A Semi‐Analytical Solution for Slug Test by Considering Near‐Well Formation Damage and Nonlinear Flow

Abstract

AbstractThis study proposes a new analytical slug test model describing confined flow considering the effects of the formation damage and non‐Darcy flow near the wellbore. The former, primarily caused by drilling fluid invasion, introduces an extra wellbore head loss near the well screen. The latter, mainly resulting from the relatively high‐velocity flow across the gravel‐pack screen, adopts the Forchheimer equation to consider the joint effects of the laminar flow and non‐Darcy flow. The proposed model is nonlinear due to the quadratic term for non‐Darcy flow in the Forchheimer equation. The new solutions for head responses in the well and formation are derived using the Laplace transform method and integration by parts formula. Furthermore, the present solution is applied to estimate the aquifer parameters via analyzing the water level data from field slug tests conducted in the Minnelusa aquifer near Spearfish, South Dakota. We found that the present solution provides very good fit to the field data from tests in fractured aquifers, notably the data exhibits a rapid decline at late times on the normalized head vs. logarithmic time plots.