What are the best applications of sonic and density logs for reservoir characterization?

1 Sonic logs

Sonic logs measure the travel time of acoustic waves through the rock matrix and the fluid-filled pores. They can be used to calculate the porosity, the compressional and shear wave velocities, and the acoustic impedance of the formations. These parameters can help to identify lithology, fluid type, and rock quality. Sonic logs can also be used to correlate well data with seismic data, to estimate the depth of the reservoir, and to detect fractures and faults.

2 Density logs

Density logs measure the bulk density of the formations, which is the mass per unit volume of the rock and fluid mixture. They can be used to calculate the porosity, the formation density, and the photoelectric factor of the formations. These parameters can help to identify lithology, fluid type, and rock quality. Density logs can also be used to estimate the hydrocarbon saturation, the shale volume, and the mineralogy of the formations.

3 Applications for reservoir characterization

Sonic and density logs can be used together or separately for reservoir characterization, depending on the objectives, the data quality, and the availability of other logs. Some of their best applications include porosity estimation, lithology identification, fluid identification, and rock quality assessment. Combining these logs can improve accuracy and reliability in complex or heterogeneous formations, discrimination and classification of lithology in mixed or shaly formations, detection and quantification of fluid type in low-permeability or tight formations, and evaluation and prediction of rock quality in fractured or anisotropic formations.

4 Advantages of sonic and density logs

Sonic and density logs have certain advantages over other types of well logs when it comes to reservoir characterization. These logs are widely available, relatively inexpensive to acquire and process, and less affected by borehole conditions and mud properties than other logs. Furthermore, sonic and density logs have high vertical resolution and depth accuracy compared to other logs, as well as direct physical meaning and simple mathematical relationships with some reservoir parameters.

5 Limitations of sonic and density logs

Sonic and density logs have some limitations and challenges for reservoir characterization, such as measurement errors or uncertainties due to tool calibration, environmental effects, or noise. Additionally, interpretation ambiguities or complexities may arise due to multiple solutions, non-uniqueness, or non-linearity. Furthermore, they may have low sensitivity or resolution for some reservoir parameters or features, such as thin beds, gas zones, or heavy oil. Finally, they may require additional information or assumptions from other sources, such as core data, fluid analysis, or petrophysical models.

6 Here’s what else to consider

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