RDR's detailed sample characterization procedures allow fault and top seal threshold pressures to be determined. RDR also specializes in the measurement of fault permeabilities for input into reservoir simulation models. This data provides key input into both exploration and production assessments and is aligned with RDR's new Petrel module to allow core calibrated data to be seamlessly integrated into the simulation and exploration processes.
Structural logging of core and wellbores enables the determination of deformation style, deformation timing, deformation distribution, scaling and clustering, and sub-seismic to seismic links.
Fault and top seal permeabilities and threshold pressures are controlled by mineralogy and chemistry, provenance, diagenesis and fluid-rock interactions, fabrics and microstructures, grain and pore networks, deformation processes and products, reactivation, and seal breaching. Scanning electron microscopy, supplemented by X-ray tomography and X-ray diffractometry as appropriate, enables us to deliver high quality results.
Petrophysics addresses quantification of the rock properties controlling fluid storage and fluid flow. We employ state-of-the art equipment for measuring the permeability and porosity and capillary properties of reservoir and seal lithologies.
Rock property databasing
We have a custom built database for fault rock and top seal properties, together with contextual and critical geohistory data. It can also be populated with data bought from reports for sale. The generation of such robust databases allows for the prediction of flow properties.
Equipment and Techniques
RDR employs a range of equipment and techniques for special core analysis. Those used most often are summarized below. Please enquire if you are interested in something not itemized as we may be able to help.
We use a variety of cutting, coring, lapping, sectioning, impregnation, and polishing equipment. Embedded in our approach is the recognition that careful sample preparation is critical to the overall success of the work program. We prepare samples in-house to ensure that appropriate handling is maintained. We prefer to sub-sample core ourselves as this enables us to select features or areas of special interest and also ensures that we avoid obvious damage. For particularly delicate samples, we employ a band saw to minimize vibration and stress. We can store frozen samples down to -45°C and can use liquid nitrogen during cutting and coring. Please note that sample preparation is offered only as an integral part of broader analytical work programs.
Scanning electron microscopy (SEM)
We use a Camscan CS44 thermal emission instrument running a LaB6 filament. Capable of imaging at sub-micron resolutions, this microscope carries a suite of detectors (secondary electron, backscattered electron, cathodoluminescence and wavelength-dispersive X-ray) that reveal information on topography and chemical composition. Micrographs are saved digitally and can be processed to quantify variables such as mineralogy and porosity. SEM has many advantages over standard (light) microscopy:
- The high magnifications that are achievable make even ultra-fine materials accessible.
- Optically dense and opaque materials can be characterized.
- Imaging relies on near surface interactions and is thus relatively insensitive to depth effects.
- X-ray analysis facilitates mineral identifications and chemical characterization.
CL detection is also fully integrated with the other imaging modes.
X-ray tomography (CT)
We have access to two CT instruments for 3D imaging of rock samples. Standard CT employs a Picker PQ2000 instrument with a resolution down to 0.25 mm. Capable of accommodating large samples (such as entire core lengths) this equipment has found various applications including: identifying core damage prior to cutting, imaging encased or frozen samples, imaging faults and fractures in order to steer coring and cutting, monitoring phase saturation's during fluid flow experiments. Micro CT employs a Phoenix x-ray Nanotom instrument with a resolution down to 2 microns. Best suited to small samples (mm-scale) the equipment can be used to investigate internal grain and pore structures.
X-ray powder diffractometry (XRD)
We have access to a Phillips PW1050 instrument for quantitative XRD analyses. Conducted on samples prepared to ensure random grain orientations and incorporating an internal standard, the technique is capable of generating mineralogical analyses accurate at the 95% confidence level to ±X0.35 where X is the concentration in wt.%. XRD is especially useful for samples where image analysis on micrographs proves problematic (e.g., fine-grained microporous top seal lithologies).
Permeametry—determining fault rock permeabilities
We have access to a wide range of instruments for measuring the permeability of rocks:
- Steady-state liquid permeametry—employs a water flow-pump instrument capable of measuring permeabilities from 10 D down to 0.005 mD and confining pressures up to 10,000 psi.
- Steady-state gas permeametry—employs a nitrogen flow instrument capable of measuring gas permeabilities from 10 D down to 0.01 mD at confining pressures up to 10,000 psi. Klinkenberg corrected permeability is obtained through repeat measurements at different gas pressures.
- Gas pulse-decay permeametry—employs a CoreLab 200 PDP instrument capable of measuring gas permeabilities from 0.1mD down to 10nD at confining pressures of up to 2,000 psi. Repeat measurements at different mean pore pressures provide Klinkenberg corrected permeabilities.
- Probe permeametry—employs an EPS Coresystems DPP200 digital instrument capable of measuring permeabilities from 1D down to 0.005 mD. The equipment is ideal for investigating fine-scale permeability heterogeneity and was specifically designed to work at low flow rates for tight rocks.
- Multi-phase flow permeametry—employs a two-phase (gas-brine or oil-brine) Core Lab Instrument capable of steady and unsteady-state relative permeability measurements at temperatures up to 150°C and pressures up to 10,000 psi. The phase saturation is monitored via CT scanning.
Porosimetry and capillary properties—determining fault rock threshold pressures
We have access to a range of instruments for investigating porosity and capillary properties in rocks:
- Helium porosimetry—employs a Quantachrome Stereopycnometer. Capable of an accuracy exceeding 0.2% and capturing pores down to around an Angstrom, the technique yields total porosity but does not give information on pore size distributions.
- Mercury injection porosimetry—employs a Micromeretics Antopore III 9420 instrument. Capable of incremental intrusion at pressures up to 60,000 psi, the technique yields both total porosity and pore size distributions. MIP is used routinely on reservoir and seal lithologies to determine the threshold pressures controlling capillary sealing.
- Capillary pressure and resistivity equipment—capable of confining pressures up to 5,000 psi and temperatures up to 200°C is used to simulate reservoir temperature and pressure conditions.