Hydraulic well testing inversion for modeling fluid flow in fractured rocks using simulated annealing: a case study at Raymond field site, California

Cluster variable aperture (CVA) simulated annealing (SA) is an inversion te chnique to construct fluid flow models in fractured rocks based on the tran sient pressure data from hydraulic tests. A two-dimensional fracture networ k; system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes element apertures for a cluster of fractu re elements in order to improve the match to observed pressure transients. This inversion technique has been applied to hydraulic data collected at th e Raymond field site, CA to examine the spatial characteristics of the flow properties in a fractured rock mass, Two major conductive zones have been detected by various geophysical logs, geophysical imaging techniques and hy draulic tests; one occurring near a depth of 30 m and the other near a dept h of 60 m. Our inversion results show that the practical range of spatial c orrelation for transmissivity distribution is estimated to be: approximatel y 5 m in the upper zone and less than 2.5 In in the lower zones. From the t eleviewer and other fracture imaging logs it was surmised that the lower co nductive zone is associated with an anomalous single open fracture as compa red to the upper zone, which is an extensive Fracture zone, This would expl ain the difference in the estimated practical range of the spatial correlat ion for transmissivity. (C) 2000 Elsevier Science B,V. All rights reserved.