A novel two-step strategy to fabricate phase-pure SnS photoelectrode with tunable conductivity: formation mechanism and photoelectrochemical properties

Tin monosulfide (SnS), as a narrow band gap semiconductor for visible-light harvesting, nevertheless the easy formation of secondary phases such as Sn2S3 and SnS2 severely restricts its photoelectrochemical properties. Herein, we proposed a novel two-step strategy to fabricate phase-pure SnS photoelectrode with tunable conductivity on Ti foil substrate and carefully investigated the formation mechanism and photoelectrochemical properties. The tunable conductivity is determined by Na2SO4 pretreatment before annealing, which is supported by the EDS, XPS, and EPR characterizations. Na+ adsorbed to the edge of the precursor SnS2 nanosheets forming a dangling bond adsorption will protect S2- against reacting with the trace oxygen in the CVD system within a certain temperature range (< 525 ℃), thereby reducing the generation of S vacancies to adjust the S/Sn ratio and further regulating the conductivity type. Moreover, the anodic photocurrent density of SnS thin films was about 0.32 mA/cm2 at 1.23 V vs. RHE with the separation and injection efficiency of 1.22 % and 72.78 % and a maximum cathodic photocurrent density can reach approximately -0.36 mA/cm2 at 0 V vs. RHE with the separation and injection efficiency 1.15 % and 5.44 % respectively. The method shown in this work provides an effective approach to control the electrical conductivity of SnS thin films with considerable photocurrent response for phase-pure SnS.

A Practical Model for Water Injection Evaluation and Optimization in Typical Offshore Reservoirs Considering Formation Heterogeneity Based on Experimental Study

A major concern with water injection in offshore oil reservoir is the water breakthrough. The formation heterogeneity is the main reason for it. In order to evaluate the water injection efficiency, a visualized 2-D experiment was carried out to obtain the distribution law of injected water and the variation of injection parameters in homogeneous and heterogeneous formation. In addition, a coupled wellbore/reservoir model was established by applying microelement method, superposition principle and imaging. This model considers the formation heterogeneity and pressure drop caused by wellbore friction. The visualized 2-D sand filling displacement experiment indicates that the injection rate at the horizontal well heel is greater than that at the toe and the injection front is more irregular in heterogeneous formation. The injection rate and injection pressure distribution along the horizontal well are obtained analytically based on the proposed model, the results show that the injection rate at the two sides of the wellbore is much higher than that in the middle when the formation is homogeneous and the wellbore is infinite-conductive. In this case, the injection rate curve along horizontal well shows a "U" shaped distribution. When a finite-conductive horizontal wellbore is considered, the injection rate at the heel of the wellbore is higher than that of the toe, although the injection rate curve along horizontal well also exhibits a deformed "U" shape distribution. For the formation heterogeneities along the horizontal wellbore, the injection rate distribution curve is not continuous anymore, but a deformed "U" shape is also observed for each wellbore segment. At last, the established model was applied to an ultra-heterogeneous offshore reservoir. It is concluded that the profile control effect of typical well is obvious. The results of this study are of great significance for the calculation of the injection rate profile and improving the water injection efficiency.

Reservoir to Tank: Fit for Purpose Integrated Workflows for Waterflood Management and Production Enhancement

Integrated solutions are important to formulate plans for mature reservoirs under waterflooding due to related dynamic changes and uncertainties. The reservoir and field management need to be handled as an integrated system, and therefore needing a multidisciplinary approach. This paper demonstrates how the integrated multidisciplinary team has developed several workflows covering water-flooding management, production enhancement and maximizing the economic recovery of reservoirs in the North Kuwait asset. Many integrated workflows were developed for water flooding and production optimization. The main integrated workflows that were implemented are as follows: PVT Properties Tool: is designed to estimate the fluid properties throughout the reservoir taking into consideration areal and vertical variations based on trends, and existing data coverage. Opportunity Maps: is a combination of updated reservoir pressure and fluids properties to provide a fast way to identify areas of opportunity to increase/decrease injection or production based on the development strategy. Waterflooding Patterns/segments Review Workflow and Allowable Tool: This integrated analytical workflow applied on predefined reservoir patterns or segments based on geological distribution and/or hydraulic communication, includes several tools like the analysis of production and injection trends, diagnostic plots to assess good vs bad water, Hall plots, Reservoir Pressure data, tracer data, salinity changes and pump intake pressure trends. Geological analysis (cross-sections, well correlations, sand thickness maps) for each layer are integrated in each pattern/segment review to support reservoir connectivity (or the lack thereof). Instantaneous and cumulative VRR are calculated and compared with the overall exploitation strategy and water injection efficiency. Other sub-workflows were developed to improve and manage waterflooding performance such as water recirculation tool and streamline sector modeling simulation. Structured integrated proactive production and ESP optimization workflows: Production optimization is a continuous iterative process (cycles) to improve production, especially in mature fields. This workflow facilitates the identification of opportunities for production optimization with a pro-active approach focusing on flowing wells and rig-less interventions to tackle production challenges and achieve production targets. The Heterogeneity Index (HI) process is utilized to rapidly demonstrate production gain opportunities. This provides family-type problems that are then represented by type-wells for detailed diagnostics. Continuous application and embedding of such structured integrated workflows as standard best practices, deliver significant value in terms of improving the understanding of reservoir performance in order to inject smart (where and when required) and produce smart (sweet healthy spots). This is done on reservoir, segment, pattern and individual well levels in multidisciplinary team domains. The ultimate results reflected in continuous improvement in waterflooding management (injection efficiency, vertical and areal sweep efficiency, sweep new oil via changing streamlines). This in turn contributes to significant added oil gain and recoverable reserves with best practices reservoir management. These integrated workflows are user friendly and can be applied across different reservoirs and fields. The application of such workflows in a structured, consistent and proactive approach improves the overall asset management in terms of maximizing production and recoverable reserves.

