Abstract:

NW margin of Junggar basin with relatively complicated structures is composed of western uplift and west part of Mahu depression. The development characteristics of present hydro dynamics fields have been studied by means of analyzing parameters of fluid physics and fluid chemistry, measuring pressure data in reservoirs, compaction and overpressure in mudstones and distribution of fluid potential. Fluid physicochemical features from various layers show different hydro dynamics distribution distinctions of its own, so as to recognize easily where gravity flow is strong and where frequent replacement of water between deep layer and shallow layer, namely; districts from Hongshanzui to Wuerhe in the Carboniferous System, Kelamay and adjacent Xia No. 40 well in the Permian, Ke No.114 wells and Feng No.1, Wuerhe in the Triassic, Baijiantan Baikouquan in the Jurassic. It is believed by measuring pressure in situ in sandstones that hydrostatic pressure is basically preserved in the Jurassic and Carboniferous, and overpressure to a certain extent would appear at some depth in the Triassic and Permian, where development of overpressure in plane occurs in Mabei and Xiazijie areas.It is indicated by calculating abnormal pressure in mudstones from compaction curves that the beginning depth of overpressure is between 1800～2300 m while the beginning corresponding layer is quite different,moreover thick layers of under compaction mudstone contribute markedly to abnormal pressure. It is believed by studying distribution of hydraulic head in the Permian and Triassic that hydrodynamic fields are present mainly as compaction flow, whereas in some high positions of structures or fractures around northwest margin of Junggar basin the fields are developed and present as gravity flow or meteoric ground water flow.

Key words: hydrodynamic, fluid physics, fluid chemistry, abnormal stratum pressure, NW margin, Junggar basin