Rahman Ashena

Wireline Continuous Coring

As discussed in Chap. 5, conventional coring suffers from extremely long tripping times. The whole drilling string must be pulled out of the hole before the whole coring assembly (including inner and outer tube assembly) can be run in the hole. Similarly, following the core-drilling, the coring string must be conventionally pulled out before the drilling string can be run in the hole again to resume drilling. This causes a considerable waste of time during tripping. To address this issue, an alternative method of coring (i.e., wireline continuous coring) has been considered and applied in the petroleum industry (Walker and Millheim 1990; Randolf 1991; Deliac et al. 1991, Bencic et al. 1998; Warren et al. 1998).

Enhanced Wireline Core Size Retrieval By Casing Drilling Coring

As one basic objective of coring methods applied, core size retrieved should be adequate (particularly in slim holes) so that appropriate results can be obtained from core analysis and also mechanical tests. However, conventional wireline continuous coring method is suffering from meeting this objective particularly in slim holes (particularly smaller than 5 ½-in) even by specialty drill pipes and jars with larger bores. Thus, in this paper, following attempting to remove the difficulties of grasping the wireline exploration drilling and translation possibility from mining to petroleum drilling, it is emphasized on utilization of casing drilling coring by replacing BHA and pipes with drill rods/casings as the most optimum method of coring to retrieve largest possible cores particularly in slim holes (holes sizes less than 5 ½-in) with some reasonable drilling rig modifications required for this purpose. It is recommended to utilize drill rods and specialty API drill pipes with modified gripping so that so that it is possible to switch to API drill pipes in ultra-deep intervals where drill rods depth capacity is exceeded.