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Collaborating Authors
Results
An Improved And Optimized Positioning Method Of Microseismic Source In Mining
Zhu, Quanjie (University of Science and Technology Beijing) | Wu, Yingkui (University of Science and Technology Beijing) | Yin, Yongming (University of Science and Technology Beijing) | Shu, Couxian (University of Science and Technology Beijing) | Yu, Zhengxing (China Academy of Safety Science and Technology) | Ju, Hongyang (Beijing Anke Technology Co., Ltd.)
Abstract: Automatically positioning a microseismic source and picking the first arrival are challenging and a focus in microseismic technology research. In order to reduce error caused by artificial picking arrival and speeds in different mediums, a new automatic-picking method is proposed in this paper to process microseismic data with MATLAB. There are four steps in the method: (1) de-noising and filtering microseismic signals using Empirical Mode Decomposition (EMD); (2) picking the first arrival using the traditional STA/LTA method with an improvement in the time-window and threshold value; (3) after finding the shortest first arrival, source positioning is evaluated with the "four-four" method; (4) after removing abnormal values from the sources positions using cluster analysis with specific dispersion threshold, optimized source positions are obtained by averaging. This method has been validated in the case study of a coal mine in China. Compared to other methods, the microseismic sources using this method can be positioned much more efficiently with high precision.
- North America > United States (0.68)
- Asia > China (0.51)
- Geology > Geological Subdiscipline (0.46)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.31)
Abstract: We present a parameter estimation method for a quasi-stationary multiphysics problem in subsurface modeling. Specifically, the modeling part for the state equation is based on the coupled Biot-Lamé-Navier system in order to describe the interaction between some pay-zone and a non-overlapping non-pay regime. The coupled system for the state is formulated within a variational monolithically-coupled framework. We propose an iterative stochastic ensemble method (ISEM) to estimate material coefficients such as permeability coefficients in the pay-zone or Lamé parameters in the non-pay zone. ISEM is based on stochastic estimation of gradients using an ensemble of directional derivatives within a Gauss-Newton iteration. The resulting update equation resembles the update step in ensemble Kalman filter. However, the inverse of the output covariance matrix in the update equation is regularized using standard truncated singular value decomposition. The proposed algorithm treats the forward simulator as a blackbox and avoids explicit derivation of the adjoint equations, which is major task for nonstationary systems. Our forward formulation and parameter estimation method are validated by some numerical tests including an extension of Mandel's problem.
Abstract: In this paper the geometry of oil reservoirs is reconstructed by using NURBS surfaces. The technique exploits the reservoir's static model simplicity to build a robust piecewise continuous geometrical representation by means of Bézier bicubic patches. Interpolation surfaces can manage the reservoir's topology while translational surfaces allow extrapolating it towards its sideburdens. After that, transfinite interpolation (TFI) can be applied to generate decent hexahedral meshes. In order to test the procedure several open-to-the-public oil reservoir datasets are reconstructed and hexahedral meshes around them are generated.
- North America > United States > Texas (0.46)
- North America > United States > California (0.28)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.81)
Abstract: We present a 3D-DDA formulation that uses an explicit time integration procedure and an efficient contact detection algorithm optimized to minimize the computational effort. The advantages of the explicit formulation are that the global stiffness matrix does not need to be assembled and the linear equations do not need to be solved by matrix inversion. Consequently, the computational effort and memory requirement can be reduced considerably, which is important for efficient solution of large 3D problems. In addition, the computational efficiency is increased by eliminating unnecessary contact computations using a grid based nearest neighbor search. The grid divides space into a number of cells of equal size and each object is then associated with the cells it overlaps. As only objects overlapping a common cell can possibly be in contact, in-depth tests are only performed on objects found sharing cells with the block tested for collision. The contacts between the blocks are detected by using Fast Common- Plane (FCP) approach. The halfedge (HE) data structure approach is used to handle the navigation into the topological information associated with polyherdral objects (vertices, edges, faces). The halfedge data structure allows for quick traversal between faces, edges, and vertices due to the explicitly linked structure of the network. Examples are provided which demonstrate the capabilities of new algorithm and the size of problem that can be analyzed.
