Seismic Sedimentology Study Of Gas Group Ⅰ And Ⅱof1St Member Of Huangliu Formation, DF13-1/2Gas Field

This dissertation studies on I and II gas group of1st member of Huangliu Formation (N1h’) in Yinggehai Basin. Under the guidance of sequence stratigraphy, sedimentology, seismic stratigraphy, especially seismic sedimentology, while with the use of amount of drilling cores, logging, well analysis and tests,3-D seismic data, this paper focuses on the researches of two problems, the inner components and the evolution stages of I and II gas group of N1h1in Yinggehai Basin and mainly analyses the sedimentary background, sedimentary facies, sedimentary microfacies and the internal evolution stages of I,II gas group, in order to construct the sedimentary models.With the integrated application of ichnofossils, foraminifera, Th/U rate, elementary analysis of Co, the characteristics of the paleotopography to analysis sedimentary background of N1h1in DF13-1/2gas field in qualitative and quantitative methods, it can be conclued as follows:in the depositional stage of I and II gas group, study area is in the inner shelf-outer shelf interactive shore sedimentary environment, with the depth of the water and the water strength evolving frequently; the absolutely depth of the water ranged from20m to115m; the sedimentary depth of I gas group was more shallow than the II gas group; the sedimentary depth of DF13-1gas field was more shallow than the DF13-2gas field.Based on the observations and the descriptions of the drilling chips in the study area, while with the guidance of the characteristics of facies indicator and the application of the grading analysis, logfacies analysis and reference to previous studies, we can draw the conclusions as follows:abyssal fan sedimentary face developed in this study area and can be subdivided into some microfacies including main stream channel, stream channel, crevasse channel, overbank, sheet sand. At the same time, neritic face also developed in this area and can be divided into shallow sand bar microface and shallow mud microface.This paper comprehensively uses key techniques of seismic sedimentary into the study areas for the first time. We first identify that I and II gas group are developed inside high-accuracy strati graphic framework of Huangliu formation, corresponding the interfaces of T301and T31. Then we make the calculations about the initial parameters like initial phase angle, spectral analysis, etc. More specifically, the initial phase angle is about3°, and dominant frequency is around35Hz, and bandwidth range is from15Hz to55Hz. We also apply90°-phase shift and frequency processing these two key techniques on the original seismic data of study areas. Basing on the rule that seismic events match the single sand body, we compare the matching relationships of different frequency phases and choose the best, namely45Hz. Moreover, petrophysical relationship of45Hz seismic data shows that the stronger negative amplitudes correspond with the higher percentage of sandstone. So we select every sandbody’s top and bottom interfaces of I and II gas group as the reference planes, and collect strata slices considering relative stratigraphic time lms as the sampling rate. Next, we find seismic facies in the study areas are high-amplitude continuous reflection folded with weak-amplitude and low-continuous seismic reflection, worm-shaped high-amplitude reflection phases, high-amplitude continuous reflection phase and also middle-high amplitude continuous reflection phases. Finally, according to the interpretation standard between seismic facies and sedimentary facies which is comprehensively observed by strata slices, seismic profiles, seismic attributes and other characteristics of the study area, we divide I and II gas group into different sedimentary facies like main stream channel facies, stream channel facies, lobes facies. Then we combine sedimentary facies with single-well analysis to get its micro sedimentary facies.In order to clarify the evolution of the I and II-gas groups, the gas groups are divided into large-scale, mesoscale and small-scale reservoir. Based on large-scale classification scheme that judged by superposed relationship of seismic event, I and Ⅱ-gas groups are divided into four stages. Based on mesoscale classification scheme that judged by the level of the lower cutting inside sand, I and II-gas groups are divided into six stages. Based on small-scale classification scheme that judged by sequence of appearing sand negative amplitude in stratal slicing, I and II gas groups are divided into nine stages.In the depositional period of low-stand system tract of1st member in Huangliu formation, DF13-1gas field has higher topography, gentle slope, shallow water and shale content which is greater than the sand content, mainly develops large amounts, small size and scattered distribution of depositional lobe. DF13-2gas field has lower topography, steep slope, deeper water and the sand content which is slightly greater than shale content, mainly develops incised main stream channel and braided stream channel.