The Research Of Seismic Sedimentology In Changxing Formation Of Upper Permian In Jiannan And Adjacent Areas

Carbonate reef, as an important reservoir type, has been playing an important role in global oil and gas field production, especially in recent years, the breakthroughs of organism reef reservoirs in the Upper Permian Changxing Formation, such as Puguang, Xuanhan, Yuanba, and Longgang in northeastern Sichuan Basin, having gained increasingly importance by researchers. Jiannan and periphery areas close to northeastern Sichuan, which is an advantage development area of reef. Since1970s, after the discovery of the first reef gas reservoirs in Changxing formation in Jiannan structure, oil and gas exploration did not get much progress. The main reason is the considerable controversy of palaeogeography framework of Changxing formation in western Hubei-eastern Chongqing region, mainly showing in the extension orientation and distribution boundary of "Kaijiang-Liangping continental shelf", which is largely restricted the further study of reef facies and reservoir distribution, greatly reducing the effectiveness of reef reservoirs of oil and gas exploration and development. Therefore, carrying out sequence stratigraphic and fine sedimentary facies study of Changxing formation in Jiannan area, not only having important theoretical significance, but also guideness significance for reef-bank gas reservoir exploration.Based on outcrop, core, logging and other information, according to re-acquisition and processing of seismic data, then using sequence stratigraphy, carbonate sedimentology and seismic sedimentology, combing with regional geological background and previous research, carrying out sequence stratigraphy, sedimentology studies, sedimentary facies plane distribution and the favorable distribution for the forecast of reef-bank zones in Changxing Formation in Jiannan areas. The mainly contents and results of knowledge lists as follows:1、Through the field outcrop observation, core description, lithology and lithofacies change analysis, response characteristics of logging, reflection configuration in seismic profile and other key sequence boundary identification, Changxing formation is divided into two type II third-order sequences and five forth-order sequences. High accuracy sequence stratigraphic framework of Changxing formation was established. From the outcrop, core information analysis, the internal structure characteristics, and restoring reef-bank forming models, geological model of reef-bank is set up;2、Two kinds of depositional models were developed in Changxing formation in Jiannan area:gentle slope pattern and platform pattern. The early stage of Changxing formation inherited the sedimentary pattern of Longtan formation, being "gentle slope model" deposits. The middle-late Changxing formation, due to the effect of tension of the hercynian movement, forming the northern and southern platform and starting "platform model" deposits, which develops open platform, platform edge reef-bank, platform front slope and continental shelf facies.3、By the lithology and sedimentary facies in the seismic waveform response characteristics and the seismic facies analysis, lithology and sedimentary facies recognition model is established. Taking seismic facies analysis as main means, analyzing concrete distribution of continental shelf characterized by "blank reflection features" in Jiannan and adjacent areas;4、By well data and seismic multi-attribute analysis, according to the seismic attribute optimization principle, optimal selection related to reservoir geological significance definite multiple seismic attribute analysis, and the coincidence rate with the single-well lithology, actual log data analysis, and finally determining seismic attributes of the reef-bank facies division and reservoir prediction. Finally, taking amplitude, frequency and phase as advantage seismic attributes, reef-bank distribution and reservoir prediction of Changxing Formation was carried out;5、Guided by seismic sedimentology, sedimentary facies belt and reef-bank development placement in Jiannan and peripheral areas were confirmed. Using isochronous stratigraphic section technology framework controlled by sequence stratigraphic, evolution rules of sedimentary facies was analyzed, clearing the main reef-bank development period and evolution mode;6、On the basis of definiting reef-bank reservoir geology and geologically physical characteristics, conventional model inversion, multi-parameter attribute inversion, frequency inversion and hydrocarbon detection technologies were used for reservoir prediction. The main reef-bank development area were optimally sorted and biological reef-bank reservoir evaluation parameters were selected. In the end, geological and geophysical information were integrated to forecast the favorable area for the development of reservoir.This study not only re-delineats "Kaijiang-Liangping continental shelf", finely describes the Changxing Formarion reef-bank distribution in Jiannan area, deepening theory connotation of carbonate rocks reservoir-sedimentology and seismic sedimentology, but also has a significant guideness in distribution prediction and oil-gas exploratory development of reef-bank reservoirs in the study area.