Pitfalls in the interpretation of hydrocarbon indicators

Abstract

Direct Hydrocarbon Indicators (DHI) are seismic anomalies that suggest the presence of hydrocarbons (oil or gas) in rocks. These anomalies occur because hydrocarbons (especially gas) can significantly reduce the speed of seismic waves and alter rock density, changing its elastic properties and generating "brightness" or specific patterns in seismic data. DHI are often relied upon as clear signals of the presence of oil or gas. However, their interpretation can be fraught with errors. This article explores the most common ones made by geoscientists, including "confirmation bias," seismic processing artifacts, and confusion caused by non-commercial gas (fizz gas). It also highlights how changes in lithology, multiple seismic measurements, and misinterpretation of gas vents can generate false positives. To mitigate these problems, this article emphasizes the importance of rigorous validation, critical thinking, and the integration of multiple tools such as geological models, well data, the use of attributes such as curvature and coherence, in conjunction with AVO/AVA analysis, as well as a clear understanding of the area's petroleum system. Success in exploration is not based on a single indicator, but on a careful and holistic interpretation of all available data.