By Henry S. Pettingill (with contributions by Roger Holeywell and Rocky Roden)

We have learned quite a lot about Direct Hydrocarbon Indicators (DHIs) in Rose and Associates’ DHI Consortium over the past 23 years. Roger, Rocky and I have generated lots of statistics on successes and failures, and we discuss the learnings from them regularly in our Consortium meetings. In several recent conferences and forums outside the Consortium, however, I have asked:  “what do you think the #1 geological outcome is for DHI failures?”

What would your answer be? In every external forum, the first person to shout out the answer has said “LSG”.

What have we learned?

First, that the overwhelming #1 cause of false DHIs is wet sand – usually thick and high-quality wet sand.  In fact, as you can see from the graph below, over 50% of our failures found wet sands, whereas LSG is tied for #2 with non-reservoirs, 18% each.

Second, that for 80% of our failures, the anomaly is caused by lithology (wet sand, non-reservoir or tight reservoir).  Only 20% are due to fluid effects – 18% from LSG and 2% from CO2 gas.

Third, what are the underlying geophysical issues (seismic, rock properties) that can fool us in these wet sand outcomes? The pie chart below addresses this question. As you can see, for three quarters of our wet sand failures, we simply don’t understand how a wet sand response can be reliably distinguished from a fluid effect, most often because of lack of well control or non-uniqueness in the solution space.

What can we do to gauge the wet sand risk?  

1) Do your regional homework, with a rigorous review o well control and well ties.  Geologists and Petrophysicists, you have a role to play here!  2) Respect the non-uniqueness of seismic amplitude causes, especially when dealing with seismic models. Avoid confirmation bias and when shown a model match, ask “what else could it be?”. 3) Consider the geophysical pitfalls such as tuning, seismic artifacts, and unexpected reservoir properties, as well as lateral changes in the encapsulating shales that could ‘brighten’ a wet sand.

Acknowledgement:  special thanks to the R&A DHI Consortium members and leadership – a group of experts who I am still learning from every day!


Pettingill, H.S., and R. Roden (2022), Integrated DHI Prospect Evaluation: Lessons Learned from Three Generations of Explorers. 2022 IMAGE Conference, Houston, August 19, 2022.