In-situ stress distribution and its implication on coalbed methane development in Liulin area, eastern Ordos basin, China

Based on well test parameters independently measured within depth from 400 to 1100 m in Liulin area, eastern Ordos Basin, China, the distribution of in-situ stress was analyzed systematically. Maximum horizontal principal stress (σHmax), minimum horizontal principal stress (σHmin), vertical stress (σv) and lateral pressure ratio variations with depth were obtained by regression analysis. Results show that the growth rate of horizontal stresses is higher than that of vertical ones. Three types of stress fields were found and calculated: the type of σv≈σHmax≈σHmin mainly distribute in relatively shallow coal seams from 400 to 700 m; the σHmax>σv>σHmin type ranges from 700 to 850 m; and, the σv>σHmax>σHmin type is dominant in depth from 850 to 1100 m. Coal permeabilities obtained during injection/falloff tests showed that the permeability was damaged under a depth of 700–850 m for the relatively high σHmax and σHmin. The correlation between strata temperature and depth was also illustrated, which showed three linear relationships in depth of 400–700, 700–850, and 850–1100 m, separately. The gas content and gas/water production data were also plotted, showing that the strata shallower than 700 m is of better gas resources and recovery rate than the deeper strata.