Changes

'''Class 1 : High impedance Gas-Sandstone'''

'''Class 1 : High impedance Gas-Sandstone'''

Class 1 sandstone has higher impedance than its cover (shale). Interface between shale and this kind of sandstone will generate a high reflection coefficient and a positive zero offset, but has amplitude magnitude decreasing in order to offset. Class 1 has greater gradient than class 2 and class 3. Sandstone at class 1 is having a change in polarity in certain angle, then the amplitude will be increasing proportionally to the offset.

Class 1 sandstone has higher impedance than its cover (shale). Interface between shale and this kind of sandstone will generate a high reflection coefficient and a positive zero offset, but has amplitude magnitude decreasing in order to offset. Class 1 has greater gradient than class 2 and class 3. Sandstone at class 1 is having a change in polarity in certain angle, then the amplitude will be increasing proportionally to the offset.

'''Class 2 : Near zero impedance contrast gas sandstone'''

'''Class 2 : Near zero impedance contrast gas sandstone'''

Class 2 sandstone has almost equally acoustic impedance with its cover (seal rock) and the amplitude which is increasing proportionally to the offset. Class 2 sandstone divided into class 2 and class 2p. class 2 sandstone has negative reflection coefficient at zero offset while class 2p has positive at zero offset.

Class 2 sandstone has almost equally acoustic impedance with its cover (seal rock) and the amplitude which is increasing proportionally to the offset. Class 2 sandstone divided into class 2 and class 2p. class 2 sandstone has negative reflection coefficient at zero offset while class 2p has positive at zero offset.

'''Class 3 : Low impedance gas sandstone'''

'''Class 3 : Low impedance gas sandstone'''

Class 3 has lower acoustic impedance than its cover.

Class 3 has lower acoustic impedance than its cover.

'''Class 4 '''

'''Class 4 '''

Class 4 has negative reflection coefficient at zero offset and amplitude that is decreasing against the offset. There is a change in polarity at a certain angle and then amplitude will increasing proportionally to the offset.

Class 4 has negative reflection coefficient at zero offset and amplitude that is decreasing against the offset. There is a change in polarity at a certain angle and then amplitude will increasing proportionally to the offset.