Rock stresses around active faults measured by using the high stiffness hydraulic fracturing technique

T. Yokoyama, M. Murakami, T. Danjo, K. Ogawa, A. Lin, W. Lin, T. Ito

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The hydraulic fracturing technique is a method to measure the stress states in the rocks based on the change of the water pressure observed when the induced fracture in the borehole wall generated by water pressure reopens or closes. A new standard of hydraulic fracturing method in Japan will have two important observation parameters as shown below. One parameter is the water pressure Ps (Shut-in pressure) at the time when the tip of the fracture begins to close after shut-in operation at stopping pressurization in a test interval. The other parameter is the water pressure Pr (Reopening pressure) at the time when the mouth of the fracture begins to open when the test interval is re-pressurized. The new hydraulic fracturing technique highlights that a compliance of the measuring system was adequate for correctly measuring Pr. The small compliance means that the capacity of the water supply system is extremely small and the water supply system has the high stiffness. Small compliance is synonymous with high stiffness, and an ideal measuring system is required to have smaller compliance. We got an opportunity to measure the crustal stress by the hydraulic fracturing technique around Nojima fault which appeared on the surface at the 1995 Southern Hyogo Prefecture Earthquake. The hydraulic fracturing test was conducted at the foot side of Asano fault which is derived from Nojima fault. The measurement depth is about 800 m. The magnitude of the measured maximum principal stress is smaller than the overburden stress, and its principal stress direction does not match the fault movement and the direction of the compression axis is greatly deviated. Therefore, the current stress state around the fault is considered to represent the stress relaxation state after the fault activity.

Original languageEnglish
Title of host publicationRock Dynamics Summit - Proceedings of the 2019 Rock Dynamics Summit, RDS 2019
EditorsOmer Aydan, Takashi Ito, Takafumi Seiki, Katsumi Kamemura, Naoki Iwata
PublisherCRC Press/Balkema
Pages638-643
Number of pages6
ISBN (Print)9780367347833
DOIs
Publication statusPublished - 2019
EventRock Dynamics Summit, RDS 2019 - Okinawa, Japan
Duration: 2019 May 72019 May 11

Publication series

NameRock Dynamics Summit - Proceedings of the 2019 Rock Dynamics Summit, RDS 2019

Conference

ConferenceRock Dynamics Summit, RDS 2019
CountryJapan
CityOkinawa
Period19/5/719/5/11

ASJC Scopus subject areas

  • Geology

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