ASTM E1675-95a
(Practice)Standard Practice for Sampling Two-Phase Geothermal Fluid for Purposes of Chemical Analysis
Standard Practice for Sampling Two-Phase Geothermal Fluid for Purposes of Chemical Analysis
SCOPE
1.1 The purpose of this practice is to obtain representative samples of liquid and steam as they exist in a pipeline transporting two-phase geothermal fluids.
1.1.1 The liquid and steam samples are collected and properly preserved for subsequent chemical analysis in the field or an off-site analytical laboratory.
1.1.2 The chemical composition data generated from the analysis of liquid and steam samples may be used for many applications important to geothermal energy exploration, development, and the long-term managed exploitation of geothermal resources. These applications include, but are not limited to, resource evaluations such as determining reservoir temperature and the origin of reservoir fluids, compatibility of produced fluids with production, power generation and reinjection hardware exposed to the fluids (corrosivity and scale deposition potential), long-term reservoir monitoring during field exploitation, and environmental impact evaluations including emissions testing.
1.1.2.1 To fully utilize the chemical composition data in the applications stated in 1.1.2, specific physical data related to the two-phase discharge, wellbore, and geothermal reservoir may be required. Mathematical reconstruction of the fluid chemistry (liquid and steam) to reservoir conditions is a primary requirement in many applications. At a minimum, this requires precise knowledge of the total fluid enthalpy and pressure or temperature at the sample point. Fluid reconstruction and computations to conditions different from the sample collection point are beyond the scope of this practice.
1.2 This practice is limited to the collection of samples from two-phase flow streams at pressures greater than 10 psig and having a volumetric vapor fraction of at least 20%. This practice is not applicable to single-phase flow streams such as pumped liquid discharges at pressures above the flash point or superheated steam flows. Refer to Specification E947 for sampling single-phase geothermal fluids.
1.3 The sampling of geothermal fluid two-phase flow streams (liquid and steam) requires specialized sampling equipment and proper orientation of sample ports with respect to the two-phase flow line. This practice is applicable to wells not equipped with individual production separators.
1.4 In many cases, these techniques are the only possible way to obtain representative steam and liquid samples from individual producing geothermal wells. The sampling problems that exist include the following:
1.4.1 Unstable production flow rates that have a large degree of surging,
1.4.2 Unknown percentage of total flow that is flashed to steam or is continuously flashing through the production system,
1.4.3 Mineral deposition during and after flashing of the produced fluid in wellbores, production piping, and sampling trains,
1.4.4 Stratification of flow inside the pipeline and unusual flow regimes at the sampling ports, and
1.4.5 Insufficient flash fraction to obtain a steam sample.
1.5 This practice covers the sample locations, specialized sampling equipment, and procedures needed to obtain representative liquid and steam samples for chemical analysis.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.
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Designation: E 1675 – 95a
Standard Practice for
Sampling Two-Phase Geothermal Fluid for Purposes of
Chemical Analysis
This standard is issued under the fixed designation E 1675; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope superheated steam flows. Refer to Specification E 947 for
sampling single-phase geothermal fluids.
1.1 The purpose of this practice is to obtain representative
1.3 The sampling of geothermal fluid two-phase flow
samples of liquid and steam as they exist in a pipeline
streams (liquid and steam) requires specialized sampling
transporting two-phase geothermal fluids.
equipment and proper orientation of sample ports with respect
1.1.1 The liquid and steam samples are collected and
to the two-phase flow line. This practice is applicable to wells
properly preserved for subsequent chemical analysis in the
not equipped with individual production separators.
field or an off-site analytical laboratory.
1.4 In many cases, these techniques are the only possible
1.1.2 The chemical composition data generated from the
way to obtain representative steam and liquid samples from
analysis of liquid and steam samples may be used for many
individual producing geothermal wells. The sampling prob-
applications important to geothermal energy exploration, de-
lems that exist include the following:
velopment, and the long-term managed exploitation of geother-
1.4.1 Unstable production flow rates that have a large
mal resources. These applications include, but are not limited
degree of surging,
to, resource evaluations such as determining reservoir tempera-
1.4.2 Unknown percentage of total flow that is flashed to
ture and the origin of reservoir fluids, compatibility of pro-
steam or is continuously flashing through the production
duced fluids with production, power generation and reinjection
system,
hardware exposed to the fluids (corrosivity and scale deposi-
1.4.3 Mineral deposition during and after flashing of the
tion potential), long-term reservoir monitoring during field
produced fluid in wellbores, production piping, and sampling
exploitation, and environmental impact evaluations including
trains,
emissions testing.
