5
average pillar pressure of more than 3,000 psi at the gas
well location and which is expected to impact the long-
wall-induced casing stresses. Figure 7 shows, prior to the
availability of the on-site gamma log, the predicted long-
wall-induced horizontal displacement and casing deforma-
tions along the fully cemented 5-½" production casing by
the FLAC3D model after first and second panel mining,
which displays nine locations of very small casing deforma-
tion and one location of moderate casing deformation at
642 feet below the surface.
Comparison with Field Measurement
Post-first and post-second panel mining 40-arm Caliper
surveys were conducted in the test well, 4H. Figure 8 shows
the post-second panel mining 40-arm Caliper survey results
in the fully cemented 4H production casing. Clearly, the
predicted casing deformations shown in Figure 7 are in good
agreement with the measured casing deformation shown
in Figure 8, except the plastic deformation detected at the
1,284-foot horizon that prevented the 40-arm Caliper tool
to pass through. Figure 8 also shows images of the moderate
Figure 6. Longwall-induced vertical pillar pressure at the deep-cover test site
Figure 7. Predicted longwall-induced horizontal deformations and production casing diameter reduction
average pillar pressure of more than 3,000 psi at the gas
well location and which is expected to impact the long-
wall-induced casing stresses. Figure 7 shows, prior to the
availability of the on-site gamma log, the predicted long-
wall-induced horizontal displacement and casing deforma-
tions along the fully cemented 5-½" production casing by
the FLAC3D model after first and second panel mining,
which displays nine locations of very small casing deforma-
tion and one location of moderate casing deformation at
642 feet below the surface.
Comparison with Field Measurement
Post-first and post-second panel mining 40-arm Caliper
surveys were conducted in the test well, 4H. Figure 8 shows
the post-second panel mining 40-arm Caliper survey results
in the fully cemented 4H production casing. Clearly, the
predicted casing deformations shown in Figure 7 are in good
agreement with the measured casing deformation shown
in Figure 8, except the plastic deformation detected at the
1,284-foot horizon that prevented the 40-arm Caliper tool
to pass through. Figure 8 also shows images of the moderate
Figure 6. Longwall-induced vertical pillar pressure at the deep-cover test site
Figure 7. Predicted longwall-induced horizontal deformations and production casing diameter reduction