Radial-Coreflood Placement Tests
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 114096, "Radial Core Flood Placement Tests," by R. Stalker, SPE, I.J. Littlehales, SPE, G.M. Graham, and G.F. Oluyemi, Scaled Solutions Ltd., originally prepared for the 2008 SPE International Oilfield Scale Conference, Aberdeen, 28-29 May. The paper has not been peer reviewed.

Effective placement of chemical squeeze treatments in heterogeneous wells and long-reach horizontal wells has proved to be a significant challenge, with various factors contributing to uneven placement of the squeeze treatment into the reservoir. Current methods to circumvent these problems often rely on expensive coiled-tubing operations, staged diversion (temporary shutoff) treatments, or designing treatments to overdose some zones deliberately to gain placement into other low-permeability zones.

Introduction

Chemical placement in complex and heterogeneous wells such as subsea wells, highly compartmentalized reservoirs, and deviated and horizontal wells can be a challenging operation, with factors such as permeability contrast, pressure gradient, and crossflow contributing to the heterogeneous nature of these wells. To achieve more-even placement in different noncommunicating zones in these environments, the industry has relied on a number of techniques. These techniques have a number of draw-backs, including higher costs, more-technically-demanding operations, and limited applicability.

To allow predictive modeling of chemical placement using viscous shear-thinning fluids, a near-wellbore simulator was developed as part of a joint industry project. This simulator can model Newtonian- and non-Newtonian-fluid behavior and propagation in highly heterogeneous reservoirs or wells. The model can give a quantitative assessment of fluid placement in a heterogeneous-reservoir environment, giving design and field engineers realistic assessments of the placement and subsequent chemical-return behavior of proposed field/well treatments. To validate the simulator, coreflood experiments using two linear cores in a dual parallel linear arrangement were designed and implemented in the laboratory. These tests investigated the placement behavior of Newtonian and viscous shear-thinning fluids when faced with permeability contrasts, pressure contrasts, or both pressure and permeability contrasts. The placement results observed in these experiments agreed closely with simulator predictions of these linear-flow tests, providing direct experimental evidence of the appropriateness of the model's treatment of shear-thinning-fluid behavior in reservoir cores.

To validate the simulator further, a dual-radial-wedge coreflood apparatus was designed, commissioned, and validated in the laboratory and then used to examine the placement behavior of a variety of fluids under radial-like flow conditions. The laboratory data obtained in these tests then were compared with model predictions to obtain additional validation of the underlying algorithms.

The essential feature of the design of the radial-wedge core, that allows fluid flow through it to assume a radial flow front rather than a linear flow front associated with a linear core, is the assumption of the cross section of a well (Fig. 1). The use of this novel radial-wedge core in laboratory studies was considered highly beneficial to the validation schemes of the simulator because the core would allow not only radial flow through it but also would imitate the flow in a typical well.