The seismic quality factors [Formula: see text] used in many applications of exploration seismology are not automatically equivalent. We identified three groups of usage of the concept of a [Formula: see text]: (1) a measure of internal mechanical friction within rocks, as implied in petrophysical interpretations, (2) several types of apparent [Formula: see text] arising from attenuation measurements, and (3) axiomatic [Formula: see text] defined in the viscoelastic theory. These groups differ by their roles in the interpretation, sensitivity to model assumptions, frequency dependences, and particularly by the temporal and spatial resolution. Among all types of [Formula: see text], those that are most robust and useful for characterizing the material are also strongly limited in resolution and accuracy. For example, from spectral coherency studies, it is known that to measure a [Formula: see text] of approximately 100 with modest accuracy of 30%, measurement time intervals of about 500 ms are required. Although several inversion techniques offer models of [Formula: see text] at much higher resolution, such detailed [Formula: see text] models are usually dominated by the effects of localized structures, such as “colored” transmission across boundaries, reflectivity, or scattering. Such types of [Formula: see text] can be called “structural,” and they differ from the [Formula: see text]-factor of the medium. Detailed [Formula: see text] images are also sensitive to theoretical models such as background geometric spreading and assumptions about the frequency dependence of the [Formula: see text]. Direct association of such [Formula: see text] with material properties may be inaccurate and unreliable. Measurement of geometric spreading and averaging of the structural [Formula: see text] produce estimates of “geometric” and scattering attenuation; however, these estimates are also strongly limited in accuracy and resolution. The viscoelastic [Formula: see text] (group 3 above) heavily relies on a specific mathematical model. Despite producing detailed images, the spatial resolution of viscoelastic [Formula: see text] is inherently limited by the nature of its relation to the frequency-dependent velocity. This resolution limit is difficult to assess quantitatively.

Using drilling fluids with optimum density is one of the most important approaches to stabilize the pressure of the bottom formation and prevent blowout through the drilling process. One of the common methods for this purpose is adding some additives with high specific gravity to the drilling fluid to tune its density. Among the possible chemicals, barite and hematite with the density of 4.2 and 5.2 g/cc are the most common additives. Unfortunately, although the application of these additives is advantageous, they have some drawbacks which the most important one is separation and settlement of solid phase called barite sag. The barite sag comes from barite, or other dense materials particles deposition resulted in undesired density fluctuations in drilling fluid can lead to mud loss, well control problems, poorly cementing and even pipe sticking which occurs in severe cases. With respect to these concerns, the current investigation is concentrated to obtain the relation between the dynamic conditions such as flow rate (0.308 and 0.19 l/s) and deviation angles of 30°,45°,60° and 90° and barite sag phenomenon through a flow loop equipment. Besides, the effect of drilling string rotational speed (70 rpm) on the barite deposition is investigated. The results not only indicate that increasing the flow rate from 0.19 l/s to 0.308 l/s can reduce the deposition rate, but also increasing the deviation angle from 45 to 60 o enhance the barite deposition to its maximum value. Graphic abstract

The depth of penetration and multidimensional characteristics of seismic waves make them an essential tool for subsurface exploration. However, their band-limited nature can make it difficult to integrate them with other types of ground measurements. Consequently, far offsets and very low-frequency components are key factors in maximizing the information jointly inverted from all recorded data. This explains why extending seismic bandwidth and available offsets has become a major industry focus. Although this requirement generally increases the complexity of acquisition and has an impact on its cost, improvements have been clearly and widely demonstrated on marine data. Onshore seismic data have generally followed the same trend but face different challenges, making it more difficult to maximize the benefits, especially for full-waveform inversion (FWI). This paper describes a new dense survey acquired in 2020 in the Permian Basin and aims to objectively assess the quality and benefits brought by a richer low end of the spectrum and far offsets. For this purpose, we considered several aspects, from acquisition design and field data to FWI imaging and quantitative interpretation.

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A model of first-arrival amplitude decay combining geometric spreading, scattering, and inelastic dissipation is derived from a multioffset, 3D vertical seismic profile data set. Unlike the traditional approaches, the model is formulated in terms of path integrals over the rays and without relying on the quality factor (Q) for rocks. The inversion reveals variations of geometric attenuation (wavefront curvatures and scattering, γ) and the effective attenuation parameter (κ) with depth. Both of these properties are also found to be anisotropic. Scattering and geometric spreading (focusing and defocusing) significantly affect seismic amplitudes at lower frequencies and shallower depths. Statistical analysis of model uncertainties quantitatively measures the significance of these results. The model correctly predicts the observed frequency-dependent first-arrival amplitudes at all frequencies. This and similar models can be applied to other types of waves and should be useful for true-amplitude studies, including inversion, inverse Q-filtering, and amplitude variations with offset analysis. With further development of petrophysical models of internal friction and elastic scattering, attenuation parameters γ and κ should lead to constraints on local heterogeneity and intrinsic physical properties of the rock. These parameters can also be used to build models of the traditional frequency-dependent Q for forward and inverse numerical viscoelastic modeling.