Unstructured Finite-Volume Model of Sediment Scouring Due to Wave Impact on Vertical Seawalls

The numerical modeling of sediment transport under wave impact is challenging because of the complex nature of the triple wave–structure–sediment interaction. This study presents three-dimensional numerical modeling of sediment scouring due to non-breaking wave impact on a vertical seawall. The Navier–Stokes–Exner equations are approximated to calculate the full evolution of flow fields and morphodynamic responses. The bed erosion model is based on the van Rijn formulation with a mass-conservative sand-slide algorithm. The numerical solution is obtained by using a projection method and a fully implicit second-order unstructured finite-volume method in a σ-coordinate computational domain. This coordinate system is employed to accurately represent the free-surface elevation and sediment/water interface evolution. Experimental results of the velocity field, surface wave motion, and scour hole formation hole are used to compare and demonstrate the proposed numerical method’s capabilities to model the seawall scour.

Production Optimization Coupling Multiple Reservoirs and Facilities With Sour Gas Re-Injection for Miscible EOR in South Oman

Effective gas utilization is critical to any gas injection development project to maximize recoveries for a given purchase of make-up gas, whilst reducing the Green Gas House (GHG) emissions. This paper describes the use of a fully implicit Integrated Production System Model (IPSM) for two inter-connected production system networks, coupling multiple, critically sour oil reservoirs undergoing Miscible Gas Injection (MGI) for Enhanced Oil Recovery (EOR) using produced sour gas from oil and condensate fields in South Oman. The IPSM model links sixteen reservoir models with varying levels of complexities to the facilities network. Complexities in the facilities include multiple nodal constraints that necessitate the use of an Equation of State model (EOS). The IPSM model honors the gas balance implicitly. Gas flood optimization includes prioritizing low GOR production wells (at reservoir and well level) whilst maintaining reservoir pressure above Minimum Miscibility Pressures (MMP). Development schedule optimization also helps in optimizing the compressor size, the key Capex component. Compositional modeling allows continuous tracking of souring levels at different nodes, providing integrity status of overall production system network. The current IPSM model helps in optimization of schedule for the phased development of the oil reservoirs and eventually the most efficient gas utilization. This has enabled low pressure operation in some reservoirs providing oil at very low unit technical cost while waiting for gas availability. Compositional tracking for H2S helps in operating the facilities within design limits whilst planning future developments to cater to this design. Some key parameters can be parameterized for quick sensitivity analysis for an informed decision making for business opportunities. The production potential of the system is also tracked to ensure there is a cushion in the system to deal with any unexpected changes. This feature helps in planning and optimizing the scheduled turn-around activities for these two inter-connected production system networks. The novelty of this work is collaboration across multiple disciplines, especially the surface and subsurface because of complex interactions between facilities constraints and reservoir performance (associated with produced gas reinjection). Compositional tracking and injection gas apportionment across multiple reservoirs is key to the overall value maximization in this complex development.

Numerical modeling of groundwater flow based on explicit and fully implicit schemes of finite volume method

This paper documents a novel numerical model for calculating the behavior of unsteady, one-dimensional groundwater flow by using the finite volume method. The developed model determined water table fluctuations for different scenarios as follows: Drainage and recession from an unconfined aquifer, and water table fluctuations above an inclined leaky layer due to ditch recharge with a constant and variable upper boundary condition. The Boussinesq equation, which is the governing equation in this domain, is linearized and solved numerically in both of the explicit and fully implicit conditions. Meanwhile, the upwind scheme is employed to discretize the governing equation. The computed outcomes of both the explicit and implicit approaches agreed well with the results of analytical solution and laboratory experiments. The main reason is that in the first half of simulation process explicit scheme obtains slightly better results and in the second half of the simulation process fully implicit scheme predicts more reliable outcomes that are hidden in the neighbor node points. As a final point, the numerical outcomes confirm that the developed model is capable of calculating satisfactory outcomes in engineering and science applications.

