Experimental evaluation of hydrocarbon detection with the Long-Offset Time-Domain Electromagnetic Method in the Cretaceous carbonates of the Tampico–Misantla basin, Mexico

Abstract

In Mexico, an experimental study with a Long-Offset Time-Domain Electromagnetic Method (LOTDEM) was carried out in the Tampico–Misantla basin of northeastern Mexico. The main objective was to evaluate this method for hydrocarbon exploration. The selected area is suitable for LOTDEM experiments because high quality seismic data, geological information and well logging data are available. The results obtained are excellent, and allow us to determine the types of fluids present in the rock pores and fractures of the studied geological structures. Resistivity anomalies correlate in position and depth with the geological structures observed in the seismic sections where the LOTDEM survey was carried out, and with well logging data from the nearby Franco Española oil field. In the studied area, these structures are 800–1200 m deep, in carbonate rocks with high clay content and are invaded by salt water. Consequently, the resistivity and primary porosities are very low. The main reservoirs of oil and gas in this region are a naturally fractured basinal facies, consisting of fine-grained limestones and shaly limestones, that corresponds to the Cretaceous units San Felipe, Agua Nueva, Tamaulipas Superior and Tamaulipas Inferior. The fractured rocks reservoirs are very difficult to detect, even with well logs. However, the results of this survey show the higher resolution, the greater depth of investigation, and the advantages that the LOTDEM method present compared to the traditional frequency domain electric and electromagnetic (FEM) methods.