Application of modeling inversion of Bouguer gravity anomalies to oil and gas exploration in the Erlian Basin

The Erlian basin is composed of many small sags, of which the Yihe sag is one. Gravity information plays an important role in surveys in basins such as "exploring edges and bottoms" and "determining depressions and choosing belts". Based on Bouguer gravity anomaly data, the two lines crossing the main subsags are visually modeled and forward fitted by using the 2. 5D modeling inversion techniques. In these procedures, the geometric parameters of the initial model are taken from the two-dimensional seismic interpretation results and the longitudinal density in physical parameters is derived from the correlation formula of the acoustic velocity and density of well logging data. Forward modeling is a key part of modeling inversion, and the lateral change of density is achieved through trial-and-error adjustment of human-computer interaction in the modeling process. The results of forward modeling show that there is a large density heterogeneity in lateral and longitudinal directions of the main subsags which are favorable for oil and gas generation. Compared with the results of seismic interpretation, the depth difference of them in the Saihan Formation-Quaternary and Tengger Formation is not obvious, but the results of the bottom fitting are different from those of the seismic interpretation. Drilling verification indicates that the depth of each sedimentary layer by forward modeling is consistent with that revealed by the drilling. However, the results of the two-dimensional seismic interpretation are relatively shallower, probably because the speed of early time-depth conversion is too small.