Chemical Enhanced Oil Recovery, Improving Asset Performance
In March 2014 Pi-Cubed Process Systems Ltd. was approached by our Client to help review field performance and efficiency of a Chemical Enhanced Oil Recovery (EOR) project. This heavy oil ASP (Alkali Surfactant Polymer) project had achieved oil production in line with expectations for the first three years but subsequent production had fallen significantly below predictions with a continuing downward trend.
- 20% increase in field production with zero increase in water cut %
- 11% reduction in chemical costs
- Zero capital equipment spend
A three phase strategy was suggested to our Client encompassing data analysis, field assessment and optimization. The data analysis phase included a comprehensive review of the original laboratory evaluation, field development, known properties of the reservoir, historical chemical injection data, historical production history data and the data gathered by the Client during the trial phase predating the commercial chemical flood.
The field assessment phase included sampling and chemical analysis of the injection fluid, review of the composition of blended chemistry both at the polymer blending plant and at injection points around the field, along with detailed review of facility operating conditions.
Optimization phase used analysis of the data captured in the first two phases to make operational adjustments to the field including polymer blending practices, flow control adjustments and monitoring improvements.
Production data and field samples showed that a portion of the field had advanced to early stages of water breakthrough as predicted in initial study findings. A further portion of the field showed early signs of stimulation however, injectivity and production were low and coupled with high injection pressures suggesting local reservoir heterogeneity effects. The larger portion of the field demonstrated mid-life chemical flood symptoms including low levels of water and chemical breakthrough yet production was lower than the reservoir model had predicted.
Blended chemical samples showed variability both in composition and physical properties across the field. It was determined that a degree of the physical variation was due to subtle differences in mode of operation and fluid transport distances however, composition differences were attributed to fluctuations in operation of the polymer blending facility. A comprehensive review of the operation and historical data of the polymer blending facility was subsequently carried out. It was verified during this analysis that fluctuations on control parameters were resulting in wide variation of the injection fluid’s chemical composition. This compositional variability was the greatest factor in the variation in injection fluid physical parameters across the field.
Operational modifications to optimization process parameters were recommended to the Client based on discussions with field operations personnel and field technical services. A follow up plan was put in place to monitor production data over the following period to confirm that field and facility optimizations achieved the desired result of stabilising production levels.
Results and Conclusion
Based on Pi-Cubed’s review of the Client’s field data and operations changes were implemented to the Client’s polymer blending facilities that resulted in improved consistency of their injection fluid. Improvement of the chemical and physical properties of the polymer blend led to a reversal of the production decline over the next three months resulting in a 20% increase in field production from 270 m3/d to 325 m3d with no net increase in water cut %.
Additionally, the modifications to the polymer blending facility led to a reduction in overall chemical usage and as a result reduced supplier and operational costs. Prior to facility modifications polymer usage was 122 tonnes per month, after changes were implemented, polymer usage was reduced to 109 tonnes per month saving 11% on raw material and associated transportation costs.
At the end of the three-month trial period it was determined that not only had the adjustment in chemical composition achieved a substantial positive effect on production and reversed the field production decline, it had allowed the Client to reduce the overall chemical usage and resulted in reduced capital costs.
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