Study On The Reservoir Conditions Of Upper T₃x² Gas Pool In Jiulongshan Gas Field In Northwest Sichuan

It has been inferred that there reserves a considerable sum of gas for exploitation in the tectonic area of Jiulongshan located in northwest Sichuan, and it will have significant implications to take a further study on the reservoir conditions of the upper secondary member of the Upper Triassic Xujiahe Famation (upper T3x2) since the previous researches have not shed enough light on this field. In this thesis, a comprehensive study on the reservoir conditions of upper T3x2 was carried out, applying large amounts of data collected which were mainly on drillings, earthquakes and geo-conditions of the area of Jiulongshan. It turned out that:1.It can be inferred that there will be a stable-high yield of gas in the area of upper T3x2, for the outcomes of experiments and core-observations indicated that the reservoirs of upper T3x2 belong to the category of crack-pore, and there diffusely distribute cracks and partial- dissolved pores, and the last, there exists a continuous distribution of thick-layered sandstones.2. The gas-reservoir of upper T3x2 can be well identified applying the two kinds of discrimination threshold defined by the sensitive parameters of logging:GR<90API is Sandstone Reservoir and wave impedance<13627 is Favorable Reservoir.It is speculated by the impedances and natural-gamma-data-volumes that it would present a banded distribution of the thickness of sandstones as well as the effective gas-reservation sandstones, with the sandstone-layers in the northern area of upper T3x2 thicker than that in the south.3. There were several features of seismic reflection of gas-bearings that can be applied to speculate the areas of effective gas- reservoir in upper T3x2. Furthermore, spectrum analysis of gas-bearings and dense layers dicated that those powerful energy-groups in the context of weak reflection of low-frequency energies would be satisfying ones to characterize the distributions of gas which were almost consistent with the real conditions of drillings.4.Two differentiated types (i.e. typeⅠand typeⅡ) of gas-reservoirs were delineated, after a comprehensive evaluation of all the stone layers, with a total area of, respectively,51 km2 and 270 km2. In addition, it has been proved that the high points of structure in the western regions of upper T3x2 were better than the eastern regions. I argue that, these conclusions will have important policy implications for the deployment of gas exploration and can be regarded as, to some extent, the basis for a further gas-trapping in the area of upper T3x2.