Chemical stratigraphy
Chemical stratigraphy is a reservoir correlation tool involving the interpretation of inorganic geochemical data.
Hierarchical zonations are developed using graphical and statistical techniques based on variations in key elements and ratios. Chemical stratigraphy can be utilised successfully on any stratigraphic interval from any geographic location. It has been effectively applied by RPS on a worldwide basis for many operating companies.
Inductively Coupled Plasma (ICP)
An inductively coupled plasma (ICP) is defined as a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction.
The two types of ICP machine used by RPS are ICP-OES (Inductively Coupled Plasma – Optical Emission Spectrometry) and ICP-MS (Inductively coupled Plasma – Mass Spectrometry). ICP-OES involves measurement of wavelengths of light and is used to acquire data for major elements (e.g. Si, Ca, Mg, K, Fe) and high abundance trace elements (e.g. Zr, Sr, Ba). By contrast wavelengths of radiation are measured by ICP-MS, which is used to generate data for low concentration trace elements (e.g. Cs, Ta, U) and rare earth elements (e.g. La, Ce, Yb).
- Employing a combination of ICP-OES and ICP-MS it is possible to generate data for c.50 elements in the range Na-U in the periodic table and to achieve detection limits as low as 1ppb.
- The potential to correlate reservoir sections that are problematic using conventional methods due to the depositional setting or thermal degradation/dissolution
- Capable of high resolution stratigraphy and applicable to all lithologies
- Direct implications for provenance, weathering and diagenetic studies
- Increasingly used to provide near ‘real-time’ data at wellsite
X-ray fluorescence (XRF)
X-ray fluorescence (XRF) involves bombarding rock material with high energy X-rays. This results in ionization of atoms and emission of radiation.
The raw data comprises a series of wavelets, each one with a unique wavelength of radiation and representing a specific element. Based on ‘peak height’ and ‘area’ of each wavelet, the concentrations of individual elements may be calculated. It is possible to obtain data for c. 43 elements in the range Na-U in the periodic table, with detection levels of c.1ppm achieved for most elements (1wt% oxide = c.10,000ppm).
- The potential to correlate reservoir sections that are problematic using conventional methods due to the depositional setting or thermal degradation/dissolution
- Capable of high resolution stratigraphy and applicable to all lithologies
- Direct implications for provenance, weathering and diagenetic studies
- Used to provide near ‘real-time’ data at wellsite.
Analysis can be performed on wet ditch cuttings, washed and dried ditch cuttings, sidewall core, core or outcrop samples, with all preparations undertaken in our own laboratory. Typically, projects can consist of up to 200 samples per well depending on the interval size and the required level of resolution
Wellsite chemical stratigraphy
RPS provides wellsite chemical stratigraphic services by offering our own high specification XRF machines capable of being mobilised to any destination globally.
Backed by our highly experienced team of chemical stratigraphers and technicians who are able to deliver the service safely and efficiently.
- Near ‘real time’ results to aid with the placement of coring, casing and TD picks
- Reduction in drilling risk and uncertainty
- Stratigraphic positioning and as a ‘look-ahead tool’
- Geo-steering and well trajectory monitoring
- Can be applied to all ages of sediment from Neogene to Pre-Cambrian
- Ability to operate in any geographical region onshore or offshore
- Fully insured, logistical and operational support
- Integrated NaviSTRAT™ with Wellsite Biostratigraphy
- 100% safety record with no LTA’s/LTI’s
Dan Atkin