Abstract
The thermal reservoir in Taiyun area mainly consists of Ordovician and Cambrian carbonate formations. The target interval of example well contains more than 95% carbonate, being thick, argilliferous and have well-developed natural fissures and rich hot water. However, sometimes stimulation is necessary to achieve the designed water production rate. In this paper, multistage alternating injection acid fracturing technology is selected according to lithologic characteristics of geothermal reservoir. A gel acid, which is a composite of 20%HCl+0.8%SHY1+2% corrosion inhibitor+1.5% iron ion stabilizer+1% cleanup additive, is optimized and developed by experimental tests. Its viscosity can reach 27 mPa·s. Then, pumping schedule of multi-stage alternate injection acid fracturing is optimized by numerical simulator of acid fracturing design. It is shown from job pressure of field sample well that resistance reduction ability of gel acid needs to be further improved. Moreover, from the analysis results of pressure decline after acid fracturing, the fluid efficiency is 42.32%, net pressure is 3.3 MPa, and the dynamic fracture length is 107m, the maximum fracture width is 8.6mm by fitting treatment pressure. The water production increase factor reaches 1.2 after acid fracturing treatment. Therefore, the acid fracturing treatment is successful.
Highlights
The development of geothermal resources is one of the main tendencies in the future
Water temperature at wellhead rose from 53°C to 78°C, and water rate increased from 10.38m3/h to 95.67 m3/h
Ji[9] reported that water production increased from less than 10m3/h to 36m3/h after acid fracturing in carbonate geothermal wells in southwestern Shandong
Summary
Geothermal formation in Taiyun area mainly consists of Ordovician and Cambrian carbonate, acid treatment usually is necessary to increase water production. This technique is an important and effective method for improving the production of carbonate reservoirs in petroleum industry[1,2,3]. Water temperature at wellhead rose from 53°C to 78°C, and water rate increased from 10.38m3/h to 95.67 m3/h. Ji[9] reported that water production increased from less than 10m3/h to 36m3/h after acid fracturing in carbonate geothermal wells in southwestern Shandong. Water production after stimulation increased from 968m3/d to 2163m3/d, and the output water temperature increased from 43.5°C to 46°C
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