肯尼亚奥卡瑞地热田主要控制因素分析

肯尼亚奥卡瑞是非洲地区首个利用地热资源进行发电的地热田。基于区域地质研究成果、地球物理资料和生产数据等,笔者对奥卡瑞地热田地温场及其主控因素进行研究。综合研究认为奥卡瑞区地热系统的主要控制因素包括:①热源,研究区热源主要是未冷却的岩浆囊,其范围和埋藏深度直接影响了热田生产能力;②断裂和裂缝分布,奥卡瑞地热田位于东非裂谷中央,裂谷由NE向转为NW向,断裂破碎带构成了深层流体上涌的主要通道。地热井的生产能力受裂缝控制;③地层岩性,东区和西区热储层岩性不同,西区热储以Mau凝灰岩为主,其原生孔隙较发育,但受后期水热蚀变改造,多数原生孔被次生矿物所充填,因此生产情况较差。东区以粗面岩为主,原生孔隙不发育,储层主要为断裂和裂缝,是目前该区主力生产区。

Analysis of main controlling factors of Olkaria geothermal field,Kenya

Kenya Olkaria is the first power generating geothermal field in Africa.Based on geological research,geophysical data and production data,the authors studied the temperature field and main controlling factors of Olkaria geothermal field.Comprehensive study indicated that the main controlling factors of Olkaria geothermal system are:①Source.Geothermal source is hot magma chamber,of which the area and depth directly affect geothermal production.②Distribution of faults and fractures.Olkaria geothermal field sites are on the central of East Africa Rift,which turns from NE-trending to NW-trending in Olkaria.Fracture zones provided channel for deep fluid,which controls the production capacity.③Lithology.West reservoir mainly consists of tuffs named Mau,with good porosity but mostly filled by secondary minerals due to thermal alteration,so production is low.East reservoir consists of trachyte with poor porosity but a lot faults and fractures,which is the main production reservoir.