1.4.4 Stratification of flow inside the pipeline and unusual
1.1.2.1 To fully utilize the chemical composition data in the
flow regimes at the sampling ports, and
applications stated in 1.1.2, specific physical data related to the
1.4.5 Insufficient flash fraction to obtain a steam sample.
two-phase discharge, wellbore, and geothermal reservoir may
1.5 This practice covers the sample locations, specialized
be required. Mathematical reconstruction of the fluid chemistry
sampling equipment, and procedures needed to obtain repre-
(liquid and steam) to reservoir conditions is a primary require-
sentative liquid and steam samples for chemical analysis.
ment in many applications. At a minimum, this requires precise
1.6 This standard does not purport to address all of the
knowledge of the total fluid enthalpy and pressure or tempera-
safety concerns, if any, associated with its use. It is the
ture at the sample point. Fluid reconstruction and computations
responsibility of the user of this standard to establish appro-
to conditions different from the sample collection point are
priate safety and health practices and determine the applica-
beyond the scope of this practice.
bility of regulatory limitations prior to use. For specific hazard
1.2 This practice is limited to the collection of samples from
statements, see Section 7.
two-phase flow streams at pressures greater than 10 psig and
having a volumetric vapor fraction of at least 20 %. This
2. Referenced Documents
practice is not applicable to single-phase flow streams such as
2.1 ASTM Standards:
pumped liquid discharges at pressures above the flash point or
E 947 Specification for Sampling Single-Phase Geothermal
Liquid or Steam for Purposes of Chemical Analysis
This practice is under the jurisdiction of ASTM Committee E-44 on Solar, 2.2 Other Document:
Geothermal, and Other Alternative Energy Sources and is the direct responsibility of
Subcommittee E44.15 on Geothermal Field Development.
Current edition approved Oct. 10, 1995. Published December 1995. Originally
published as E 1675 – 95. Last previous edition E 1675 – 95. Annual Book of ASTM Standards, Vol 12.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1675
ASME Code Section VIII, Division 1(1986), Pressure Ves- 5.2 Ports are ideally located on the top and bottom of the
sel Design, Fabrication and Certification pipeline at least eight diameters downstream and two diameters
upstream of major flow disturbances such as pipe bends,
3. Summary of Practice
reductions, valving, etc. (see Fig. 1).
3.1 Samples are collected from a pipeline carrying two-
5.2.1 In cases where the fluid contains substantial quantities
phase geothermal fluids by using a sampling separator that
of solid debris that may plug the sample port, the liquid port
separates liquid and steam phases through centrifugal force. A
can be located at a 45° angle from the bottom, provided that a
fraction of the separated steam is condensed and a fraction of
sufficient liquid phase is present.
the separated liquid is cooled. Portions of the condensed steam
5.2.2 If the flow regime is known, the number of ports may
and cooled liquid are collected in appropriate sample contain-
possibly be reduced to a single port located either on the side,
ers for subsequent chemical analysis.
top, or bottom of the two-phase pipeline. Sufficient quantities
of each phase must be available at the single port to allow
4. Significance and Use
collection of representative steam and liquid samples.
4.1 The objective of this practice is to obtain representative
5.2.3 The sample ports must be at least 1-in. diameter and
samples of the steam and liquid phases as they exist in the
configured with a full-open port ball or gate valve. This
pipeline at the sample point, without allowing steam conden-
requirement is necessary to ensure that only a minimal pressure
sation or additional liquid flashing in the separator. A signifi-
drop occurs through the port valve and associated piping. Scale
cant feature of the practice is the use of a cyclone-type
and debris often reduce the effective inner diameter of the port,
separator for high-efficiency phase separation which is oper-
therefore smaller ports are not recommended. The port size
ated at flow rates high enough to prevent significant heat loss
restriction also provides a safety margin given the weight of the
while maintaining an internal pressure essentially the same as
separator and force needed to install and remove fittings from
the pipeline pressure.
the port.
4.2 Another significant feature of the practice is to locate the
5.3 Sample ports should never be located on side-stream
sampling separator at a point on the pipeline where the
piping from the main flow line unless only the side-stream
two-phase flow is at least partially stratified to aid in the
fluids are to be characterized. The proportions of each phase
separation process. It is neither necessary nor possible to pass
are not likely to remain the same in a flow stream split off from
representative proportions of each phase through the sampling
the main flow line. Any pressure reduction in the side stream
separator to obtain representative samples. The separator is
piping will change the steam and liquid compositions to an
usually attached to an appropriately oriented port to collect
unknown degree.
each specific phase—normally on top of the line for steam and
6. Equipment
at the bottom for liquid. In some cases, piping configurations
can generate unusual flow regimes where the reverse is
6.1 Sampling Separator—A cyclone-type separator rated to
required. If the ratio of one phase to another is not extreme,
the pipeline pressure at the sample point, including a pressure
representative samples of each phase can often be obtained
gage, temperature probe, and sight glass (optional). The
from a horizontal port on the side of the pipeline.
separator should be designed to attach directly to the sample
4.3 This practice is used whenever liquid or steam samples,
port to minimize heat loss and pressure drop.
or both, must be collected from a two-phase discharge for
6.1.1 A typical sampling separator is shown in Fig. 2. This
chemical analysis. This typically includes initial well-testing
is a cyclone-type separator with a 1-in. pipe inlet attached at a
operations when a well is discharged to the atmosphere or
tangent to the separator body. The separator is rated to 500 psig
routine well production when a well discharges to a fluid
at 500°F. A pressure gage and thermocouple are located at the
gathering system and power plant. The combined two-phase
top of the separator, and steam and liquid sample valves are
flow of several wells producing through a common gathering
located at the bottom. Steam is drawn from the top of the
system may also be sampled in accordance with this practice.
