Evaluation of Time-Domain Controlled-Source Electromagnetic Method for Detecting Hydrocarbon Targets in East Malaysia Environment

Abstract

This reference is for an abstract only. A full paper was not submitted for this conference. Abstract The time-domain Controlled Source Electromagnetic (tCSEM) method is emerging as a practical tool for oil and gas exploration on land and shallow marine environments (Wright et al., 2002; Ziolkowski et al., 2007). In particular, it can overcome the airwave interference problem faced by frequency-domain CSEM method in shallow water (Weiss, 2007). We have used a 1D broadband tCSEM inversion technique developed in-house. The forward problem is solved using the algorithm of Edwards (1997) while the inverse problem is solved using a variety of nonlinear parameter estimation methods (Meju, 1992, 1994). The inversion method generates either blocky sharp-boundary model or the smoothest model that fits the data recorded for different offsets and various transient times. In this work, a layered-earth resistivity model was constructed using the local borehole resistivity log and served as the test model (ground-truth). The parameters of this model were systematically varied and used to generate forward model responses enabling us to determine the effect of target depth, thickness and resistivity variations. The synthetic data for the ground-truth model were finally inverted to test the detection capability of tCSEM. The aim of our research was to evaluate the applicability of tCSEM technology in East Malaysia environment by studying the effect of target and water depth, target thickness, target resistivity variation, and target detection limits using a combined numerical modelling and inversion approach. The results of modeling and inversion studies suggest that the tCSEM method is capable of detecting hydrocarbon reservoirs in East Malaysia environment. The inversion responses become more significant when dealing with thick, strong resistivity, and shallow marine hydrocarbon target. From the case of target depth variation, the inversion responses capable to distinguish hydrocarbon target at difference depth. From this study, we capable to investigate in detail about the strength and limitation of this method in East Malaysia environment and this beneficial information can become a guideline for future feasibility study and tCSEM survey planning. Furthermore, this method also can be used as an alternative method to provide technical solution and reduce exploration risk especially in shallow marine environment.