Responding in Critical Times

Dave Rensink in July on NBC Nightly News, one of multiple interviews he’s provided for the national and international media regarding the Gulf of Mexico.
Dave Rensink in July on NBC Nightly News, one of multiple interviews he’s provided for the national and international media regarding the Gulf of Mexico.

This is a crucial month for the Gulf of Mexico in specific and the oil industry in general. This is the month BP expects to have a relief well in a position to stop the flow of oil from its deepwater well in Mississippi Canyon Block 252.

With luck, BP could already have stopped the flow by the time this issue of the EXPLORER reaches your desk, but the uncertainties of the weather and drilling operation could just as well push it beyond BP’s target of an August completion. This catastrophe has significantly raised the public’s awareness of offshore drilling operations, but certainly, not in the manner we would have preferred.

AAPG has provided background information to the media on offshore operations during this period. Talking to the media carries the risk of being misquoted, and some of my statements have been taken out of context and qualifiers have been deleted.

However, I believe remaining silent carries a greater risk. As petroleum geologists, we have a unique perspective on drilling operations. Many of us have spent a significant part of our careers on and around onshore and offshore drilling rigs.

We also have the ability to gather information from multiple sources, provide a coherent, objective interpretation and present it in a manner that can be understood by non-technical people. We have been selling geologic prospects to non-technical managers and executives for years.

The members of the media have received an education in science and engineering as a result of their coverage of the spill. That is evident in the questions they ask and their improved ability to comprehend the answers.

The knowledge we petroleum geologists have collected through education and experience, and which we largely take for granted, is foreign to many within our industry and to virtually all of those outside of it. We truly are a tribe, and the dialect we speak is not well understood beyond the tribe. We need to work on that.


The oil spill has once again raised the call for the United States to wean itself from its oil addiction.

In as much as we use 18-20 million barrels of oil per day – and approximately 75 percent of that is used for transportation – it is unlikely that will occur in the near future.

However, it is worth reviewing the U.S. and world oil consumption trends for the last 30-35 years. The two consumption rates do have similar trends, as noted on the accompanying chart – but do not get caught up in the fact that the two curves seem to overlap. That is a scaling issue.

U.S. oil consumption flattened out after 2004 and declined from 2007 to 2009. The decline in 2008 and 2009 can be attributed to the decline in the U.S. economy. It will be interesting to see if the trend will reverse as the economy improves in 2010 and beyond. The flattening from 2004 to 2006 is similar to a stabilization of demand from 2000 to 2003.

It is tempting to speculate that the period from 2000 to 2006 represents the amount of oil 300 million people require to maintain the current standard of living.

It also is tempting to say that M. King Hubbert may have been right.

Hubbert, in an article published in 1956, proposed that the depletion of a finite resource can be approximated by a normal distribution – a bell shaped curve. This led to the controversial concept of peak oil. His prediction that U.S. oil production would peak in the late 1960s was actually fairly close to reality; U.S. oil production peaked in the early 1970s.

Inspection of the world consumption since 1981 could lead the bold to suggest the world is on the left arm of a broad, normal curve, and that the world consumption is flattening at approximately 85 million barrels of oil per day. Besides the fact that a few points do not necessarily constitute a trend, it would be hard to rationalize that interpretation with the increasing energy demands of China and India.

Therefore, I like an interpretation suggested by Matt Simmons in the February 2010 issue of World Oil. His position is that we may be seeing the effects of an aging infrastructure. We are not limited by the size of the resource. We have simply reached the capacity of the system.

That observation may apply to the United States as well as it does to the world.


I want to leave you with these words – Search and Discovery. If you have not been on our open access Search and Discovery website, you are missing an impressive petroleum geology database that is growing every month.

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President's Column - David G. Rensink

David G. Rensink, AAPG President (2010-11), is a consultant out of Houston. He retired from Apache Corp in 2009.

President's Column

AAPG Presidents offer thoughts and information about their experiences for the Association. 

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Umiat field in northern Alaska is a shallow, light-oil accumulation with an estimated original oil in place of more than 1.5 billion bbl and 99 bcf associated gas. The field, discovered in 1946, was never considered viable because it is shallow, in permafrost, and far from any infrastructure. Modern drilling and production techniques now make Umiat a more attractive target if the behavior of a rock, ice, and light oil system at low pressure can be understood and simulated.

The Umiat reservoir consists of shoreface and deltaic sandstones of the Cretaceous Nanushuk Formation deformed by a thrust-related anticline. Depositional environment imparts a strong vertical and horizontal permeability anisotropy to the reservoir that may be further complicated by diagenesis and open natural fractures.

Experimental and theoretical studies indicate that there is a significant reduction in the relative permeability of oil in the presence of ice, with a maximum reduction when connate water is fresh and less reduction when water is saline. A representative Umiat oil sample was reconstituted by comparing the composition of a severely weathered Umiat fluid to a theoretical Umiat fluid composition derived using the Pedersen method. This sample was then used to determine fluid properties at reservoir conditions such as bubble point pressure, viscosity, and density.

These geologic and engineering data were integrated into a simulation model that indicate recoveries of 12%–15% can be achieved over a 50-yr production period using cold gas injection from five well pads with a wagon-wheel configuration of multilateral wells.

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Gas generation is a commonly hypothesized mechanism for the development of high-magnitude overpressure. However, overpressures developed by gas generation have been rarely measured in situ, with the main evidence for such overpressures coming from source rock microfractures, the physical necessity of overpressures for primary migration, laboratory experiments, and numerical modeling. Indeed, previous in-situ observations suggest that gas generation only creates highly localized overpressures within rich source rocks. Pore-fluid pressure data and sonic velocity–vertical effective stress plots from 30 wells reveal that overpressures in the northern Malay Basin are primarily generated by fluid expansion and are located basinwide within the Miocene 2A, 2B, and 2C source rock formations. The overpressures are predominantly associated with gas sampled in more than 83% of overpressure measurements and have a sonic-density response consistent with gas generation. The association of fluid expansion overpressures with gas, combined with the sonic-density response to overpressure and a regional geology that precludes other overpressuring mechanisms, provides convincing in-situ evidence for basinwide gas generation overpressuring. Overpressure magnitude analysis suggests that gas generation accounts for approximately one-half to two-thirds of the measured excess pore pressure in the region, with the remainder being generated by coincident disequilibrium compaction. Thus, the data herein suggest that gas generation, if acting in isolation, is producing a maximum pressure gradient of 15.3 MPa/km (0.676 psi/ft) and not lithostatic magnitudes as commonly hypothesized. The gas generation overpressures in this article are not associated with a significant porosity anomaly and represent a major drilling hazard, with traditional pore-pressure prediction techniques underestimating pressure gradients by 2.3 plusmn 1.5 MPa/km (0.1 plusmn 0.07 psi/ft).
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Information on fractured reservoirs is often controversial. Engineers see lost circulation, negative skin and fracture well test signatures. Geologists see only matrix properties in their cores.

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Carbon capture and sequestration (CCS) is perhaps commercially viable but not proven at commercial scale, according to 100 clean-energy experts that recently released their recommendations to the White House: "Powering Forward: Presidential and Executive Agency Actions to Drive Clean Energy in America."

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