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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.

Pages using the property "BestPractices"

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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.  +
Hyperspectral Imaging +  *Hyperspectral datasets are very large and cumbersome to work with (imagine 224 pieces of information—one for each band—stored for each pixel in an image). Data can be interpreted into maps so that the information can be shared in much more manageable datasets. Though many in the industry still appreciate the 7-band LANDSAT images (which can be made through data aggregation of hyperspectral images), there are four common types of maps that are created from hyperspectral data for use in geothermal exploration, including mineral maps, cultural maps, vegetation maps, and high-resolution photographs. *There are many commercial vendors that provide data products from calibrated radiance to surface reflectance to derived mineral maps. Since processing techniques vary widely in creating surface mineral maps it's a good practice for derived products to be reviewed by geologists for quality control.  +
L
LiDAR +LiDAR data are very helpful for the expert in the 3D visualization of geothermal data for exploration and reservoir interpretation purposes. Managers and investors in hydrothermal exploration projects are more used to looking at bulls-eye type images that will tell them where a resource is located and where the best locations are to drill. This can be addressed by taking a particular mineral or mineral assemblage of interest and creating a mineral contour map.  +
Long-Wave Infrared +Typically, LWIR imaging as a hydrothermal exploration technique has been replaced by [[Hyperspectral Imaging]]  +
M
Magnetotelluric Techniques +• Remote referencing techniques should be utilized to reduce the effects of local noise sources on MT data.<br><br> • A parallel sensor test should be performed at the beginning of the survey to QC the magnetometers, instrument channels ad verify all equipment appears to be functioning properly.<br><br> • Salt water and bentonite may be used during the electrode installation to reduce contact resistance at the electrode-soil interface.<br><br> • All wires and electrical connections should be carefully monitored for corrosion and replaced or re-spliced if corrosion exists.<br><br> • MT stations should be moved as far from cultural noise sources as possible while maintaining an even grid for the MT stations.<br><br> • Wires must be as close to the ground as possible for overnight recordings to reduce or prevent wind noise or animals tripping on the cables.<br><br> • Wires should be closely checked when picking up each station for chew marks or breaks in the wire from animals nibbling or chewing on the wires. <br><br> • If it is possible to view the time series in the field, it is recommended to run a brief test on the equipment and setup as a QC check prior to initiating the overnight recording.<br><br>  +
Mud Logging +Mud logging is standard practice during drilling operations and is important for documenting the geology that a well passes through. Preserving and storing the rock cuttings in an organized filing system is normal procedure.  +
Multispectral Imaging +Relative mineral determinations should always be verified in the field to ensure that distributions determined using multispectral data are accurate. Increasingly, multispectral imaging as a hydrothermal exploration technique has been replaced by [[Hyperspectral Imaging]].  +
N
Near Infrared Surveys +Near infrared surveys are best conducted in conjunction with other electromagnetic bands during [[Multispectral Imaging|multispectral]] or [[Hyperspectral Imaging|hyperspectral imaging]] surveys.  +
Neutron Log +It is best to use neutron logging in addition to other logs to best determine the rock type and porosity. The use with gamma ray logging can reduce the possibility of potentially mistaking a shale as a high porosity zone since shales have a different gamma ray signal than sandstones.  +
P
Paleomagnetic Measurements +It is best to collect core samples from outcrops and exposed layers of rocks such as road cuts, where multiple layers can be easily accessed.  +
Passive Sensors +Many geothermal areas are in remote areas which are difficult to access so passive remote sensing methods can be extremely valuable for gathering initial information about an area at low cost and low impact to the environment.  +
Portable X-Ray Diffraction (XRD) +Identification of an unknown requires a small amount of sample material, a device for grinding the sample, and a sample holder. Approximately 15 mg of pure sample is ground into a powder (<150 micron grain size or 100-mesh) in the field prior to analysis. Additional sample preparation details are included in the Field Procedures section of this page (above).  +
Pressure Temperature Log +Allowing the well to reach equilibrium with the surrounding formation is going to provide the most accurate reservoir temperature (Blackwell, et al., 2010).  +
Production Wells +Firm evidence from multiple exploration techniques is very important when deciding where to drill production wells. A solid reservoir model should be in place when deciding on the best drilling locations.  +
R
Radiometrics +<br> * Because this techniques maps surface feature, it is important to have a solid understanding of surface processes (e.g. weathering) and the interaction of these processes with bedrock.  +
Reflection Survey +See [[Active Seismic Techniques]]  +
S
Single-Well and Cross-Well Resistivity +-In the oil and gas industry downhole resistivity data is often analyzed in conjunction with [[Acoustic Logs]]. -This type of logging must be done before well casing is installed or beneath the last well casing. Measurements will be unreliable through well casing.  +
Step-out Well +A step-out well should be drilled where there is some evidence of a permeable formation linked with the main reservoir. The well should be drilled in a location to where if it is an unsuccessful production well it might still be useful as an injection well.  +
Stereo Satellite Imagery +Clear skies are needed to obtain optical images for stereo satellite images. Optical images must be collected during daytime.  +
Stress Test +Stress tests normally begin with imaging of the borehole walls for analysis of fracture patterns and indications of stress zones. After a visual analysis hydraulic fracturing is conducted and the borehole walls should be imaged again to analyze how the well responded and determine any zones where permanent permeability might be established.  +
Surface Gas Sampling +Surface 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.  +
Surface Water Sampling +Surface water 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.  +
T
Telluric Survey +• Non-polarizing electrodes are the preferred electrode type to reduce noise and distortion to the measurements.  +
W
Water Sampling +Surface and downhole water sampling are fundamental tools in geothermal exploration, and are typically subjected to [[Compound and Elemental Analysis|chemical]] and [[Isotopic Analysis- Fluid|isotopic]] analyses in order to characterize hydrothermal systems and allow for estimation of reservoir temperatures through the application of various chemical [[Geothermometry|geothermometers]]. Data from these analyses can also provide useful information regarding the source of thermal fluids and help to constrain the age of the hydrothermal system.  +
Well Deepening +A well that is going to be deepened should have a large enough diameter required for the new well parameters needed; widening a well would not be practical. Reasons for why the existing well was abandoned should be known before trying to deepen it because there may be lost equipment or collapses down hole that would make deepening it extremely difficult.  +
Well Testing Techniques +Well tests are normally conducted upon completion of drilling, but before removal of the drill rig so that the drill rig pump can be used for some of the tests.  +