A Field Trial to Assess Asphaltene Related Production Impairment—Marrat Reservoir, Magwa Field, Kuwait

Abstract

Asphaltene deposition in the reservoir, wellbore and facilities has long been recognized as a problem in the Marrat reservoir in the Magwa field, Kuwait. One option of avoiding asphaltene problems in the reservoir, including the near wellbore region, is to maintain reservoir pressure and flowing BHPs above the asphaltene onset pressure (AOP). Given that there is a large pressure difference between AOP and the bubble point pressure and that natural flow is possible at pressure well below AOP, there may be economic benefits in operating the reservoir at pressures below AOP. Benefits relate the reduced and delayed costs of water injection facilities. There may also be some additional recovery related to fluid expansion. Potential problems relate to possible adverse changes to relative permeability due to asphaltene related wettability changes, productivity impairment due to near well-bore asphaltene deposition and increased asphaltene problems in the wellbore. The second and third of these potential problems have been assessed by a field trial. This paper describes the selection of a candidate well and the design of a field trial to assess these problems. The selected well was produced first with FBHP well above the AOP. Asphaltene deposition in the tubing was monitored, fluid samples were taken and pressure transient tests were performed to diagnose well inflow performance. No decline in well productivity was seen in this period. Asphaltene deposition in the tubing was a problem and the well required cleaning during this period. The well was then produced at high rate, with flowing BHP well below AOP and a similar surveillance program was carried out. Finally the well was returned to low rate production. Analysis of the data from the high rate and subsequent low rate production periods indicated that there had been a limited decrease in well productivity. These data also showed that asphaltene deposition in the tubing was less of a problem during the high rate test than during the preceding low rate test.

Unified Model to Predict Asphaltene Deposition in Production Pipelines

“…As can be seen, the thickness profile decreases with increasing the flow rate. The same behavior was witnessed in Al-Qattan et al's 26 field study. As stated earlier, sticking probability decreases with increasing the oil velocity, resulting in a lower deposition rate and thickness.…”

Review of Asphaltene Deposition Modeling in Oil and Gas Production

“…Al-Qattan et al 36 presented a field trial that was designed to study asphaltene deposition near a wellbore and in the wellbore at the Marrat reservoir in Magwa field, Kuwait. Three different scenarios were considered: production with a FWHP below the AOP, a high rate of production with FBHP below AOP, and a low rate of production with FWHP below AOP.…”

“…(1b) Chokes can be used to promote a higher velocity that prevents the deposition of asphaltenes . In addition, entrainment reduced asphaltene deposits at high velocities as a result of its ability to break the large particles and move them along the flow. , (2b) Asphaltene aggregation does not imply the presence of asphaltene deposition . The authors suggest such behavior based on field trial and experience.…”

Analysis of the Modern State of Researches on Deposition of Asphalt-Resin Substances, Paraffin and Modeling Methods Review Part I: Precipitation of Asphaltenes

“…The recent increase in the number of scientific publications [61][62][63][64][65][66][67][68][69] devoted to a detailed analysis of various approaches to modeling RAC by world scientists proves the importance and prospects of developing improved mathematical models for predicting RAC.…”