Abstract
A condensate gas reservoir is an important special oil and gas reservoir between oil reservoir and natural gas reservoir. Gas injection production is the most commonly used development method for this type of gas reservoir, but serious retrograde condensation usually occurs in the later stages of development. To improve the recovery efficiency of condensate oil in the middle and late stages of production of a condensate gas reservoir, a gas injection parameter optimization test study was carried out, taking the Yaha gas condensate reservoir in China as an example. On the premise that the physical experimental model and key parameters met the actual conditions of the formation, the injection method, injection medium, injection-production ratio, and other parameters of the condensate gas reservoir were studied. Research on the injection method showed that the top injection method had a lower gas-oil ratio and higher condensate oil recovery. The study of injection medium showed that the production effect of carbon dioxide (CO2) injection was the best injection medium, and the maximum recovery rate of condensate oil was 95.11%. The injection-production ratio study showed that the injection-production ratio was approximately inversely proportional to the recovery factor of condensate gas and approximately proportional to the recovery factor of condensate oil. When the injection-production ratio was 1 : 1, the maximum recovery rate of condensate oil was 83.31%. In summary, in the later stage of gas injection development of the Yaha condensate gas reservoir, it was recommended to choose the development plan of CO2 injection at the top position with an injection-production ratio of 1 : 1. This research can not only provide guidance for the later formulation of gas injection plans for Yaha condensate gas reservoirs but also lay a foundation for the research of gas injection migration characteristics of other condensate gas reservoirs.
Highlights
With the continuous improvement of the level of exploration technology and exploration degree at home and abroad, the proportion of condensate gas reservoirs discovered is increasing year by year
The results show that for condensate gas reservoirs rich in condensate oil and with a large ground pressure difference, the development effect of the top cycle gas injection after depletion development to the dew point pressure is better
The use of different gas injection methods in condensate gas reservoirs will have a serious impact on the recovery rate and recovery rate of condensate gas and condensate oil
Summary
With the continuous improvement of the level of exploration technology and exploration degree at home and abroad, the proportion of condensate gas reservoirs discovered is increasing year by year. Condensate gas fields occupy a important position in the development of gas fields in the world. Condensate gas reservoir is different from ordinary oil reservoir or gas reservoir; it has the dual characteristics of oil reservoir and gas reservoir [1]. Due to the special fluid phase characteristics, its extraction technology and development difficulty are much more complicated than general gas reservoirs and oil reservoirs [2,3,4]. Condensate oil will separate out of the gas phase and accumulate in a large amount in the nearwellbore zone, which will block the original seepage pores, thereby reducing the final recovery rate of condensate gas and condensate oil [5,6,7,8,9]
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