an integrated steady-state - International Geothermal Association

162
Although the e cannot in itself address concerns about NaCl or content values to be entered into the simulator.
the a particular drawdown it
the user with a choiceof such relahonshipsto apply.
The resultant lower bound profiles can be displayed
Lower bound analysisis described in
Gunn et al. (submitted).
pre of e is of an ongoing study
it is to extend the
scope of the package to include the of transient
STEADY-STATE SIMULATION FEATURES
effects.
The module of the packa e is the steady-state simulation
SIMULATION AND ANALYSIS MODULES
includes the
features.
liquid, two-phase, and superheated steam flow.
The packa e includes five main simulation and analysis
Incorporates dissolved solids content by an equivalent
modules, are as follows.
percent of NaCl.
non-condensable gas content by an
Discharge Test Simulation
This is the core module of the packa e. It allows the
simulation of steady-state flow in a well at a
single mass flowrate, The features, assumptions and
module are discussed more
later of paper.
Preprocessing Fluid Composition and Properties
The input parameters for a discharge test include fluid
and fluid sition, some of which ma be
or other measurements.
values will not all be consistent with to
each other, and in some cases various parameters will be
Inconsistenciescan be due to measurement error,
but typical1 measured enthal y values may not be
appropriate to the resence or dissolved solids.
Inconsistencies may result related measurements
having been observed at different times. Wellhead and
deepestfeed conditions into the simulationmodule are
preprocessed to ensure that a consistent and/or
complete set of input is used in the discharge test
simulation. A is not allowed to proceed without
such a step having first been performed
Output Test Simulation
In the real world a number of actual discharge tests on a
geothermal well can be performed to the well's
characteristic output or
this is an
expensive o package a module for
such a series of discharge test
simulations produce an estimateof the output curve. Such
a procedure termed an out ut test As part of the
simulation the module can requested to calculate suitable
drawdown parameters at the dee feed zone.Results can
be presented
in a text format. An
example of procedure is the case study in the
final section of
Matching Analysis
As above analysis is a tool can be
used to calibrate the mput parameters to the simulator.
Measured downhole pressure and
can be
entered into the package to allow their subsequent comparison
against simulated results. The profiles can be compared
allow ' matching, or a simple
matchmg report can be produced.
Lower Bound Analysis
As noted above, observed downholeprofiles in discharging
wells can be subject to significant measurement error.Lower
bound anal is a for estimating the of
measured for to matching analysis.
method works by simply analysing the consistency of
measured pairs of two-phase pressure and temperature
measurements taken at intervals down the wellbore. The
analysis estimates the minimum C02 or NaCl content
for each pair to satisf saturation condition, If these
minimum values, or lower have considerable
the then the data can considered
to be of use for or flwd parameters.
In some cases such analysis can aid the
or
verification of feed zone locations, and also suggest calibrated
equivalentweight percent of
Estimates the effectof both NaCl and
on fluid liquid
of on fluid vapour phase
and on superheatedsteam properties.
Allows or deepest calculation.
Models secondary feed zones, and calculates fluid
compositionat feeds.
Allows linear, quadratic, or superheated steam
drawdown relationshipsto be specified at each
calculating mass flowrate.
Allows multiplechangesof casin and liner diameter,
roughness to be (A of standard casing
and liner sizes is included).
Models the effect of deviations in the wellbore from
vertical on the pressure,
Models the rock formation
and well
Provides results at each depth of interest for:
pressure; temperature; enthalpy; dryness; wei ht percent
of NaCl the liquid phase; pressure
flowrate; flow regime or fluid.type; and, frictional,
and
pressure
Provides
of simulated downhole pressure
and
SIMULATION ASSUMPTIONS AND
CORRELATIONS
The stead -state simulation module of the has been
and su uently the two
and by
ad n for superheated steam flow.
programsit has been assumed that:
flow is steady and
are
constant a depth
and
dissolved solids and non-condensable gases can be
resented by an equivalent NaCl content and eqwvalent
C content
Fluid Properties
The formulae evaluating fluid are those outlined
in Hadgu (1989). is considered toaffect:
overall fluid pressure, and the partial pressure of is
determined from the relationship by Sutton (1976) and
from Henry's Law (the reason for using Sutton's
relationship as a ainst that found
Dalton's
Law is GUM and Freeston (m
of the vapour phase only (from et
enthalpy of both liquid and vapour phases (from Hadgu,
1989);and
viscosity of the vapour phase only (from Pritchett et al.,
1981).
NaCl is considered to affect
pressure (from Haas, 1976);