Abstract:

The Eastern edge of the Ordos basin has a wide north-south span where the regional hydrodynamic conditions are still
unclear. Based on the data of the porosity, permeability, drilling water production, hydro-chemical and isotope composition and
coalbed methane (CBM) concentration, the control of the hydrodynamic condition to the CBM generation and accumulation in the
area was discussed. It was shown that the sandstone aquifers and their pores and permeability develop much well in north part of
the basin than in its south. Limestone aquifers in the Taiyuan Formation are most developed in the Sanjiao-Jixian area, resulting
in the higher CBM content of the Shanxi Formation than that of the Taiyuan Formation. Drilling water production and the calcium
and magnesium ion concentrations are higher in the north than in the south, and the water mineralization is positively correlated
to CBM content. It was indicated that the groundwater in the area is more active in the north than in the south. Hydrodynamic
condition in the north is stronger in the Shanxi Formation than in the Taiyuan Foramtion but it is opposite in the Sanjiao-Jixian
orea of the south. Weak run-off to stagnant groundwater in the middle and high coal-rank area located in the south of the Bode orea
is in favor of the CBM accumulation. Active groundwater and good cap-rocks in the low and middle coal-rank area in the north of
the Baode provide a key for the generation and accumulation of the secondary bio-gas.