The Geological Model of Hydrothermal Activity in Outcrop and the Characteristics of Carbonate Hydrothermal Karst of Lower Paleozoic in Tarim Basin

Key words: 
• Tazhong

Abstract: Along with the continuously proceeding of petroleum exploration in the Lower Palaeozoic carbonate in Tazhong area, a series of hydrothermal minerals such as fluorite, sphalerite, schatzite, baritite, anhydrite, pyrobitumen, and hydrothermal quartz and their associations are found in the Ordovician reservoir in outcrops and the relative exploration wells of Tazhong area repectively, More and more geological data show that the hydrothermal karst reservoir may be an important type neglected in the Lower Palaeozoic carbonate petroleum exploration in Tarim Basin.By the observation and measurements of outcrop hydrothermal karst phenomena in the recent six years, large amount of thin sections observation, mineral energy spectrum detecting, formation water strontium isotopes analysis, and study about faults nature of the Ordovician reservoir in well field of Tazhong 82 and 24,The active characteristics of the hydrothermal corrosion fluid and its controlling factor on the formation of quality reservoir are in deep study, The hydrothermal karst reservoir geological model is established finally. The results show that the hydrothermal minerals are mainly developed in the associating structural dissolution fractures along faults, corrosional vugs and the faults,they are the main pathway for hydrothermal fluid migration and the important factors controlling the formation of quality reservoir. The hydrothermal corrosion altering reservoir are widely developed in the Ordovican reservoir in the proximity of the strike faults formed in Hercynian in Tazhong area, which can be the petroleum exploration targets of the Upper Ordovician strata along the strike faults in the western part of Tazhong.