The aging process of petroleum wells causes reduction in reservoir pressures and an increase in the hydrostatic head of liquid in the production tubing. When used in gas field applications, aqueous surfactants containing foamers and condensate foamers have successfully unloaded well fluids and increased production. However, neither technology is effective for crude oil wells.
Research to develop a black oil foamer (BOF) was conducted utilizing laboratory foam column testing. The application of an effective BOF could provide several benefits to oil producers. Potential benefits of a BOF include reducing liquid loading in flowing oil wells, maximizing oil and gas production, minimizing slugging and downtime of cycling wells, improving suboptimal gas lift performance, and helping restart wells temporarily shut in due to liquid loading or maintenance.
To meet numerous field application requirements, the BOF needed to be effective over a wide range of crude oil, and be suitable for batch applications and continuous applications by umbilical, capillary, or gas lift. In addition, the BOF also needed to be thermally stable at wellbore temperatures and pressures, and not negatively impact asset integrity, and be non-emulsifying. The BOF also needed to create a foam that was sufficiently stable to unload liquid from the well but not so stable that common de-foamers could not resolve it. This paper describes several successful field applications of the new BOF.
Results from two field applications of the BOF are discussed in this paper. The first application discussed occurred at a land-based well in south Texas. This well produced intermittently and experienced a rapidly decreasing production curve. After switching from the incumbent aqueous foamer to the BOF, the duration of continuous production increased from 7 to 12 days, and increased average production rates of oil and gas increased from 13 to 100 BOPD and 122 to 400 Mcf/D, respectively.
Subsequently, the BOF was applied into a subsea oil well located in the Gulf of Mexico. This well experienced severe slugging and a short production cycle; the well flowed intermittently for only two weeks. Consequently, the well needed to be shut in for six months to allow enough gas pressure to build up for the well to flow. After the well had been shut in for two months, the BOF was applied via umbilical and it successfully unloaded the flow line and riser. The production cycle increased from two to eight weeks and annualized oil recovery from 100,000 to 550,000 barrels oil. The foamer did not negatively impact oil/water separation or overboard water quality.