Property:BestPractices

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Property Name BestPractices
Property Type Text
Description List of best practices that could be applied while using this technique.


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2

2-M Probe Survey +Probes can be arrayed in any manner desirable, but initial reconnaissance should be in a grid or in transects across and along faults, if known.

A

Acoustic Logs +Probes are constructed of low-velocity materials, producing the shortest travel path for the acoustic pulse through the borehole fluid and the adjacent rocks, which have a velocity faster than that of the fluid.
Active Sensors +Many geothermal areas are in remote areas which are difficult to access so active remote sensing methods can be extremely valuable for gathering initial information about an area at low cost and low impact to the environment. Active remote sensing techniques are also very useful for monitoring a geothermal reservoir before, during, and after development. An advantage of active sensors is that they can be used at any time of day and don’t require any outside source. Some active sensors such as radar can penetrate cloud cover and even thick forest canopy.
Airborne Electromagnetic Survey +In the case of airborne systems, the receiver coils are usually in a towed bird and the transmitter may be a large coil encircling a fixed wing aircraft, e.g. INPUT systems, or one or more small coils in the same bird that houses the transmitting coils
Analytical Modeling +In analytical modeling it is very important to identify the main factors defining the complex system. Doing this can help provide guidance and what needs to be measured to understand the subsurface processes.
Audio-Magnetotellurics +See [[Magnetotelluric Techniques]]

C

Caliper Log +A single axis caliper provides a single diameter at a specific chord across the borehole. A multi-axis caliper has multiple arms and can measure the diameter of the well bore in multiple locations simultaneously. This provides useful information as to the shape of the borehole and when run in conjunction with a orientation tool can give understanding to the stress orientation.
Cement Bond Log +Analysis and interpretation of a cement bond log is necessary to assure integrity of the cement job, and if an adequate bond is not present throughout the interval the drilling contractor will be required to place plugs and perforate the casing and squeeze cement (perf and squeeze) into the zone. A cement bond log is required to determine whether the perf and squeeze was effective.
Cross-Dipole Acoustic Log +-Sonic logs can be performed through cemented well casing. -The instrument does not operate properly in air, so the well must be filled with some type of fluid.

D

Data Collection and Mapping +Advantages and ideal implementation methods are specific to the technique to be applied and to the geothermal area under investigation. Consult the individual technique pages linked in the “Related Techniques” section above for information regarding best practices for applying different data collection techniques in the field.
Density Log +If the density log is taken as part of a wireline measurement, to minimize the influence of mud on the results, a pad is pressed into the borehole wall to focus the source and detector sensors into the formation. If instead the density measurement is taken during well drilling, a sleeve can be added around the sensors to exclude the mud coming between them. To further reduce the influence of mud, two or more sensors at different spacings can be used.
Development Drilling +Developmental drilling should only begin once a dependable reservoir model has been established and there is a good amount of certainty that the reservoir will be productive.
Direct-Current Resistivity Survey +• It may be necessary to water the electrodes with pure or salt water to lower contact resistance at the electrode interface.<br><br>
Downhole Fluid Sampling +Sampling of geothermal reservoir fluids is best carried out by a qualified hydrologist, geologist, or geochemist familiar with current sampling standards. A practical understanding of how various processes affect the bulk chemistry of the reservoir fluids as they are brought to the surface ensures that appropriate sampling procedures are used to obtain a sample that is representative of reservoir conditions. A working understanding of geothermal systems is also ideal for the purposes of data interpretation, application of various chemical and isotopic [[Geothermometry|geothermometers]], and [[Modeling-Computer Simulations|geochemical modeling]] of the reservoir.
Drilling Techniques +Preform less expensive shallow [[Exploration Drilling|exploration drilling]] techniques first. Once a confident reservoir model is established Development Drilling

E

Electrical Techniques +Raw electrical field data always have to be properly interpreted in order to derive models of the electrical structure of the subsurface. Most modern interpretation methods involve either or both forward modeling or inversion, In forward modeling, as proposed resistivity model of the subsurface is constructed and the response of this model to the particular electrical method being used is computed for comparison with the observed data. The model is adjusted until there is a sufficient match to the observed data. In the inversion method, the process of comparison is done within the computer program. Electrical interpretation software is very sophisticated and must be used by experienced experts for reliable results. As noted below, the models yielded are almost always non-unique, but independent geological or geophysical data can be used to reduce non-uniqueness.

F

Field Mapping +<br> *It is important to spend more time in the field developing detailed geologic maps. Oil and gas companies typically spend more time than geothermal companies mapping prospective locations, and it has helped to explain why individual projects have succeeded and failed. Even for currently operating geothermal systems, often there is not a solid understanding of the underlying geology. *Reiterating a previous point, a well-trained geologist is important to developing geologic maps. Although modern computer processing and mapping software have promoted the ubiquitous generation of maps, the can also result in the erroneous use of automated contouring of non-uniform data point distributions (Klein, 2007).
Fluid Inclusion Analysis +Only have a qualified fluid inclusionist analyze the samples. Know the samples and the system they came from. Make sure the observations in the fluid inclusion analysis align with what is known of the hydrothermal system.<br:/>Plot the data properly so that each fluid inclussion assemblage is discernable, becasue each assemblage represents a different period of fluid evolution.

G

Gamma Log +If multiple wells are drilled within a geothermal field, correlating the gamma radiation data with depth can help to correlate lithologies between wells. Natural faulting of the system can alter the depth to the various layers between the wells.
Gas Flux Sampling +The limitations of different accumulation chambers for measuring the flux of various types of gases should be considered when selecting equipment for use in the field. The distribution and placement of accumulation chambers across the area under study must also be dense enough to achieve adequate resolution when flux measurements are plotted as gas concentration maps during data visualization.
Gas Sampling +Gas sampling is best carried out by a qualified hydrologist, geologist, or geochemist familiar with current sampling standards. A practical understanding of how different surface features relate to hydrothermal processes within the geothermal system is also ideal for the purposes of data interpretation, application of various chemical and isotopic [[Geothermometry|geothermometers]], and [[Modeling-Computer Simulations|geochemical modeling]] of the reservoir.
Ground Gravity Survey +In the survey design planning:<br><br>• The line direction should be positioned perpendicular to the dominant geologic strike direction.<br>• Measurement spacing should be designed to include at least five magnetic measurements per anomaly.<br>• Line spacing and station interval need to be spaced finely enough to characterize spatial distribution of anticipated anomalies.
Ground Magnetics +In the survey design planning:<br/>• The line direction should be positioned perpendicular to the dominant geologic strike direction<br>• Measurement spacing should be designed to include at least five magnetic measurements per anomaly<br>• Line spacing and station interval need to be spaced finely enough to characterize spatial distribution of anticipated anomalies<br>
Groundwater Sampling +Groundwater sampling is best carried out by a qualified hydrologist, geologist, or geochemist familiar with current sampling standards. While groundwater sampling is relatively simple compared to in-situ [[Downhole Fluid Sampling|thermal fluid sampling]], a practical understanding of how various processes can affect the bulk chemistry of sampled waters as they are brought to the surface ensures that appropriate sampling procedures are used to obtain a sample that is representative of subsurface conditions. A working understanding of fluid recharge and mixing in geothermal systems is also ideal for the purposes of data interpretation, application of various chemical and isotopic [[Geothermometry|geothermometers]], and [[Modeling-Computer Simulations|geochemical modeling]] of the reservoir.

H

Hydroprobe +Due to the direct push technology a hydroprobe survey must be conducted over soil, loose sediment, or alluvium.
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