摘要:
重庆市岩溶储层地热资源丰富,开发利用历史悠久,但地热资源勘探风险较大。本文利用模糊综合评价法建立了风险评价模型,该模型中包含了热储构造开启程度、热储构造部位、沟谷切割程度、物探效果、热储埋深、热储厚度、热储岩层倾角、热异常情况、热储层位9个风险因子,每个因子划分为风险小、风险中等、风险大3级,并对其进行量化处理。最后对全市23个高隆起背斜两翼46个相对独立的山地型高隆起岩溶地热田共79个地热单元进行了地热资源勘探风险模糊数学综合评判。结果表明,有18个单元为风险小,42个单元为风险中等,19个单元为风险大。风险小的地热田一般热储汇水面积较大、补给径流循环条件好、热储顶板埋深1000~1800 m、热储厚度≥300 m、热储岩层倾角25~40°、深部裂隙较发育;风险大的地热田热储汇水面积较小、补给径流循环条件差、热储顶板埋深≥2500 m、热储厚度<200 m、热储岩倾角<20°或≥40°、深部裂隙不发育;风险中等地热田的地质特征则介于二者之间。评价结果较好地反映出了重庆市岩溶热储地热资源勘探风险状况。
Abstract:
Geothermal resources of karst reservoir are rich in Chongqing,belonging to the mountain type. The karst thermal reservoir,stripped in shape and distributing independently in the thermal field,is located in both wings beside 23 high uplift anticlines and 1-2 km from the axis of the anticlines in the city.The geo-thermal resources exploration has a long history,but there are risks.In this study,in order to quantitatively or semi-quantitatively evaluate the risk of the exploration a risk assessment model is established with the fuzzy comprehensive evaluation method.The model contains 9 risk factors:the opening degree of thermal reservoir structure,thermal storage structure,alley cutting degree,geophysical prospecting effect,buried depth,thickness of geothermal reservoir,thermal reservoir strata dip angle,thermal anomalies and thermal reservoir layer.Each risk factor can be divided into three levels,including small,medium and big risk level. Quantitative processing is carried out for this model.Comprehensive evaluation of geothermal resource ex-ploration risk with fuzzy mathematics on 23 high uplift anticlines,46 high mountain uplift karst geothermal fields (a relatively independent geothermal field on each legs)and 79 geothermal units in this city was per-formed.The evaluation results indicate that there are 18 units in small risk,42 units in medium risk and 1 9 units in high risk.The geothermal field with small risk generally has large heat reservoir catchment’s area and good recharge runoff circulation conditions,with roof heat reservoir being buried 1 000-1 800 m deep, thermal reservoir thickness bigger than 300 m,thermal reservoir strata dip angle being 25 -40°,and deep fissure developed,such as the evaluation unit of Xishan anticline at the northern section of the west wing. The geothermal field with high risk has smaller catchment’s area and poor recharge runoff circulation condi-tions,with roof heat reservoir being buried more than 2 500 m deep,thermal reservoir thickness smaller than 200 m,thermal reservoir strata dip angle <20°or ≥40°,and deep fissure undeveloped,such as the e-valuation unit at the southern section of the Xindianzi anticline.The geological characteristic of geothermal field with medium risk is between the two.The evaluation results have nicely reflected the risk state in ex-ploration for the geothermal resources in the karst heat reservoir in Chongqing.
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