Rock quality

Creaney S. and Passey Q. R. (1993) Recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework. Am. Assoc. Petrol. Geol. Bull. 77, 386-401. 

Dahl J. E. P., Moldowan J. M., Teerman S. C., McCaffrey M. A., and Sundararaman P. (1994) Source rock quality determination from oil biomarkers I. A new geochemical technique. Am. Assoc. Petrol. Geol. Bull. 78(10), 1507-1526. 

Seifert W. K. and Moldowan J. M. (1980) The effect of thermal stress on source rock quality as measured by hopane stereochemistry. Phy. Chem. Earth 12, 229—237. 

It is concluded that the relation between cap rock quality, uplift and erosion and tectonic reactivation and hydrocarbon leakage in the southwestern Barents Sea is still obscure, and will remain so until more rock mechanical data from the cap rocks become available. It is, however, still possible to assess a risk evaluation on both regional and field scales by applying the data presently available form the area. 

Fig. 4. Source rock quality described by TOC and HI in the 34/7-15S well, penetrating the assumed source rock in the area Draupne Formation).

Another possible explanation of the low GORs in the Field is the imperfect seal over the reservoir. Shows of petroleum resembling the Snorre population have been found several hundreds of metres over the reservoir interval (Caillet 1993 Leith et al. 1993 Leith Fallick 1995), even though the field probably has never reached fracture pressure. It is clear that the poor cap rock quality on the relatively shallow and underfilled Snorre structure makes this a perfect candidate for a Type 3 trap as explicitly classified by Sales (1997), i.e. the GOR of the Snorre petroleum charge is determined more by the cap rock properties than by SR quality and its kinetic properties. The oil inferred by Leith et al. (1993) may have leaked from the reservoir as the cap rock section has very low pore entry pressures and micro fracturing is also observed in the cap rock section. One can therefore speculate that the leakage may be a prerequisite to maintain black oil in the Snorre Field. 

Isaksen, G. H. Ledie, K. H. 1.2001. Source rock quality and hydrocarbon migration pathways within the greater Utsira High area. Viking Graben, Norwegian North Sea. AAPG Bulletin, 85,861 -883. 

The Bossier shale is not only the basal formation for much of the Cotton VaUey Group, but is also interbedded with isolated sands throughout most of eastern Texas and northwestern Louisiana. These shales are typically black, organic-rich, calcareous, fossiliferous, marine deposits which are the primary source rock for much of the entire Upper Jurassic and Lower Cretaceous vertical section. Thinner shale intervals in the western part of the basin thicken to the east correlative to general depositional patterns in the East Texas Basin. Source rock quality is generally poorer in the western and northwestern parts of the basin, but improves significantly easterly towards the basin centre. From west to east, the near-shore sand and low-stand fan deposits are usually completely encased in the marine Bossier shale. 

Kerogen type, content and maturity. The source rock quality and hydrocarbon generation... 

Examination of rock quality to verify quality and consistency throughout the socket length. 

Measuring and Estimating the Impact of Phosphate Rock Quality Factors.lH... 

J.R. Lehr, Impact of phosphate rock quality on market use, Industr. Miner., May 1984. 

Table 2.5. Classification of rock quality in relation to the incidence of discontinuities...

These dynamic moduli correspond to the initial tangent moduli of the stress-strain curve for an instantaneously applied load and are usually higher than those obtained in static tests. The frequency and nature of discontinuities within a rock mass affect its deformability. In other words, a highly discontinuous rock mass exhibits a iower compressional wave velocity than a massive rock mass of the same type. The influence of discontinuities on the deformability of a rock mass can be estimated from a comparison of its in situ compressional velocity, /pf, and the laboratory sonic velocity, /p, determined from an intact specimen taken from the rock mass. The velocity ratio, /pf/t/pi, reflects the deformability and so can be used as a quality index. A comparison of the velocity ratio with other rock quality indices is given in Table 2.7. 

Bieniawski (1974, 1989) maintained that the uniaxial compressive strength of rock material the rock quality designation the spacing, orientation and condition of the discontinuities and groundwater inflow were the factors that should be considered in any engineering classification... 

Rock quality designation RQD 1. Where RQD is reported or measured as < 10 (including 0), a nominal 3... 

The slope had many fractures zone, joints inclined to slope direction, and many faults and poor rock qualities. This slope had also experienced three failures, including deformation, deflection and collapse in the upper and lower parts. 

Discussions and data showed that in addition to these factors, the rock quality (which influences the size of the crater) and the venting characteristics of the storage chamber (which influence the total energy available for the throw-out of the crater material) play some role. For several reasons, however, it was decided to develop a model valid only for strong (good) rock and unvented chambers as a first step. Since venting of the chamber reduces the pressure driving the debris throw, this is a conservative assumption. 

The Cover Depth Parameter. The total mass of rock material thrown into the surroundings is unquestionably a direct function of the crater volume produced by the explosion. The crater dimensions (depth, radius, volume) depend primarily on the depth and to some extent on the rock quality. 

The construction phase may be divided into subphases so that a new phase cannot commence before the regulator e.g. has approved the detailed plans for some important structure or system to be implemented. During the construction of a repository, it is advisable to ensure the quality of host rock arotmd the planned disposal area by performing an at-depth recormaissance programme as soon as the access tunnel or shaft has reached Ae plarmed disposal depth. Relocation of the disposal rooms or holes should be considered if these investigations indicate unexpectedly poor rock quality. 

Documentation of sampling and coring depths, types, and lengths (e.g., sample type, blow count [for driven samples], and sample length for soil samples core run, recovery, and Rock Quality Designation (RQD) for rock cores) as well as in situ test depths and lengths... 

Reese (1997) proposed a procedure to calculate p-y curves for rock using basic rock and rock mass properties such as compressive strength of intact rock q. Rock Quality Designation (RQD), and initial modulus of rock E-. A description of the procedure is presented in the following. 

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