PEMEX Deep Water Exploration Improvement in the Gulf of Mexico (Seismic and Electromagnetics 3-D Prospecting)

Salazar, Humberto¹; Vazquez-Garcia, Marco; Escalera-Alcocer, J. A.; Roth, Friedrich; Baltar, Daniel; Ricoy, Valente; and Gabrielsen, Pal
¹[email protected]

PEMEX has acquired more than 9500 km² of 3D controlled-source electromagnetic (CSEM) data as part of its deep water exploration program since 2010. The acquisition campaign is carried out systematically on a portfolio level based on 3D seismic and is designed to provide resistivity imaging.

Modern oil and gas exploration is driven by the integration of geophysics and geology. The presented examples demonstrate how 3D CSEM contributes to this integration and helps solving complex exploration challenges: direct hydrocarbon identification for prospect risking, reduce uncertainty in geological probability success and resource estimation, gas hydrate detection for evaluation of potential drilling hazards, study of diapirism for petroleum system analysis, identification of fluid migration pathways or sealing of faults.

We present four examples of integrated interpretation with 3D seismic, demonstrating the information that can be extracted from 3D CSEM data and applications of this information. The first example focuses on prospect maturation, where a resistivity anomaly is used as a direct hydrocarbon indicator (DHI). We discuss how evaluation of anomaly characteristics, such as correlation to seismic attributes and field size estimation based on the area and strength of the anomaly can influence a prospect’s probability of economic success. In the second example, we study potential drilling hazards and show how CSEM can help to identify gas hydrate variability in terms of thickness and concentration over a bottom simulating reflector (BSR). The third example relates to petroleum system analysis where CSEM inversion results are used to study the composition of diapirs, i.e. salt versus shale, and identify fluid migration pathways resulting from faulting. The last example describes regional mapping of resistivity, which may indicate variations in lithology, identify potential shallow hazards and even generate new leads.

The cases we present show the value of using CSEM systematically in a large frontier exploration program. It is therefore essential to integrate CSEM into the common exploration workflows. It is equally important to recognize and address CSEM specific challenges and limitations: low sensitivity as a result of low resistivity pay, ambiguity in reconstructing target depth and resolving stacked objectives due to limited vertical resolution and imaging prospects in the proximity of salt or in rough bathymetric terrain.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013