In-situ stress prediction and its distribution mechanism of multiple coal seams: A case study of Panguan syncline, Guizhou Province, China

Abstract

The logging prediction method is especially suitable for in-situ stress prediction in multiple coal seam areas. This study investigates different blocks in the Panguan Syncline, Guizhou, China. Using conventional logging data from 14 boreholes and constrained by measured in-situ stress and static mechanical parameters from 8 parameter wells, in-situ stress prediction models at the block scale are constructed to reveal the mechanism of in-situ stress distribution. The combined spring model, modified Ge's model and Anderson modified model are suitable for in-situ stress prediction in the Northwest block, Jinjia block and Huopu block, with accuracies of 92.62 %, 92.74 % and 93.15 %. The stress mechanism of coal seam has the characteristics of vertical zoning. The coal seams at depths shallower than 600 m are dominated by strike-slip faulting stress regime (σ_H>σ_v>σ_h), while all the coal seams above 800 m are in normal faulting stress regime (σ_v>σ_H>σ_h). The depth of 600–800 m is affected by both strike-slip and normal faulting stress regimes, which form a stress transition zone. Coal reservoir permeability decreases nonlinearly with increasing burial depth and increases significantly near the stress transition zone. Considering factors such as in-situ stress and pore pressure, 12#, 13# and 15# can be regarded as continuous coal seams for coalbed methane (CBM) development.