Genetic Model and Development Potential of the Guantao Formation Sandstone Geothermal System in the Zhongmu Sag, Kaifeng Depression

doi:10.19657/j.geoscience.1000-8527.2024.019

Abstract

Abstract:

Research on the genetic mechanisms of geothermal systems and the detailed evaluation of geothermal resources are fundamental to understanding the efficiency of regional geothermal development.In this study, the Zhongmu Sag in Kaifeng Depression is chosen as a case study.Based on the regional geological structural characteristics, and combined with data from geothermal wells and hydrochemical analysis, factors such as the geothermal field, thermal reservoir distribution, and hydrochemical characteristics of the sag are analyzed.We also developed a conceptual model of the geothermal system and carefully evaluated the geothermal resources using a stratification approach.The results indicate that the heat source of the geothermal system in the Zhongmu Sag is primarily derived from heat conduction in the crust and mantle, with a heat flow value of approximately 45-65 mW/m².The Jiaozuo-Xinxiang-Shangqiu fault in the northern Zhongmu Sag served as a favorable channel for the upward transport of deep heat flow.The thermal reservoir is the Guantao Formation sandstone, which is consistently distributed throughout the area.The depth of the reservoir floor ranges from approximately 1600 to 2200 m.Between 30 and 48 vertical sand layers can be identified within the thermal reservoir.They have a cumulative thickness of approximately 130-420 m, a porosity ranging from 16% to 32%, and a reservoir thickness ratio of up to 67%.The thermal reservoir of the Guantao Formation sandstone in this sag exhibits characteristics where the eastern part is superior to the western part, and the lower section of the Guantao Formation is superior to the upper section.The water temperature of the sandstone geothermal wells in the Guantao Formation ranges from approximately 68 to 85 ℃.The water volume for a single well is between 106 and 155 m³/h, and the hydrochemical solution is primarily Cl-Na, with a salinity of around 10000 to 30000 mg/L.The Upper Quaternary and Minghuazhen Formation have a combined thickness of approximately 1200 m and serve as a good cap rock.The source of geothermal water is primarily replenished by atmospheric precipitation in the western and southwestern mountainous areas.This water then undergoes deep heat conduction and warming before laterally replenishing the thermal reservoir.The geothermal resources of the thermal reservoir are approximately 2245.41×10⁸ GJ, with annual exploitable geothermal resources amounting to 5.61×10⁸ GJ, which is equivalent to about 1.92×10⁶ t of standard coal.The annual exploitation of geothermal resources can support a heating area of approximately 6770×10⁴ m², demonstrating substantial development potential.

Key words: geothermal system, genetic model, resource evaluation, sandstone geothermal reservoir, Guantao Formation, Zhongmu Sag

CLC Number:

P618.1

HE Tingting, DU Li, TAN Xin, LIU Junrong, LUO Lu, ZHANG Hui, LI Hao. Genetic Model and Development Potential of the Guantao Formation Sandstone Geothermal System in the Zhongmu Sag, Kaifeng Depression[J]. Geoscience, 2024, 38(06): 1557-1570.

Figures/Tables 13

Fig.1 Administrative map of Henan Province (a) and geological and fault distribution maps of the Precenozoic bedrock in the Zhongmu Sag (b)

Fig.2 Profile of the geothermal reservoir and temperature distribution (a), and profile of heat flow and geothermal gradient distribution in the Zhongmu Sag (b)

Table 1 Testing data geothermal boreholes in the Zhongmu Sag and its adjacent areas

构造单元	地区	位置	井名	取水层段(m)	馆陶组底面埋深垂深(m)	温度范围/ 井口水温(℃)	地温梯度及均值 (℃/hm)		资料来源
太康隆起	郑州	市区		410~1071.6	800~900	20~45	2.03~3.79(2.89)		河南省地热资源现状调查评价与区划
太康隆起	通许	县城		370.3~1171.1	1100~1200	29~55	3.04~3.74(3.5)
汤阴凹陷	新乡	市区		421.5~1215	1000~1100	25~73	2.22~4.82(3.15)
汤阴凹陷	新乡	京华园		926.5	1000~1100	42	2.93	2.93
东濮凹陷	长垣	县城北		2400	2100~2200	93	3.26	3.26
东濮凹陷	封丘	曹岗		2100	2000~2100	88	3.49	3.49
中牟凹陷	开封	市区	DJ2	1716~2150	2150	82	3.46	3.43	中石化实钻地热井数据
	开封	市区	DJ4	1819.13~2289.06	2135	85	3.4	3.43
	兰考	市区	ZY1	1381.82~1890.22	1909.39	74	3.6	3.27
			LW1	1552.12~2137.45	1905.16	71	3.03
			DR4	1602.61~1927.15	1903.36	71	3.16
	新乡	平原新区	XX1	1378.49~1753	1753	53	2.4	2.4

