The Preliminary Analysis Of Helium Reservoir Forming Characteristics In Weihe Basin

Since the70s of last century, oil exploration wells and geothermal wells of Weihe basin were found a large number of helium, but the helium has not been industrial used, mainly because of the helium reservoir forming characteristics (enriching) study of Weihe basin is relatively weak, which affected the helium industrial evaluation. In this paper, based on the study of geology, gas logging, gas analysis testing, geochemical, seismic and logging data of the Weihe basin to analyze the causes and sources of helium, the spatial relationship of helium source rocks and helium bearing formations, the migration characteristics of the helium bearing water and its relationship to the zone of containing helium, and the temperature variation during helium bearing water migration and its relationship to helium-rich region.On the basis of those studies to preliminarily analyze the helium reservoir forming characteristics of Weihe basin.Mainly achieved the following understanding:1. Helium of Weihe basin is mainly crust (radiogenic) helium. Helium gas source rocks are mainly the granite distributed in the periphery of the Weihe basin and (?)2. Helium source rocks of granite is mainly distributed in the Qinling Mountains which located in the southern, southeastern boundary of Weihe basin. And the rocks in south basement of Weihe basin (south region of Weihe fault) may be helium source rocks. Lantian-Bahe formation, Gaoling group and Zhangjiapo formation are main helium bearing formations of Weihe basin.3. Granite of Qinling Mountains developed massive cracks and faults which can make meteoric water downward penetration. Helium can be first move to the granite fracture pores after generated, and then dissolved in water and migrate along with water. Helium bearing water migrate from south to north along the fault and sand to basin, in the west Gaoling helium bearing water can spread to the north of the Weihe River, and in the east of Gaoling, helium bearing water only spread to the Weihe River. Helium containing wells only distribute in the spread range of helium bearing water.4. During the process of helium bearing water migrates to basin, pressure and temperature variations can be preliminarily divided into three bands, with the band of pressure lifting and cold-hot alternating, the band of pressure and temperature variations are relatively stable, and the band of pressure droping and hot-cold transformation. The band of pressure lifting and cold and hot alternating and pressure droping and hot-cold transformation are relatively enriched with helium,the former is under pressurized condition,helium solubility in hot water high,hot water will be extracts helium dissolved in cold water that makes helium-rich in hot water,latter is the catchment area of helium bearing water,helium bearing water constantly bringing together and this caused much helium enrichment,while helium bearing water will upward discharge along faults that makes pressure and temperature lowering and helium solulility in water decreased.there may be free hrliurn gas production.