Analysis of Field Responses to Low-Salinity Waterflooding in Secondary and Tertiary Mode in Syria

Abstract

Low-salinity water injection is an emerging IOR/EOR technique, applicable to mixed-to-oil-wet sandstone reservoirs. This paper describes the field response for two large fields: Omar (secondary flood) and Sijan (tertiary flood). The data were analyzed using analytical and numerical modelling tools. This included evaluation of scaling numbers, mixing and dispersion and calibration. Insight was obtained on relevant drive mechanisms. The responses to low-salinity flooding differ for the two fields: In Omar, a dual-step water-cut development was observed, which is characteristic for a change in wetting state. Our interpretation is that in this field, viscous forces provide the dominant drive mechanism, which is favorable to low-salinity flooding. We were able to history match the low-salinity response using a simple conceptual model.In Sijan, the low-salinity flood appears to be still immature and breakthrough of low-salinity water has not (yet) been observed. The reasons for the muted response thus far are explored, including a rather strong buoyancy effect caused by the higher permeability of the block, and the significant effect of injectant mixing with the highly saline aquifer. A proposal is made for a workflow on how to apply this analysis to future low-salinity flooding implementation in field cases.

Calcite Dissolution Behaviour During Low Salinity Water Flooding in Carbonate Rock

“…The Omar field has been flooded with low salinity brine over 10 years in secondary recovery [Mahani et al 2011]. From production data, a dual step water break through has been observed, which is indicated by Mahani et al (2011) as an effect of wettability alteration from oil to water wet.…”

“…From production data, a dual step water break through has been observed, which is indicated by Mahani et al (2011) as an effect of wettability alteration from oil to water wet. An incremental oil recovery of 10-15% OIIP is created by the wettability alteration.…”

“…Water with a salinity of 200,000 ppm was injected during the ten years of secondary flooding and water with a salinity of 500 ppm was injected during the tertiary flooding [Mahani et al 2011]. According to Mahani et al (2011) Chapter 2. Literature Review 7 the LSF flood is still immature and no low salinity water break through has occurred.…”

“…No clear LSF response has been observed yet from this field. According to Mahani et al (2011), this is probably due to the high contrast in salinities between the secondary and tertiary flooding, which creates significant mixing effect. This mixing of low salinity and high salinity brine inhibits the LSF effect.…”

Mechanistic Study of the Wettability Modification in Carbonate and Sandstone Reservoirs during Water/Low Salinity Water Flooding

“…The field response to low salinity water flooding as secondary and tertiary modes were also addressed in another research work by Mahani et al (2011). For one field, it was documented that dual step water cut is developed and the viscous force is the dominant mechanism which can be interpreted as a characteristic of change in wetting state; in contrast for another case study, the low salinity water flooding is immature and the breakthrough of low salinity brine was not yet observed due to strong bouncy effect caused by high vertical permeability of reservoir (Mahani et al 2011).…”