Sequence stratigraphic features of the Jurassic succession in Central Junggar Basin were investigated by integrating multiple materials including cores, well and seismic data. Due to their unique formation mechanism, sequences of the target interval were analyzed with a binary systems tract mode (each complete sequence contains a transgressive systems tract and a highstand systems tract) rather than the traditional one. Basic principles and analytical methods of high-resolution sequence stratigraphy were also applied to this research. By adopting cyclic correlation and hierarchical control techniques, eight sequences (Sq1-Sq8) were identified in the target interval. Especially, coal seams are of great significance in the sequence identification and they were considered to be closely relevant to maximum flooding surfaces (mfs).
With the method of the high resolution sequence stratigraphy and sedimentology theory, oil-bearing sand bodies have been accurately recognized and descripted which could provide precisely geological data for 3-D modeling and numerical simulation. It has the vital significance for the development of oilfield during the late stage of high water cut. According to the drilling, logging, seismic and analytical experiments data, the results show that the study area can be divided into one long-term base level cycle, four middle-term base level cycles, sixteen short-term base level cycles and twenty-eight super short-term base level cycles. Based on the classification of base-level cycles, control functions of cycles which have effects on the sediment environment have been discussed. And with the application of the chronostratigraphic correlation fine stratigraphic correlation, 10 high resolution sequence stratigraphic frameworks are established in the direction that is parallel and perpendicular to the source.
Interlayer is a kind of rock body that reflects the seepage barrier in the reservoir sandstones. As the interlayer playing a blocking role of hydrocarbon accumulation, we can better understand the characteristics of the reservoir heterogeneity through the analysis of the causes and spatial distribution of the interlayer. Empirically, identification of four types of interlayer, including muddy interlayer, calcium interlayer, physical layer, and indistinguishable interlayer, contributes to effective production of tight gas sandstones. Each category of interlayer has a separate characteristic of the lithology and logging curves. Identifying interlayer provides a way to analyzing spatial distribution of interlayer in the tight gas field. 2-D and 3-D geological models corresponding to the distribution of interlayer can be able to establish to characterize distribution variations within the reservoirs, which show the space matching relation serving for the tight gas production.
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