Chevron (China)

Mesoporous Y (Meso-Y) zeolites are an emerging class of catalysts with mesopores (typically smaller than 9 nm in diameter) for accommodating sterically bulky reactant molecules, such as those commonly encountered in biomass and polymer waste upcycling. Here, in this manuscript, we report the synthesis, physicochemical characterization, and catalysis of novel Meso-Y zeolites consisting of tunable mesopores ranging from 9 to 20 nm in diameter and mesopore volumes of approximately 0.6 cm3/g. Our synthetic approach involves partial dissolution of the zeolite framework and zinc redistribution during calcination and hydrothermal treatment (HT) of conventional Meso-Y zeolites. The synthesis proceeds through an intermediate zinc-rich zincoaluminosilicate (ZnAlSi) phase, which was characterized by scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX) before HT as a phase partially separated from the zeolite in syntheses involving high zinc concentrations. SEM-EDX characterization of these materials after HT demonstrates large mesopores, accompanied by zinc levels redistributing to the same uniformly low values throughout the material. Data from SEM, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS), and high-angle annular dark-field–scanning transmission electron microscopy (HAADF-STEM) show the synthesis of large mesopores after HT within the zeolite. H/D exchange and n-decane hydroconversion data prove acid-site accessibility in our catalysts under thermodynamically and kinetically controlled conditions, respectively, which is similar to a conventional Meso-Y control catalyst.

Summary We present a semi-analytical method to analyze the multistring response of tubulars in offshore wells with a mudline suspension system (MLS). Though the governing equations are linear, structural redundancies at the mudline hangers (MLH) require a one-step iterative solution. The iteration ensures that the final response of the MLS and the tubulars is consistent with restrictions at the wellhead and mudline. Our method is computationally simple and can be implemented in a spreadsheet. We apply the method to an offshore well with six strings, four of which are suspended at the mudline. The hangers at the mudline are arranged such that a suspended string transfers its weight to the next outer string. Furthermore, the MLS hardware is such that a lifted-off string raises its immediate inner neighbor. In the model, the tubulars are regarded as elastic springs, and the load transfer pathways at the MLH shoulders are represented by displacement constraints. The length changes created by pressure and temperature changes during well operations are combined with the installed conditions to determine the contact force at the MLH. The model shows that the net movement at the surface and the forces on the structural members depend on the installed condition, the preload in the casing strings, and annular pressures at the surface wellhead. Furthermore, the reduction of annular pressures significantly reduces the force on the conductor slip lock in the wellhead. Cold injection creates a net downward force at critical locations in the MLS. Finally, the model was used to show that the net downward force did not exceed the design capacity of the MLS hardware and to define annulus pressure management procedures to maintain well integrity.

Hydrogenation-dehydrogenation cycles enable the efficient storage, transport, and release of hydrogen via chemical means. Practical kinetic, thermodynamic, and H-density considerations make cyclic hydrocarbons the preferred organic hydrogen carriers. This study addresses the mechanism of methylcyclohexane (MCH) dehydrogenation to toluene (TOL), through methylcyclohexene (MCHE) intermediates on Pd nanoparticles (2–11 nm diameter) dispersed on Al2O3, SiO2, MgO, and CeO2. Turnovers occur on Pd surfaces densely covered with MCH-derived intermediates differing in isomeric structure and reactivity via sequential C–H activation elementary events, irrespective of nanoparticle size or support. The kinetically relevant step shifts from the second to the first H-abstraction step in MCH as temperature increases (from 453 to 553 K). The reactivity of Pd nanoparticle surfaces is insensitive to their size but supports with more competent Lewis acid–base (LAB) pairs lead to higher rates and stronger rate enhancements (relative to SiO2) with decreasing temperatures, which reflect the lower coverages of less reactive intermediates when supports can scavenge desorbable species. These dense adlayers retain interstices within which dehydrogenation turnovers occur, but no longer expose the most distinctive low-coordination atoms prevalent on small nanoparticles, leading to the observed structure insensitivity of turnover rates. The prevalence of such adlayers leads to surfaces without the saturation hydrogen coverages expected for Pd surfaces devoid of such organic species. These mechanistic insights are consistent with (i) the elimination of support effect by titration of LAB pairs; (ii) initial rate transients that are inhibited by competent supports; (iii) the relative reactivity of metal-free supports for dehydrogenation of MCHE and methylcyclohexadienes (but not MCH); and (iv) measured kinetic effects of MCH, MCHE, and H2 on turnover rates. The support effects provide strategies for maximizing the exposure of bare atom ensembles during dehydrogenation reactions. Its conceptual impact and practical significance are not restricted to the subject reaction in this study.

