Numerical investigation of production behavior of deep geothermal reservoirs at super-critical conditions

Numerical simulations have been performed to predict pressure transients in deep geothermal reservoirs at sub- and super-critical temperatures. First, pressure drawdown and buildup tests of reservoirs with different initial c onditions were simulated. The calculated pressure responses are dominated b y non-linear changes of fluid kinematic viscosity and compressibility. The pressure of a super-critical zone is shown to cause complex behavior. Short - and longterm production tests in both unbounded and bounded reservoirs we re then simulated. Unbounded and bounded reservoirs exhibit very similar sh ort-term production behavior near or above the critical temperature (375-40 0 degrees C). Unbounded reservoirs of low transmissivity (kh = 1 darcy-mete r) exhibit long-term production behavior that depends on whether the reserv oir is sub-critical (300-375 degrees C) or super-critical (400 degrees C); substantial increases in flowing enthalpy and declines in feedpoint pressur e occur at early times in the super-critical reservoir. (C) 1998 CNR. Publi shed by Elsevier Science Ltd. All rights reserved.