Wednesday, February 28, 2018
Top floor of Total Building- Access to the Downtown tunnel system
Social 11:15 AM, Luncheon 11:30 AM
Cost: $35 pre-registered members; $40 for non-members/ALL walk-ups;
$35 for Emeritus/Life/Honorary; $15 for HGS student members if pre-registered and pre-paid.
To guarantee a seat, you must pre-register on the HGS website and pre-pay with a credit card. You may walk up and pay at the door if extra seats are available. Please cancel by phone or email within 24 hours before the event for a refund. Online & pre-registration closes Tuesday, February, 27 at 5:00 AM
Speaker: John Karlo
Your next dry hole will most likely be caused by seal failure
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. In part as a consequence of this, the primary cause for dry holes and sub-economic discoveries has now shifted to being 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 this describing a lookback study of exploration drilling by Exxon for a ten year period and finding that 50% of their dry holes were owing to trap failures and this percentage actually increased to 60% of dry holes in mature well understood plays. Despite this, there is a major mismatch between the importance of seals in hydrocarbon trapping and the sophistication of seal evaluation. In most workflows, 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 frustratenon-specialist’s efforts. Firstly, there is no consensus amongst 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 of whether fault gouge acts as a static seal – 59% of respondents said it often did but 27% said it did not. Secondly, larger companies have done large amounts of research but data and conclusions have mostly been kept proprietary and key concepts are under-documented in the literature. Those doing evaluations are forced to extrapolate globally from a very limited number of local studies. It is unfortunately 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, for example, 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) 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”.
John Karlo has a BA from Rutgers, an MA from Univ. Missouri and a Ph.D. in structure and tectonics from S.U.N.Y. He taught structure and geophysics at Central Michigan University before joining the industry. He spent 30 years with Shell followed by 5 years with Maersk Oil and 2 years with Repsol. He has had positions in play development and prospect evaluation, regional teams, deepwater exploration, merger and acquisition and for 10 years was a senior advisor in Quality Assurance overseeing rigor in structural interpretation. He has worked in rifts, passive margins, fold belts and turbidites in over 25 basins worldwide. Some of the high points in his career include the first regional synthesis of the Dutch North Sea tectonics, groundbreaking work on Gulf of Mexico salt tectonics and deepwater exploration leading to world-class discoveries in Nigeria. His current focus is on the complex subject of seal evaluation and the seismic expression of structural styles, subjects where he feels he can contribute to the education of the upcoming generation of geoscientists.