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Collaborating Authors
The "gold" standard for permeability is to make measurements on core samples and to determine permeability with the methods outlined in APIRP 40.[1] All other techniques are calibrated back to core measurements. However, because core measurements sample such a minute part of the reservoir, we must rely on techniques that can be applied in a widespread fashion across the reservoir. These methods rely on measurements on sidewall samples, correlation to wireline logging responses, interpretation ofnuclear magnetic resonance (NMR) logs, wireline formation tester pressure responses, and drillstem tests. This technique is valid for slightly to unconsolidated sandstone rock types.
- Europe > United Kingdom > Irish Sea > East Irish Sea > Morecambe Bay > East Irish Sea Basin > Morecambe Bay > Block 110/8a > Morecambe Field (0.99)
- Europe > United Kingdom > Irish Sea > East Irish Sea > Morecambe Bay > East Irish Sea Basin > Morecambe Bay > Block 110/7a > Morecambe Field (0.99)
- Europe > United Kingdom > Irish Sea > East Irish Sea > Morecambe Bay > East Irish Sea Basin > Morecambe Bay > Block 110/3a > Morecambe Field (0.99)
- Europe > United Kingdom > Irish Sea > East Irish Sea > Morecambe Bay > East Irish Sea Basin > Morecambe Bay > Block 110/2a > Morecambe Field (0.99)
- Information Technology > Knowledge Management (0.41)
- Information Technology > Communications > Collaboration (0.41)
Estimating reservoir permeability with borehole radar
Zhou, Feng (China University of Geosciences (Wuhan), Delft University of Technology) | Giannakis, Iraklis (University of West London) | Giannopoulos, Antonios (The University of Edinburgh) | Holliger, Klaus (University of Lausanne) | Slob, Evert (Delft University of Technology)
ABSTRACT In oil drilling, mud filtrate penetrates into porous formations and alters the compositions and properties of the pore fluids. This disturbs the logging signals and brings errors to reservoir evaluation. Drilling and logging engineers therefore deem mud invasion as undesired and attempt to eliminate its adverse effects. However, the mud-contaminated formation carries valuable information, notably with regard to its hydraulic properties. Typically, the invasion depth critically depends on the formation porosity and permeability. Therefore, if adequately characterized, mud invasion effects could be used for reservoir evaluation. To pursue this objective, we have applied borehole radar to measure mud invasion depth considering its high radial spatial resolution compared with conventional logging tools, which then allows us to estimate the reservoir permeability based on the acquired invasion depth. We investigate the feasibility of this strategy numerically through coupled electromagnetic and fluid modeling in an oil-bearing layer drilled using freshwater-based mud. Time-lapse logging is simulated to extract the signals reflected from the invasion front, and a dual-offset downhole antenna mode enables time-to-depth conversion to determine the invasion depth. Based on drilling, coring, and logging data, a quantitative interpretation chart is established, mapping the porosity, permeability, and initial water saturation into the invasion depth. The estimated permeability is in a good agreement with the actual formation permeability. Our results therefore suggest that borehole radar has significant potential to estimate permeability through mud invasion effects.
- Europe (1.00)
- Asia > China (0.69)
- North America > Canada (0.46)
- Geology > Geological Subdiscipline (0.93)
- Geology > Rock Type > Sedimentary Rock (0.46)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.48)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/7 > Snรธhvit Field > Stรธ Formation (0.99)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/7 > Snรธhvit Field > Nordmela Formation (0.99)
- Europe > Norway > Barents Sea > Hammerfest Basin > License 100 > Block 7121/5 > Snรธhvit Field > Stรธ Formation (0.99)
- (32 more...)
Two highprecision continuous temperature gradient logs have been produced in a 600-m partially cased, waterfilled borehole for which a nearly complete core is available. The agreement between these gradient logs, obtained using a logging speed of 8 m/minute, is good; there is virtually no dc offset less than 0.03C/km, and the mean absolute error is approximately 0.5C/km. A comparison of these profiles with detailed geologic logs of the core shows excellent precision and resolution. In situations where the thermal resistivity contrast is 50100 percent, isolated strata as thin as 0.5 m are clearly indicated on the temperature gradient log. More subtle lithologic changes extending over larger depth intervals are also detectable. In several instances gradient contrasts on the order of 1C/km extending over several meters have been clearly resolved. Comparison of the gradient logs with a thermal resistivity profile from laboratory measurements on the core material indicates that the steel well casing has no observable effect on the temperature gradient profile.
We create a log of intrinsic dispersion and attenuation for the Antelope Shale formation of the Buena Vista Hills field, San Joaquin Valley, California. High dispersion or low Q values correlate with thin sand and carbonate beds within the Antelope Shale. These beds are at least ten times as permeable as the host shale formation, so this effect provides a possible avenue for seismic prediction of permeability. The dispersion log is formed through comparison of crosswell seismic velocities measured at approximately 1 kHz and sonic log velocities measured at approximately 10 kHz. In order to provide a proper basis for comparison, the sonic log must first be adjusted for field anisotropy, scaling effects, and resolution of measurement. We estimate a local shale anisotropy of about 20% based on correlations generated from published measurements of other shale fields. We apply resolution enhancement to capture the thin sand and carbonate beds, and windowed Backus averaging to match the measurement scales. A modeling study verifies the technique, and shows that beds of thickness greater than 30 cm have a measurable signature. The actual resolution is on the order of the crosswell Fresnel length, or about 7 m for the model study.
- North America > United States > California > Kern County (0.71)
- North America > United States > Texas > Stephens County (0.62)
- North America > United States > California > San Joaquin Basin > Buena Vista Hills Field (0.99)
- Oceania > Papua New Guinea > Eastern Highlands > Petroleum Retention License 15 > Petroleum Retention License 15 (PRL 15) > Elk and Antelope Fields > Puri Formation (0.98)
- Oceania > Papua New Guinea > Eastern Highlands > Petroleum Retention License 15 > Petroleum Retention License 15 (PRL 15) > Elk and Antelope Fields > Mendi Formation (0.98)
- (4 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Near-well and vertical seismic profiles (0.94)
We modeled permeability k estimation based on porosity , electrical formation factor F, and nuclear magnetic resonance NMR relaxation time T, using periodic structures of touching and overlapping spheres. The formation factors for these systems were calculated using the theory of bounds of bulk effective conductivity for a twocomponent composite. The model allowed variations in grain consolidation degree of overlap, scaling grain size, and NMR surface relaxivity. The correlation of the permeability k with the predictor a was slightly higher than i.e., a correlation coefficient of 0.98 versus 0.95. The exponent b ranged from 1.4 for a pure grain consolidation system to 2 for a pure scaling system. Variations in surface relaxivity are shown to cause significant scatter in the correlations.