Jj. Rathmell et al., DEVELOPMENT OF A METHOD FOR PARTIALLY UNINVADED CORING IN HIGH-PERMEABILITY SANDSTONE, SPE formation evaluation, 10(2), 1995, pp. 65-71
A newly designed polycrystalline-diamond-compact (PDC) core bit and wa
ter-based muds with bridging solids are shown to provide 4-in. diamete
r cores with a 2.5-in. uninvaded center. High-permeability sandstones
were cored at rates exceeding 90 ft/hr in laboratory and field tests.
The mechanisms controlling filtrate invasion are quantified.