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Analysis of Shale-Water Interactions and Flowback Water Chemistry for Fracture Characterization
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- Author / Creator
- Ashkan Zolfaghari Sharak
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Extensive imbibition experiments are performed to investigate shale-water interactions at different conditions. Effects of rock-surface area, rock volume, temperature, and pressure are investigated on the ion concentration during the imbibition experiments. The experimental results of ion concentration are compared with the flowback chemical data to characterize the fracture network complexity, fracture surface area (Af), and invaded reservoir volume (IRV).
Experimental results indicate that the barium ions in the flowback water of wells drilled in the Horn River Basin (HRB) are primarily originated from natural fractures. The results from this study suggest that the barium ion concentration profile during the flowback process is a signature of the connectivity between the natural fractures and the induced primary fractures. The well with a steep increase in the barium concentration profile has a more complex fracture network compared with the well with a slow increase in the barium concentration profile and a more simple fracture network. Furthermore, a model is proposed to characterize the fracture network complexity using flowback salt concentration transient. According to the model results and during the flowback process, the wells with a continuous increase in their salinity profile have more complex fracture network as opposed to the wells with a plateau in their salinity profile. Comparison between the ion concentration data in the flowback water and in the seawater suggests that 〖Na〗^+, 〖Cl〗^-, and 〖Mg〗^(2+) ions primary originate from formation water, while dissolution of rock constituents in the fracturing fluid is potentially the major source of K^+ and 〖Ca〗^(2+) ions in the flowback water.
Experimental results indicate that the total ion produced (TIP) increases by increasing rock surface area, rock volume, and temperature, while pressure has negligible impact on TIP. A scale-up procedure is proposed to estimate Af and IRV using the experimental results of ion concentration during the imbibition experiments. The estimated A_f values for two wells completed in the HRB are ≈〖5×10〗^6 m^2 which have similar orders of magnitude to those calculated from rate-transient analysis (≈〖10〗^6 m^2 ). The estimated IRV values for the target wells are about 〖5×10〗^5 m^3. The well with higher estimated IRV value has lower water recovery in the field as opposed to the well with lower estimated IRV value and higher water recovery in the field.
A modified water sorption isotherm is proposed (a) to investigate the role of clays on water adsorption and desorption and (b) to characterize the organic and inorganic pore size distributions (PSDs) of gas shales. Experimental results indicate that clays tend to adsorb and retain most of the capacity for water at low relative humidity conditions. Moreover, hydrophilic pores have wider PSDs compared with those of hydrophobic pores. Also, majority of the hydrophobic pores are smaller than 5 nm, while majority of the large pores (>10 nm) belong to the hydrophilic pore system. -
- Graduation date
- Fall 2018
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.