Simulation of immiscible water-alternating-CO2 flooding in the Liuhua Oilfield Offshore Guangdong, China

In this paper, the immiscible water-alternating-CO2 flooding process at the LH11-1 oilfield, offshore Guangdong Province, was firstly evaluated using full-field reservoir simulation models. Based on a 3D geological model and oil production history, 16 scenarios of water-alternating-CO2 injection operations with different water alternating gas (WAG) ratios and slug sizes, as well as continuous CO2 injection (Con-CO2) and primary depletion production (No-CO2) scenarios, have been simulated spanning 20 years. The results represent a significant improvement in oil recovery by CO2 WAG over both Con-CO2 and No-CO2 scenarios. The WAG ratio and slug size of water affect the efficiency of oil recovery and CO2 injection. The optimum operations are those with WAG ratios lower than 1:2, which have the higher ultimate oil recovery factor of 24%. Although WAG reduced the CO2 injection volume, the CO2 storage efficiency is still high, more than 84% of the injected CO2 was sequestered in the reservoir. Results indicate that the immiscible water-alternating-CO2 processes can be optimized to improve significantly the performance of pressure maintenance and oil recovery in offshore reef heavy-oil reservoirs significantly. The simulation results suggest that the LH11-1 field is a good candidate site for immiscible CO2 enhanced oil recovery and storage for the Guangdong carbon capture, utilization and storage (GDCCUS) project

Screening and simulation of offshore CO2-EOR and storage:A case study for the HZ21-1 oilfield in the Pearl River Mouth Basin, Northern South China Sea

CO2-enhanced oil recovery (CO2-EOR) and storage is currently the most effective and economic technology for reducing CO2 emissions from burning fossil fuels in large scale. This paper is the first effort of proposing a modelling assessment of CO2-EOR and storage in the HZ2-1 oilfield in the Pearl River Mouth Basin in northern South China Sea offshore Guangdong Province. We attempt to couple the multi-parameter dimensionless quick screening model and reservoir compositional simulation for optimization of site screen and injection simulation. Through the quick screening, the reservoirs are ranked by FOR dimensionless recovery R-D, and by CO2 storage in pore volume SCO2. Our results indicate that SCO2 is highly pressure dependent and not directly related to R-D. Of these reservoirs, CO2-EOR and storage potential of the M10 was estimated through a compositional simulation as a case study based on a 3D geological model. Nine scenarios of CO2 injection operations have been simulated for 20 years with different well patterns and injection pressures. The simulation results represent an obvious improvement in oil production by CO2 flooding over No - CO2 production. The best operation for M10 is miscible CO2 flooding, which led to the higher recovery factors of 52%(similar to)58% and CO 2 stored masses of 8.1 x 10(6 similar to)10.8 x 10(6)t The optimum operation for CO2 injection should be set well pattern in region of injector I1 and high injection pressure for miscible flooding. In a whole, the HZ21-1 field can be used as a candidate geological site for GDCCUS project. We are fully aware of the limitation in the primary modelling including reservoir and fluid properties and production history matching, and regard this study as a general and hypothetic proposal

Development of CCUS Technology in the Context of Carbon Neutrality and Assessment of the Potential for Offshore Storage in Guangdong Province

[Introduction] Carbon capture, utilization and storage (CCUS) is one of the key technologies for achieving carbon neutrality. The coastal area of Guangdong Province is a potential area for offshore CO2 storage projects in China. Understanding the development status of CCUS technology in the context of carbon neutrality and analyzing the offshore CO2 storage potential in the coastal area of Guangdong Province are conducive to provide the basis for large-scale CCUS projects, especially the offshore storage projects in the future in China. [Method] The technical routes and development trends of all aspects of CCUS were summarized. The offshore geological storage potential of CO2 in the Pearl River Mouth Basin and the Beibu Gulf Basin off the coast of Guangdong Province was discussed. The problems of offshore CO2 storage in China were summarized, and relevant suggestions were put forward. [Result] In recent years, China has made significant progress in CCUS technology, but some key technologies in transportation and storage has been still at the R&D demonstration stage. The Pearl River Mouth Basin and the Beibu Gulf Basin have enormous geological storage potential of CO2 and an excellent matching relationship with large CO2 emission sources in the coastal area of Guangdong Province, making it an ideal locations for offshore CO2 storage projects. However, offshore CO2 storage still faces problems such as immature technology, high storage costs, uncertain environmental impacts, and inadequate policy and regulation frameworks in China. It is necessary to focus on technological development, promoting cluster projects, and improving policies and relevant regulations to advance the development of offshore CO2 storage. [Conclusion] In the future, China should strengthen research, development and promotion of CCUS, especially the offshore storage technology, to promote the progress of carbon neutrality

Stability of synchronous solutions in a directed Kuramoto-Oscillator network with a pacemaker

In this brief, we investigate the stability of a directed Kuramoto-oscillator network with a pacemaker for two kinds of synchronous solutions. Sufficient conditions on the coupling strength and initial phases to achieve such synchronous solutions are explicitly provided under the assumption that the augmented digraph has a directed spanning tree rooted at the pacemaker. Moreover, the minimum number of pinned oscillators is determined under the given conditions

More or less controllers to synchronize a Kuramoto-oscillator network via a pacemaker?

