SIMULATION OF CIRCULATION TESTS AT THE HIJIORI HOT DRY ROCK WELLS

Abstract

Hijiori hot dry rock test system was built with an injector and two producers which are connected by hydraulic fractures in two separate zones about 250 m apart in depth. Hydrothermal recovery tests were conducted by circulating water through the network for 25 days. Pressures, temperatures and rate changes were continuously measured at the wellheads, and production logs were run periodically through the tests.

In order to interpret the flow mechanism and to evaluate the efficiency of hydrothermal recovery in this system, simulation studies were conducted with a 3D model where hydraulic fractures were implemented by thin grids. Through matching the data, dynamic phenomena of the hydraulic fractures in the deep zone were necessarily simulated by a dynamic fracture growth/shrinkage option of the used simulator. For a reasonable match, areal propagation of the fractured zones was assumed in addition to linear propagation of the hydraulic fractures. Backflow through the wellbores and crossflow in formation need to be modeled appropriately for better matching of pressure behavior if the production wells.