Study on the Plugging System of the Lower Ancient High Loss Zone in Changqing Gas Field

At present, in the workover operations of old gas wells in the Changqing Gas Field, due to years of exploitation in the production layer, pressure deficits, and general leakage during the well killing, the well must be plugged before the well can be killed. In particular, the fracture-cavity type fractures of the lower paleocarbonate reservoirs have serious leakage. Traditional plugging materials and traditional plugging materials and methods have some limitations in dealing with leakage problems. Therefore, a composite plugging system using polymer solution as the base carrier fluid, multi-particle size rigid particles, expandable particles and modified fibers is developed. Its formula is: water + 2% polyacrylamide + 0.1% N, N-methylene bisacrylamide polymer gel is the base carrier fluid;the formulation of the particle plugging agent was continuously optimized through the CDL-II high temperature and high pressure dynamic and static plugging ability to plug the core. The final formulation of the plugging agent is: 1) 20% rigid particles (5 mm, 1 mm, 0.5 mm CCP-3 ratio 4:2:1) + 1% 3 mm expanded particles SMK-1 + 1% 1 ~ 2 mm fiber SRXW-10;2) 20% rigid particles (3 mm, 0.1 mm, 0.05 mm CCP-3 ratio 3:2:1) + 1% 3 mm expanded particles SMK-1 + 1% 1 ~ 2 mm fiber SRXW-10. The water swelling multiples of the granular plugging agent in salt water are all above 7 times, which meets the requirements of leak-proof plugging operations under high salinity;3% HCl is selected as the gel breaker, and the plugging system has a gel breaking rate of 95%;through the water plugging and profile control experimental system, the sand-filled pipe is used to simulate the plugging effect under high temperature and high pressure, and the plugging system can be sealed for 5 days at a high temperature of 110°C and a high pressure of 20 MPa to achieve a good plugging of the formation. It is expected that the developed plugging system has a good application prospect in future workover operations.

Response Characteristics of Flexible Risers in Offshore Compressed Air Energy Storage Systems

With the rapid development of marine renewable energy technologies, the demand to mitigate the fluctuation of variable generators with energy storage technologies continues to increase. Offshore compressed air energy storage (OCAES) is a novel flexible-scale energy storage technology that is suitable for marine renewable energy storage in coastal cities, islands, offshore platforms, and offshore renewable energy farms. For deep-water applications, a marine riser is necessary for connecting floating platforms and subsea systems. Thus, the response characteristics of marine risers are of great importance for the stability and safety of the entire OCAES system. In this study, numerical models of two kinds of flexible risers, namely, catenary riser and lazy wave riser, are established in OrcaFlex software. The static and dynamic characteristics of the catenary and the lazy wave risers are analyzed under different environment conditions and internal pressure levels. A sensitivity analysis of the main parameters affecting the lazy wave riser is also conducted. Results show that the structure of the lazy wave riser is more complex than the catenary riser;nevertheless, the former presents better response performance.

Synthesis and Performance Evaluation of Anti Temperature and Salt Resistant Polymer Filtrate Reducer

In the experiment,the filtrate loss of synthetic fluid loss control fluid was recorded in room temperature and high temperature in the composite brine base and sodium chloride brine base slurry,and compared with the filtrate loss before base polymer addition.In this way,the effect of filtration loss and salt resistance and temperature resistance of synthetic polymers were evaluated.The influence of the synthesized polymer on the rheological properties of the composite brine was also evaluated by determining the viscosity of the drilling fluid added to the base slurry and polymer.In the end,the structure of the synthetic polymers was characterized through the infrared spectrum,which initially analyzed through the mechanism of its function in reducing the filter loss.Finally,the products produced according to the recipe are given to the site and added to the two wells to record the drilling fluid performance data.

Epidemiological feature analysis of SVEIR model with control strategy and variant evolution

The complex interactions were performed among non-pharmaceutical interventions,vaccinations,and hosts for all epidemics in China's Mainland during the spread of COVID-19.Specially,the small-scale epidemic in the city described by SVEIR model was less found in the current studies.The SVEIR model with control was established to analyze the dynamical and epidemiological features of two epidemics in Jinzhou City led by Omicron variants before and after Twenty Measures.In this study,the total population(N)of Jinzhou City was divided into five compartments:the susceptible(S),the vaccinated(V),the exposed(E),the infected(I),and the recovered(R).By surveillance data and the SVEIR model,three methods(maximum likelihood method,exponential growth rate method,next generation matrix method)were governed to estimate basic reproduction number,and the results showed that an increasing tendency of basic reproduction number from Omicron BA.5.2 to Omicron BA.2.12.1.Meanwhile,the effective reproduction number for two epidemics were investigated by surveillance data,and the results showed that Jinzhou wave 1 reached the peak on November 1 and was controlled 7 days later,and that Jinzhou wave 2 reached the peak on November 28 and was controlled 5 days later.Moreover,the impacts of non-pharmaceutical interventions(awareness delay,peak delay,control intensity)were discussed extensively,the variations of infection scales for Omicron variant and EG.5 variant were also discussed.Furthermore,the investigations on peaks and infection scales for two epidemics in dynamic zero-COVID policy were operated by the SVEIR model with control.The investigations on public medical requirements of Jinzhou City and Liaoning Province were analyzed by using SVEIR model without control,which provided a possible perspective on variant evolution in the future.