A Comprehensive Downhole Capillary Surfactant Injection Screening & Optimisation for Liquid Loaded Gas Wells

Abstract

Abstract Depletion of the reservoirs leads to a decrease in field production rate. Wells production rate continue to drop below the minimum critical velocity, at which point the liquid that was previously carried upward by the gas begins to fall back. The produced liquid accumulates in the well creating a static column of liquid, therefore creating a backpressure against formation pressure and reducing production until the well ceases production. Down hole Capillary Surfactant Injection (DCSI) is installed on the wells to overcome the liquid loading symptom by generating foam, thereby reducing the surface tension, lowering the fluid density, and lowering critical rate. This paper discusses the improvement to obtain higher success ratio of DCSI installation project on the observed field. Analysis and improvement is done to improve the success of DCSI installation through a comprehensive wells screening, continuity laboratory test, and field optimisation. The screening including the selection of liquid loaded wells & laboratory test (foam test, pH, and salinity test) were corrected with the actual temperature to obtain an accurate foam performance. Correlation is generated to correct the effect of foam build rate and decay rate against critical parameters. Validating well performances with the results of laboratory tests is conducted by continuously field optimisation. The laboratory test is significantly important to screen DCSI well candidate. Surfactant concentration, temperature, & condensate content are critical variables for foam build up and decay performances. Uncertainty variable and un-matching well performance previously not assessed can be reduced by these improvement steps, thus increasing the success ratio DCSI project. The improvement DCSI screening proposed is used as a reference to start the DCSI project to obtain higher success ratio.