The giant Daniudi gas field

located in the north of Ordos basin

is of a tight and low-permeability type.Its main gas-bearing horizons from bottom to top are the Taiyuan Formation of the Upper Carboniferous and Shanxi Formation and lower Shihezi Formation of the Lower Permian

forming a complete set of sedimentary sequences of marine tidal flat-paralic-delta-terrestrial braided channel.The sequences

with a thickness of 250 m to 280 m and a stable lateral distribution

are in a shape of a huge box

to which the commercial gas pools are confined due to a dual tight sealing of favorable lithophysics and anomalous pressure of the regional cap in the upper Shihezi Formation.Layered lithologic traps overlap with one another and hydrocarbon reservoiring in them is characterized by near-source and box-like traps.To solve the problems caused by lithologic trap

tight and low-permeability sand reservoirs

and low natural production of the field

core technologies

such as description and evaluation of stacked lithologic traps and seismic prediction of coal bed reservoirs

have been developed during the exploration and development of the Daniudi gas field.And corresponding technologies of quick drilling aiming at protecting gas reservoirs and large-scale fracturing intending to promote gas production of tight reservoirs have also been advanced.