Reference P-wave velocity in coal seams at great depths in Jastrzebie coal mine

Abstract

In the study, the determining of the reference velocity of the P-wave in coal seams used in seismic profiling to assess increases and decreases in relative stresses at large depths has been presented. The seismic profiling method proposed by Dubinski in 1989 covers a range of depth up to 970 m. At present, coal seams exploitation in Polish coal mines is conducted at greater depths, even exceeding 1200 m, which creates the necessity for a new reference velocity model. The study presents an empirical mathematical model of the change of the P-wave velocity in coal seams in the geological conditions of the Jastrzebie coal mine. A power model analogous to the Dubinski’s one was elaborated with new constants. The calculations included the results from 35 measurements of seismic profiling carried out in various coal seams of the Jastrzebie mine at depths from 640 to 1200 m. The results obtained cause changes in the result of calculations of seismic anomalies. Future validation of the proposed model with larger data set will be required.

Gospodarka Surowcami Mineralnymi - Mineral Resources Management

“…3. the calculated average of the P-wave velocity, equal to 2,356 m/s, is also approximately consistent with the empirical relationship given by Kokowski et al (Kokowski et al 2019).…”

“…Figure 8 shows the relationship of Dubiński (Dubiński 1989) with a black dashed line and the relationships given by Kokowski et al (Kokowski et al 2019) marked with orange (exponential) and green (linear). the dependence of Kokowski et al (Kokowski et al 2019) was calculated to supplement the data provided by Dubiński (Dubiński 1989) with data gathered at the Jastrzębie coal mine. As shown in Figure 8, the new point location corresponds to the analytical extension of relationships of the Dubiński (Dubiński 1989) and Kokowski et al (Kokowski et al 2019).…”

“…the values of the calculated parameters have minor standard deviations from 1.44 to 4.31%. the point with the new calculated P-wave velocity at a depth of 1,260 m was introduced on a graph of velocity V P changes with depth given by Kokowski et al (2019) (figure 8).…”

“…the dependence of Kokowski et al (Kokowski et al 2019) was calculated to supplement the data provided by Dubiński (Dubiński 1989) with data gathered at the Jastrzębie coal mine. As shown in Figure 8, the new point location corresponds to the analytical extension of relationships of the Dubiński (Dubiński 1989) and Kokowski et al (Kokowski et al 2019). Based on the measurements of the P-wave velocity, it is difficult to unequivocally confirm whether the increases in the P-wave velocity are smaller with the increase in depth and the increase in the primary stress.…”

“…An attempt was also made to develop such a relationship up to approx. 1,200 m for the local conditions of the Jastrzębie mine (Kokowski et al 2019). Measurements of the velocity of P-and S-waves at a depth of 1,260 m will allow for these relationships to be verified.…”