The Geochoke Well Test Response in a Catalogue of Systematic Geotype Curves

摘要

A new well test response has been identified. A distinctiverestriction – shown as a hump on the derivative curve – is seenin double matrix porosity (dual permeability) reservoirs. Highpermeability lenses intersecting the well bore give rise to anegative geoskin response at early time. After the middle timeperiod of flow restriction caused by the limits of the lensesconnecting to the wellbore and the presence of additionallimited extent, discontinuous, high permeability lenses withinthe reservoir. This phenomenon has been shown in a series ofnumerical models and is also observed in two field well tests.The two field examples come from testing in a braided fluvialoil reservoir. Other interpretational possibilities (e.g., sub-seismicfaulting, fluid changes), which might also beconsidered given the non-uniqueness of pressure data, areeliminated by careful consideration of the geophysicalinterpretation, the depositional environment and the fluidproperies. Sub-seismic faults are often interpreted in well testsfrom braided fluvial reservoirs. However, we consider that theresponse in these cases, and possibly in a wider range of cases,is due to geological effects of sedimentary heterogeneity dueto secondary channels within the braided system. Braidedfluvial sedimentary processes result in heterogeneousreservoirs with double matrix porosity. The heterogeneity andthe double matrix porosity nature of these reservoirs areevident from the Lorenz Plot. Such sandstones can produce avariety of well test responses as the two matrices interact atvarious length scales.The geochoke model in double matrix porosity reservoirs is anend-member response for reservoirs with short lateral andvertical correlation length. A family of geotype curves can begenerated to consider a range of correlation lengths tosystematically explore the limits of early, middle and late timeresponses for specific reservoir cases.