Productivity Evaluation Method For Directional Wells In Multilayer Heavy Oil Reservoirs And Field Application

For the purpose of slowing down the decline of production rate and maintaining the reservoir pressure,the development model of wide wells spacing and general water injection of directional well in multi-layers is adopted.The interlayer and plane contradiction is becoming serious and the productivity difference of production wells is obvious owing to the conditions of different development stages,formation physical property,fluid property and heterogeneities.Thus,revealing the seepage law of multilayer commingled production of interlayer interference phenomenon,quantitative characterization of the interlayer interference coefficient in different development period and dynamic prediction of directional wells productivity,could provide the forefront technology support for the efficient development of offshore heavy oil reservoir.Based on the dynamic statistics of well tests and laboratory physical simulation experiments,the influence of physical properties of reservoirs and crude oil on interlayer interference is studied from two aspects in this paper,which are permeability ratio and viscosity ratio.The change rule of interlayer interference in different water cut stage is described with oil and liquid production index introduced.From the perspective of layered testing data in the actual oil field,the mechanics and the main influencing factors of interlayer interference is studied.Combinded with the details of typical production wells in actual oil field,the interlayer interference phenomenon of different water cut stages during the multilayer commingled production process of conventional heavy oil reservoirs is quantitatively characterized with dynamic inversion.The dynamic characteration relationship between the productivity index of oil and liquid during the multilayer commingled production process is established.Considering the influence of threshold pressure gradient on interlayer interference,the directional well productivity equation of Vandervlis was modified,and the prediction method of directional well productivity suitable for commingling production of offshore heavy oil reservoirs is established,and production wells in typical zones were chosen to verify this method.Results showed that the prediction accuracy of wells productivity is improved with consideration of interlayer interference,and directional well productivity equation can be better applied to field production.Based on the experimental results,theoretical derivation and calculation,a series of research results were obtained,such as the change law of interlayer interference and quantitative characterization method of interference factor in different period.The productivity evaluation and prediction methods of directional wells used in conventional heavy oil reservoirs commingling production were proposed,which has an important significance to the reasonable subdivision and measure adjustment of multi-layer sandstone reservoir in the middle to high water cut period and provides theoretical and technological support for high-efficient development of multi-layer offshore heavy oil reservoirs.