Abstract:

The geostress characteristics of coal reservoir has a close relationship with the generation, migration and enrichment of coalbed gas, and a good understanding of the geostress characteristics is vital for the exploration and development of the gas field. Referring to the logging data at 18 coalbed gas well in Changzhi block of southern Qinshui basin, the distribution of the vertical stress, the minimum and maximum horizontal stresses is evaluated using an Anderson model with residual tectonic stress. The results show that the vertical stress basically presents a symmetric distribution from east to west, and the stresses in the east and west are higher than that in the middle, ranging from 15.2 MPa to 16.5 MPa. The minimum horizontal stress presents a change pattern of high→low→high→low from west to east, and ranges from 10.2 MPa to 19.3 MPa. The maximum horizontal stress presents a similar pattern, and ranges from 13.0 MPa to 34.2 MPa. The results suggest that the influence of the buried depth is bigger than the tectonic influence in the eastern area, whereas the tectonic influence is bigger than that of the buried depth in the western area. This finding indicates that the geostress distribution has a high correlation with the gas output of the coalbed well, and can offer a good data reference for the coalbed gas exploration, development, safe production and etc.

Key words: geostress, coalbed gas, Anderson model, Qinshui Basin