Stripping

3D stripping

The principle

We have 3D density model and we perform a 3D stripping according to the observed Bouguer anomaly. We compute the gravity effect of the suitable layer (or several layers) and remove their effect from the real Bouguer anomaly

Stripped anomalies

The input model

The density model

Our density model have 6 layers. We need 5 steps to reach the end of the stripping. Note: hereafter, the remaining anomaly is the anomaly remaining after the stripping

Stripping step 1

Density model

Real Bouguer anomaly

Gravity effect

Remaining anomaly

Strip the 1st layer

The Bouguer anomaly is well reduced (see the remaining anomaly) compared to the initial Bouguer anomaly.

Stripping step 2

Density model

Real Bouguer anomaly

Gravity effect

Remaining anomaly

Strip the 1st and the 2nd layers

The Bouguer anomaly is interestingly more reduced indicating that the stripped first 2 layers (step 2) satisfy the observed data

Stripping step 3

Density model

Real Bouguer anomaly

Gravity effect

Remaining anomaly

Strip the 1st, the 2nd and the 3rd layers

We not reduce the anomaly compared to the previous step (i.e. step 2)

Stripping step 4

Density model

Real Bouguer anomaly

Gravity effect

Remaining anomaly

Strip the 1st, the 2nd, the 3rd and the 4th layers

Again, the stripped anomaly is no more reduced, we doing completely the reverse

Stripping step 5

Density model

Real Bouguer anomaly

Gravity effect

Remaining anomaly

Strip the 1st, the 2nd, the 3rd and the 4th layers

We are completely in the opposite of what we are expected.

Conclusion

From this stripping, we understand that our model is « correct » from the surface till the 3rd layer but down it’s not the case. As the model geometries comes from seismic, we understand that the densities of layers 4 and 5 are overestimated according to the observed data. The density decreases could more probably caused by the faults and fractures which are large in this area. This conclusion is so important for instance for exploration of deep geothermal target

Stripping

Stripped anomalies

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