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Many Viewpoints, One Vision
Part 7

Date: 10/05/2012

Trap, Reservoir, Charge, and Seal

No matter how sophisticated the model used or the level of detail of the data input, managing exploration risk essentially comes down to understanding four factors— trap, reservoir, charge, and seal. For over 30 years, operators have used these factors to define the degree of risk that each exploration prospect presents. Trap concerns the likelihood that the prospect contains a geological mechanism to trap any hydrocarbons that have formed over time. Reservoir refers to the presence of porous, permeable rock in which the hydrocarbons can accumulate. Charge considers the presence of nearby source rock for forming the hydrocarbons together with a path for hydrocarbon migration to the reservoir rock. Finally, seal expresses the degree to which the trap is strong enough to keep the hydrocarbons in place.

Basin and petroleum system modeling assesses the four risk factors of trap, reservoir, charge, and seal in a systematic way. Advances in seismic technology have made significant contributions to improving the evaluation of trap and reservoir risks, but almost three-quarters of exploration well failures result from an inadequate understanding of charge and seal risks. Assessing charge risk requires an understanding of how the source rock matured relative to the timing of formation of the trap. The key is that the trap—and seal—must be present when the hydrocarbons migrate through the basin fill. Seal risk has to do with whether the integrity of the seal has remained uncompromised until penetrated by the exploration well.

A full, integrated evaluation of exploration risk can now be conducted in a unified analysis using the Petrel E&P software platform. Schlumberger has introduced new functionality that complements existing Petrel platform geology and geophysics modules, including a new geological structural framework tool, the Petroleum Systems Quick Look module, and integration with the Techlog wellbore interpretation platform. Techlog software, developed by Techsia, a Schlumberger company acquired in May 2009, forms another complement to Petrel earth models through the integration of all measurements made in the wellbore. Development of the Petrel-based exploration system has also benefited from the Schlumberger acquisitions of IGEOSS in April 2010 to add modeling capabilities, particularly for areas of complex geology, and of IES Integrated Exploration Systems Inc., the developer of PetroMod petroleum systems modeling software, in 2008.

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This is a continuing series about Schlumberger Reservoir Characterization Group, the leading provider of technology services and products for oil and gas exploration. Articles in the series will address how the Reservoir Characterization Group unites the many disciplines needed to help achieve exploration success.