TY - CONF
T1 - Continuous depth profile of the rock strength along a borehole based on drilling performance parameters
AU - Hamada, Yohei
AU - Hirose, Takehiro
AU - Suzuki, Takahiro
AU - Sanada, Yoshinori
AU - Sugihara, Takamitsu
AU - Saito, Saneatsu
AU - Moe, Kyaw
AU - Yamada, Yasuhiro
N1 - Funding Information:
The authors wish to thank Mantle Quest Japan for operating the vessel and drillings. We received generous supports from Technology Department in CDEX. We gratefully acknowledge the support provided by the operational staff of D/V Chikyu and the onboard laboratory technicians (Marine Works Japan).
Publisher Copyright:
Copyright © SPWLA ,JFES 2019. All rights reserved.
PY - 2020
Y1 - 2020
N2 - In-situ rock strength with depth under the ground/seafloor is a critical parameter for various studies in geosciences. The measurements on rock/core samples, however, hardly have been done with success due to lack of drilled cores and sufficient knowledge about the in-situ conditions such as pressure and temperature. Recently, a new indicator of the strength, equivalent strength (EST) was proposed developing previous mechanical parameter, Mechanical specific energy, which is converted only from drilling performance parameters; drillstring rotational torque, bit depth and drillstring rotational per minute. The data processing method was applied to the drilling data taken from International Ocean Discovery Program (IODP) expeditions and Indian National Gas Hydrate Program Expedition 02 (NGHP-02). The calculated EST was used for comparison with other physical properties and interpretation of geology, indicating the validity of EST. In order to correlate EST with rock strength measured by conventional laboratory experiments, drilling experiments using a high-speed rotary-shear apparatus were performed in the laboratory. Metal drill bits with diameter of 20 mm, fitted to the apparatus, were manufactured, and a standard rocks and sediments were drilled at a rotational speed of 0.01 to 10 RPM under axial load of 0.2-1.0 kN (equivalent to 1.6 to 8.1 MPa). Drilling torque and penetration speed at each condition were measured. The mean EST calculated based on the recorded drilling data shows comparable values to the uniaxial rock strength of the test samples. No significant influence of rotation speed on EST was found in the experiments.
AB - In-situ rock strength with depth under the ground/seafloor is a critical parameter for various studies in geosciences. The measurements on rock/core samples, however, hardly have been done with success due to lack of drilled cores and sufficient knowledge about the in-situ conditions such as pressure and temperature. Recently, a new indicator of the strength, equivalent strength (EST) was proposed developing previous mechanical parameter, Mechanical specific energy, which is converted only from drilling performance parameters; drillstring rotational torque, bit depth and drillstring rotational per minute. The data processing method was applied to the drilling data taken from International Ocean Discovery Program (IODP) expeditions and Indian National Gas Hydrate Program Expedition 02 (NGHP-02). The calculated EST was used for comparison with other physical properties and interpretation of geology, indicating the validity of EST. In order to correlate EST with rock strength measured by conventional laboratory experiments, drilling experiments using a high-speed rotary-shear apparatus were performed in the laboratory. Metal drill bits with diameter of 20 mm, fitted to the apparatus, were manufactured, and a standard rocks and sediments were drilled at a rotational speed of 0.01 to 10 RPM under axial load of 0.2-1.0 kN (equivalent to 1.6 to 8.1 MPa). Drilling torque and penetration speed at each condition were measured. The mean EST calculated based on the recorded drilling data shows comparable values to the uniaxial rock strength of the test samples. No significant influence of rotation speed on EST was found in the experiments.
UR - http://www.scopus.com/inward/record.url?scp=85079570153&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85079570153&partnerID=8YFLogxK
M3 - Paper
AN - SCOPUS:85079570153
T2 - SPWLA 25th Formation Evaluation Symposium of Japan, JFES 2019
Y2 - 25 September 2019 through 26 September 2019
ER -