Table 2 Hydrochemical data of the Zhongmu Sag

井名	井深(m)	pH值	溶解性总固体 (mg·L^-1)	水化学类型	离子含量(mg·L^-1)
井名	井深(m)	pH值	溶解性总固体 (mg·L^-1)	水化学类型	Na⁺	Ca²⁺	Cl^-	$SO 4 2 -$	$HCO 3 -$
DJ2	2170	6.57	2.71×10⁴	Cl-Na	6295.57	1877.61	14535.83	361.34	105.91
DJ4	2310	6.56	2.53×10⁴	Cl-Na	6178.76	1745.58	13102.75	346.49	105.04
DR4	1980	6.90	1.41×10⁴	Cl-Na	4172.40	573.76	7340.40	598.28	152.92
LW1	2200	6.73	1.43×10⁴	Cl-Na	4248.75	586.42	8001.65	661.96	152.73
ZY1	1946	7.56	1.90×10⁴	Cl-Na	5361.38	914.47	9859.78	907.22	129.20
FHC2	2150	7.80	1.61×10⁴	Cl-Na	5115.00	871.54	9070.95	609.98	133.63
XX1	1782	7.96	0.89×10³	HCO₃-Na	329.00	10.17	132.94	119.93	580.01

Table 2 Hydrochemical data of the Zhongmu Sag

井名	井深(m)	pH值	溶解性总固体 (mg·L^-1)	水化学类型	离子含量(mg·L^-1)
井名	井深(m)	pH值	溶解性总固体 (mg·L^-1)	水化学类型	Na⁺	Ca²⁺	Cl^-	$SO 4 2 -$	$HCO 3 -$
DJ2	2170	6.57	2.71×10⁴	Cl-Na	6295.57	1877.61	14535.83	361.34	105.91
DJ4	2310	6.56	2.53×10⁴	Cl-Na	6178.76	1745.58	13102.75	346.49	105.04
DR4	1980	6.90	1.41×10⁴	Cl-Na	4172.40	573.76	7340.40	598.28	152.92
LW1	2200	6.73	1.43×10⁴	Cl-Na	4248.75	586.42	8001.65	661.96	152.73
ZY1	1946	7.56	1.90×10⁴	Cl-Na	5361.38	914.47	9859.78	907.22	129.20
FHC2	2150	7.80	1.61×10⁴	Cl-Na	5115.00	871.54	9070.95	609.98	133.63
XX1	1782	7.96	0.89×10³	HCO₃-Na	329.00	10.17	132.94	119.93	580.01

Fig.3 Distribution of heat flow (a) and geothermal gradient (b) in the Zhongmu Sag

Fig.4 Temperature and depth variation curves of the geothermal well in the Zhongmu Sag (red dotted line representsing temperature after reaching steady state)

Fig.5 Contour maps of the buried depth (a) and temperature (b) of Guantao Formation in the Zhongmu Sag area

Fig.6 Characteristics of a single well in the sandstone geothermal reservoir of the Guantao Formation in the Zhongmu Sag(well ZY1)

Fig.7 Profile of the sandstone geothermal reservoir in the Zhongmu Sag

Fig.8 Piper diagram of geothermal fluid (a) and δD-δ18O relationship diagram (b) in the Zhongmu Sag

Table 3 Elevation calculation for the geothermal water supply area in the Zhongmu Sag

井名	地热水δD (‰)	地热水δ¹⁸O (‰)	取样点海拔 (m)	补给区海拔 (m)
DJ4	-69.81	-7.8	70	557
LW1	-72.30	-7.8	70	668
DR4	-73.08	-7.8	72.5	705
TXGS	-68.80	-8.615	80	522

Fig.9 Genetic model of the geothermal system in the Zhongmu Sag

Table 4 Evaluation parameters and calculation results of the geothermal resources in the Guantao Formation

层位	热储层段	平均有效厚度(m)
馆陶组	Ng1	32.9	20.7	50.2	147.86	5046.44	36.97	1261.61
	Ng2	48.2	22.3	54.9	250.24	8540.52	62.56	2135.13
	Ng3	56.6	21.4	60.1	329.19	11235.17	82.30	2808.79
	Ng4	40.7	20.5	64.8	263.61	8997.07	65.90	2249.27
	Ng5	173.3	23.4	70.2	1254.51	42815.97	313.63	10703.99
合计		351.7			2245.41	76635.16	561.35	19158.79

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