Drilling strategy, operations plan, and downhole measurements

To meet the scientific and engineering objectives, primary operations in Hole C0002F will be to drill using LWD/measurement while drilling (MWD) until the 16 inch casing is set at 2300 mbsf (Fig. F4). Cuttings and mud gas will be collected and analyzed during riser drilling from 860.3 (bottom of 20 inch casing) to 2300 mbsf. Wireline coring will be conducted in Hole C0002F between 2300 and 2400 mbsf using a rotary core barrel (RCB) to obtain the highest quality and most complete core samples. Drilling and LWD/MWD logging and cuttings and mud gas analysis will continue to 3600 mbsf where the 13⅜ inch casing will be set.

Operations plan

The operations plan and time estimate (Table T1) are based on formations and depths inferred from seismic and regional geological interpretations combined with data from previous drilling operations at nearby sites. We will use these operations and data to guide the operations described during Expedition 338. The primary operational plan is to conduct operations in one hole at Site C0002 (Fig. F3); however, contingency plans have been developed. An abbreviated list of primary sites, holes, drilling depths, and contingency plans can be found in “Contingency plans.”

Hole C0002F

During Expedition 326 in 2009, a 36 inch conductor casing was run and cemented to 54 mbsf. Following this, a 26 inch hole was drilled to 860.3 mbsf, cased with 20 inch casing, and then cemented. During Expedition 338, we will use reaming-while-drilling (RWD) technology, which allows for LWD/MWD analysis behind a 10⅝ or 12¼ inch bit while simultaneously opening the hole behind the LWD/MWD bottom-hole assembly to 20 or 17.5 inches (Fig. F5). The first drilling interval will be from 860.3 to 2300 mbsf, and we will set and cement the 16 inch casing (Fig. F4). We will then RCB core from 2300 to 2400 mbsf. A second RWD/MWD interval will extend the hole to 3600 mbsf, where the 13⅜ inch casing will be set and cemented. If there is enough time after setting the 13⅜ inch casing, a second coring interval may be added as a contingency option.