Abstract

Exploratory drilling in the Faroe-Shetland Basin of the northeast Atlantic Ocean has been ongoing for several years. One of the greatest challenges of such drilling programs is cost-effectively drilling through the thick layers of Paleogene volcanic rock, which has thicknesses and depths that vary depending on the location of the regional tectonic geography. With the high expense inherent to remote offshore operations, total drilling costs will increase when expected penetration rates and interval lengths are limited due to drillbit inefficiency.

An operator planned to drill a second well in the Brugdan prospect, which lies in License 006, Block 6104/21 off the Faroe Islands. The challenge of drilling through a hard, long section of basalt/volcanic sequence presented a great opportunity for investigating and implementing new drillbit materials and design changes to diamond-impregnated bits. A study for materials testing was focused on diamond grit/matrix combinations for wear, durability, and ROP on two representative basalt outcrop columns provided by the customer. The analysis of the physical characteristics of the rock provided an insight of the matrix and diamond combinations for blade material and grit hot-pressed inserts (GHIs) that would offer a reliable product to meet the challenge and drill the long section. Materials testing followed at the drillbit manufacturing facility to find the appropriate diamond-impregnated recipe.

A competitive diamond-impregnated bit was developed for the 12¼-in section, resulting in an internal world record and an unprecedented drilling performance in the extremely hard and long volcanic sequence.

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