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A Research Of The Ordovician Hydrothermal Geological Processes And Its Reservoir Significance In South Of Tahe Oilfield

Posted on:2016-04-20Degree:MasterType:Thesis
Country:ChinaCandidate:H LiFull Text:PDF
GTID:2180330461455582Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
The Tarim Basin had a strong magma volcano activity in late Hercynian period(Permian), and the related drilling reveals that the south of Tahe oilfield during the Ordovician has been effected by deep hydrothermal fluid alteration. In order to further confirm the Hydrothermal geological effect and the meaning of reservoir storage, In this paper, on the basis of previous research results, combined with the regional geological, well logging and drilling data, through the core observation and thin section analysis, geochemical analysis, single well reservoir anatomy and the reservoir comprehensive anatomy and analysis method, The main results of this research are as follows:(1) Through the core observation and thin section analysis based on the related hydrothermal well of the Ordovician in the study area, and the results show that the Ordovician in the study area had the fairly obvious hydrothermal fluid activity.we summarized the identification mark of petrology and mineralogy, the hydrothermal alteration of typical rocks in the study area, irregular hydrothermal breaking cracks, the development of hydrothermal genesis siliceous rock, the widespread development of a series of hydrothermal dissolved pores, the development of hydrothermal minerals and hydrothermal mineral assemblage, such as fluorite, saddle dolomite, barite, quartz, anhydrite, pyrite, luorite-quartz assemblage, barite-anhydrite mineral assemblage and so on.(2) There were a series of geochemical analysis for the hydrothermal calcite and carbonate surrounding rock in the study area, the results showed that: Through the cathodoluminescence, the results show that the cave calcites alterated by the late Hercynian hydrothermal are highly bright orange red light, the part of the marl faded late Hercynian hydrothermalis also bright orange red light, The calcite and carbonate rocks not by hydrothermal alteration are dark orange red light, They relate to the content of Mn and the ratio of Fe/Mn; The change of δ13C is less than the microcrystalline, and the δ18O of Hydrothermal fissure calcite is relatively low, less than-10%‰PDB, it reveals that there was no effect of the atmospheric water added, but may be hydrothermal temperature enhanced thermal fractionation, resulting in lower 18 O value of hydrothermal calcite; The fissure calcite alterated by hydrothermal fluid is rich in Ba and Mn, higher than the microcrystalline limestone(carbonate rock) ten times or even several times, and have a high Mn/Sr ratios; Rare earth elements in hydrothermal calcite samples distribution curve are relatively flat. Most of the performance of light rare earth enrichment, and show the obvious positive Eu anomaly, and Y/Ho is relatively high, it may be associated with experienced in Permian magmatism; Hydrothermal calcite has the lower value of 87Sr/86 Sr, also be lower than carbonate wall rock and the seawater of the same period. And it is mainly controlled by strontium from the mantle source and affected by the buffer of the wall rock heavy soluble strontium.(3) There were a series of fluid inclusion analysis for the hydrothermal calcite and hydrothermal minerals in the study area, the results showed that: The homogenization temperature range of hydrothermal mineral fluorite is between 197.7℃ and 231.5℃, and the average temperature is 214.4℃, the salinity is between 22.5wt% NaCl and 24.3wt% NaCl, the average salinity is 23.5wt% NaCl; The homogenization temperature range of saddle dolomite is 158.2℃ and 219.2℃, and the average temperature is 184.7℃, and the salinity is between 17.4wt% NaCl.and 23.1wt% NaCl, the average salinity is 21.4wt% NaCl, The homogenization temperature range of calcite alterated by hydrothermal is 135℃ and 250℃, and the average temperature is 171℃, and the salinity is between 18.7wt% NaCl and 21.4wt% NaCl.They were higher than the burial temperatures above 40 degrees, and are 3 ~ 5 times of the normal water salinity, that is affected by the high temperatures and high salinity hydrothermal fluid.(4) There are research showed that hydrothermal fluid maybe from magmatic hydrothermal fluid deep crust, it is realted to volcanic eruption in late Hercynian period. It is important channel of hydrothermal fluid migrate that rupture and fracture zone, the hydrothermalism main distribution in rupture and fracture zone near, and probes into the mechanism and patterns of hydrothermal process.(5) The Ordovician reservoir space of the hydrothermal origin in the study area is mainly dissolved holes and dissolved pores. The hydrothermal reservoir types are divided into the solution fissure-hole type reservoirs and the solution pore type reservoirs, the solution fissure-hole type reservoirs further divided into the solution hole type reservoirs along the fissure, the solution hole type reservoirs, the silicified silicalite dissolution hole type reservoirs and the solution pore type reservoirs. According to the core and thin section observation, combination of logging data and logging data, this four type reservoirs were anatomied through well profiles respectively. The reservoir storage property of the solution hole type reservoirs along the fissure is best, the solution hole type reservoirs is less, the silicified silicalite dissolution hole type reservoirs and the solution pore type reservoirs developed only in individual wells. The four type reservoirs mainly developed in the Yijingfang formation. we are analyse the distribution of the solution hole type reservoirs along the fissure further, and mainly developed in the micrite and grain limestone, due to the effect of control of the lithologic factors, that shows more developed in the Yijingfang formation, only a small reservoirs developed in the Upper Ordovician formation. It is the key controlling factors of reservoir development that from north to south through the fracture zones, and the solution hole type reservoirs along the fissure and mainly developed and distribution along the fracture zone or near fault; Therefore, we are divided into the three development area of the favorable reservoirs, respectively T760─S115─S112 fracture zone or near fault, S1101─AT5-2—AT5 fracture zone or near fault and S101─AT21─AT23X fracture zone or near fault.
Keywords/Search Tags:South of Tahe Oilfield, Ordovician, Hydrothermal processes, Geochemical characteristics, Fracture zone
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