A New Multi-Frequency Array-Dielectric Logging Service: Tool Physics, Field Testing, and Case Studies in the Permian Basin Wolfcamp Shale
- S. Forgang (Baker Hughes, a GE Company) | B. Corley (Baker Hughes, a GE Company) | A. Garcia (Baker Hughes, a GE Company) | A. Hanif (Baker Hughes, a GE Company) | F. Le (Baker Hughes, a GE Company) | J. Jones (Baker Hughes, a GE Company) | E. Frost Jr. (Baker Hughes, a GE Company) | S. Perry (Anadarko Petroleum Corporation)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- SPWLA 60th Annual Logging Symposium, 15-19 June, The Woodlands, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2019. held jointly by the Society of Petrophysicists and Well Log Analysts (SPWLA) and the submitting authors
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A new wireline multi-frequency, multi-spacing dielectric logging service has been developed.
The service is based on the performance of a new multiarray electromagnetic propagation instrument operating in a frequency range from tens of Megahertz up to one Gigahertz. The sensor section has been built on an articulated pad which is firmly pressed against the borehole wall, even in enlarged or rugose borehole conditions. The array scheme utilizes four one-inch spaced receivers with three pairs of transmitters placed symmetrically above and below. Each transmitter and receiver antenna operates as a magnetic dipole with polarization along the borehole longitudinal axis. The instrument provides borehole-compensated propagation wave attenuation and phase difference measurements at five discrete frequencies at multiple depths of investigation (up to 8 inch).
The instrument’s operating principles are described in detail. The tool calibration, depth-of-investigation and vertical resolution are discussed in conjunction with modeled synthetic responses. Measurement results are presented from the laboratory environment as well as from a test well near Austin (Texas).
A two-step inversion algorithm has been implemented to process the acquired raw data. First, the “EM Inversion” module utilizes numerical forward modeling to convert calibrated attenuation and phase difference measurements to borehole-corrected apparent formation resistivity and permittivity values. Next, a second inversion module applies one of several workflows to produce petrophysical deliverables including flushed zone resistivity, water-filled porosity, water salinity and rock textural parameters.
The instrument response and petrophysical results will be discussed in detail using examples from wells drilled in the Permian Basin Wolfcamp formation in Texas, and having two contrasting borehole environments (oil- and water-based mud systems), both very challenging for dielectric data acquisition and interpretation. Dielectric inversion, for water-filled porosity and pore connectivity are complemented with nuclear magnetic resonance (NMR) log data to further understand fluid types and bound versus moveable fluid fractions.
Dielectric wireline logging tools have been around since the late 1960s. The logging technique was originally designed to facilitate evaluation of hydrocarbon-bearing reservoirs containing fresh to brackish waters. In low water salinity reservoirs, water-bearing and oil-bearing horizons appear very similar on resistivity logs, due to a lack of sufficient resistivity contrast. In comparison, dielectric permittivity of water, at any salinity, is distinctly different from the permittivity of all other normal formation constituents. Where total porosity is independently determined, the measurement of dielectric permittivity allows for a reliable estimation of hydrocarbon saturation irrespective of formation water salinity. Multi-frequency dielectric tools, measuring at frequencies of a few tens of MHz to near one GHz, additionally provide predictable dispersion data in complex formations, allowing for the investigation of petrophysical properties such as water salinity, rock texture and clay cation exchange capacity (CEC). Dielectric logging has found wide application in reservoirs particularly challenging for resistivity-based evaluation techniques such as those with fresh, mixed or unknown water salinity environments, carbonates with variable textural properties, formations with altered wettability and shaly sands with their textural and CEC effects on conventional resistivity. Where properties of mud filtrate and formation fluids differ, identification and quantification of fluid invasion is used for finding permeable layers, such as in complex granite wash, or for moveable oil in heavy oil reservoirs.
|File Size||3 MB||Number of Pages||21|