Construction of geology, thermal anomaly and pressure distribution of a geothermal system in the early stage of exploration where data is limited is described using a 3-D software, Leapfrog geothermal. The geological ...
Construction of geology, thermal anomaly and pressure distribution of a geothermal system in the early stage of exploration where data is limited is described using a 3-D software, Leapfrog geothermal. The geological 3-D model was developed from a topographic map (derived from DEM data), geological map and literature studies reported in an early geological survey. The isothermal 3-D model was constructed using reservoir temperature estimation from geothermometry calculated from chemical analyses on surface manifestations, available shallow gradient temperature hole data and the normal gradient temperature (3°C/100m) for a nonthermal area. The isobaric 3-D model was built using hydrostatic pressure where the hydrostatic pressure is determined by the product of the fluid density, acceleration due to gravity, and depth. Fluid density is given by saturated liquid density as a function of temperature. There are some constraints on the modelling result such as (1) within the predicted reservoir, the geothermal gradient is not constant but continues to increase, thus, creating an anomalously high temperature at depth, and (2) the lithology model is made by interpolating and extrapolating cross-sections whereas usually only two to three geology sections were available for this study. Hence, the modeller must understand the geology. An additional cross section was developed by the modeller which may not be as suitable as the geologist constructed sections. The results of this study can be combined with geophysical data such as gravity, geomagnetic, micro-tremor and resistivity data. The combination of geological, geochemical, isothermal, isobaric and geophysical data could be used in (1) estimating the geometry and size of the geothermal reservoir, (2) predicting the depth of top reservoir, and (3) creating well prognosis for exploration and production wells.
Mercury analysis from soil survey is one of the standard methods in geothermal exploration surveys conducted by Center for Survey and Geological Data or PSDG (formerly DIM). The objective of this paper is to analyze t...
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Mercury analysis from soil survey is one of the standard methods in geothermal exploration surveys conducted by Center for Survey and Geological Data or PSDG (formerly DIM). The objective of this paper is to analyze thresholds of four non volcanic geothermal systems in Sulawesi, i.e. Suwawa, Marana, Pincara and Mangolo. The value of Hg (ppb) is differ from one prospect to another. Its value ranges from tens ppb up to few thou sands ppb, depends on the geology and geothermal system; in high temperature volcanic geothermal system, or in non-volcanic geothermal system. Therefore determination of threshold that separate background and anomaly is important for better delineation of Hg anomaly area. Prior to threshold determination, a probability plot is used to examine the normality and the existence of sub population within the data. Sub population located at the end left of probability graph or sub population with the lowest range value is assumed containing the background and threshold information. The threshold is then calculated using mean plus one standard deviation of data within this sub population. Comparison of the calculated number with the published threshold value shows very significant difference in term of anomaly area coverage for further exploration target. This paper demonstrates Exploratory Data Analysis (EDA) techniques that can be applied as a tool to determine threshold value. The results suggest that this statistical methodis able to assist and support a better threshold value determination.
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