Alkali-Surfactant-Polymer ASP Flooding Field Test Using Horizontal Wells: Design, Implementation and Evaluation

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Abstract An Alkali-surfactant-polymer (ASP) field test using 2 horizontal injectors and 3 horizontal producers (HASP) was conducted to check the combination of horizontal wells and ASP flooding technology as well as recovering remaining oil in higher position due to gravity effect. Designed chemical slug is 0.675PV with four slugs (0.0375PV pre-slug high concentration polymer+ 0.30 main ASP slug+0.15PV vice ASP slug+0.20PV post polymer slug). This four-slug design was very common in many previous field tests, although this practice remained to be optimized. ASP slug viscosity was designed 40 cP at injectors wellhead and ultra-low interfacial tension (IFT) between ASP and Daqing oil was basic requirement. Actual viscosity of chemical slugs was well implemented, while the chemical slug size was increased. Reference water flooding started in January 2008 until May 2009 when pre-slug started. ASP slug started in January 2010, and finished in April 2012. Post polymer slug started in April 2013 after vice ASP slug. As of December 2015, 0.919 PV chemical slug with dosage 1890.23 mg/LPV and 0.323 PV post water flooding have been injected. Incremental oil recovery factor (IORF) is 29.66% original oil in place (OOIP) and IORF in main ASP injection stage is 17.46%. Vice ASP and post polymer slug contributed an IORF of 4.63% and 3.64% OOIP respectively. HASP IORF was 10% larger than the other vertical well ASP (VASP) with an IORF of 20% OOIP. Water cut decrease was 3.7% higher than VASP. Injection index and fluid production index were higher than VASP. Chemicals breakthrough was later than VASP. Horizontal well pattern was predicted better than combination of vertical and horizontal wells. However, up to present, whether HASP has been widely used in Daqing remains unknown. This test indicated that horizontal wells can be used to recovery gravity caused bypassed remaining oil in the upper layers even separate layer injection is adopted. Gravity effect should be given more attention for thick layers or multiple layers. Incremental oil recovery in HASP can be as high as 30% OOIP under Daqing reservoir condition.