From RAW Quarry stone to standard:
22 standards, each of them composed of four octagonal rock slabs, are stored in 11 steel cylindrical tanks. Most of them are made of limestone, others of dolomites or quartzitic sandstones coming from different quarries around the world.
The rock standards are totally saturated (Drying and imbibition cells coring workshop), with fresh water or with brines of different salinity.
To become a standard, each raw stone is characterized by petro physical and mineralogical measurements. This term is used for an apparatus or material defined with a given quantity, a stated value and an associated measurement uncertainty, used as a reference. To ensure our references, all our measurements are checked by an accredited calibration laboratory, and our measurement processes are analyzed. All measurements are done using the International System of Units.
Owing to the measurement management system selected, the Calibration Center could apply for accreditation and become a certification center. TEP ASD will be accredited by ISO 17025, ISO 10012 and/or COFRAC.
ROCK STANDARDS TANKS
The tanks are four meters high and two meters in diameter, and each one holds two rock standards. 4.45-m rat hole is located below each tank to allow logging tool detectors to be set at the right position in front of each rock standard. Standards are 1.5m thick and 1.5m in diameter and drilled with a central hole. Each one is made of four individual octagonal rock slabs.
Rock facies were selected based on geological, geochemical and petrophysical criteria including:
- Three main lithologies; Limestone, Sandstone and Dolomite.
- Petrographic facies containing as much calcite or quartz or dolomite as possible. The objective is to obtain "clean" facies (Volume of main mineral = 0.99-0.95 v/v) so that the Grain Densities (RhoG) are as close as possible to 2.710, 2.654 and 2.870 g/cc.
- A wide range of porosities (0 to 0.40 v/v) in the three main lithologies.
- Uniform petrophysical parameters (mainly porosity) across the slabs and standards.
- Limited occurrence of:
- Clay minerals.
- Any hydrated minerals (or with hydrogen ions in the crystal, giving them a Hydrogen Index (HI). This includes minerals such as hydrated silicates (opal), micas (including glauconite), and certain evaporites or hydrated oxides such as Goethite or Limonite, zeolithes, amphiboles, etc.
- Organic materials (coal, bitumen, etc ...)
- Any elements with a high neutron capture section such as gadolinium or samarium, which skew neutron measurements at very low concentrations (a few ppm).
The different selected facies are shown in the following table. The final choice for different facies is still subject to change however.
22 ROCK STANDARDS
22 standards (in 11 tanks) are located in the basement of the building and consist of 3 main lithologies limestone (shown in blue), dolostone (pink) and sandstone (yellow), 3 different water-based fluids (0 to 200g/l NaCl), 5 different porosity ranges and 4 different borehole sizes (106 to 300mm). 5 extra tank slots are available in the building basement for future use (grey).
FROM RAW QUARRY STONES TO ROCK STANDARDS
Transforming a raw quarry stone block to a rock standard is a lengthy process. The different stages include geometrical cuts, sampling for geoscience analyses and geometrical characterization and QC. The main stages are summarized below:
The rock slab sampling and analysis policy is summarized in the figure below. A complete set of petrophysical and geochemical analyses are measured on the slab central cores and lateral plugs to obtain a complete rock slab characterization. Most of the rock standard characterizations will be handled by the Total laboratories in Pau.
The different analyses are:
- Petrophysical measurents such as: helium porosity, permeability, grain density of plugs and grain density of rock powder.
- Organic matter Rock Eval analysis (optional)
- Geochemical major elements from XRF and Leco C-S measurements. Trace elements from ICP-MS mass spectrometry.
- Qualitative mineralogy using Raman spectrometry mapping (See example below)
- Quantitive mineralogy using QemScan analysis (Quantitative Evaluation of minerals by Scanning Electron Microscopy (FEI company) . This technique uses both EDX analysis from four dispersive X-ray Bruker detectors in combination with data from a Back Scattered Electrons (BSE) dectector. The images and Qemscan analysis exemples below shows how mono-mineral the calibration standards are. Dual Energy Ct Scan, on the central cores, lateral slabs and central core plugs.
- Artax XRF, natural spectral gamma rays, gamma-gamma density, Vp and Vs logs on central cores.
- Surface velocity mapping of the octogonal rock slabs .