Integrated Petrophysical Study of the Fractured Tuff in Junggar Basin

Yuanzhong Zhang
China University of Petroleum, Beijing, China

Tuff is a of kind of igneous rock, which can be divided into some types such as tuff, deposition tuff, tuffaceous sandstone, tuffaceous glutenite, tuffaceous breccia based on the size fraction and the mineral component. In recent years oil and gas has been found in tuff reservoir of the carboniferous in Junggar Basin of Xinjiang Province in China. Tuff reservoir has common characteristics of low porosity, low permeability and fractured. Fluid identification and fluid evaluation are always difficult because of complex logging response. Especially electrical resistivity logging is hard to reflect the pore fluid property change. Tuff is a complex lithology, and the pore configuration are often consists of pore and fracture. The integrated petrophysical study is conducted in the paper to investigate the pore fluid characteristic of the tuff for formation evaluation. 42 samples have been measured with the different method including density, X ray energy spectrum, SEM, magnetic susceptibility, porosity, permeability, acoustic velocity, NMR and so on. The experiment results show that the relationship between the density and porosity is negative line correlation, whereas the compressional velocity and porosity is approximate line correlation, the cause of low porosity and low permeability is weak in matrix pore and fracture is main percolation channel, and the paramagnetic effect of matrix on T2 is to reduce the NMR signal amplitude. And the results also imply that the combination of acoustic velocity and T2 can help direct fluid identification and fluid evaluation.

AAPG Search and Discovery Article #90092©2009 AAPG Rocky Mountain Section, July 9-11, 2008, Denver, Colorado