Subsurface Characterization Using Geophysical Methods at the Proposed Site of Block 11 and Block 12, Universiti Teknologi PETRONAS.

Abstract

Subsurface study is an essential component not just in oil and gas industry but also in construction engineering. Geophysical methods are among the approaches that could be applied to map the subsurface condition such as electrical resistivity imaging (ERI) and seismic refraction surveys. Four lines of ERI survey and two lines of seismic refraction survey had been carried out at the proposed site of academic blocks (Block 11 and Block 12), Universiti Teknologi PETRONAS (UTP) to investigate the shallow subsurface condition and bedrock identification. Shallow subsurface tomography profiles were produced by using Res2DInv and GeoGIGA Software for ERI and seismic refraction respectively. Based on the results of both methods, relating to the geophysical parameters and borehole data, in general, three subsurface layers were found which are alluvium, weathered bedrock (parent material) and bedrock. The alluvium consists of water saturated zones and compacted layer indicated with resistivity range and seismic velocity of 30-200 ohm.m (except for the compacted layer; 800-1000 ohm.m) and 1500 m/s respectively. The second layer which is moderately weathered bedrock consists of 150-800 ohm.m resistivity range and a seismic velocity of 3000 m/s. the bottom layer is a fresh sedimentary bedrock with the value of 800-2500 ohm.m resitivity range and a seismic velocity of >3000 m/s. Both profiles showed a correlatable result particularly when it ties slightly identical to the borehole data.