Papers - 2022 (newest first)
Dielectric Spectroscopy Applications While Drilling in the Vaca Muerta Formation
Scott J. Jacobsen, Eric Decoster, James Hemingway, Frank Shray , Barbara I. Anderson, Peter R. Swinburne
NoHiddenPay LLC
Production-flow profiles in a large population of unconventional lateral wells often continue to exhibit inefficient behavior. Flow rates of gas or liquids can vary surprisingly from stage to stage and even from cluster to cluster in drainholes, which are assumed to be drilled and completed in homogeneous pay from heel to toe. Production laterals, penetrating ever-longer intervals of the target reservoir, seldom have more extensive petrophysical data than a simple near-wellbore GR measurement. Thus, with increasing horizontal distance from the pilot hole the assumption of a directionally homogeneous target formation becomes progressively less reliable. And with a limited assessment of reservoir property variations in the near-wellbore region along the horizontal trajectory, remedial action becomes difficult. In the Vaca Muerta formation drilling and completion practices have achieved tremendous progress in cost-effectiveness. Further improvement may be achieved by a superior description of formation properties during horizontal-well placement
We have implemented a recently published mechanistic model that describes wideband EM phenomena in earth formations. Petrophysical analysis from field logs is input to simulate logs of dielectric permittivity and conductivity at various logging-tool frequencies. To investigate the relationship between formation properties of Vaca Muerta and the associated EM response to these properties, a composite vertical-reservoir section has been constructed using typical petrophysical data. The model was used to simulate well trajectories through this section and the respective dielectric permittivity and conductivity curves that would result while drilling with typical LWD resistivity tools.
We are also field-testing a vendor-neutral process to directly invert the measured attenuation and phase-shift data from LWD resistivity-tool acquisition to obtain formation conductivity and permittivity. The algorithm was developed anew from previously published work by reimplementing the solution from Maxwell’s equations in a more computationally efficient manner. The inversion provides independent conductivity/resistivity log curves and permittivity log curves at the various LWD tool frequencies used.
This study presents utilization of this new forward-simulation and the new LWD inversion algorithm. These two complementary algorithms relate the measured conductivity and permittivity to key reservoir properties. The results are self-consistent: the forward simulation followed by the inversion reliably reproduces the original input results and vice versa. The LWD inversion has been tested on legacy data from pilot holes, high-angle, and lateral production wellbores to gain a new insight into the reservoir.
Dielectric Inversion of LWD Propagation-Resistivity Tools for Formation Evaluation
Barbara I. Anderson (1), Frank Shray (1), Keith J. Bartenhagen (2), Jim Hemingway (1),
Eric Decoster (1), Scott J Jacobsen (1), Peter R. Swinburne (1)
(1) NoHiddenPay, LLC (2)EOG Resources
Oilfield exploration and production drilling companies commonly use Logging-While-Drilling (LWD) measurements provided by propagation-resistivity tools. These tools emit radio waves at frequencies from 400 kHz to 2 MHz and measure signal attenuation and phase shift between receiver pairs. In this frequency range, the measurements are sensitive to both the electric conductivity and dielectric permittivity in surrounding rock formations. Tool response to these two parameters has been characterized by modeling and is well known after many decades of study and analysis.
However, dielectric permittivity as a formation parameter is still poorly understood. Over the frequency range in question, the permittivity shows considerable dispersion. The first-order effect of dispersion is to decrease as frequency increases. In addition, laboratory studies under controlled conditions have shown that several competing effects of grain-surface structure and metallic inclusion combine and distort the dielectric signature of the propagation-resistivity measurements. Also, fluid parameters can introduce surface effects. Clearly, there is no simple petrophysical answer to such a complex formation response.
One way to analyze the problem is to directly invert the measured attenuation and phase shift data to obtain formation conductivity and permittivity. The inversion must be separately performed at each operating frequency to account for dispersion. The algorithm described in this paper was developed anew from previously published work by rederiving the solution from Maxwell’s equations in a more computationally efficient manner. The inversion provides independent conductivity/resistivity log curves and permittivity log curves.
For quality control, the dielectrically inverted resistivity curves are compared to the conventionally processed phase-shift and attenuation resistivity curves. The dielectrically inverted resistivity will always fall between the two conventionally processed resistivities.
There is no simple relationship between the dispersive, frequency dependent permittivity and any formation or fluid parameter, comparable to Archie’s simple water-saturation relationship. Both microscopic and macroscopic formation parameters contribute to dispersion: water-filled porosity, CEC, conductive minerals, and formation factor. Past studies in research and in log interpretation have provided some insights on these reservoir property dependencies of permittivity in shaly sands. On the other hand, carbonate rocks with their widely varying pore structure impose additional uncertainties. Still, there appear some underlying common trends among many logs studied to date with dielectric inversion quantities.
On the reservoir scale, dielectric measurements in general have proven to be a useful tool for estimating water saturation independently of water salinity. Dielectric inversion of LWD array propagation measurements provides this information at radial depths away from the borehole wall much deeper than the dedicated wireline GHz-pad tools. Thus, the water-saturation estimates from array tools may indicate hydrocarbons even in the presence of deeper invasion.
The new dielectric-inversion algorithm accommodates any vendor’s axisymmetric LWD propagation-resistivity array tool that is featured in the SPWLA Resistivity-SIG catalogue. The dielectric inversion has been successfully applied to legacy logs. It applies equally well to real-time processing while drilling. The algorithm is implemented as do-it-yourself service on the Cloud for any operator using any LWD service provider. It will hopefully fill a missing gap between raw tool measurements and true petrophysical interpretation.
