| IODP Proceedings Volume contents Search | |||||
 | |||||
| Expedition reports Research results Supplementary material Drilling maps Expedition bibliography | |||||
|
doi:10.2204/iodp.proc.322.201.2013 Temperature estimationThe thermal conductivity coefficient (k) can be measured directly from core samples (Blum, 1997) and relates to heat flow (q) across a steady-state temperature (T) difference over distance (x):
The change in temperature over a set distance (ΔT/Δx) is the thermal gradient and can be used to give an estimate of downhole temperature. At Site C0011, no LWD temperature measurements were available, so core data were used to generate a temperature estimate. Surface heat flow in Hole C0011B was determined to be 89.5 mW/m2, with a surface temperature of 1.7°C and an average thermal gradient of 93.1°C/km (Expedition 333 Scientists, 2012). Temperature gradients were calculated using core-based thermal conductivity coefficients from Holes C0011B and C0011D, obtained during IODP Expeditions 322 and 333, respectively (see the “Site C0011” chapter [Expedition 322 Scientists, 2010]; Expedition 333 Scientists, 2012) (Fig. F1). Average thermal conductivities were determined for the entire data set, for each of the lithologic units, and for the two main lithologies encountered (Table T1). Using the core thermal conductivity measurements, four temperature profiles were generated (Fig. F1). Two were generated from constant temperature gradients: Temp C1 was based on the constant thermal gradient of 91.3°C/km reported during Expedition 333 (Expedition 333 Scientists, 2012) and Temp C2 was based on a thermal gradient of 80.7°C/km, which was calculated from the average thermal conductivity of both Hole C0011B and C0011D core data. Additionally, two variable temperature profiles were calculated: Temp V1 was based on the thermal gradient of each lithologic unit and Temp V2 was based on the average thermal gradient of the dominant lithology (Table T1). The dominant lithology was chosen on the core-based lithologic units converted to meters below seafloor based on the log depth measurement (LWD depth below seafloor). Each temperature profile yields a different bottom-hole temperature (Table T2), but none can be verified in the absence of a bottom-hole temperature measurement. However, each temperature profile can be used to calculate a temperature-corrected Rw, and the subsequent porosity profiles can be compared to core porosity to determine the most accurate calculation. |
|||||
Figures