A Novel Data-Driven Model for Dynamic Prediction and Optimization of Profile Control in Multilayer Reservoirs

Establishing reservoir numerical simulation and profile control optimization methods considering the mechanism of profile control has always been a difficult research problem at home and abroad. In this paper, firstly, a physics-based data-driven model was established on daily production data of injection and production wells following the principle of material balance. Key parameters including transmissibility, control pore volume, water injection allocation factors, and injection efficiency are derived directly from history matched model, and the dominated flow channels could be quantitatively identified. Then, combined with the evaluation results of the plugging ability of the plugging agent, imaginary well nodes are added to the existing interwell relationship to characterize the heterogeneity of interwell-specific parameters. This process performs flow processing along the interwell control units, forming a new and rapid method for simulation and prediction. Lastly, based on the calculated interwell transmissibility, water injection efficiency, and allocation factors, injection wells with low water injection efficiency can be preferentially selected as profile control wells. In addition, taking the production rates, injection rates, and the amount of plugging agent as optimization variables, we established an optimal control mathematical model and realized the parameter optimization method of the profile control. We demonstrated the results of one conceptual model and two indoor experiments to verify the feasibility of the proposed method and completed two actual field applications. Model validation and actual field application show that the proposed method successfully eliminates the complicated geological modeling procedure and the tedious calculation process associated with the profile control treatment in traditional numerical simulation methods. The calculation speed improves tens or hundreds of times, and water channeling paths are accurately identified. Most importantly, this method realizes the overall decision-making of profile control well selection, dynamic production prediction, and parameter optimization of profile control measures quickly and accurately by mainly using the daily production data of wells. The findings of this study can help for better understanding of the optimization design and application of on-site profile control schemes in large-scale oilfields.

An injection optimization decision-making tool using streamline based fuzzy logic workflow

This paper presents an adaptive approach to optimize field injection strategies using streamline-based well allocations coupled with fuzzy logic. The strength of our approach comes from the fact that streamlines are generated by running a full-physics reservoir simulator. Streamlines provide great insights about well pattern connectivity and good allocation factors allowing the injection efficiency (IE) for each pattern to be determined. Fuzzy logic can simulate human thinking and handle different categories of information including linguistic, imprecise, approximate, and overlapping to name a few. This paper presents a genuine approach for field injection optimization using a streamlined-based fuzzy logic system. In this work, we present an adaptive streamline-based fuzzy logic system that uses three input parameters namely injection efficiency (IE), water cut (WC), and injection loss to aquifer to assign an injector ranking index (IRI) according to injector performances. The workflow then smartly redistributes water injection by accounting for operational constraints and number of connected producers in a pattern in addition to the IRI. The workflow examines the low performers (i.e., low and medium IRI categories) and assigns different injection reduction factors for each injector in these categories. Then, the total amount of reduced injection is assigned to high performers (i.e., high IRI) while ensuring no operational constraint is violated, such as bottom-hole pressure (BHP) and capacity of pumps. This approach has been tested on a dual-porosity dual-permeability (DPDP) conceptual simulation model. The area of interest has two rows of injectors: downdip and updip. The updip injectors are the focus of the study. The results of applying this approach show noticeable improvements in injection efficiency for most wells in the area of interest ensuring better sweep, good pressure support, and improving cumulative oil production. We believe combining both technologies, namely streamlines and fuzzy logic, can provide reservoir engineers with a robust decision-making tool to attain a more successful field-wide water injection strategy.

Design study of CEPC lower emittance booster

The CEPC booster needs to provide electron and positron beams to the collider at different energy with required injection efficiency. At Higgs energy, only the on-axis injection from booster to collider can be fulfilled in CDR. With a consideration of keeping the off-axis injection scheme for safety and reliability, a new booster design based on TME lattice is considered to reduce the emittance by three times after CDR. The new booster design has reached an emittance of 1.3 nm at 120 GeV and the DA without errors is even better than CDR. The geometry of new booster is designed carefully in order to share the same tunnel with collider. The design status of CEPC new booster including parameters, optics, dynamic aperture and geometry is discussed in this paper.