Kazakhstan journal for oil & gas industryKazakhstan journal for oil & gas industry2707-42262957-806XKMG Engineering10899910.54859/kjogi108999ANALYSIS OF THE EFFECTIVENESS OF SURFACTANT APPLICATION IN ENHANCED OIL RECOVERY METHODSRakhmetBirzhan Gabidenulybirzhan.rakhmet01@gmail.comhttps://orcid.org/0009-0006-9394-7624kbtu821505202608062026Copyright © , Rakhmet B.G.<p><strong>Abstract (eng.). </strong>The decline in oil recovery at late-stage oilfield development is one of the most pressing challenges in the petroleum industry. The oil recovery factor (ORF) under conventional waterflooding typically does not exceed 35–40%, leaving a significant volume of residual oil trapped by capillary forces in the reservoir pore space. Surfactants (surface-active agents) applied within chemical enhanced oil recovery (Chemical EOR) methods enable the reduction of oil–water interfacial tension (IFT) to ultralow values and the alteration of rock wettability, thereby mobilising residual oil that cannot be extracted by hydrodynamic pressure alone. This study presents laboratory-based experimental results on the selection and evaluation of surfactant systems under the reservoir conditions of X Field (western Kazakhstan). Compatibility tests, incoming quality control, Bottle Test demulsification studies, and core-flooding experiments were conducted on six surfactant samples and four core models from the Cretaceous and Jurassic productive horizons. It was established that alkaline-surfactant-polymer (ASP) flooding with 0.02% lauryl sulphate + 0.6–0.8% NaOH + 2,500–3,000 ppm HPAM polymer provides an incremental ORF of 17.7–19.2% above baseline waterflooding. Key factors influencing surfactant performance — reservoir temperature, water mineralisation, polymer concentration, and rock porosity–permeability characteristics — were identified and systematically analysed. An economic assessment confirmed the high commercial viability of ASP flooding technology at the studied field.</p> <p><strong><em>Keywords: </em></strong><em>surfactant, EOR, chemical flooding, ASP flooding, interfacial tension, wettability alteration, heavy oil, oil recovery factor, X Field, Kazakhstan, HPAM, core flooding, capillary number.</em></p>surfactantenhanced oil recoveryChemical EORASP floodinginterfacial tensionwettability alterationheavy oiloil recovery factorHPAMcore floodingX FieldKazakhstanББЗбеттік-белсенді заттармұнай өндірісін арттыруChemical EORASP-суландыруфазааралық керілусуланужоғары тұтқырлы мұнаймұнай өндіру коэффициентіГПААфильтрациялық зерттеулерX кен орныҚазақстанПАВповерхностно-активные веществаувеличение нефтеотдачиChemical EORASP-заводнениемежфазное натяжениесмачиваемостьвысоковязкая нефтькоэффициент извлечения нефтиГПААфильтрационные исследованияместорождение XКазахстан