Owing to advances in seismic technology two of the major components in conventional prospects, trap geometry and reservoir presence, can be so fully evaluated that these components often carry minimal exploration risk. As a consequence the primary cause for dry holes and sub-economic discoveries has now shifted to being the result of seal failure. A survey done by Schlumberger proposes that 45% of industry dry holes are owing to lack of seal. A recent paper by Rudolph and Goulding (2017) supports idea. A post mortem study of exploration drilling by Exxon over a ten year period found that 50% of the dry holes resulted from trap failure and this percentage increased to 60% in mature or well understood plays. Despite these findings there is a lack of understanding regarding importance of seals in hydrocarbon trapping and the sophistication of seal evaluation. In most work flows seal evaluation is commonly done with little technical rigor during the time squeeze at the end of a prospect evaluation and the seal evaluation is often so superficial as to be nearly meaningless.

Part of the reason for a lack of rigor is complacency, a misplaced attitude of - I have a thick shale so how can there be seal risk? But beyond this there are systemic factors that confuse, misdirect and frustrate non-specialist's efforts. First, there is no consensus among practitioners about sealing mechanisms and how to evaluate them - i.e. there is no accepted seal evaluation workflow. During the 2012 EAGE conference on seals a poll was conducted and on nearly every question sizable minorities disagreed with the majority views. For example, on the question whether fault gouge acts as a static seal, 59% of respondents said it often did and 27% said it did not. Second, larger companies have conducted research in this area, but data and conclusions are proprietary and key concepts are under documented in published literature. Those doing evaluations are forced to extrapolate globally from a very limited number of local studies. It is common to have a major concept based on a single published study. A cynic, with justification, may see the foundations of seal evaluation as so weak that the whole effort is invalid.

To do better and realistic seal evaluations leading to fewer dry holes, requires three things:

1. A good technical understanding of seal failure mechanisms including misconceptions and evaluation pitfalls. As cases in point knowing when gas chimneys are positive risk features or why blown traps in the North Sea are still often drilled as discoveries.

2. A Play Based Exploration approach that fundamentally asks "What do you know and where do you know it?" Doing play focused lookbacks that establish baseline statistics on seal failure and comparison of your prospect's seal to both known successes and failures in terms of facies, seismic character, physical properties, etc. As an example, typical deepwater shales in Brazil retain less than half the hydrocarbon column of typical deepwater shale seals in the Gulf of Mexico.

3. 3. A coherent risking philosophy that weighs both confidence in the seal model and the technical conclusions from that model. A philosophy that takes the degree of uncertainty in the seal model as part of the risking input. Quotes from statistician George Box are relevant to this, All models are wrong but some are useful and How wrong do they have to be to not be useful.