| Based on the former integrated geological researches in the north fringe of Qiadam Basin, particularly on the evaluation on the potential capability of hydrocarbon source rock in the region, the developing strata of hydrocarbon source rock and their distribution, the contrast between oil source and gas source, the process and the model of the forming of oil and gas pool, and favorable exploration targets in the region have been studied and discussed thoroughly in this paper. A series of systematic theories including contrast analytical technology between oil source and gas source, classification and evaluation technology of hydrocarbon source rock, technology of thermo history and hydrocarbon creation history, and limitation technology of reservoir formation period were applied or adopted during the researches. Through the researches, a good sag of generating hydrocarbon in the region is determined; and the main factor of controlling the oil and gas and the law of accumulating oil and gas are identified as well. In addition, favorable exploration areas and targets in the region are pointed out in the paper.The north fringe of Qiadam Basin is located in the north-east part of the basin, the area is about 30000 km2, and the sedimentation strata include Jurassic (J) and Cretaceous (K) of Mesozoic (Mz), and Tertiary (R) and Quaternary (Q) of Cenozoic (Kz). According to the content, the type and the maturity of organic matter in hydrocarbon source rock, two sets of hydrocarbon source rock in the region are determined. One is lower Jurassic hydrocarbon source rock and the other is middle Jurassic hydrocarbon source rock. The abundance of organic matter in both hydrocarbon source rocks is relatively high. The type of organic matter in lower Jurassic hydrocarbon source rock mainly belongs to mixed type (type â…¡2), and the maturity is from middle to high. The type of organic matter in middle Jurassic hydrocarbon source rock mainly belongs to type â…¢, but â…¡2 petroliferous shale also exist partially (J2d7), and the maturity of organic mater is from middle to low. In terms of molecular geochemistry indexes, the hydrocarbon source rocks both in lower Jurassic and middle Jurassic can be classified as lake facies and swamp facies. For the hydrocarbon source rock in lake facies, both the ratio of Pr/Pn and the ratio of C19/C21 of tricyclic terpenes are lower, but the ratio of C26 of tricyclic terpene to C24 of quartcyclic terpenes and the ratio of gammaceran to C30 of hopane are higher; in addtion, C27 regular steranes is relatively abundant but the C29 regular steranes is relatively poor. Contrary to the hydrocarbon source rock in swamp facies, the ratios ofabove parameters are the very reverse. Correspondingly, crude oil in the region can be classified as lake facies and swamp facies according to above molecular geochemistry indexes; besides, mixed crude oil with the characteristics of lake facies and swamp facies simultaneously exists in the region. Based on the distribution of hydrocarbon source rock and the comparison of oil-source, the oils and gases in Lenghu and Nanbaxian structure belt come only from lower Jurassic hydrocarbon source rock; on the other hand, the oils and gases in the areas of Yuqia, Mabei, Hongshan and Luliangshan come from middle lower Jurassic hydrocarbon source rock only.In t erms o f the characteristics o f hydrocarbon so urce rock and the analysis o f oil-source in north fringe of Qiadam Basin, two main oil and gas systems can be classified, one of them is J1-J1/ E/ N system of Kunyite Sag and the other is J2-J3/E/N system of Saishenteng-Yuqia-Gaqiu Sag. The distribution area, static geological elements, and the basic geological functions of the two oil and gas systems have been analyzed and discussed in the paper. On the basis of elaborate analyses on the typical oil and gas pools in north fringe of Qiadam Basin, the characters of oil/gas forming and the law of oil/gas accumulation are summarized. Furthermore, favorable exploration areas are pointed out.
|
PDF Full Text Request