separator through an axial pipe extending up from the bottom
4.4 This practice is not typically employed when individual
of the vessel. Liquid is drawn directly off the bottom. Internal
wells produce to dedicated production separators. In these
baffles prevent liquid films from rising up the inner walls of the
cases, the separated steam and liquid at the outlet of the
vessel with the steam flow to the sample valves. Vortex
production separator is sampled in accordance with single-
breakers are placed in the bottom of the vessel to prevent steam
phase sampling methods (Specification E 947).
entrainment in the liquid flow to the sample valves.
6.1.1.1 The vent valve on the side of the sampling separator
5. Sample Location
(No. 2 in Fig. 2) can be used to maintain an excess flow of
5.1 Sample locations vary and are dependent upon the gross
steam and liquid through the separator, beyond the amount
quantities of each phase at the sample point. If sample ports are
needed for sample collection. If sufficient quantities of each
properly oriented on the two-phase pipeline, a certain degree of
phase are present, the side vent valve will maintain a liquid
phase stratification will have occurred prior to sampling,
level about 2 in. above the liquid sample valve (No. 5 in Fig.
facilitating further separation of the target phase through the
2). This allows collection of both steam and liquid samples
sampling separator.
from the separator without the need to adjust the liquid level.
6.1.1.2 An optional sight-glass (PFA-fluorocarbon) for liq-
uid level is located along one side of the separator to aid in
Available from American Society of Mechanical Engineers 345 E. 47th St. New
York, NY 10017. proper separator operation and confirm the position of the
E 1675
NOTE 1—Minimum pipe diameters required upstream and downstream of major flow disturbances (piping bends, reductions).
FIG. 1 Two-Phase Flowline Sampling Separator Ports
liquid level. The sight glass is only rated to 250 psig and must increase the risk of contamination and chemical deposition
be removed for higher pressure operation. during liquid sampling due to low fluid velocities and longer
6.2 Sample Hoses—Sample hoses are PFA-lined stainless residence times within the tubing. In cases where the liquid
steel braided hoses rated to 500 psig and 450°F. JIC type contains substantial quantities of particulate matter, 0.375-in.
fittings or quick-disconnect fittings attach hoses to the separa- outside diameter tubing coils may be used to minimize cooling
tor and condenser. Hoses are dedicated to either steam or liquid coil plugging problems.
service to prevent cross-contamination. The inner diameter of 6.3.2 In cases where the noncondensible gas concentration
the hose should not exceed 0.375 in. Stainless steel tubing may in steam exceeds approximately 5 % by weight, the outlet of
also be used (0.25 to 0.375-in. outside diameter), although it is the steam condenser coil should be at an elevation below the
less convenient. Convoluted, flexible stainless steel hose is inlet with a continuous down-slope in the tubing from inlet to
specifically excluded due to potential entrapment and contami- outlet. This allows the small volume of condensate to freely
nation problems caused by the internal convolutions. drain out of the condenser and prevents hold-up within the
6.3 Condenser—A sample condenser configuration with coils.
two sets of stainless steel tubing coils is recommended. One set 6.4 Condenser cooling can be achieved by an ice/water bath
of coils is dedicated for condensing steam and the other is surrounding the coils or by a continuous overflow of cooling
dedicated for cooling liquid. The steam condenser coil has a water running into the vessel holding the coils (configuration
pressure/vacuum gage located at the sample outlet and a shown in Fig. 3 and Fig. 4). Alternate configurations may
regulating valve at the inlet. The steam flow can be precisely include a water-tight jacket around the coils through which a
regulated at the inlet as opposed to regulating the flow of constant source of cooling water flows. A source of coolant
condensate and gas at the outlet that can result in large pressure may be a glycol/water mixture circulated through the con-
surges and the hold-up of gas or condensate phases in the coils. denser jacket and an external fan-cooled heat exchanger.
The liquid cooling coil has a regulating valve at the outlet and 6.5 Pressure Gage—For the measurement of separator pres-
an optional pressure gage. Regulating the outlet flow prevents sure. Bourdon-tube type gages or pressure transducers may be
flashing of liquid at the inlet to the condenser where chemical used. A pressure-snubbing device is recommended to minimize
deposition could occur. Dedicated condensers with single sets the pressure spikes and surges common in two-phase flow
of tubing coils for sampling either steam or liquid also can be lines. The full-scale pressure range of the gage should not
used (see Fig. 3 and Fig. 4). exceed two times the measurement reading. The gage should
6.3.1 The condenser coil tubing must not exceed 0.25-in. be calibrated at monthly intervals when in routine use and
outside diameter to prevent the segregation of gas and conden- every six months for intermittent use. The measurement
sate phases during sampling of steam. Larger tubing sizes also accuracy of the gage should be at least 61 % of full-scale.
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