Aspects of Multiscale Flow Simulation with Potential to Enhance Reservoir Engineering Practice

Summary A multiscale sequential fully implicit (MS SFI) reservoir simulation method implemented in a commercial simulator is applied to a set of reservoir engineering problems to understand its potential. Our assessment highlights workflows where the approach brings substantial performance advantages and insight generation. The understanding gained during commercialization on approximately 40 real-world models is illustrated through simpler but representative data sets, available in the public domain. The main characteristics of the method and key features of the implementation are briefly discussed. The robust fully implicit (FI) simulation method is used as a benchmark. The implementation of the MS SFI method is found to faithfully reproduce FI results for black-oil problems. We provide evidence and analysis of why the MS SFI approach can achieve high levels of performance and fidelity. The method supports the solution of unique problems that would benefit from incorporating multiscale geology and multiscale flow physics. The MS SFI implementation was used to successfully simulate a typical sector model used for field pilots at extremely high “whole core” scale resolution within a practical time frame leveraging high-performance computing (HPC). This could not be achieved with the FI approach. A combination of MS SFI and HPC offers immense potential to simulate geological models using grids to capture mesoscopic or laminar scale geology. The method, by design, demands fewer computing resources than FI, making it far more cost-effective to use for such high-resolution models. We conclude that the MS SFI method has a distinct capability to enhance reservoir engineering practice in the areas of high-resolutionsimulation-driven workflows in context of subsurface uncertainty quantification, field development planning, and reservoir performance optimization. NOTE: This paper is published as part of the 2021 SPE Reservoir Simulation Conference Special Issue.

Towards the Question on the Zero Subject in English

Introduction. The article considers the case, when no subject is present in an impersonal English sentence. Many linguists believe that the subject in this case is implicit, because the sentence preserves its predicativity. In addition, the subject “it” is sometimes substituted in impersonal English sentences by the formal particle “there”. However, the question whether this particle performs the function of subject is still open. That is why it is rather pertinent to consider all cases of subject, both explicit and implicit one, including the cases, when the sentence contains the formal particle “there”. The objective of this work is to build a formal logical model of implicit subject in impersonal English sentence. Implicit subject is often named as zero subject.Methodology and sources. The research methodology is based on traditional approaches towards studying the phenomenon of zero subject, as well as on the binomiality idea, having been developed since 1993 at ETU. On the material of English the status of the issue, whether it is eligible to consider the implicit subject as the zero one, is investigated. The examples illustrating the functional features of the implicit subject in English sentence were selected by means of the method of continuous sampling from 7 corpora. To represent the structural features of the implicit subject the method of formal logical modelling is applied.Results and discussion. The article presents the diversity of subject structures in English sentence. There is dealt with the question on the functions of the formal particle “there” in hypothetical comparison with the formal particle “it”. In this regard, a formal logical modelling of English subject is undertaken, for declarative and interrogative sentences. Herewith both independent and dependent sentences are modelled. Questions to the subject are out of the present consideration. The implicit subject has been assumed to be a “trace” of the explicit subject and may not be recognized as the absolute zero subject.Conclusion. Linguistics has elaborated a variety of original views on the reasons, why “incomplete” subjects emerge. Our language models allow, however, to come to more original and, as we hope, objective conclusions. Dependent on its environment the subject in English can be implicit fully or partly. If the subject is fully implicit, it is a strong or weak implicit semifinitive, fixed in the weak specifier. If the subject is partly implicit, it is a weak implicit semifinitive, fixed in the strong specifier. The English subject appears to be fully implicit much less frequent, than partly implicit. Making the subject fully implicit is possible by means of additional elements. Making the subject partly implicit is possible by means of the strong specifier “there”; no additional elements are then needed.

Parallel Implementation of the SHYFEM Model

This paper presents the MPI-based parallelization of the three-dimensional hydrodynamic model SHYFEM (System of HydrodYnamic Finite Element Modules). The original sequential version of the code was parallelized in order to reduce the execution time of high-resolution configurations using state-of-the-art HPC systems. A distributed memory approach was used, based on the message passing interface (MPI). Optimized numerical libraries were used to partition the unstructured grid (with a focus on load balancing) and to solve the sparse linear system of equations in parallel in the case of semi-to-fully implicit time stepping. The parallel implementation of the model was validated by comparing the outputs with those obtained from the sequential version. The performance assessment demonstrates a good level of scalability with a realistic configuration used as benchmark.