3D DC resistivity modeling of steel casing for reservoir monitoring using equivalent resistor network

Abstract

Energized steel casings in oilfields channel electric currents generated for a surface resistivity survey down to the depth of target reservoir, enabling the use of electric methods in reservoir monitoring. Numerical simulation of such a survey often requires refined meshes to simulate the casing. In order to avoid the use of small cells, we propose a method that treats the earth’s conductivity model as a 3D equivalent resistor network (ResNet), and a casing as a parallel-circuit wire conductor. Numerical comparisons with a cylindrically symmetric code and with a finite element code show that ResNet provides accurate and efficient solutions to the current along the casing and to the electric field on the surface. Using ResNet, we further study how the current distributes along a casing: (1) The casing current approaches a nearly linear decay if the casing conductivity is sufficiently high; (2) The casing current is more sensitive to variation in the extent of a conductive injectate than that of a resistive one; (3) Under special circumstances the current can flow into the casing from the surrounding.

Presentation Date: Wednesday, October 19, 2016

Start Time: 1:30:00 PM

Location: 174

Presentation Type: ORAL