Search

The productivity equation of a gas well is, in the final analysis, an expression that describes the relationship between the production of a gas well and its bottom-hole flowing pressure. There are two kinds of productivity equations in common use at present: binomial productivity equation and exponential productivity equation. Combined with the modified isochronal well test, the test data are interpreted, and it is found that the open flow rates calculated by the two productivity equations are basically the same when the pressure difference at the test point is large, and the deviation of the exponential productivity equation is large when the pressure difference at the test point is small. Using binomial productivity equation and modifying isochronous well test, we established the single-point deliverability formula for the Jingbian sector of the Yan’an gas field. The field experience formula and production data are used to verify it. Their average errors are 2.59% and 7.12%, respectively; and the coincidence rate of productivity evaluation is 90%. The one-point productivity formula established has high precision and is suitable for productivity analysis of gas wells in paleozoic reservoirs in the Jingbian sector of the Yan’an gas field. This paper provides insights into the one-point productivity evaluation and its future application in the gas field.

Information on interwell connectivity is important in reservoir field dynamic analysis. However, all conventional methods, such as the tracer test, interference well test, and numerical simulation, have disadvantages. These disadvantages include the length of time taken, high costs, and the effect on oilfield production. Thus, research focus has been directed toward the development of approaches that use production and injection data to obtain interwell connectivity data. Prevailing interwell connectivity models are sensitive to shut-ins, and their corresponding inversion methods are unreliable. The improved interwell connectivity model presented in this study exhibits enhanced robustness to shut-ins. The application of seepage theories and numerical simulation methods enables the main model parameters to absorb prior geological knowledge to characterize the reservoir and improve the initial estimate of connectivity. Corresponding inverse methods for model parameters are implemented based on Bayesian inverse theory and the projection gradient method and obtain greater robustness for the model parameter, compared with those in previous studies. Testing of a heterogeneous synthetic reservoir and a Z16 reservoir block demonstrates that the methodology can precisely determine the interwell connectivity and can be used in real oilfields. [ABSTRACT FROM AUTHOR]

Corona discharge is extensively researched due to the wide applications in the fields of electrostatic precipitator, flow control, thermal management, and so on. Previous researches observe that the characteristics of the corona discharge, such as the average current in the Trichel pulse regime, could be influenced by the airflow velocity. In this paper, the effect of the airflow rate on the corona discharge is further investigated by using a needle-mesh discharge structure. The experimental results show that the discharge is transferred from a large amplitude, long pulse interval time condition to a small amplitude, short interval time condition when increasing the airflow rate and, at the same time, the discharge region is shrunk toward the centerline of tube channel (i.e., shrinking regime). However, after a stable regime around a certain airflow rate, the above-mentioned parameters are changed toward the opposite direction and the discharge region is expanded, when further increasing the airflow rate (i.e., expanding regime). This nonmonotonous phenomenon has not been observed in literature before, and we further investigate it under different tube channel diameters. It is found that, under a larger tube channel diameter, the transition point (corresponding to the minimum pulse amplitude and interval time) moves toward a larger gas flow rate. The physical mechanisms for this phenomenon are analyzed by considering the transport effect by airflow under different Reynolds numbers. It can be caused by a comprehensive effect of the mass transfer, heat transfer, movement process of particles, and frictional loss in the discharge space. The phenomenon revealed in this paper is possibly utilized to improve the application of corona discharge under airflow. [ABSTRACT FROM AUTHOR]

The dielectric-barrier discharges (DBDs) under airflow have been widely used in the fields of airflow control, plasma-assisted combustion, and surface modification. Our previous work demonstrates that the discharge intensity under airflows could be adjusted by a discharge configuration with upstream and downstream electrodes. In this paper, a further investigation of discharges under airflows is processed with a multicathode DBD configuration. With the injection of airflows to the discharge region, the first upstream region produces a decrement of discharge intensity, while the following downstream region always provides greater discharge intensity than that of the adjacent upstream discharge region. An optimal discharge configuration is found by appropriately selecting the distances between the cathodes, wherein the last downstream region can produce maximum discharge intensity. The mechanisms are analyzed by considering the transport effect of airflows and the lifetime of charged and metastable particles. The charged and metastable particles are transported to the downstream region, and these particles always act as the responsible seeds to enhance the downstream discharges. In addition, due to the limited lifetime of charged and metastable particles, the enhancement effect may be weakened under long transport distances. Finally, potential applications for multicathode DBDs are also provided. [ABSTRACT FROM AUTHOR]