长江下游区域地温场特征及其能源意义

doi:10.13745/j.esf.2020.1.4

摘要/Abstract

摘要：

区域地热特征及深部温度估算对于油气勘探和地热能资源评价和开发利用具有重要意义,长江下游地区是我国东部经济社会高度发达的地区,其能源需求大,区域热状态研究能为该区地热资源评价提供关键约束。通过整合长江下游地区已有的温度数据和实测岩石物性参数,勾勒出该区的现今地温场特征,并进一步估算其1 000~5 000 m埋深处的地层温度。研究表明,长江下游地区现今地温梯度为16~41 ℃/km,且以18~25 ℃/km居多,苏北盆地区呈现高地温梯度。大地热流值为48~80 mW/m²,其均值为60 mW/m²,表现为中等的地热状态,有利于油气和地热能形成。此外,长江下游地区深部地温估算表明,1 000 m埋深处的温度范围为30~54 ℃,2 000 m时温度范围为50~95 ℃,3 000 m时温度范围为65~130 ℃,4 000 m时温度范围为80~170 ℃,5 000 m时温度范围为100~210 ℃。区域深部地温的展布趋势呈NE向,高温区域集中在安徽南部和江苏东北部。结合60 ℃和120 ℃等温线的埋深分布及区域地质、地球化学和地热特征,初步探讨了该区油气与地热资源的有利区带及其相应的开发利用类型。

关键词: 长江下游, 热状态, 深部地温, 地热资源

Abstract:

Geothermal energy, considered as one of new and emerging energies, has attracted increasing attention from academia and industry recently, owing to its huge potential and desirable attributes. Regional geothermal characteristics and deep temperature estimation are of great significances for geothermal energy exploration and utilization. The lower reaches of the Yangtze River in Eastern China is a region with well-developed socio-economic conditions and extremely large energy demand. However, the current regional geothermal regime is not well understood and needs further update with newly acquired geothermal data to provide insights into energy potential assessment in the region. In this article, we outlined the present-day geothermal gradient and heat flow pattern of the Lower Yangtze and estimated the temperatures at 1000-5000 m depth by integrating previously available regional geothermal data and newly measured thermal properties. The results showed that the geothermal regime of the Lower Yangtze area is mainly controlled by the neo-tectonics within the area. The geothermal gradient ranged from 16 to 41 ℃/km, with most areas between 18-25 ℃/km and an exception of 28-35 ℃/km in the northern Jiangsu area. While the heat flow varied from 48 to 80 mW/m² with a mean value of 60 mW/m², high heat flow was also found in the northern Jiangsu area and near the Tan-Lu fault zone, indicating the Lower Yangtze area is of a moderate to high geothermal regime favorable for hydrocarbon generation and geothermal energy exploitation. The estimated temperatures-at-depth were 30-54 ℃ at 1000 m, 50-95 ℃ at 2000 m, 65-130 ℃ at 3000 m, 80-170 ℃ at 4000 m, and 100-210 ℃ at 5000 m. Generally, the geothermal gradient showed a remarkable SW-NE striking, with high temperature anomalies distributed in the southern Anhui and northeastern Jiangsu areas, suggesting potential targets of geothermal energy utilization in the two areas. In addition, we also determined the isothermal depth patterns at 60 and 120 ℃. On the basis of geological, geochemical and geothermal conditions, we propose that the Lower Cambrian Hetang Formation and the Permian Longtan Formation of the northern Jiangsu area are the preferable hydrocarbon targets. In terms of regional geothermal energy utilization, the shallow (1400-2100 m) and deep (2100-3000 m) geothermal energy in the northern Jiangsu area can be used for heating and power generation or other industrial utilizations, respectively.

Key words: the lower reaches of the Yangtze River, geothermal regime, deep temperature, geothermal resources

中图分类号:

P314

朱戈, 刘绍文, 李香兰, 吴迪. 长江下游区域地温场特征及其能源意义[J]. 地学前缘, 2020, 27(1): 25-34.

ZHU Ge, LIU Shaowen, LI Xianglan, WU Di. Geothermal regime of the lower reaches of Yangtze River and implications for resource exploration[J]. Earth Science Frontiers, 2020, 27(1): 25-34.

图/表 12

图1 下扬子区构造格架和岩石热物性采样点分布(底图改自文献[19])

Fig.1 Tectonic subdivision and distribution of sampling location in the Lower Yangtze area. Modified from [19].

图2 下扬子区地温资料数据点分布图

Fig.2 Distribution of geothermal data collection points in the Lower Yangtze area

图3 下扬子地区古生代泥页岩的热物性分布直方图

Fig.3 Histogram of the thermal properties of Paleozoic shales in the Lower Yangtze area

图4 下扬子地区现今地温梯度分布图

Fig.4 Present-day geothermal gradient pattern in the Lower Yangtze area

图5 下扬子地区现今大地热流图

Fig.5 Present-day heat flow distribution pattern in the Lower Yangtze area

图6 下扬子地区1 000 m深度时的地温分布特征

Fig.6 Predicted temperature pattern at a depth of 1000 m in the Lower Yangtze area

图7 下扬子地区2 000 m深度时的地温分布特征

Fig.7 Predicted temperature pattern at a depth of 2000 m in the Lower Yangtze area

图8 下扬子地区3 000 m深度时的地温分布特征

Fig.8 Predicted temperature pattern at a depth of 3000 m in the Lower Yangtze area

图9 下扬子地区4 000 m深度时的地温分布特征

Fig.9 Predicted temperature pattern at a depth of 4000 m in the Lower Yangtze area

图10 下扬子地区5 000 m深度时的地温分布特征

Fig.10 Predicted temperature pattern at a depth of 5000 m in the Lower Yangtze area

图11 油气储层“黄金温度带”理论的概念示意图(据文献[29])

Fig.11 Conceptual diagram showing the “golden temperature zone” of oil and gas reservoirs. Adapted from [29].

图12 下扬子区60 ℃和120 ℃等温深度图(a为60 ℃等温深度;b为120 ℃等温深度)

Fig.12 Depth contour map of the Lower Yangtz area (a:60 ℃; b:120 ℃)

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