AAPG Annual Convention and Exhibition

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The Whys and Wherefores of Geochemistry and Basin Modeling From Exploration to Production


Petroleum geochemistry and basin modeling, also known as petroleum systems analysis, are used along the entire subsurface value chain from exploration to production. Traditionally these disciplines have been applied mainly in Regional Exploration and Prospect Evaluation to evaluate source rock properties, charge and fluid property risk. Exploration wells have for decades been a key way to acquire data on source rock properties and thermal maturity, which are used in further evaluation of a basin. Fluid data from discovery wells are used to calibrate basin models, as well as in Appraisal and Development. Geochemistry plays a key role in the assessment of failure in dry holes, which can be critical in evaluation of remaining prospectivity in a basin. A detailed fluid property description across a field from geochemical and PVT fluid data, combined with a thorough filling history from basin modeling, can be used in Appraisal and Development of a field to help assess connectivity and compartmentalization. These data can also help predict the likelihood of compositional grading, tar mats, flow assurance issues (wax, asphaltenes and organic soaps), and biodegradation (heavy oil). Petroleum geochemistry can be used to help address a wide range of Production issues. These include routine monitoring, allocation, casing issues, water injection problems, compartmentalization, H2S generation or tar mobilization in heavy oil fields. This is probably the main area where geochemistry is currently underutilized. Basin models have been mainly used in the past as a “one way” technology, where the output is the end product, and not used routinely to model at field scales. However, this has slowly changed over the last two decades, as basin modeling has become more integrated into an iterative, full cycle workflow. Rock properties from seismic are fed into basin models, and pore pressure predictions back into seismic until the pressure and rock properties are in agreement. Reservoir quality prediction on a prospect scale uses basin modeling derived pressure and temperature (p-t) histories as inputs to a reservoir quality models, which are used to either predict porosity, or evaluate if the p-t history can explain the measured porosities. An overview of these synergetic technologies and workflows, and their importance in constraining many subsurface uncertainties, will be presented using published and in house examples.