Experimental Investigation into Revaporization of Retrograde Condensate by Lean Gas Injection

Abstract Re-injection of produced gas is a common strategy to maintain pressure and to meet environmental regulations in gas condensate reservoirs and also to store gas until the market available. Although the best idea to prevent liquid loss is the full pressure maintenance development above the dew point pressure, the partial pressure maintenance process below dew point may be desirable for economic reasons, as the dew point pressures in some gas condensate reservoirs discovered in recent years is very high. In this case one major concern is whether gas cycling above the dewpoint is more profitable than below the dewpoint. Therefore, a knowledge of accurate condensate recoveries under two different development schemes is vital for making the accurate economic assessment and making final decisions. To the end, a series of experiments have been done to investigate the condensate recovery based on the above two different development strategies and quantitatively determine the revaporization efficiency of retrograde condensate by lean gas injection. First the gas injection below the dewpoint was performed in a long-core apparatus. In order to calculate the quantitative amount of the revaporized condensate, other two parallel tests of gas injection above the dew point in a long core system and gas injection below the dew point in the PVT cell were conducted as a comparative basis. The actual gas condensate fluid and a long core system are employed here. The gas condensate used is rich and highly waxy. As a complete study, the routine phase behavior is first detailed, including constant mass expansion and constant volume depletion. An interesting finding in PVT cell shows that lean gas can not only effectively revaporize the intermediate but also C20 plus components. Comparison of the tests in long-core system illustrates that more condensate above the dewpoint is recovered than below the dewpoint. This is consistent with the conventional idea that the full pressure maintenance is superior to the partial pressure maintenance according to the condensate recovery. It should be noted that all the condensate recoveries reported here in three runs don't include the additional withdrawal of condensate in the slowdown process to abandonment pressure.