CHARACTERISTICS OF WS-A GLUTENITE RESERVOIR AND ITS INTEGRATED EVALUATION

The low-permeability reservoirs are large in reserve in the western South China Sea, but the utilization rate is quite low up to date. The major payzone of WS-A oilfield is of glutenite type. So far, few studies have been contributed to the characteristics of glutenite reservoir and its integrated evaluation. It is necessary to carry out the study of the microscopic pore structures so as to determine the potential and the difficulties which may be encountered in oil and gas production and development. In this paper, we selected some representative rock samples from the WS-A oilfield, and had various physical simulation experiments, such as constant velocity mercury intrusion, nuclear magnetic resonance, nonlinear test, clay mineral analysis and wettability measurement. Based on the characteristics of the microscopic pore-throat structure of the reservoir, a integrated reservoir evaluation method on six-element parameters was established for reservoir evaluation. It is found that in the WS-A low permeability glutenite oilfield, if the integrated classification coefficient of reservoirs is less than 5 or the permeability is less than 1×10⁻³ μm², it belongs to the third type of reservoir and is very difficult to develop indeed; if the integrated classification coefficient of reservoirs is between 5-8 or the permeability vary between 1-30×10⁻³ μm², it belongs to the second type of reservoirs, which is difficult to develop; if the integrated classification coefficient of reservoirs is greater than 8 or the permeability greater than 30×10⁻³ μm², it belongs to the first type of reservoirs, which is easy to develop.