A 3D model of the Wathlingen salt dome in the Northwest German Basin from joint modeling of gravity, gravity gradient, and curvature

Abstract

In the past few decades, numerous attempts have been made on modeling of salt tectonics and deciphering the geometry of salt domes, which is a key challenge in petroleum exploration. We have derived a 3D density model of the Wathlingen salt dome, situated in the southern part of the Northwest German Basin from joint modeling of reprocessed torsion balance measurements. Gravity, gravity gradients [Formula: see text], curvature derived from horizontal gravity gradients [Formula: see text], and horizontal directive tendency are jointly modeled to decipher the geometric structure of the salt dome. The model was constrained by geologic and borehole information. We found that the Wathlingen salt dome is a mushroom-structured salt body, which is 14-km long, 4–8-km wide extending up to [Formula: see text] depth. The top mushroom structure of the salt is horizontally spread up to [Formula: see text]. It would not have been possible to derive the complex 3D structure from modeling of gravity data alone.

Multiple-linear regression to best-estimate of gravity parameters related to simple geometrical shaped structures

“…The lowest one of the three reached values of RM SE -V , RM SE -H and RM SE -S with the highest one of the three reached values of R 2 -V , R 2 -H and R 2 -S are obtained for the semi-infinite vertical cylinder, meaning that, the field residual gravity anomaly could be preferably modeled as a semiinfinite vertical cylinder. The depth obtained in this case (z = 2.9155 km) is found to be in a good agreement with that reported by Dubey et al (2014) and by Abdelrahman and Gobashy (2017) by using a statistical approach (z = 3.2 km).…”

“…Fig. 8 shows a field residual gravity anomaly obtained over an area situated in the southern part of the North-West German Basin, Germany (Dubey et al, 2014;Abdelrahman and Gobashy, 2017). The field gravity anomaly is reinterpreted by the new proposed approach, where the results are shown in Table 6.…”

Depth and shape solutions from residual gravity anomalies due to simple geometric structures using a statistical approach

“…The shape value thus obtained by the present method suggests that the shape of the source body can be represented by a 2D horizontal cylinder buried at a depth of about 3.2 km. This is in good agreement with the dome form estimated by Dubey et al (2014) who derived a 3D density model of the Wathlingen salt dome from joint modelling of gravity, gravity gradients, curvature derived from horizontal gradients and horizontal directive tendency, geological and borehole information. They found that the Wathlingen salt dome is a mushroom-structured salt body, which is 14 km long and 4-8 km wide extending up to about 4 km depth.…”

“…An excellent detailed review of the geology of the salt dome is given in Dubey et al (2014). It is evident that the peak of the salt diapirism in North Germany was probably at the end of the Late Jurassic and came to an end during the Lower Cretaceous.…”

“…During the ascent of the salt, the overlying horizontal beds were heavily inclined. Figure 6 shows the observed gravity anomaly over the Wathlingen salt dome (Dubey et al, 2014). A central profile of a short length (5 km) of this anomaly was digitized at an interval of 50 m ( Figure 7) and was used to determine the depth and the shape of the buried salt dome using the present method.…”