Identifier

etd-05202016-175422

Degree

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

Document Type

Dissertation

Abstract

Unfavorable consequences of geochemical reactions, such as calcite and silica scaling, in geothermal power plant surface facilities have been discussed in many recent studies. However, the impact of brine-rock interactions related to geothermal projects on reservoir properties has not been addressed fully. In this study, interactions between geothermal fluid and reservoir rocks in two fields located in Vermilion Parish, LA, and Chocolate Bayou, TX, are examined using geochemical modeling. The studied reservoir belongs to the Frio formation. In the geochemical models, the brine is cooled down to the estimated output temperature of a geothermal heat exchanger and re-equilibrated. Then, brine-rock interactions at reservoir temperature are simulated, and the changes of rock composition due to geochemical reactions are anticipated. Results show that the pore space volume change is negligible. Feldspar transformation to clay minerals, however, has been observed as a mineral conversion process which is expected to impact permeability. Pore Network Modeling has been utilized to investigate the impact of the geochemical interactions on the reservoir permeability. To build the pore network, micro-CT scan images were acquired from three core samples. The image segmentation was done considering the results of rock characterization studies. After completing the objective segmentation, the anticipated geochemical changes were incorporated into the micro-CT scan images using a computer code. Permeability of the resulted image was calculated and compared to the initial permeability calculations. The impact of the micro-porosity of newly formed clay minerals was estimated using an innovative method. Results indicate that the newly generated clay minerals due to the geochemical reactions may cause important damage, as high as 50 percent, to reservoir permeability.

Date

2016

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Thompson, Karsten

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