Application Of Multi-layer And Variable-rate Testing In Reservoir With Low Permeability And Low Injectivety

Well-testing is a widespread technique used in field exploration and development of oil and gas.Compared to well logging method,well-test interpretation results shows the macroscopic properties of reservoir in a large range.However,many tests only conducted at a sigle-step rate.It is hardly to discover the mobile change of reservoir parameter,such as permeability,fracture length and skin factor.At present,in some multi-layer reservoirs,existing multi-layer model can't represent the single layer parameters.For example,in jidong low permeability reservoir,the reservoir has two remarkable characteristics in waterflooding stage,the one is strong heterogeneity,the other one is low injectivity at low injection pressure.In order to understand layer's mobile changes under the complicated injection condition,this paper proposed multi-layer and variable-rate testing method.In order to obtain better interpretation results,modeling methods are used to simulate different plots under different reservoir situations and different models.These plots provide basis for model selection.Through modeling pressure changes of variable-rate injection period and pressure falloff period,the influence of different rate injection on plot can be understood.Through modeling pressure diffusion in low preability reservoirs,the interference of offset wells can be neglected.Meanwhile,numeric modeling method is used to simulate the IPR curve and the impact factor of production.Finally,the interpretation methods are based on superposition principle.Deconvolution method is used in interpretation.It indicates that this method can discover the mobile change of reservoir parameters in variable-rate test situation,such as permeability,skin factor,pressure and fracture length.This method is proved to be a accurate way to evaluate reservoir behavior in practice,and it has an important effect in detecting reservoir behaviors.