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Penn State's Seal Evaluation Consortium (SEC)
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Penn State


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The Seal Evaluation Consortium (SEC) is an international group of oil companies that support research at Penn State on the nature of brittle fracture under overpressured conditions in sedimentary basins. Brittle fracture under fluid pressure is important in the migration of hydrocarbons from source rock to reservoir rock and to the development of fractured reservoirs at depth. High pore pressure has that unique ability to counteract the effect of confining pressure that gives rock considerable strength at depth. The process of brittle fracture starts at pore-scale pockets of overpressured fluids, where microcracks develop to enhance bulk rock permeability and allow the initiation of primary migration of hydrocarbons through source rocks. The further growth of cracks can generate a significant fracture permeability but at the risk to seal integrity through breaching of caprock seals by joint propagation (i.e., a process called natural hydraulic fracturing). A second mechanism for loss of seal integrity is by breaching of fault seals during frictional slip. Either of these mechanisms for seal failure is a consequence of pore pressure exceeding a certain limit at or near the magnitude of the total least horizontal stress in a sedimentary basin. Conditions favoring either one or both mechanisms must develop before secondary migration becomes active. Secondary migration, of course, is an equally important consideration in understanding the evolution of reservoirs associated within the overpressured environment. The stated goal of SEC is to develop a strategy for predicting risk to seals in the vicinity of overpressured zones and to understand the concomitant development of fractured reservoirs in this environment.


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Penn State


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The Seal Evaluation Consortium (SEC) analysis of risk to seals will be designed for those geologists who may not have a high level of technical proficiency in fracture mechanics. The risk analysis will lead the exploration geologist through a simple flow chart, the template of which is shown above. The SEC template lists the major components that affect seal integrity through either natural hydraulic fracturing or fault slip.

Each component is, in itself, not sufficient to cause the propagation of a natural hydraulic fracture through a seal or cause fault slip on a bounding seal. However, certain combinations will lead to breaching and, hence, place a seal at risk. The first five components in the flow chart for risk analysis are concerned with factors which control the total normal stress within a basin and the last four components deal with flaw size, shape, and fracture toughness for jointing through a top seal. All the components in the flow chart are a measure of resistance to joint propagation and, in a sense, act against pore pressure to keep joints from propagating in sedimentary basins. At the same time the top components in the flow chart are a measure of resistance to fault slip.

For each of the major components there is a range of values expected in hydrocarbon-rich sedimentary basins. Since its inception in 1993, research by SEC has made considerable progress on generating the quantitative data to fill out each component of the risk analysis template.


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The following are companies that have contributed to the success of SEC during the period from late 1993 through March 1998:



Agip
Arco
Chevron
Elf-Aquitaine
Exxon
Marathon
Mobil
Shell
Texaco
Total



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PDF launchpad SEC research has covered a variety of topics that can be divided according to the risk analysis flow chart shown above. The following is a list of papers published by Penn State faculty and students whose work has benefited from the support of SEC companies. Some industrial support extends back prior to the formal organization of SEC in 1993 and papers from such support are included in the following list.



These files were saved in a Rich Text Format (rtf). Once you have downloaded the file you can view a file on your computer using any word processor application that can read rft, or just print out the file for whatever purpose you might have.

Select downloadable documents from the table below.



References for risk to seals and development of fractured reservoirs

File Content  File to Download
 Component 1: Pore Pressure ref01.rtf
 Component 2: Hydrocrabon Column Depth & Height ref02.rtf
 Component 3: Tectonic Configuration of Basin ref03.rtf
 Component 4: Lithology ref04.rtf
 Component 5: Poroelasticity ref05.rtf
 Component 6: Size of Flaws ref06.rtf
 Component 7: Nature of Flaws ref07.rtf
 Component 8: Shape of Flaws ref08.rtf
 Component 9: Fracture Toughness ref09.rtf


For further information please contact:

Terry Engelder
Department of Geosciences
The Pennsylvania State University
University Park, PA 16802

phone: (814)-865-3620
fax: (814)-863-7823
e-mail: engelder@geosc.psu.edu


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