Estimating permeability of carbonate rocks from porosity and vp ∕ vs

Abstract

We present a method for predicting permeability from sonic and density data. The method removes the porosity effect on the ratio v p /v s of dry rock, and it addresses the specific surface as an indirect measure of permeability. We look at ultrasonic data, porosity, and the permeability of 114 carbonate core plugs. In doing so, we establish an empirical relationship between the specific surface of the solid phase ͑as calculated by Kozeny's equation͒ and v p /v s ͑linearly transformed to remove the porosity effect͒. One must view the specific surface derived by using Kozeny's equation as an effective specific surface because Kozeny's equation only holds for homogeneous rock with interconnected pores. The ratio v p /v s of dry rocks, on the other hand, seems to be controlled by the true specific surface, pointing to an inherent limitation in the method. The 114 carbonate plugs originate in three geological settings and comprise 83 calcitic and 31 dolomitic samples. Their depositional texture varies from mud-dominated to grain-dominated and recrystallized types. Our research applies the relationship to 137 carbonate samples from two different depositional settings. We find a reasonable match between predicted and measured permeability. The match is better for samples with carbonate mud-filled depositional textures than for carbonate mud-poor depositional textures. Diagenetic factors such as vuggy porosity decrease the predictability of permeability.

Detection of Porous and Permeable Formations: From Laboratory Measurements to Seismic Measurements

“…The attenuation may reach a maximum for frequency in the order of 10 kHz, which is the domain of full waveform acoustic logging. It is the reason why several authors (Morlier and Sarda, 1971;Dupuy et al, 1973;Morlier, 1983, 2010;Klimentos and MacCann, 1990;Yamamoto, 2003;Fabricius et al, 2007; Figure 2…”

“…The objective of this borehole is to complement the geological and hydrogeological knowledge of this formation. This formation consists essentially of limestone deposited in a vast sedimentary platform (Ferry et al, 2007). The limestone facies, which vary from one borehole to another, are generally bio-detritic with reef constructions.…”

“…To establish Equation (4), Fabricius et al (2007) have looked at ultra-sonic data, porosity and the permeability of 114 carbonate core plugs.…”

Contribution of Seismic and Acoustic Methods to Reservoir Model Building

“…In a vertical well, these tools are used to record five propagation modes: the refracted compression wave, the refracted To compute permeability from eq 1, it is necessary to measure the P-wave attenuation and the porosity of the formation and calculate the effective specific surface of the formation. Ida L. Fabricius et al ( 2007) have found that specific surface with respect to grain volume ( Sg) is apparently independent from porosity. In an attempt to remove the porosity effect on Vp/Vs and mimic a reflected φ vs log (Sg) trend, they propose to use the following relationship between porosity φ, Vp/Vs ( Vs: S-wave velocity) and Sg: …”

Pore Radius and Permeability Prediction from Sonic Velocity

“…His results on smectite and kaolinite aggregates suggest that the permeability of smectitic clays may be up to five orders of magnitude lower than that of kaolinitic clays with the same porosity, density, velocity or rock mechanical properties. Mari et al, (2011) described a methodology for obtaining a permeability log based on acoustic velocities V p and V s , porosity φ, P-wave attenuation and frequency, their calculation of the specific surface S of the formation was based on the relationship between porosity φ, V p /V s and S proposed by Fabricius et al (2007). Fabricius (2011) indicate that pore radius and thus permeability of shale in the depth interval of mechanical compaction may be predicted from porosity and sonic velocity.…”