CycloLog is a specialised software package designed for well log interpretation within the petroleum industry. Developed by ENRES International in the Netherlands, it provides geologists and petroleum engineers with a suite of tools to analyse and process well log data, focusing on generating stratigraphic and sedimentological information. The software is particularly valuable in hydrocarbon fields where traditional biostratigraphic or chemostratigraphic data are unavailable or insufficient for accurate well correlation. By offering a data-driven, unbiased approach, CycloLog aims to enhance the speed and accuracy of interpretation, providing reproducible results that reduce time spent on correlating wells and discussing stratigraphic models.
The core functionality of CycloLog centres on well correlation, a critical process in understanding subsurface geology and identifying potential hydrocarbon reservoirs. The software incorporates the INPEFA® (Inverted Fourier-Filtered Phase Accumulation) technique, which allows users to better recognise well correlation points and depositional trends. INPEFA® can be applied to multiple well logs of various types and resolutions with a few simple clicks, making it a fast and versatile tool. This method is data-driven, which limits bias compared to model-driven interpretations, and is designed to support the workflow of petroleum geologists working with well logs. The software also facilitates the generation of log-based well correlations and zonations, and it allows for an in-depth analysis of logs within an established stratigraphic framework through several functions.
Beyond correlation, CycloLog offers advanced spectral analysis functions to decompose composite waveforms into simple sine and cosine waves. Given that the spectral properties of geological data can vary throughout a well, the software employs a sliding-window approach. This involves performing analysis repeatedly on successive, overlapping windows of data, typically starting from the bottom of the well and moving upward. The length of the window is user-configurable, with a default of 40 metres. The spectral analysis methods available in CycloLog include Fourier Transform, Maximum Entropy (spectral estimation), Wavelet (Gabor), Wavelet (Modified), and Walsh Transform. The Fourier Transform is suitable for data expected to conform to continuous waves, while the Maximum Entropy approach differs by focusing on the information content (entropy) of the dataset, though its results are expressed as a power spectrum similar to Fourier analysis.
The software also includes a Petrophysics Module, which provides functions for log analysis and processing. A key feature within this module is porosity calculation. CycloLog can calculate porosity from density and neutron logs. The combined porosity is computed as the root-mean-square of the porosities derived from the density and neutron logs separately. For accurate calculation, the lithology of the matrix must be known, and standard density values are provided for common rock types such as sandstone (2.648 g/cm³), limestone (2.710 g/cm³), and dolomite (2.850 g/cm³). Fluid density is also required, with freshwater typically at 1.0 g/cm³ and brine at 1.1 g/cm³. Alternatively, the matrix density can be obtained directly from the log data. The workflow involves selecting the relevant logs and specifying the depth interval for calculation through a dialog box in the software.
Another significant capability is the calculation of Total Organic Carbon (TOC) from well logs. The TOC curve in CycloLog is calculated using the Δ log R technique, as described in Passey et al. (2009). This method involves overlaying a porosity log (such as sonic, neutron, or density) on a resistivity curve. The curves are baselined in a fine-grained, non-source rock interval. Organic-rich intervals are identified by the separation of the two curves, known as the Δ log R, which is linearly related to TOC and is a function of maturity. CycloLog supports several log combinations for this purpose, including resistivity–sonic, resistivity–neutron, and resistivity–density, with each log required to be in specific units (e.g., resistivity in ohms, sonic in µsec/ft).
CycloLog is a Windows-based software package and is the result of specialised consultancy services by ENRES International, which pioneered research into the relationship between sequence stratigraphic concepts, cyclostratigraphy, and sedimentology. The software is a product of this research. It is marketed through a technical alliance between PanTerra Geoconsultants B.V. and ENRES, with PanTerra being the entity that holds the copyright for the software and its associated documentation, such as the user guide for the Petrophysics Module. The software and its registered trademark, INPEFA®, are protected by copyright laws. The user guide is updated as of 2021 (Version 2021), and while every effort is made to ensure accuracy, the information is subject to change without notice.
For potential users or those interested in the software, the provided sources indicate that direct contact with the provider is the method for obtaining further information or expressing interest in CycloLog®. The sources do not provide information on pricing, licensing, or trial versions, nor do they detail any promotional offers or free samples related to the software. The focus of the available information is strictly on the technical capabilities, workflow support, and application of the software within the petroleum industry's well log interpretation processes.
Conclusion
CycloLog is a comprehensive software solution for well log interpretation, offering advanced tools for well correlation, spectral analysis, porosity calculation, and Total Organic Carbon assessment. Its data-driven approach, particularly through the INPEFA® technique, provides petroleum geologists with a faster, more accurate, and unbiased method for analysing well logs and generating stratigraphic models. The software is designed to work with various log types and resolutions, supporting efficient workflows in the field. While the sources provide a detailed overview of its functionalities, they do not contain information on commercial aspects such as availability, cost, or any free trial opportunities. Interested parties are directed to contact the provider for further details.