Numerical simulation of the dual laterolog response to fractures and caves in fractured-cavernous formation

To study the response characteristics of dual laterolog in fractured-cavernous reservoirs, a model of fractures and caves was built, and the 3-D finite element method was utilized to simulate its logging responses. Caves of certain size have influence on the response of dual laterolog within certain space. With the cave size increasing, the logging apparent resistivity becomes lower, and the apparent resistivity ratio of deep laterolog to shallow laterolog decreases. Within less than the one-cave radius scope, the dual laterolog is more sensitive to the cave to borehole wall. The logging response of fractured-cavernous formation is mainly affected by fractures, and low angle fractures result in a negative difference of dual laterolog which is contrary to high angle fractures, but the existing caves do not change the matching relationship between the shallow and deep resistivity and fracture dip. The apparent conductivity of dual laterolog in fracture-cave formation presents a linear relationship with fracture aperture.