Effect Of Fracture Characteristics Research Articles

Effect of fracture characteristics on groundwater flow adjacent to high-level radioactive waste repository

In the study, a 2-D numerical model-delineating the high-level radioactive waste repository surrounded by hosting granite-rock was designed to evaluate pressure build-up, elevated temperature, and fracture flow caused by heat generation at the repository. During the early stage (0.1 years), build-up pressure at the repository induced radial groundwater flow. On the other hand, buoyancy-driven vertical flow was dominant during the late stage (2,000 years). The pressure build-up and elevated temperature varied significantly in bentonite, excavation-damaged zone and granite, resulting in different groundwater velocity. Fracture flow in both single and intersecting fractures were also influenced by the pressure and temperature, but their impact varied depending on the geometrical properties (e.g. orientation, elevation, lateral position) of the fracture. In complex discrete fracture network models, build-up pressure in the early stage mainly generated preferential fracture flow through few pathways, while in the late stage, convection-circulating flow induced by the buoyancy was distinct. In the early stage, higher density and connectivity of fracture network did not lead to an increase in average fracture flow, whereas the circulating flow in the late stage became more frequent and larger. Especially, long fractures served as both preferential flow pathways in the early stage and conduits for circulating flow in the late stage. The circulating flow was highly dependent on the spatial distribution of the long fractures, causing a significant uncertainty of average fracture flow in the late stage. The low angle of intersection between fractures resulted in low connectivity that decelerated the average fracture flow in both stages.

Effect of fracture characteristics on history matching in the Qamchuqa reservoir: a case study from Iraq

Carbonate reservoirs in the Middle East hold a significant proportion of the remaining conventional oil reserves, which most of them were classified as naturally fractured. These reservoirs are well known for their low recoveries compared with their counterpart clastic unfractured reservoirs. Therefore, boosting their recoveries can assure to sustain the energy supply to the global oil markets. In this work, an example from the Middle East has been used to evaluate the impact of the fracture characteristics on the reservoir performance using four decades of production history. The characteristics of natural fractures have a remarkable impact on fluid flow behaviour in fractured reservoirs. Besides, these characteristics, such as fracture intensity, determines the matrix block dimensions, which in turn, influence the matrix recovery. However, it is challenging to estimate the fracture characteristics accurately due to the scarcity of the fracture data from subsurface measurements. Therefore, outcrop analogue data can be utilised to enhance the fracture modelling in fractured reservoirs and to fill the data gap between the seismic scale and well scale. In this work, we have integrated the outcrop fracture data with the core observations to improve the fracture modelling in the studied reservoir. Furthermore, a sensitivity study was carried out to investigate the impact of flow curves, gravity drainage mechanism, and its parameters, as well as the fracture storativity on the history matching in fractured reservoirs. Excellent matching results were obtained for the majority of the wells, as indicated by the low mismatch values. The obtained results highlighted the importance of fractures on the fluid flow behaviour, and hence the reservoir performance. Therefore, fracture properties should not be abusively modified using multipliers and local adjustment to avoid nullifying the reservoir characterisation efforts and degrade the simulation model capability for a future prediction.

Effect of Fracture Characteristics on Behavior of Fractured Shale-Oil Reservoirs by Cyclic Gas Injection

Summary The current technique to produce shale oil is to use horizontal wells with multistage stimulation. However, the primary oil-recovery factor is only a few percent. The low oil recovery and abundance of shale reservoirs provide a huge potential for enhanced oil-recovery (EOR) process. Well productivity in shale oil-and-gas reservoirs primarily depends on the size of fracture network and the stimulated reservoir volume (SRV) that provides highly conductive conduits to communicate the matrix with the wellbore. The fracture complexity is critical to the well-production performance, and it also provides an avenue for injected fluids to displace the trapped oil. However, the disadvantage of gasflooding in fractured reservoirs is that injected fluids may break through to production wells by means of the fracture network. Therefore, a preferred method is to use cyclic gas injection to overcome this problem. In this paper, we use a numerical-simulation approach to evaluate the EOR potential in fractured shale-oil reservoirs by cyclic gas injection. Simulation results indicate that the stimulated fracture network contributes significantly to the well productivity by means of its large contact area with the matrix, which prominently enhances the macroscopic sweep efficiency in secondary cyclic gas injection. In our previous simulation work, the EOR potential was evaluated in hydraulic planar-traverse fractures without considering the propagation of a natural-fracture network. In this paper, we examine the effect of fracture networks on shale oilwell secondary-production performance. The impact of fracture spacing and stress-dependent fracture conductivity on the ultimate oil recovery is investigated. The results presented in this paper demonstrate that cyclic gas injection has EOR potential in shale-oil reservoirs. This paper focuses on evaluating the effect of fracture spacing, the size of the fracture network, fracture connectivity (uniform and nonuniform), and stress-dependent fracture-network conductivity on well-production performance of shale-oil reservoirs by secondary cyclic gas injection.

