Two-Dimensional Conductivity Image from the Data Measured by Electromagnetic Cross-Well Tools

摘要

The predicting and monitoring of fluid movement during a steam-injection operationis much important in an EOR process. A crosswell two-dimensional conductivty imaging technique is developed to monitor the injection or production profiles by inverting formation conductivity from crosswell electromagnetic measurements. The tool responses are calculated from electromagnetic field equations using perturbation approach. Maximum entropy constraint is used to regularize the inversion problem. To assure the stability and fast convergence, the inversion procedure is conducted in three steps: homogeneous inversion that assumes the formationwith an unique conductivity; one-dimensional inversion that generates horizontally layered formation; and two-dimensional inversion that regards the conductivity anomalies both in vertical and radial directions. An initial guessed value of homogeneous background is needed for the program at the beginning. The calculated result of homogeneous medium is then used as the initial value of one-dimensional inversion, and the reconstructed alyered conductivity profiles are the initial input for the two-dimensional inversion. By the steps from homogeneous to heterogeneous inversion, the misfit between measured and calculated data decreases sharphy. The examples for both synthetic data nd field data are illustrated. The inversion results show that the reconstructed conductivity images are in agreement with the known formation characters within given error tolerances.