Title: Comparative study of tectonic evolution and oil–gas accumulationintheRi-Qing-Wei basin and the Jiaolai basin
Abstract:
The Ri-Qing-Wei basin is located in the central Sulu Orogeny on the eastern side of the Tanlufault zone in eastern Shandong province. To the north, the Jiaonan uplift separates it fromtheJiaolai basin, where drilling in the lower Cretaceous sedimentary rock of the Laiyang grouphasindicated good oil and gas reserves. Drilling in the Ri-Qing-Wei basin, in contrast, is inthepreliminary exploration stage. Lingke 1, the only scientific well, is on Lingshan Islandonthebasin boundary, and it encountered a large set of source rocks 700 m thick. The two basins werecomprehensively compared and analyzed based on comprehensive fieldwork, drilling, coredata, seismic profiling, sedimentary filling sequence, tectonic evolution history, basin burial history, geothermal history, and geochemical characteristics of the source rocks,. The results showedthree things: (1) From the late-Jurassic to the early Cretaceous (the Laiyang period), subductionof the paleo-Pacific plate under the Eurasian plate delaminated the lithospheric mantle of theSulu Orogeny, thus forming a series of passive continental rift basins. Of these, the Ri-Qing-Wei is central and the Jiaolai is its branch. After the active rift stage in the Qingshan periodandthedepression stage in the Wangshi period, the burial depth of the source rocks in the Ri-Qing-Wei basin was up to 6000 m, while the maximum burial depth in the Jiaolai basin was about 3000m. The paleogeotemperature of both basins exceeded 125 °C, indicating that the source rocks werevery mature. (2) A comprehensive comparison of their geochemical characteristics––organicmatter abundance, type and maturity––showed that both basins have oil-generating potential. It isworth noting that the magmatic activity in the Qingshan period had a positive effect ontheevolution of the source rocks but was not the key factor: burial depth was. (3) Oil and gas failedto accumulate in the Jiaolai basin because of lateral tectonic movement had been destroyed. During the right-lateral strike-slip stage (50±5 Ma) during the late Wangshi, the Jiaolai basinwasstrongly uplifted over a range of more than 1000 m by the Tanlu and Wulian-Mouji fault zonesalong the boundary. The Wangshi group, as a cap rock, was eroded, and oil and gas overflowedalong the fault that reached the surface. The late Wangshi period uplift of the Ri-Qing-Wei basinwas less than 1000 m because the source rock was deeper, and the reverse faults in the basinwere sealed well. The uplift did little damage to the oil in the Ri-Qing-Wei basin. Aboveall, tectonic evolution was the main controlling factor of oil accumulation in the study area, andthelayers of the Laiyang group in the Ri-Qing-Wei basin have oil and gas potential, makingit aprospective target for unconventional offshore oil and gas exploration.
Biography:
Dr. Zhang obtained his BSc (Geology) from the Yangtze University and her PhD(Geology) fromtheChina University of petroleum （ east China ） . She is previously worked for the Oil andGasexploration at the Exploration and Development Research Institute of Shengli Oilfield, Sinopec. Her PhDresearch was based on the Geotectonic structure in eastern coastal area of Shandong Province, China. Shehas published various papers in peer reviewed journals.