This paper extends our previous work on synchronizing a network of Kuramoto-oscillator digraph with a pacemaker. Compared with the minimal driven or pinned nodes of two linear coupling models, those nodes forced by the pacemaker are relative conservative in our Kuramoto model with nonlinear couplings. Comparative analyses of the results and dynamics are made among these three models. For two given directed networks, discussion are given to test whether less nodes forced by the pacemaker are feasible to achieve phase agreement or frequency synchronization in a Kuramoto-oscillator network

Quick assessment to ascertain technical rational well spacing density in artificial water flooding oilfield

Optimization of technical rational well spacing density (TRWSD) is a crucial part of the study of oilfield development. However, the methods widely used previously have some disadvantages as followings: (1) Some quoted theories and formulas for algorithms are intractable. (2) Some are incompatible with the reality as they assumed too many conditions which are more ideal. (3) The influence factors considered by other algorithms are not comprehensive and irrational. (4) In applications, the applicable conditions are ignored by some algorithms. Aiming at the problems above, this paper has built a quick estimation model of TRWSD and proposed a new optimizing method of TRWSD, based on the comprehensive investigation of pressure distribution and the theoretical model of rational ratio of oil to water wells (RROWW) in artificial water flooding oilfield. Verification by reservoir numerical simulation model and actual data of the field implementation shows that the TRWSD model is reliable, and practical. It is revealed from the studies that the injection-production pressure system factors are the main ones to control TRWSD except water cut, such as the oil-bearing area of producing geological reserves, liquid productivity index, injection-production ratio and number of injection-production wells, and so on. And compared with the previous ones, the TRWSD method comprehensively takes into account such the factors as injection-production unbalance, density difference between oil and water, volume factor, start-up pressure gradient of injection wells, start-up pressure gradient of production wells and so on. Hereinafter, the new model can be applied for the calculation of the TRWSD and related parameters at any injection-production development stages, reservoir types and reservoir pressure distributions in artificial water flooding oilfield, all of which means that the new method has a strong promising adaptabilities and prospects in the water flooding oilfield with close well spacings or during high water cut stage

Chemical and Quality Analysis of Beauty Tea Processed from Fresh Leaves of Tieguanyin Variety with Different Puncturing Degrees

Beauty tea with special flavor can be affected by the degree of leafhopper puncturing. The present research adopted widely targeted metabolomics to analyze the characteristic metabolites of fresh tea leaves and beauty tea with different degrees of leafhopper puncturing. Low-puncturing beauty tea (LPBT) exhibited a superior quality. Altogether, 95 and 65 differential metabolites, including tea polyphenols, saccharides, and lipids, were identified from fresh leaves and beauty tea, respectively. The partial least squares regression (PLSR) analysis results showed that isomaltulose, theaflavic acid, and ellagic acid, may be the characteristic metabolites that form the different taste outlines of beauty tea. Based on odor activity values (OAVs) and partial least squares discriminant analysis (PLS-DA), dihydrolinalool and cis-linalool oxide were identified as characteristic volatile components, which may be essential for the formation of the different aroma characteristic of beauty tea. The results provide a theoretical basis for selecting raw materials, performing quality research, and developing beauty tea industrially

Mechanical and tribological behavior of dual-phase ductile iron with different martensite amounts

Ferrite-martensite (F/M) dual-phase ductile iron with different relative amounts of martensite was fabricated via intercritical quenching in the present study. The mechanical properties and tribological behavior were investigated. The strength of ductile iron increased linearly with the increase of martensite level, while the ductility decreased rapidly. Fracture surface morphology analysis indicated that ductile fracture was predominant when the proportion of martensite in ductile iron was less than 20%. However, the samples with more than 40% martensite exhibited brittle fractures. Wear tests indicated that F/M dual-phase ductile iron exhibited a significantly lower friction coefficient compared with directly quenched ductile iron. Additionally, the martensite amounts affected the tribological behavior of ductile iron significantly. Abrasive wear was predominant in ductile iron with small amounts of martensite, while delamination wear was the main wear mechanism in case of ductile iron with high amounts of martensite