3D Numerical Reconstruction of Poorly Connected Porous Sandstones
Zheng, Jiangtao (China University of Mining & Technology) | Ju, Yang (China University of Mining & Technology) | Wang, Jinbo (China University of Mining & Technology) | Yang, Yongming (China University of Mining & Technology) | Zhao, Xi (China University of Mining & Technology) | Gao, Feng (Lawrence Berkeley National Laborato)
Abstract: The poorly connected porous sandstones are the mainly concerned materials in a variety of engineering practices which naturally involves a large number of discontinuous and geometry- irregular micro-pores. These pores significantly affect the physical and mechanical properties of the rock. A reliable numerical reconstruction porous rock model provides an effective and economic way for the research of the influences of the micro-pores to the rock macro-properties. In this paper, we present a novel numerical method to reconstruct poorly connected porous sandstone. A fractal descriptor is employed to characterize the complex morphology of pore structures. Additionally, a modified simulated annealing algorithm was developed to accelerate the 3D reconstruction process. Besides, the finite element models are established based on the real rock CT configuration and the reconstructed configuration. Based on them, the mechanical properties of the sandstone can be analyzed. The analysis indicates that the 3D reconstruction model has better pore-geometry similarity with real rock model, higher reconstruction efficiency, and more accurate predictions of mechanical properties of the poorly connected porous sandstone.
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.94)
- Well Drilling > Wellbore Design > Wellbore integrity (0.77)
- Reservoir Description and Dynamics > Fluid Characterization > Fluid modeling, equations of state (0.71)
Abstract: The displacement discontinuity method (DDM) is frequently used in geothermal and oil industry applications for modeling the behavior of fractures embedded in linear-elastic rocks. The DD method requires O(N) memory and O(N) floating point operations (where N is the number of degrees of freedom) to construct the coefficient matrix and solve the linear system of equations by direct methods. Therefore, the conventional implementation of DDM is not computational efficient for very large systems of cracks, often limiting its application to small-scale problems. This work presents an approach for solving large-scale fracture problems using the Fast Multipole Method (FMM). The approach uses both the DDM and a kernel-independent version of the FMM along with a preconditioned Generalized Minimal Residual Algorithm (GMRES) to accelerate the solution of linear systems of equations using desktop computers. Using the fundamental solutions for constant displacement discontinuity in an elastic medium, several case studies involving fracture networks representing naturally fractured reservoirs are treated. Results show a good agreement with analytical solutions and demonstrated the efficiency and accuracy of the FMM implementation of the DD for large-scale situations.
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
- Well Completion > Hydraulic Fracturing (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Naturally-fractured reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Information Technology > Hardware (0.48)
- Information Technology > Mathematics of Computing (0.46)
Abstract: World-wide mining operations utilize block caving as one of the most cost-effective techniques for ore extraction. Block caving has been addressed in the past by numerous discontinua methods to include Discrete Element Method (DEM), Discontinuous Deformation Analysis (DDA), Combined Finite-Discrete Element Method (FDEM), etc. However, most of these analyses were either limited to 2D or to elastic material representation. In this paper a representative 3D block caving problem is simulated using FDEM. Los Alamos National Laboratory’s Geophysics team conducted the modeling utilizing their in-house FDEM code, MUNROU. MUNROU is a fully parallel, 2D/3D FDEM code which utilizes material models that account for a number of plasticity effects, as well as has the capability to model explosive effects, irregular shapes and fracture initiation and propagation. Previously problems of this nature and size were un-tractable in 3D. However, the recent performance improvements seen in MUNROU through the implementation of state of the art parallelization algorithms (see Computational Mechanics of Discontinua, Wiley 2011), have prompted our team to begin intensive efforts to address real world problems, such as block caving. The code’s inherent capability to address fracture and fragmentation processes at laboratory scale level has been consistently proven in the past. In this paper the feasibility of extending MUNROU to large space scales in 3D is demonstrated. With this improved capability it is now expected that future analyses efforts can concentrate on 3D phenomenological considerations such as jointing, frictional fault behavior, etc.
- North America > United States > California (0.28)
- North America > United States > New Mexico > Los Alamos County > Los Alamos (0.25)
- Energy (0.67)
- Materials > Metals & Mining (0.48)