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Geothermal Productivity Evaluation and Numerical Simulation of Xwz Geothermal Field
Geothermal energy has become one of the most important alternative energy sources after coal and oil. It is also an important member of the new energy family such as solar energy, wind energy and biomass energy. It is a clean green energy with no pollution or very little pollution. It has important research value and practical significance for local economic development, reducing environmental pollution. On the basis of the research on the regional structure and the characteristics of the thermal reservoir in the XWZ geothermal field of the Taiyuan basin, this paper uses the thermal storage method to calculate the geothermal static resources in the study area. We use two methods to predict the outflow of the geothermal reservoir by the method of pumping data fitting formula and the fur formula, and established the prediction model of the single well productivity. The parameters of the study area are calculated and the water volume prediction model is selected for productivity calculation and evaluation. We established the water—thermal numerical simulation model of XWZ geothermal field by using PETRASIM-TOUGH2 software. The change of the pressure field and temperature field of the underground hot water was predicted. The productivity prediction was carried out at the same time. The well network optimization scheme was proposed according to the problems in the study area. The main understanding is as follows: 1. According to the well temperature logging data, the average temperature increasing rate of the Triassic and Permian strata from 220m to 1000m is 2.32℃ / hm, and the average temperature increasing rate from the base of Permian and Carboniferous is 3.09 ℃ / hm, and the average temperature increasing rate of Majiagou formation form 1300 to 1600m is 3.62 ℃ /hm. The thicker the thermal reservoir, the higher the water temperature. 2. According to the comparison with actual production data, fur formula method is more suitable for productivity calculation in XWZ geothermal field. According to the fur formula method, the geothermal level is 1248.90m3/d and the total productivity is 53.87MW, which belongs to the medium and large geothermal field. According to the 100 year evaluation period of the middle and low temperature geothermal fields, the underground hot water can be 1.939×1011MJ, and the single day total productivity is 82.03MW according to the numerical simulation, the underground hot water is recoverable. It can be 2.952 ×1011MJ 3. The bottom wellbore temperature of the reservoir in the West temperature field is generally higher than the wellhead temperature by 5-10 degrees centigrade, and the temperature difference is mostly between 0.02-0.033℃ and /hm, and for some wells the temperature difference is very large, which may be caused by the high heat loss due to the cementing technology. 4. The geothermal geological structure, regional geology and heat controlled thermal storage in the West temperature field are complex, and the initial temperature pressure in the western region is relatively high and relatively stable. The fault water conduction and thermal performance of the western development is good, which is the main supply of underground fluid and pressure in the study area. 5. Through numerical simulation, it is found that the underground temperature field in the XWZ geothermal field will reach a balance in a simulated period (121 days), that is, the temperature field can remain relatively stable. The equilibrium point increases with the increase of the number of wells. 6. The west of XWZ geothermal field has higher pressure, larger production potential and less pressure in the East, so that the well pattern can be optimized. In the western part of the study area, 4 production wells are deployed to further increase production; 2 recharge wells are deployed in the east to supplement formation pressure.