The seismic response feature and the distribution prediction of oolitic beachs of Feixianguan Formation in the northern Sichuan Basin
Zhou Lu1, Ren Benbing1,2, Wu Yong1, Li Dong3, Li Fei4, Liu Zhimin1, Yuan Bing1
1. State Key Laboratory of Reservoir Geology and Development, Southwest Petroleum University, Chengdu 610500;
2. Exploration and Development Research Institute, Xinjiang Oil Company, PetroChina, Karamay, Xinjiang 834000;
3. Research Institute of Hangzhou Geology, PetroChina, Hangzhou, Zhejiang 310023;
4. Southwest Oil and Gas Field Company Sichuan Petroleum Gas Field, PetroChina Co. Ltd., Suining, Sichuan 629000
Downhole drilling and seismic data showed that multiple sets of oolitic beach reservoir were found in Lower Triassic Feixianguan Formation in northern Sichuan Basin, which was the main natural gas reservoir of Feixianguan Formation. Through well-seismic calibration of oolitic beach reservoir section and combined with analysis of seismic forward digital modeling, four seismic response patterns of corresponding various oolitic beach reservoir were established and anomalous characteristics of seismic response in different parts of the oolitic beach reservoir were summarized. Two-dimensional seismic facies analyses of 1st, 2nd and 3rd Members of Feixianguan Formation were analyzed respectively. Based on corresponding relations between seismic and sedimentary facies, sedimentary facies features of 1st, 2nd and 3rd Members of Feixianguan Formation were recovered. Integrating seismic anomaly characteristics of oolitic beach reservoir and sedimentary facies distribution range, distribution characteristics in the region were predicted. The sedimentary system of platform foreslope-platform margin-open platform facies mainly developed in 1st and 2nd Members of Feixianguan Formation. Platform margin oolite beach facies in the east and west on both sides showed banded distribution along the north-west shelf with more than 4 400 km2 distribution area, while 3rd Member of Feixianguan Formation turned into open platform deposits in targeted area. The oolitic beach were mainly distributed in Longgang-Yuanba, Jiange, Jiulong Mountain, Heba-Heichiliang, Puguang-Tieshanpo and other regions with a total area of 15 000 km2. Therefore, exploration potential of oolitic beach reservoir in Lower Triassic Feixianguan Formation in northern Sichuan Basin is tremendous.