PSI - Issue 6

Chebyshev Igor et al. / Procedia Structural Integrity 6 (2017) 252–258 Chebyshev I.S./ Structural Integrity Procedia 00 (2017) 000–000

254

3

individual optimum bit speed calculation is necessary. The choice of a bit type also depends on the rock strength and core bit form (Hettema, 2002). The optimum core lifting mode depends on the bubble point and gas-oil ratio (GOR) value. The compete core lifting mode choice has an impact on the core safety and quality (Fig. 2).

Fig. 2. Different quality of extracted core.

3. Transportation

Serious problems with core quality, generally, do not appear while its transportation. The core safety is guaranteed by the suitable extracting program. Currently the most common coring tool is of the isolated type (70 75% of all coring works in Russia). It is highly recommended for careful the core tool extraction in order to maintain the initial core state and to use special transportation programs (including isolation agent selection, special fixing foam usage) when transporting poorly cemented core on a long distance (S.B. Johns, 1981).

4. Main research question

After delivering to the laboratory, the core is subjected to matching and documentation. Then the necessary size samples are cut out and further research is carried out.

5. Dynamic elastic modulus

Dynamic tests with hydrostatic pressing are performed before or during the compression static tests. All the samples should have 30 mm in diameter and 60 mm in height. The sections where P-waves are registered on piezosensor are shown on Fig. 3.a. The sections where P- and S-waves are not registered while dynamic test on the weakly consolidated sample are shown on Fig. 3.b. One of the reasons not to be able to register P- and S-waves arrival time may be incorrectly selected sensor frequency.

a.

b.