Analyses have been completed to evaluate different operating strategies for the Hijiori Long Term Circulation Test (LTCT). To ensure that the Geocrack2D model used to represent the LTCT was valid, 1991-1996 testing at Hijiori was first simulated. After reasonable matches were obtained with the existing data, the model was used to predict behavior during the two year long LTCT. Five cases were analyzed: (1) a nominal case with injection flow of 16 kg/s, (2) a case with half the nominal flow, (3) a case with double the nominal flow, (4) a case where HDR-2a was blocked at the lower fracture (selected to block the observed cold flow at the lower fracture in HDR-2a), and (5) a case with enhanced connectivity between the lower and upper fracture. In all cases, injection was in HDR-1, with production from HDR-2a and HDR-3.

For the nominal case, the HDR-2a mixed production temperature is predicted to reduce from 240 C to 180 C while the HDR-3 temperature remains approximately constant at 240 C. The highest production temperatures occur for Case 4, when the lower fracture is blocked in HDR-2a, with the final production temperature after two years being 214 C.

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