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The hydraulic fracturing (also called fracturing, or fracking) technique has been widely applied in many fields, such as the enhanced geothermal systems (EGS), the improvement of injection rates for geologic sequestration of CO2, and for the stimulations of oil and gas reservoirs, especially for unconventional reservoirs with extremely low permeability. The key point for the success of hydraulic fracturing operations in unconventional resources is to connect and reactivate natural fractures and create the effective fracture network for fluid flow from pores into the production wells. To understand hydraulic fracturing technology, we must to understand some other affecting factors, e.g. in-situ stress conditions, reservoir mechanical properties, natural fracture distribution, and redistribution of the stress regime around the hydraulic fracture. Therefore, an accurate estimation of the redistribution of pore pressure and stresses around the hydraulic fracture is necessary, and it is very important to find out the reactivations of pre-existing natural fractures during the hydraulic fracturing process. Generally, fracture extension as well as its surround pore pressure and stress regime are affected by: poro- and thermoelastic phenomena as well as by fracture opening under the combined action of applied pressure and in-situ stresses. In this thesis, the previous studies on the hydraulic fracturing modeling and simulations were reviewed; a comprehensive semi-analytical model was constructed to estimate the pore pressure and stress distribution around an injection induced fracture from a single well in an infinite reservoir. With Mohr-Coulomb failure criterion, the natural fracture reactivation potential around the hydraulic fracture were studied. Then, a few case studies were presented, especially with the application in unconventional natural fractured shale reservoirs. This work is of interest in interpretation of micro-seismicity in hydraulic fracturing and in assessing permeability variation around a stimulation zone, as well as in estimation of the fracture spacing during hydraulic fracturing operations. In addition, the results from this study can be very helpful for selection of stimulated wells and further design of the re-fracturing operations.

Bacteriophage Mu exhibits low specificity for the 5 bp sequence it selects as its transposition target, but shows regional biases in its insertion choices. For example, Mu prefers AT-rich DNA in vitro, exhibits a 1000-fold bias in target preference within the E. coli chromosome, and avoids targets carrying Mu end sequences. The Mu transposase is responsible for recognition of the 5 bp target consensus, but depends on the accessory protein MuB for efficient target capture. MuB preferentially binds to AT-rich DNA, explaining this particular regional preference. We have uncovered opposing roles for MuB in target capture and integration. We show while MuB-bound AT-rich DNA is favored for integration, the bound DNA itself is refractory, and that transposition occurs adjacent to, but not within the bound region. We show that this property of MuB is likely responsible for immunity of Mu from self-integration, since MuB was found to be strongly bound within the Mu genome. Genome-wide analysis of MuB binding on the E. coli chromosome showed that Mu target preference is positively related to MuB binding profile, and that MuB binding is insulated by the nucleoid-associated protein Fis but not by transcription events. Since Fis binding to the chromosome responds to the frequency of A-tracts, a chromosome domain structure signal, Mu transposition must also respond to chromosome domain signals. Work in this dissertation has provided a new understanding of how MuB influences and controls Mu target choice, and of reciprocal interactions between a bacterial chromosome and a transposable element.