Abstract: There are large errors between the designed productivity and the actual productivity of directional wells in heavy oil reservoirs with multi-layer combined production. Taking PY10-2 Oilfield in the eastern part of the South China Sea as an example, a reasonable characterization study of flow characteristics of heavy oil reservoirs was carried out. Based on logging curves considering the longitudinal permeability ratio, a productivity model and evaluation method were developed that integrated the influences of factors such as the power-law of heavy oil fluid, longitudinal heterogeneity, start-up pressure, and stress-sensitivity to characterize the strong longitudinal heterogeneity in such reservoirs finely. Good results were achieved in the evaluation of actual oilfield productivity. The research results show that the prediction accuracy of this model is dramatically improved compared with the traditional method, and the average errors of the predicted productivity are less than 10.0%. The productivity of directional wells decreases with the decrease of the power law exponent; the influence of the power-law index on the production capacity increases when the bottom hole flow pressure decreases; the increase in productivity index decreases when the producing pressure drop of the directional wells rises. This study is of great significance for evaluating the reasonable productivity of similar offshore reservoirs.

Key words: heavy oil reservoir, directional well, longitudinal permeability ratio, power-law fluid, productivity evaluation