Sustained production is needed to satisfy the contractual demands of both Trinidad's domestic and LNG markets. To unlock the value of existing fields on production, comprehending the case histories of produced water drive reservoirs is necessary.
This study analyses production, reservoir and well data to understand trends in 12 water drive gas reservoirs from production to abandonment. These reservoirs were produced by 16 wells, from 5 fields located off the South East coast of Trinidad.
From the analysis, relative permeability Corey exponents were matched to fractional flow curves in a numerical simulator. The Buckley-Leverett-Wedge (B-L-W) technique was applied to predict the flooding order of the reservoirs, but was not found to be reliable because of its inability to compensate for layering and thick reservoir intervals. Nevertheless, the shape of the relative permeability curves could be used in some cases to identify a general grain size distribution. The endpoint values of the water curves in particular were correlated with the water-wettabilities of the reservoirs.
It was discovered that Recovery Factor (RF) before Water Breakthrough (WBT) was better with the high production rate reservoirs. Meanwhile improvement in RF after WBT depended on having a higher initial gas column. The pre-WBT result may have been caused by successfully outrunning the aquifer. The effect of increasing aquifer size was to lower RFs.
Single well completion reservoirs' WGR profiles depended on completion orientation. Vertical completions experienced WBT between 80 and 85 percent RF compared to horizontal and deviated wells at greater than 95 percent RF.
At conditions close to abandonment by water-out, phenomena such as liquid loading and condensate blocking were prevalent in a few reservoirs based on production trending.
A study limitation that may have led to incorrect conclusions was the inability to keep all other variables constant whilst manipulating only one. This could be remedied by a study with a larger number of reservoirs.