corrosive species and scaling in wells at olkaria ... - Orkustofnun

atmospheric pressure. The results demonstrate that at discharge enthalpy close to that of dry steam and
at low vapour pressures close to atmospheric pressure, most of the liquid is evaporated and the solutes
become highly concentrated in the residual water.
8.4 Scales deposited at well OW-34
Scales formed from Olkaria well
OW-34 fluids during production
were in the two phase line, inside
the separator and in the separated
water line. The wellhead pressure
in well OW-34 during the time the
well was in production was ~ 6 bar
g. The fluids are separated at 6 bar
g in the wellhead separator. The
separated water line is exposed to
the atmosphere at the atmospheric
silencer. Atmospheric pressure at
Olkaria is ~ 0.8 bars. The layout
of the flowline and wellhead
equipment where the scale samples
were collected is shown in Figure
41.
A
In February to March 2003 a
discharge flow test was conducted
and the discharge gear left on the
well pad after the tests until
December 2004. The master valve
of this well was leaking and in the
process formed a scale in the two
phase flow line. This scale was ~
1 inch thick at the Tee connection.
The layout of the discharge test
gear and the location where the
scale sample was collected are
shown in Figure 41 b.
During production of the well in
2001-2002 the heaviest scale
formed in the two phase pipeline at
B
FIGURE 41: a) Layout of wellhead for well OW-34 fluids
showing where the scale that formed during production from
March 2001 to September 2002 was collected;
b) Layout of wellhead during discharge tests in
which scale samples were collected
a sharp bend that lead to the steam separator station. The thickness of this scale was about 1 inch after
about 18 months of the well being connected to the steam gathering system. The scale constricted the
two-phase pipeline and drastically reduced the amount of fluid that flowed in the pipe and the total
steam output of the well. The scale in the two phase line at location 2 (see Figure 41 a) is shown in
Figure 42. Scale sample # 3 was collected from inside the separator vessel, as shown in Figure 43.
Other scale samples were collected from the wellhead Tee connection after the master valve (Figure
44). The texture of the scale deposited at the well head Tee connection was similar to those deposited
in the two phase pipeline, though the thickness of the scales varied. About ½ inch of scale was
deposited and was hard. The fourth scale sample was collected from the separated waste water line.
This scale was mainly white in colour, with a little brown tinge. The deposit formed globules and
ripples and was about ½ inch in thickness. The scale deposited from the waste water line is shown in
Figure 45.
43