Estimation of minimum principal stress from an extended leak-off test onboard the Chikyu drilling vessel and suggestions for future test procedures

Abstract

Investigation of in situ stress at depth is a necessary and important outcome of IODP drilling programs such as NanTroSEIZE. Fortunately, the availability of the new research vessel Chikyu means that LOT and XLOT procedures can be readily undertaken during future riser-drilling programs; these will yield important information about in situ stress magnitude as well as providing some of the data needed for drilling operations (e.g., borehole stability analysis). We used data from the 2006 Chikyu Shimokita shakedown cruise to demonstrate the feasibility of using XLOT data to determine the magnitude of the in situ minimum principal stress at depth. The procedures that we have recommended for the application of XLOT to determine stress magnitude during future riser-drilling programs of the Chikyu represent the most important outcome of this work.