Analysis of design and technological parameters of gas-water ejector for associated gas utilization

The article is devoted to the ways of efficiency gains of the gas-water ejector, used for the injection of low-pressure associated gas into the reservoir through the reservoir pressure maintenance system for its utilization. Several alternative ways of designing the unit convergent sections for optimization and coefficient of gas utilization are analyzed in the article. The results of pilot tests of the units, the comparative analysis of the results, determined advantages and disadvantages of each modification and the range of application are set out in the article. In addition, the analysis of the ejection operation of the plant is based on statistical data from intermittent test of all process parameters of the unit. Basic parameters with the significant influence on the volume of gas utilized are determined in the article.
Materials and methods
The alternate design of the ejector was tested experimentally. On the basis of statistical methods technological parameters of the ejection unit were analyzed.
Results
Experiments of the alternate design of improved flow channels of the ejector parts (a nozzle with three through bores, a nozzle with a retractable needle, the unit of the mixing chamber) were carried out, advantages and disadvantages, a field of application were identified.
1) A nozzle with a retractable needle allows to change quickly the flow area of the nozzle, but the installation of the needle is characterized by difficulties, concerning with needle detent, that is the reason for some design improvements to provide rigid attachment;
2) According to the analysis of the nozzle with three through bores, the necessary condition for the installation of jet nozzle is changing a pump to heavier, taking into account the design of the flow area is characterized by a high level of hydraulic losses;
3) Integration of the cylindrical mixing chamber into the ejector design allows to increase the level of associated gas utilization, to stabilize its work, though the upgrade involves the use of facilities in the low-pressure injection into the well reservoir pressure maintenance system;
4) Elevated level of gas utilization is correlated to different conditions, not only basic (reducing of the pressure at the outlet of the ejector, increasing of water injection under the unchanged upstream pressure), but some others, for example, providing the increased pressure in the gas line. In the ejector unit, this parameter is the increased pressure in the gas line not lower than 5 atm. In addition, the correlation between the gas flow rate through the ejector and its temperature was identified; it was found that the temperature increasing above 29°C is usually followed by the increasing of gas fl w rate.
Conclusions
The comprehensive analysis of technological parameters of the unit, that can influence on the parameters of gas utilization was carried out. Necessary conditions of increasing the associated gas flow rate were found. Tests of the alternate design of the ejector (a nozzle with a retractable needle) were carried out in order to provide the possibility of the exit area versatile tuning and adaptation to changing parameters of the unit, particularly, water flow rate. This alternate design of the ejector was applied for a patent.