effect of acid–rock reaction on the mechanical properties of tight limestone. Microscopic characteristics of dissolution in limestone were evaluated by scanning electron microscope. The results indicated that limestone samples exhibited ultra-low porosity of less than 2.5%, ultra-low permeability of less than 6.00 × 10−17 m2 and tight microstructure with compactive grains and few intercrystal pores. Acid could hardly penetrate deep into the core samples with continuously high pumping pressure up to 8 MPa, showing that acid–rock reaction mainly occurred on the rock inlet surface. The size of dissolved pores and corrosion fractures created by acid–rock reaction were closely correlated with acid type and acid concentration, reflecting the changing rules of mechanical properties. Gelled acid could penetrate into the whole rock inlet surface and the size of dissolved pores and corrosion fractures evidently enlarged as acid concentration increased, comparable with the monotonically decreasing trend of surface hardness and Young's modulus. Crosslinked acid mainly penetrated into partial areas of the rock inlet surface and the size of dissolved pores and corrosion fractures increased slightly, consist with the phenomenon that surface hardness showed volatility and Young's modulus reduced stably. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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