Stoneley Wave Analysis

Stoneley-wave attenuation and velocity are sensitive to fracture and formation permeability, especially at low frequencies. Stoneley-wave velocity declines, and its attenuation increments, as permeability increments. Beginning endeavors (started in the 1970s) to get permeability information from Stoneley information was unsuccessful because neither the significant low-frequency instruments nor the proper handling techniques had been created. The parallel advancement of present day multi-pole array tools and complicated inversion- and semblance-processing techniques empower calculation of continuous profiles of formation permeability from monopole Stoneley-wave information. Ordinarily, these strategies first model the non-permeability impacts
The permeability causes from vugs and fractures can be evaluated by the contrast of these two measurements in carbonate formation. A blend of these two measurements measured utilizing wireline formation tester data empowers enhanced permeability estimation in these reservoirs.
Gas Detection. Stoneley-wave properties, utilized as a part of conjunction with other information, promote recognition of intervals that consists gas. A gas-saturated formation interval has distinctive compressibility and fluid mobility contrasted with those of the encompassing formations. In the vicinity of gas, Stoneley-derived permeability is overestimated given expanded compressibility and pore-fluid mobility (decreased viscosity), and NMR permeability will be underestimated because of reduced hydrogen index.
If first calibrated in an interval consists gas, separation of the two permeability curves shows the presence of gas (Figure 12). The plot likewise indicates the neutron-density cross plot is compelling in distinguishing the gas zone and may be more responsive in certain
From X740 to X800m, P-wave slowness increases (Track 2) across the interval of thin gas sands followed by low density values (Track 2) and multiple Stoneley-wave reflections (Track 3) (courtesy of Baker Atlas).

Fracture Evaluation. The fluid-borne, pressure-driven nature of Stoneley waves makes them responsive to fluid movement, and thus, to open fractures. The impacts of open fractures on Stoneley waves are an occurrence of mode conversion, amplitude reduction, an increase in Stoneley slowness, and the occurrence of Stoneley reflections.
The NMR does not react to fracture permeability while Stoneley wave does thus, the NMR permeability is lower than Stoneley-wave permeability in the vicinity of fractures. The combined utilize of NMR- and Stoneley-derived permeability gives a fracture indicator in both carbonates (Figure 14) and sandstones (Figure 15). Figure 14 Correlation between Stoneley reflections and azimuthal anisotropy. A fracture zone in a U.S. mid-continent well causes both Stoneley-wave reflections and shear-wave splitting in the anisotropy map (left), brighter colors show greater anisotropy. The azimuth of the quick shear arrival is east/west (center). The fractures intersecting the borehole cause significant down- and up-going Stoneley-wave reflections seen in Stoneley-waveform amplitudes (right) (courtesy of Baker