Preliminary study on thermal structure and prediction of high temperature anomaly area in Gulu geothermal field
The Gulu geothermal field which located in the Naqu-Nimu geothermal belt of Tibet,is a representative high-temperature geothermal field.Comprehensive study on its subsurface thermal structure and establishing an accurate model of temperature distribution holds significant practical and scientific value.In this study,we proposed an empirical formula for converting resistivity to temperature specifically tailored for the Gulu geothermal field by utilizing classical resistivity and temperature conversion formulas along with measured values obtained from drilling sites as estimation standards.With the guidance of resistivity ratio and stratification constraints on depth,relevant empirical coefficients were determined.To validate the rationality of our proposed temperature estimation method,we evaluated the effectiveness of inversion results of resistivity derived from audio magnetotelluric sounding profiles,and assessed the goodness-of-fit between measured temperatures at drilling sites and the estimated values.Finally,we performed calculations from resistivity to temperature based on these assessments.The calculated results successfully constructed the underground temperature structure models within areas indicated by two audio magnetotelluric sounding profiles which are then utilized for mineralization prediction.The results of prediction indicate that the high-temperature anomaly zone No.Ⅲ is consistent with known drilling achievements.Therefore,it iwas inferred that there are four shallow high-temperature anomaly zones(No.Ⅰ,Ⅱ,Ⅳ,Ⅴ)and three deep high-temperature anomaly zones(No.Ⅵ,Ⅶ,Ⅸ)in the two profiles;among them,the No.Ⅶ anomaly is closely associated with the spatial distribution of fault F4-2 and exhibits an upward migration tendency from deeper regions,suggesting a higher likelihood of reflecting deep thermal reservoirs in this location.The anomalies No.Ⅵ and Ⅸ are closely linked to fault F4-1 and present new targets for future exploration.The calculation of relevant empirical coefficients in this paper is based on the fact that the lithology of this area is mainly granite.It should be noted that parameters required in conversion formulas need to be re-determined based on actual lithology and borehole temperature measurement results when applied in different exploration areas.
GuLu geothermal fieldthermal structureresistivitytemperature structureprediction of high temperature anomaly area
国家科技期刊平台
NSTL
万方数据
