北京凤河营地热田东北部综合地球物理勘探

Integrated geophysical exploration in northeast Fengheying geothermal field,Beijing

凤河营地热田位于北京通州区东南部,是北京平原区十大地热田之一,面积262.51 km^2。热田的东北部是地热资源勘探开发的空白区。为查明这一带的地质构造发育情况,完成高精度重力勘探7 km^2、可控源音频大地电磁测深剖面2条(总长度4 km)以及微动测深2个测点。多方法研究成果具有较好的一致性,发现在西集镇发育一条夏垫断裂次级断裂F_1,走向近东西,倾向南,倾角约75°,断距大于1 000 m。该断裂可能构成了热水的良好通道,在断裂南侧,热储盖层厚度大,成为地热资源进一步勘探开发的有利靶区。在地球物理工作基础上,于有利靶区内施工一眼勘探孔,成井深度3 588.88 m,出水量3 072.64 m^3/d,出水温度92℃。温度、水量均达到经济开采条件。综合研究表明凤河营地热田东北部中—低温地热资源潜力较大。

The Fengheying geothermal field,located in the southeast of Tongzhou District of Beijing with an area of 262.51 km^2,is one of the top ten major geothermal fields in Beijing plain.The northeast of the geothermal field is a blank area for geothermal resource exploration and development.In order to reveal the geological conditions of this area,the authors carried out 7 km^2 gravity survey,4 km controlled source audio-frequency magnetotelluric sounding survey in profiles,and 2 points microtremor.All the geophysical prospecting interpretation results consistently show that a secondary fault of Xiadian fault is developed in Xiji Town.The fault is nearly EW-striking and the fault planes dip southward at 75 °,with the displacement more than 1 km.It is inferred that the further favorable targets for exploration and development of geothermal resources might be on the south side of this fault where the fault may form a good channel for deep hot water,and the water reservoir cap is relatively thick.On the basis of the geophysical results,a exploratory hole was drilled in the favorable targets area,with depth 3588.88 m,water flow 3072.64 m^3/d and temperature 92℃.Water quantity and temperature of this hole have all achieved economic mining conditions.All researches show that the northeastern area of the Fengheyin goethermal field has good potential for medium-low temperature geothermal resources.