University of Oklahoma
Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS.
Degree: PhD, 2019, University of Oklahoma
Enhanced or engineered geothermal systems (EGS) could enable extraction of significant geothermal energy from hot relatively dry rock reservoirs. However, issues related to reservoir creation in different type of rocks and stress conditions, reservoir monitoring during reservoir creation and consequent production, better knowledge of the fluid/heat flow in the induced fracture, field management and optimization need be addressed before successful commercial development. As an effort to help solve these essential questions, a novel lab-scale EGS test system was developed to perform EGS simulation experiments on rock blocks under high pore pressure/elevated temperature and representative in-situ stress regimes while simultaneously recording Acoustic Emission (AE), self-potential (SP), temperature/pressure and tracers to characterize the reservoir creation, heating mining and flow characteristics of the system. The tests were performed on the 330 mm × 330 mm ×330 mm cubic igneous rock blocks. Two kinds of igneous rocks with different texture and permeability were tested with one injection hole and four producers (five-spot pattern). The great potential of EGS was demonstrated by the fact that about 50 watts of power was obtained by fluid flowing through the induced fracture with length of 8.9 cm and rock temperature less than 80 °C.
Analysis of the test results sheds light on the use of acoustic emission for better understanding of hydraulic fracturing. Also, self-potential analysis indicates SP response was mainly controlled by electrokinetic coupling and the impact of thermoelectric coupling on recorded SP is negligible as demonstrated in some field observations and modeling while the fluid concentration (salinity) has a great influence on the SP response compared with temperature gradient when the concentration contrast between the injection fluid and the pore fluid is large due to the streaming potential coefficient reduction by the high concentration liquid. The heat circulation test shows that it is the effective fracture area instead of the total fracture area that controls the heat mining in EGS and thus the distance between injection/production wells or the location of the producer(s) and flow path tortuosity need be optimized to increase the effective heat exchange area in reservoir stimulation practice and the heat mining should be operated in a proper way to avoid well competition when multiple producers are connected to the same injection well by natural/man-made fractures. Excessive fracture propagation and high injection pressure was avoided during circulation tests by increasing the injection rate step by step. The cooling effect of the rock matrix i.e., increased fracture conductivity and lowering of the injection pressure is clearly manifested in the circulation experiments.
As the first lab-scale tracer test on EGS, the obtained result was promising. The existing of two linear tracer tail was observed in Sierra White granite test and tracer result does show a good correlation between hydraulic…
Advisors/Committee Members: Ghassemi, Ahmad (advisor), Pranter, Matthew (committee member), Roegiers, Jean-Claude (committee member), Wu, Xingru (committee member), Fahes, Mashhad (committee member).
Subjects/Keywords: Engineering, Petroleum.; Geothermal energy; Heat mining
to Zotero / EndNote / Reference
APA (6th Edition):
Hu, L. (2019). Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/322839
Chicago Manual of Style (16th Edition):
Hu, Lianbo. “Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS.” 2019. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2020.
MLA Handbook (7th Edition):
Hu, Lianbo. “Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS.” 2019. Web. 25 Jan 2020.
Hu L. Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS. [Internet] [Doctoral dissertation]. University of Oklahoma; 2019. [cited 2020 Jan 25].
Available from: http://hdl.handle.net/11244/322839.
Council of Science Editors:
Hu L. Laboratory Characterization of Reservoir Stimulation and Heat Extraction with Application to EGS. [Doctoral Dissertation]. University of Oklahoma; 2019. Available from: http://hdl.handle.net/11244/322839