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Fracture analysis of Yufutsu gas field.

1996; Japanese Association for Petroleum Engineers; Volume: 61; Issue: 1 Linguagem: Inglês

10.3720/japt.61.45

1881-4131

Takashi Agatsuma, Satoru Yokoi, Mitsuru Inaba,

Rock Mechanics and Modeling

This paper discusses the methodology for fracture detection and fracture porosity evaluation through core description, mud log and well logs, using data from Yufutsu gas field, Hokkaido, Japan. The youngest fracture group observed on core (System C) consists mainly of open fractures and roughly correlates with the conductive type fracture image on FMI. The remaining core fracture groups (System A and B) are filled by minerals and correlate with the resistive type fracture image. These results suggest that a substantial part of fracture pore space is associated with System C. The drill stem test results show that the most reliable fracture indications on mud log and conventional well logs are lost circulation while drilling, spiky peak of showing and abnormaly low values of RLLD. The values of φFMI and φRLLD-RLLS are low and nearly equal because both are probably close to the minimum fracture porosity. The trend of SPI (φD-φS) is similar to those of φFMI and φRLLD-RLLS, but the values of the former are several times larger than those of the latter. As above mentioned, the value of fracture porosity is various due to the difference of estimation formula and quantitative fracture porosity evaluation of the study area is still on the trial and error stage. So, further study will be needed for establishing more reliable method of fracture porosity evaluation.