Compositional Density Porosity: Leveraging Geochemical Data as an Exploration and Petrophysical Tool

Abstract

A critical part of oil and gas exploration is the process of identifying, correlating, and mapping zones of interest using geophysical well logs. Typically, a series of standard logs (gamma ray, density and neutron porosity, resistivity, etc.) are used to interpret reservoir properties such as lithology and porosity, with the latter parameter being particularly important for identifying and mapping pay. We show that XRD and XRF data from core and cuttings can be used in conjunction with wireline bulk density data to generate “compositional” density porosity logs. Whereas standard density porosity logs are computed using a homogenous quartz, limestone (calcite), or dolomite matrix density value, the compositional log uses a changing average matrix density based on the actual mineralogical composition of the pertinent stratigraphic horizons. In absence of more sophisticated laboratory data, this approach allows the exploration geologist or petrophysicist to make improved interpretations about a particular reservoir, without invoking assumptions about rock composition or homogeneity. This process is particularly useful for investigation of bypassed or otherwise poorly understood zones, but it also provides time- and cost-savings where more exhaustive analytical methods are either logistically impractical or prohibited by project budgets. Examples are presented here in which laboratory porosity values are compared with compositional and wireline density porosity data from hydrocarbon-producing wells in the Montney Formation of the Western Canada Sedimentary Basin. The data are used to demonstrate the rationale and application of the process.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016