天然ガス田における地表沈下に関する研究 (第2報)

抄録

This paper presents the prediction method for time-dependent development of the ground movements in natural gas field.
The analytical method we used is almost similar to that of 1st report. But, in order to take the time-dependent change of piezometric head in gas seam, Theis equation for unsteady flow to a well is used. It is found that Theis equation can be fully applied to ‘gas well’ and the calculated results agree well with the actual measurements.
And also, in order to take the influence of depth of gas seam upon the ground movements, finite element analysis is carried out.
So, the following results were obtained.
Increasing the depth of gas seam, the values of ground movements decrease, when the drawdown curve in gas seam is same in all cases.
The vertical ground movement (surface subsidence) which is given by our analytical method is slightly different from the profile with finite element technique, but it is sufficient to understand the outline of subsidence in natural gas field.
Finally, we find that the ground movements in natural gas field consist of the vertical and horizontal components. So, in natural gas field, we must consider not only the surface subsidence but also the horizontal ground movement.