Capturing the two-way hydromechanical coupling effect on fluid-driven fracture in a dual-graph lattice beam model

Fluid-driven fractures of brittle rock is simulated via a dual-graph lattice model. The new discrete hydromechanical model incorporates a two-way coupling mechanism between the discrete element model and the flow network.By adopt- ing an operator-split algorithm, the coupling model is able to replicate the transient poroelasticity coupling mechanism and the resultant Mandel-Cryer hydromechanical coupling effect in a discrete mechanics framework. As crack propagation, coalescence and branching are all path-dependent and irreversible processes, capturing this transient coupling effect is important for capturing the essence of the fluid-driven fracture in simulations. Injection simulations indicate that the onset and propagation of fractures are highly sensitive to the ratio between the injection rate and the effective permeability. Furthermore, we show that in a permeable rock, the borehole breakdown pressure, the pressure at which fractures start to grow from the borehole, depends on both the given ratio between injection rate and permeability and the Biot coefficient

Displacement of oil from hydraulic lines

This thesis treats the laminar motion of two immiscible fluids in a pipe, where the original fluid occupying the pipe is much more viscous than the replacing fluid. Earlier works have shown that the less viscous fluid tends to form a core in the center of the pipe, while some of the more viscous fluid is left as a layer at the wall. It is expected that the thickness of the film of oil left in the pipe will be reduced as time goes by, but the asymptotic behavior of the drainage rate of this viscous film appears not to have been studied at all. The main topic is the development of a one-dimensional hydraulic model able to describe the displacement process. We start by finding analytical results for a steady, fully developed flow, and then simulate the flow using FLUENT. A hydraulic model is developed, and stability of the equations is studied. We then solve the equations in the hydraulic model numerically, and try to validate the model by simulating flows with well established solutions, hereunder core annular flow. We also compare the results from the hydraulic model with results found using another model. Finally, we find results for how fast the layer of oil at the wall is washed out, and find an analytical approximation able to describe the drainage rate in some detail

Capturing the two-way hydromechanical coupling effect on fluid-driven fracture in a dual-graph lattice beam

Fluid‐driven fractures of brittle rock is simulated via a dual‐graph lattice model. The new discrete hydromechanical model incorporates a two‐way coupling mechanism between the discrete element model and the flow network. By adopting an operator‐split algorithm, the coupling model is able to replicate the transient poroelasticity coupling mechanism and the resultant Mandel‐Cryer hydromechanical coupling effect in a discrete mechanics framework. As crack propagation, coalescence and branching are all path‐dependent and irreversible processes, capturing this transient coupling effect is important for capturing the essence of the fluid‐driven fracture in simulations. Injection simulations indicate that the onset and propagation of fractures is highly sensitive to the ratio between the injection rate and the effective permeability. Furthermore, we show that in a permeable rock, the borehole breakdown pressure, the pressure at which fractures start to grow from the borehole, depends on both the given ratio between injection rate and permeability and the Biot coefficient

Formation of Natural Magnesium Silica Hydrate (M-S-H) and Magnesium Alumina Silica Hydrate (M-A-S-H) Cement

Occurrences of natural magnesium alumina silicate hydrate (M-(A)-S-H) cement are present in Feragen and Leka, in eastern and western Trøndelag Norway, respectively. Both occurrences are in the subarctic climate zone and form in glacial till and moraine material deposited on ultramafic rock during the Weichselian glaciation. Weathering of serpentinized peridotite dissolves brucite and results in an alkaline fluid with a relatively high pH which subsequently reacts with the felsic minerals of the till (quartz, plagioclase, K-feldspar) to form a cement consisting of an amorphous material or a mixture of nanocrystalline Mg-rich phyllosilicates, including illite. The presence of plagioclase in the till results in the enrichment of alumina in the cement, i.e., forms M-A-S-H instead of the M-S-H cement. Dissolution of quartz results in numerous etch pits and negative quartz crystals filled with M-A-S-H cement. Where the quartz dissolution is faster than the cement precipitation, a honeycomb-like texture is formed. Compositionally, the cemented till (tillite) contains more MgO and has a higher loss of ignition than the till, suggesting that the cement is formed by a MgO fluid that previously reacted with the peridotite. The M-(A)-S-H cemented till represents a new type of duricrust, coined magsilcrete. The study of natural Mg cement provides information on peridotites as a Mg source for Mg cement and as a feedstock for CO2 sequestration

Resistivity and permeability of core samples from the Samail ophiolite, Oman (Oman Drilling Project)

This dataset presents analyses of resistivity and permeability of core samples collected by the Oman drilling project (Samail ophiolite). Resistivity was measured using impedance analyzer (Agilent 4294A) at the drilling vessel Chikyu, and permeability was calculated from the Hashin-Shtrikman upper bound and the cubic law between permeability and porosity