Pollutant migration behavior in slurry ponds at Ordos Basin gas well sites
With an acceleration in the rate of gas exploration in Ordos Basin, more and more waste drilling mud has been discharged. After a series of treatment, the waste mud had been buried in some slurry ponds. So a significant number of ponds are scattered in the basin, which give more harm to the fragile ecological environment. But until now, there is little research focusing on real environmental effects of pollutants in slurry ponds. This research chose five slurry ponds used in succession during 2005 and 2009 as targets. The migration behavior of organics, oil and sulfide was studied, and their possible effects on shallow groundwater were forecasted. The results showed that the order of these three pollutants' effects on environment was sulfide>;oil>;organics. According to the migration behavior of mentioned pollutants, it came to conclusion that the sulfide and oil in the slurry ponds used over two years should have brought much influence on shallow groundwater.
Asphaltene structure in reservoir affected by discharge of secondary condensate oil: laboratory simulation
The oil accumulated probably changed in chemical characters due to discharge of natural gas and condensate oil generated later. This process has been simulated by the adding of petroleum ether to crude oil instead of condensate oil, and the structure of asphaltenes from the Well Lunnan 1, Tarim Basin precipitated under various petroleum ether: crude oil ratio was investigated by flash pyrolysis-GC-MS. It is found that the chemical structure of asphaltene precipitated from oil have not been changed yet when petroleum ether was added continuously. The pyrolysate of asphaltenes can be used as the substituent of low molecular compounds for oil-source rock correlation and also for identification of oil source whatever the oil reservoir in superposition basin was discharged by secondary gas or condensate oil. The major contributors to these alkyl components might be non-saponifiable and aliphatic biopolymers in the cell walls of some algae species. The high abundance of 1,2,3,4-tetramethylbenzene in the pyrolysate of the asphalting may derived from photosynthetic green sulphur bacteria, which indicated the precursor of the oil from the Well Lunnan1 were formed under strongly reducing conditions.
Evaluation and Control of Collapsible Soils
Some compacted soils wetted under certain conditions of compaction and loading may exhibit additional settlement (collapse). To investigate the effect of the soil type, compaction water content, initial dry unit weight and applied pressure at wetting on collapse potential, 138 single‐oedometer tests were conducted on eight different soils. The results indicate that well‐graded soils tend to collapse more than poorly graded ones under similar conditions. Furthermore, collapse potential decreases with an increase in (1) The difference between the sand and clay percentages; (2) compaction water content; and (3) initial dry unit weight, while it increases with pressure at wetting. A multiple regression analysis was performed on the laboratory results to provide a collapse‐predictive model that was substantiated by data reported by several researchers. A chart is presented to estimate (1) The collapse potential of soils under various conditions; and (2) the critical water content beyond which no collapse is ex...