A METHOD TO EVALUATE RESERVOIRS AND ESTIMATE SATURATION BY DYNAMIC-RESPONSES OF DUAL-INDUCTION LOGGING TOOLS

The invasion of drilling mud-filtrate into a reservoir is a dynamic pr ocess. Formation-resistivity profiles are therefore invasion-time depe ndent. The dynamic response model for resistivity logs is established and solved by numerical methods. The present model gives more physical understanding to the invasion process than the conventional step mode l does. The dynamic resistivity responses are sensitive to the variati ons of formation-water saturation, hence an effective method to evalua te reservoirs is suggested by history matching the dynamic dual-induct ion logging readings. Field examples are illustrated that distinguish oil reservoirs, water zones, and oil/water zones, as well as define th e oil-water interface by the responses of induction logs at different logging times after drilling. (C) 1998 Elsevier Science B.V.