Each reservoir presents unique parameters and challenges in optimization. The Probe Reservoir Analysis System is configured using a gamut of production logging sensors and state-of-the art pulsed-neutron sensors. The production logging sensors accurately describe the wellbore environment and performance. This data is enfolded in the pulsed-neutron workflow for characterization and interpretation of the reservoir parameters. This combination of sensors creates a comprehensive data set, thus providing a complete solution for reservoir characterization.
The versatile RAS pulsed-neutron features multiple acquisition modes. Depending on water salinity and hydrocarbon type, it can acquire data for Sigma (the thermal neutron capture cross-section), C/O (carbon-oxygen logging), or, a combination paradigm. The inversion of the pulsed-neutron data for reservoir fluid requires knowledge of the wellbore environment and reservoir fluids, as well as, information on the reservoir porosity and facies. The four processing objects below work in concert using the RAS data and other available data sources, such as open-hole and LWD logs, mud logs, cores and field history to generate accurate results for reservoir optimization.
RAS-Sigma
This module uses the Sigma data set to predict reservoir water saturation, and can also be applied to determine reservoir gas saturation. The program uses the variable-matrix model to incorporate rock matrix variations into the inversion. The RAS-Sigma can be coupled with the RAS-CO module to determine gas saturation in 3-phase reservoirs.
RAS-CO
Accurate determination of oil saturation from carbon and oxygen measurements requires a comprehensive description of the wellbore environment and reservoir rock parameters. This module uses a multi-parametric inversion for oil saturation based on empiricism; a characterization database for the specific reservoir and wellbore parameters is used as the basis for the inversion.
RAS-Lith
This module provides rudimentary rock type (i.e. lithology) for the calculation of effective porosity and for rock parameters used in RAS-Sigma and RAS-CO.
RAS-GasPhi
This module provides the porosity inputs for RAS-Sigma and RAS-CO. Calculated parameters include the total and effective porosity of the reservoir.
Reservoir Characterization
Accurate results require the creation of a measurement database that incorporates parameters of the specific reservoir. To generate this empirical data for the characterization, Probe Petrophysics have developed computer-based models of the RAS pulsed-neutron sonde using the radiation transport code MCNP. Using this environment, the characterization database for inversion can be specifically matched to reservoir parameters such as reservoir rock chemistry, hydrocarbon type and wellbore environment.