The Method of Tooth Bending Strength Calculation for Gears Made of Phenolic Resin Reinforced by Cotton Woven Cloth

In this research, three steps were taken to reach the conclusion. At first, the influence of the anisotropy of the FRP material, difference of module and gear materials on the strength of tooth root was examined. And, the effect of fracture characteristics and fiber orientation of the gear made of laminated material on the strength is examined by the experiment. Second, until now, this research examines the method of making bending strength equation for isotropic materials such as the metal adjust to FRP gear. Finally, when the gear is used actually, the life of FRP gear is required. The fatigue test is performed in order to understand the life of FRP gear. In conclusion, this research is to establish the way of constructing a design technique for calculating fatigue strength on FRP gears. In this paper the process of calculating fatigue strength is shown.

Finite Difference Modeling for Scale-Dependent Dispersivity in a Fractured Medium

A new finite difference model is developed to characterize solute transport in a fractured medium. In the model, the dispersivity of individual fractures is employed as a variable increasing with travel distance from a source. To demonstrate the applicability of the model, the effect of fracture characteristics on flow and solute transport in a fractured medium is simulated. The fracture characteristics are described by a power law fracture length distribution and fracture spatial density, which are characterized by length exponent (a) and proximity to percolation threshold (Δρ), respectively. The results show that neither the average linear velocity nor the breakthrough time of solutes change significantly with increasing Δρ. For constant Δρ, as a becomes larger, the average linear velocity decreases while the breakthrough time increases. The megascopic dispersivity increases slightly at first, and then decreases afterwards with increasing Δρ.

Numerical Study on the Effect of Fracture Characteristics on Flow and Solute Transport in a Fractured Medium

This study simulates the effect of fracture characteristics on permeability, average linear velocity, breakthrough time, and megascopic dispersivity of a fractured medium. The authors use a power law for fracture length distribution and a fractional Brownian motion for hydraulic fracture aperture spatial distribution, which can be characterized by a and H , respectively. A new finite difference model is developed for solute transport that considers advection, adsorption, first-order decay, and scale-dependent dispersivity of a single fracture using a numerical dispersion term caused by finite difference approximation. The ranges of 1 . 4 h a h 2 . 2 and 0 . 1 h H h 0 . 9 are considered. The results show that the permeability is not very affected by a , but increases slightly with increasing H . The average linear velocity decreases with increasing a , but increases with increasing H . Both the breakthrough time and the megascopic dispersivity increase as a becomes larger, but decrease as H becomes larger. Finally, the megascopic dispersivity is proportional to the linear size of a medium by the power of i , which increases from approximately 0.65 to 0.85 with increasing a , which shows the analogy of the fractured medium to a highly heterogeneous porous medium.

Interfacial reaction layer of Nb/MoSi 2 laminate composites and its effect of fracture characteristics

Interfacial reaction layer of Nb/MoSi 2 laminate composites and its effect of fracture characteristics

1987 Student Professional Paper: Graduate Division: The Influence of Joint and Fracture Roughness on the Shear Strength of Rock

It is known that rock discontinuities exert a powerful control on the strength of a rock mass. A determination of the effect of fracture characteristics on the strength of a rock mass is thus an important aspect in predicting the response of that rock mass to an applied load. In practice it is often difficult to determine the shear strength along discontinuities within a rock mass. As a consequence of the difficulty of determining the effect of discontinuities directly, it is preferable to assess the ultimate shear strength along joints and fractures using approximated values of joint roughness.