Proceedings of the 7th New Zealand Geothermal Workshop 1985. Mathematical modelling of subsidence at Wairakei geothermal field. New Zealand Geothermal Workshop [7, 6-8 Nov. 1985, New Zealand].

Herd, M.A. McKibbin, R.

1985

1067
CIENA

0-86869-065-1

A multi-dimensional model is required at Wairakei in order to account for the significant observed horizontal deformations. From the subsidence models and subsidence/compaction relationship examined, a finite element model was chosen for its potential to reproduce such deformations and for its ability to utilise either linear or nonlinear, nonhomogeneous material models. Using the ADINA finite element progam, a simple two-layer model was developed incorporating the Pumice and Wairakei pumice breccia layers as the overburden, and the Huka formation as the reservoir. The deformation in the Waiora formation was considered to be less significant and was neglected. Using suitable estimates for the elastic properties of each layer (Young's modulus and Poisson's ratio) and by depressurising in the reservoir a zone whose lateral extent corresponds approximately to the point of inflection on the observed vertical deformation profile, a good fit was obtained, particularly to the vertical profile. Features of both models are apparent al Wairakei. ABSTRACT. INTRODUCTION. MODEL CHARACTERISTICS. SOLUTION TECHNIQUES. One dimensional consolidation. Nucleus of strain mothods. Finite element methods. Other methods. ADINA FINITE ELEMENT PROGRAM. WAIRAKEI CASE STUDY. Pressure decline. Material properties. System geometry. Model one - lateral variation in pressure decline. Model two - lateral variation in compressibility. SUMMARY. REFERENCES.

Presenta gráfs.

NUEVA ZELANDIA; ENERGIA GEOTERMICA; GEOTERMIA; MODELOS MATEMATICOS; CAMPOS GEOTERMICOS; ADINA;