ABSTRACT In this study, we conduct laboratory experiments reproducing fracture slip on both propped and unpropped fractures in Marcellus shale to explore the role of shear deformation as a primary control on permeability evolution and its correlation with initial stress state, shear stress magnitude and loading rate, and proppant loading concentration. For tests on unpropped fractures, we incorporate the complexity in both form and response of natural fracture topography by using pristine natural fractures directly split along bedding planes. Under low shear stress, unpropped fracture is prohibited from slipping by strongly mated interlocking asperities. As we increase shear stress exceeding the frictional strength of the contact, it exhibits great conductivity enhancement upon fracture reactivation followed by immediate and continuous decay. If shear stress is loaded incrementally instead of instantaneously – broadly representing different fracking fluid injection rate – fracture conductivity response to shear deformation is considerably muted. Unpropped fracture behaviors are also found to be strongly related to fracture roughness and fidelity of the interlocking asperities, while less sensitive to background stress state. For propped fractures, we use manually ground fractures to specifically focus on the proppant impacts. In contrast to unpropped fractures, conductivity enhancement upon shear reactivation only presents where proppant is placed as non-uniformly distributed monolayer, which can be attributed to the generation of interparticle highly permeable flow paths. Otherwise, conductivity decreases as a result of proppant embedment, crushing, and compaction, however the reduction is muted with thicker proppant pack. INTRODUCTION The shale gas revolution dramatically changed the mix of energy supply in the United States over the past decade. The deployment of horizontal drilling and massive hydraulic fracturing to generate highly permeable flow paths has unlocked the massive store of hydrocarbons held in deep, ultralow-permeability shale reservoirs (Warpinski and Teufei, 1987; Maxwell et al., 2002; Taleghani and Olson, 2011; Taleghani et al., 2016).

Abstract In this work, we study a waterflood field containing over 1,000 wells and the modern field management techniques with full-fidelity 3D geo-cellular reservoir models become computationally prohibitive. To overcome the difficulty, we developed a novel flow-network data-driven model, GPSNet, and used it for rapid history matching and optimization. GPSNet includes physics, such as mass conservation, multiphase flow, phase changes, etc., while maintaining a good level of efficiency. To build such a model, a cluster of 1-D connections among well completion points are constructed and form a flow network. Multi-phase fluid flow is assumed to occur in each 1-D connection and the flow in the whole network is simulated by our in-house general-purpose simulator. Next, to effectively reduce the uncertainty, a hierarchical history-matching workflow is adopted to match the production data. Ensemble Smoother with Multiple Data Assimilation (ESMDA) is utilized to reduce the error at each step of the history matching. Next, a best-matched candidate is selected for numerical optimization to maximize oil production rates with constraints satisfying field conditions. Excellent history-matching results have been achieved on the field level and good matches have also been observed for key producers. In addition, the history matching consumes mere 4 hours to finish 1,100 simulation jobs. The successful application of the GPSNet to this waterflood field demonstrates a promising workflow that can be used as a fast and reliable decision-making tool for reservoir management.

