Effect of Grid Stations Against the Measured Depth Gravity Field and Their Effects to Order of Polynomial TSA

Abstract

In gravity survey it well known that the grid between measurement stations gives effect to resolution of the measurement results. Grid station also was influential in the depth of the target. However, in reality, most of surveyor in such oil and gas exploration and geothermal exploration has paid less attention to this aspect. Some measurements even consider the ease of access along the road rather than consideration of the homogeneity of the grid. Simulation tests have been conducted on a data anomaly shallow depth (geotechnical and archeological cases), moderate depth (case of mineral) and deep in depth (geothermal case). The aim of research is to examine the relationship between grid stations with depth and its effect on the use of the polynomial order of trend surface analysis. The polynomial method is usually used to obtain regional anomaly from the Bouguer anomaly data. The simulation results show that the grid to depth ratio (¦¤x/z) is about 9%, meaning that the larger the grid the station, the deeper of measurable gravitational field effect. Also obtained the result that to detect the anomaly object at certain depth, the more width of grid station, the higher-order polynomial to use. This means that the higher-order polynomial is used, the shallower the cut-off areas of regional-residual anomaly data. However, if the grid station meets the criteria of ¦¤x/z ¡Ö 9% it is recommended to order polynomial TSA used is a second order polynomial (n = 2).