Permeability confirmation method of low porosity and permeability reservoirs based on pore distribution and T2 spectrum

Key words:  nuclear magnetic resonance (NMR) logging  low porosity & permeability reservoir  T₂ spectrum  pore size distribution  permeability contribution factor

Abstract:

To accurately calculate the permeability of low porosity and permeability reservoirs, we use a low porosity and permeability reservoir in an oilfield in Bohai to study the influence of pore size distribution on permeability. The pore size distribution information of reservoir rocks can be characterized based on the mercury penetration pore size distribution and the nuclear magnetic resonance (NMR) logging T₂ spectrum. The T₂ spectrum data of different pore size intervals can be obtained by using the pore size distribution histogram data to calibrate the NMR logging T₂ spectrum data. Permeability contribution values are used to determine the contribution factor of the pore size per unit porosity component to the permeability of each T₂ spectral interval. A calculation method for permeability of low porosity reservoirs based on pore size distribution and T₂ spectrum is then established. The results show that this method avoids the blindness of the previous calculation method of permeability based on the pore size distribution in the division of T₂ spectral range, and avoids the unreliability of the contribution value of different intervals empirically determined. The established permeability model based on pore size distribution and T₂ spectrum provides a good guidance to evaluate permeability of low porosity reservoirs.