Abstract The solution of nonlinear equation-system resulting from the Fully Implicit Method (FIM) remains a challenge for numerically simulating multi-phase flow in subsurface fracture media. The Courant numbers can vary orders of magnitude across discrete fracture- matrix (DFM) models because of the high contrasts in the permeability and length-scale between matrix and fracture. The standard Newton solver is usually unable to converge for big timestep sizes or poor initial guesses. Limited research has been conducted on nonlinear solver techniques for multi-phase compositional flow-transport in fractured media. We make an extension of a new dissipation-based continuation (DBC) algorithm to compositional and DFM models. Our goal is to prevent time-step cuttings and sustain efficient time-stepping for FIM. The DBC algorithm builds a homotopy of the discretized conservation equations through the addition of numerical dissipation terms. We introduce a continuation parameter for controlling the dissipation and ensuring that accuracy of the computed solution will not be reduced. Under the nonlinear framework of DBC, general dissipation operators and adaptive methods are developed to provide the optimal dissipation matrix for multiphase compositional hyperbolic systems. We assess the new nonlinear solver through multiple numerical examples. Results reveal that the damped-Newton solver suffers from serious restrictions on timestep sizes and wasted iterations. In contrast, the DBC solver provides excellent computational performance. The dissipation operators are able to successfully resolve the main convergence difficulties. We also investigate the impact of star-delta transformation which removes the small cells at fracture intersections. Moreover, we demonstrate that an aggressive time-stepping does not affect the solution accuracy.

Abstract Black-oil simulations with phase changes are challenging, because of the complex interactions between the different components and the equilibrium behavior of the phases. The common method for solving this type of nonlinear problem is to use a fully-implicit approach. However, the conventional black-oil model can lead to difficulties with converging using Newton's method. Discontinuities in discrete system can occur when a phase transition happens, which can lead to oscillations or even failure of the Newton iterations. The goal is to design a smoothing formulation that eliminates any sudden changes in properties or discontinuities that occur during phase transitions. We first employ a compositional formulation based on K-values to describe the standard black-oil model. Next, the coupled system is reformulated such that the discontinuities are carried over to the phase equilibrium model. In this manner, a single, succinct non-smooth equation is obtained, which allows for deriving a smoothing approximation. A mixed complementarity problem (MCP) for phase-equilibrium in the area of chemical process modeling served as the foundation for the reformulation. The new formulation is non-intrusive and simple to implement, requiring minor changes to current black-oil simulator frameworks. We analyze and demonstrate that phase changes lead to the changes of fluid-properties and discrete system, under the conventional black-oil formulation. By comparison, the newly proposed formulation uses a smoothing parameter to ensure smooth transitions of variables between the phase regimes. It also generates unique solutions that are valid for all three phases. Several complex heterogeneous problems are tested. The conventional black-oil model experiences many time-step cuttings and wasting nonlinear iterates. On the contrary, the smoothing model exhibits excellent convergence behaviors. Overall, the new formulation addresses the issues with convergence caused by phase-changes, while barely affecting solution results.

Abstract To design accurate inflow control device (ICD) completions in high water cut wells, it is critical to have a thorough understanding of the downhole flow profile and zonal phase contribution across the zone of interest. The situation becomes more complex when dealing with an open hole horizontal section with complex trajectory, where the presence of stagnant water sumps and oil humps is common and can lead to in-accurate determination of water and oil entry zones.Production logging tools typically deployed in such environments will require to have their data quality checked, as the well conditions can either leave the spinners clogged or the holdup probes sticky with downhole debris or emulsion. Production logging tools will also need to reach the deepest point within the lateral section to ensure complete coverage of the potential flow area across the open hole section.Electrical line enabled coiled tubing (CT) technology was considered to overcome the conveyance challenges to deploy these production logging tool. The selected rugged design of the coil-to-wireline interface increased the reliability and the safety of the intervention.In this paper, a case study will be presented detailing how careful operational planning, integration between the conveyance method and the production logging tool resulted in the detailed and accurate downhole flow profile, which was then utilized in the ICD design for this well.

Summary The article presents a framework designed for standardized cross-platform benchmarking of seismic imaging kernels. This framework aims to standardise the benchmarking process, providing reference implementations for various architectures and enabling reproducible experiments. The system uses GitHub Actions for automation, a development cluster composed of different computer architectures, and on-demand runners on AWS. This setup allows for easy comparison of different methods, hardware, while also enabling the integration of more tools and servers. Preliminary results are presented for 3D isotropic acoustic and Fletcher Du Fowler TTI benchmarks, using Giga-points per second (GPts/s) as a performance unit, providing more practical insights compared to the standard FLOPS (Floating Point Operations Per Second) metric.