An ABAQUS Implementation of the XFEM for Hydraulic Fracture Problems

A new finite element has been implemented in ABAQUS to incorporate the extended finite element method (XFEM) for the solution of hydraulic fracture problems. The proposed element includes the desired aspects of the XFEM so as to model crack propagation without explicit remeshing. In addition, the fluid pressure degrees of freedom have been defined on the element to describe the fluid flow within the crack and its contribution to the crack deformation. Thus the fluid flow and resulting crack propagation are fully coupled in a natural way and are solved simultaneously. Verification of the element has been made by comparing the finite element results with the analytical solutions available in the literature

Architectural design of an open cultural space for a cultural heritage art museum

Starting from the interaction between art museums and the public and the way to get along with them, art museums can be closer to the life of the public, and provide the public with spiritual enjoyment, while also playing a certain role in promoting the dissemination and inheritance of local and even national culture. The audience, as the receiver of the exhibition information of the art museum, is also the medium of cultural dissemination of the art museum. This interactive relationship is exactly what we want to explore in the process of art museum design

An Approximate Solution for Predicting the Heat Extraction and Preventing Heat Loss from a Closed-Loop Geothermal Reservoir

Approximate solutions are found for a mathematical model developed to predict the heat extraction from a closed-loop geothermal system which consists of two vertical wells (one for injection and the other for production) and one horizontal well which connects the two vertical wells. Based on the feature of slow heat conduction in rock formation, the fluid flow in the well is divided into three stages, that is, in the injection, horizontal, and production wells. The output temperature of each stage is regarded as the input of the next stage. The results from the present model are compared with those obtained from numerical simulator TOUGH2 and show first-order agreement with a temperature difference less than 4°C for the case where the fluid circulated for 2.74 years. In the end, a parametric study shows that (1) the injection rate plays dominant role in affecting the output performance, (2) higher injection temperature produces larger output temperature but decreases the total heat extracted given a specific time, (3) the output performance of geothermal reservoir is insensitive to fluid viscosity, and (4) there exists a critical point that indicates if the fluid releases heat into or absorbs heat from the surrounding formation

Evaluating hydraulic-fracture effectiveness in a coal-seam-gas reservoir from surface tiltmeter and microseismic monitoring

The hydraulic-fracture effectiveness in a coal-seam-gas reservoir from surface tiltmeter and microseismic monitoring was evaluated. Surface tiltmeters were deployed around the center of the Ridgewood fracture wells to ascertain the azimuth, dip, and volume of the created hydraulic fractures. Their positioning allowed monitoring of both horizontal- and vertical-fracture orientations, and they were arrayed around the wells to account for the expected vertical fracture direction. The estimated static rock-mechanical and derived stress properties were entered directly from the 1D mechanical Earth model (MEM), and permeability was used as a pressure history-matching parameter. The principal stresses determined by constructing the 1D MEM were very close to one another in magnitude, which suggested that hydraulic fractures may not be guided strongly in the maximum-stress direction and could follow a natural-fracture system

Fuel Pyrolysis through Porous Media: Coke Formation and Coupled effect on Permeability

International audienceThe development of hypersonic vehicles (up to Mach 10) leads to an important heating of the whole structure. The fuel is thus used as a coolant. It presents an endothermic decomposition with possible coke formation. Its additional permeation through the porous structure involves internal convection. This implies very complex phenomena (heat and mass transfers with chemistry). In this paper, the n-dodecane pyrolysis is studied through stainless steel porous medium up to 820 K and 35 bar (supercritical state). The longitudinal profiles of chemical compositions inside the porous medium are given thanks to a specific sampling technique with off-line Gas Chromatograph and Mass Spectrometer analysis. By comparison with previous experiments under plug flow reactor, the conversion of dodecane is higher for the present experimental configuration. The pyrolysis produces preferentially light gaseous species, which results in a higher gasification rate for a similar pyrolysis rate. The effects of the residence time and of the contact surface area are demonstrated. The transient changes of Darcy's permeability are related to the coke formation thanks to previous experimental relationship with methane production. A time shift is observed between coke chemistry and permeability change. This work is quite unique to the author's knowledge because of the complex chemistry of heavy hydrocarbon fuels pyrolysis, particularly in porous medium