Slug Test Data Analysis in Reservoirs With Double Porosity Behavior

Abstract

ABSTRACT Pressure analysis for a slug test which corresponds to the flow period of a Drill Stem test is extended to wells in reservoirs with double porosity behavior. The modelling of fluid flow within the reservoir is achieved by considering reservoirs having homogeneously distributed regions of primary (matrix) and secondary (fissure) porosity. The matrix acts as a source and fissures connect with the well. The well conditions include wellbore storage and skin effect. Solutions were obtained for either pseudostate, or transient interporosity flow. The distinctive features of both solutions are identified. Results presented are applicable to both naturally fractured and layered reservoirs as long as only the high permeability layer conducts to the wellbore. An interpretation method based on type-curve matching is proposed. Type curves based on pseudosteady or transient interporosity flow are presented. These type curves are similar to existing single layer type curves with the addition of interporosity flow lines indicating double porosity behavior. Application of the type-curve matching technique can provide the interporosity flow parameter λ, the storativity ratio, ω, in addition to transmissivity kh/μ, and skin effect S. Ramey et al. presented type curves for a single homogeneous layer which required empirical correlation in terms of CDe2s and tD/CD. A formal solution showing wellbore pressure as a function of CDe2s and tD/CD for a homogeneous reservoir is presented. This permits discussion of the approximation involved in Ramey et al. study.