SUN Gang (1978-), male, Engineer. E-mail: sungang@cosl.com.cn
High-temperature high-pressure (HTHP) working conditions of oil-well cement paste alter the expansive mechanism of MgO expansive agent, thus significantly accelerating the expansion speed and increasing the ultimate expansion. The free expansion rate of shrinkage-compensating pastes with MgO expansive agent at different contents was investigated. The microstructural characteristics, including morphology and porosity, were evaluated to reveal the expansive mechanism of MgO expansive agent in HTHP environment. It is indicated that the shrinkage of oil-well cement paste can be compensated by admixing MgO expansive agent at proper contents and reactivity. At 150℃ and 20 MPa, S-type (220 s) MgO with a relatively low reactivity is recommended and its dosage is less than 4%. At HTHP, the migration of Mg2+ from MgO particles is accelerated. Besides the formation of expanding mircocracks, Mg(OH)2 crystals also are interlocked with tobermorite crystals as a hydration product of cement, thus enlarging their gap and causing an extraordinary expansion, compared to the expansive binder cured at normal temperature and pressure.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |