Gas Hure Oilfield is the biggest one in the Qaidam Basin. Through intensive sampling and GC-MS a- nalysis, the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield. The re- sults...Gas Hure Oilfield is the biggest one in the Qaidam Basin. Through intensive sampling and GC-MS a- nalysis, the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield. The re- sults show that the crude oils have even-odd carbon predominance for n-alkanes. In shallow reservoir, part of crude oils suffered biogenic degradation. As for normal oils, they have low Pr/Ph ratios with abundant gammac- erane and C35 homohopane, which indicate that the crude oils are formed in strong reducing salt water environ- ment. Compared deep ( E~ ) reservoir with shallow ( N1 - N2^1 ) reservoir, the ancient salinity of sedimentary en- vironment of Nj-N1 crude oils is slightly higher than that of E3^1crude oils; the C21-/C22+ ratios of crude oils are 1.02-1.71 with a higher abundance of C27sterane, which shows that their mainly origin matrix are bacteria and algae; the C29 sterane 20S/(20S + 20R)is generally low, the ratio in deep E3^1 reservoir distributes between 0.31 and 0. 40, but in shallow reservoir is relatively low with 0. 29-0. 36. At the same time, C29sterane αββ(αββ +ααα) and Ts/Tm both are extremely lower. All the above show that the crude oils in Gas Hure are mainly low mature oils, although the maturity of deep reservoir crude oils is slightly higher than shallow one.展开更多
基金Supported by the National Natural Science Foundation of China (No. 40973041)
文摘Gas Hure Oilfield is the biggest one in the Qaidam Basin. Through intensive sampling and GC-MS a- nalysis, the authors analyzed the geochemical characteristics of the crude oils in the Gas Hure Oilfield. The re- sults show that the crude oils have even-odd carbon predominance for n-alkanes. In shallow reservoir, part of crude oils suffered biogenic degradation. As for normal oils, they have low Pr/Ph ratios with abundant gammac- erane and C35 homohopane, which indicate that the crude oils are formed in strong reducing salt water environ- ment. Compared deep ( E~ ) reservoir with shallow ( N1 - N2^1 ) reservoir, the ancient salinity of sedimentary en- vironment of Nj-N1 crude oils is slightly higher than that of E3^1crude oils; the C21-/C22+ ratios of crude oils are 1.02-1.71 with a higher abundance of C27sterane, which shows that their mainly origin matrix are bacteria and algae; the C29 sterane 20S/(20S + 20R)is generally low, the ratio in deep E3^1 reservoir distributes between 0.31 and 0. 40, but in shallow reservoir is relatively low with 0. 29-0. 36. At the same time, C29sterane αββ(αββ +ααα) and Ts/Tm both are extremely lower. All the above show that the crude oils in Gas Hure are mainly low mature oils, although the maturity of deep reservoir crude oils is slightly higher than shallow one.