Deep Salinity-Independent Water Saturation from Low-Frequency-Dielectric Rock Properties
Scott J Jacobsen (1), Keith Bartenhagen (2), Barbara I. Anderson (1), Frank Shray (1),
James Hemingway (1), Eric Decoster (1), Peter R. Swinburne (1)
(1) NoHiddenPay, LLC (2) EOG Resources
Formation conductivity (or resistivity) is the single leading quantity for input to various saturation models. However, conductivity by itself intrinsically combines water saturation with water salinity, which petrophysicists constantly struggle to determine in many situations. This is particularly critical in fresh water formations, where a low resistivity contrast between oil and water is present. For mature fields with water or steam injection secondary recovery processes, remaining oil saturation determination is critical for reserves calculations, reservoir modeling studies and operational decisions. The accuracy of this determination is compromised in common cases where the injection water and virgin formation water salinities differ greatly.
Wireline dielectric measurements at high frequencies can decouple and distinguish water salinity and water saturation. However, analysis from wireline pad dielectric tools is typically that of Sxo rather than Sw.
Modeling studies show that despite the low operating frequency of Logging-While-Drilling (LWD) propagation-resistivity tools, the dielectric permittivity of the formation inverted from the measurements show a good sensitivity to water-filled porosity while maintaining an acceptable insensitivity to water salinity, in clean carbonates and low-clay volume clastics. LWD surveys also offer both early-time and deep-reading electromagnetic measurements. The early-time surveys are only subject to quasi-instant spurt invasion, which tends to be radially shallow.
This resulting water-filled porosity can now be considered to reflect the un-invaded reservoir and in conjunction with total porosity determined from nuclear or other logs, a salinity-independent, deep, water saturation is computed.
LWD propagation-resistivity array tools comprise multiple transmitters with varying axial spacings from the measurement reference point: the midpoint between two receivers. The radial response of these measurements increases with axial transmitter spacing. In LWD situations where deep invasion may have occurred, these array tools offer a radial resistivity profile, which identifies and allows quantifying formation invasion. The radial response applies equally well to the conductivity and permittivity measurements. Thus, the new dielectric-inversion algorithm provides the radial permittivity profile, which directly leads to a radial water-saturation profile. The radial depth of this profile depends on the transmitter spacing; it may reach out to a radius of forty inches, so is truly deep for the early-time surveys while drilling.
We present several field-log examples which clearly illustrate the presence of invasion and the need for a radial profile of dielectric permittivity. Our log examples illustrate how the radial permittivity response serves to discriminate invaded from virgin formation and accurately locate the movable hydrocarbons in situ.
Formation Permittivity and Conductivity Simulation from Petrophysical Volumetric Analysis
Scott J Jacobsen (1), Eric Decoster (1), James Hemingway (1), Frank Shray (1),
Barbara I. Anderson (1), Peter R. Swinburne (1)
1NoHiddenPay, LLC
For many decades formation evaluation and petrophysics have relied on electric conductivity (or resistivity) to input to saturation models for water saturation. However, water salinity strongly affects this estimate and may lead to incorrect results. At measurement frequencies of about 1 MHz and above the permittivity becomes increasingly less sensitive to water salinity in low clay formations, and so facilitates a more reliable water saturation.
Directional drilling and well placement in both conventional reservoirs and in unconventional resource plays requires an early, but reliable prediction of water saturation, immune to uncertainty in water salinity estimates. Such an early water-saturation estimate then permits drilling through and staying in the reservoir “sweet spot” and allows early quantification of potential producible hydrocarbon for near-term operating decisions in the expensive rig-on-location time frame.
Logging While Drilling offers comprehensive formation evaluation at the earliest possible moment: in real time during the drilling process. The LWD tools include propagation-resistivity measurements, which operate at moderately low frequencies from a few 100 kHz up to 2 MHz. The tools provide phase shift and attenuation measurements from a radio wave between a pair of receivers. Traditionally, these two independent measurements were converted to two, independent, apparent resistivities. More recently, the two measurements were also simultaneously inverted for apparent conductivity and permittivity.
Permittivity is also very dispersive: it rapidly diminishes with increasing frequency because of several unrelated and competing effects. Some recent wireline dielectric log measurements at multiple frequencies utilize dispersion characteristics to deduce formation properties via various effective medium models. We propose to investigate utilizing dielectric dispersion at LWD frequencies for similar derivations.
We have implemented a recently published mechanistic model that describes wideband EM phenomena in earth formations. For practical application, we present case examples where we input petrophysical analysis results from field logs to this model and simulate logs of dielectric permittivity and conductivity at LWD frequencies. This study presents utilization of this new forward-simulation and the new LWD inversion algorithm. These two complementary algorithms relate the measured conductivity and permittivity and attendant dispersion to water-filled porosity, salinity, and other key reservoir properties such as CEC, formation factor, and permeability. The results are self-consistent: the forward simulation followed by the inversion reliably reproduces the original input results and vice versa. The new algorithm offers critical low-clay-formation water-saturation estimates and other properties from LWD propagation-resistivity and porosity measurements in real and during the drilling and well-placement process.
© Copyright 2024, NoHiddenPay LLC . All rights reserved.
We need your consent to load the translations
We use a third-party service to translate the website content that may collect data about your activity. Please review the details in the privacy policy and accept the service to view the translations.