Study On The Cooperation Of Different Surfactants With Oil Main Layers

Through efficient development in Daqing Oilfield during the past40years, wemeet a stage with high content of water in oil mail layer. It has been predicted that theultimate oil recovery is only35-40%with water injection method. If we use polymerflooding technology, oil recovery will increase more than10-12%. Now Alkali/surfactant/polymer ASP flooding technology can further improve the efficiency andbecomes the major tertiary oil recovery technology.From “the Eighth Five-Year Plan”, ASP flooding technology has been practised inDaqing oil field, some experiments have been made in several mines, and someapplication fruits have been obtained. However, due to using alkali in ASP floodingsystem, some problems appeared such as the filthy on shaft and difficulty to handlethe fluid product. Therefore, how to dissolve these problems becomes a researchhotspot in recent years. At present, some research groups have developed severalsuitable surfactant with weak base or alkali free, even some polymeric surfactantproducts. Until now it is necessary to study on the cooperation of different surfactantswith oil main layers on the condition of alkali, soft alkali and alkali free system.In this work, we practice and study the properties of the surfactants with base free,strong base, weak base and polymeric surfactant products, separately. We try to findthe effect on reservoir flooding system to study the compatibility, and different typesof surfactant flooding system formulation and performance evaluation of flooding,and provide a theory for oil field applications.1. We selected different types of surfactant condition with base free, strong base,weak base and polymeric surfactant products, the viscosity, surface tension, stability,emulsifying properties and adsorption properties of surfactants and other physicsproperties were characterized. The results indicate that, JBJ Ⅲ molecules possess thelargest area, petroleum sulfonate molecules possess the smallest area, and the amountof surface adsorption for petroleum sulfonate is maximum, but JBJ Ⅲ shows theminimum amount of surface adsorption. With increasing the salinity degree, thecritical micelle concentration (cmc values) of multi-alkyl phenyl sulfonate will bereduced; This improves the activity and the adsorption amount of the surfactants; JBJⅢ gives the minimum dynamic surface-activity, and emulsifying properties of surfactants are improving depending on the increaing carbon number of alkane groupsfor the multi-alkyl phenyl sulfonate, the binary surfactants, petroleum sulfonate, andpolymeric surfactant. The petroleum sulfonate and polymeric surfactant JBJ Ⅲexhibit more excellent emulsifying properties than the others due to possessing highermolecular weight. Thus, the increase of the system’s viscosity results in the improvingstability of the emulsion oil phase.2. The cooperation of four different surfactants with oil main layers has beenstudied. The effect of a variety of ions on the surfactant activity has been examined.The content and structure of the target layer has been characterized by atomicabsorption spectroscopy and XRD. Meanwhile, the solubility and rheology propertiesof surfactants have been studied. The results indicate that, the basic composition ofthe rock for the target layer consist of albite and anorthite, PI and SⅡ7-8mainlycontain siltstone, Gaotaizi reservoir is silty mudstone. The mineral composition ofthese rocks is very complex, which particle size is relatively small at0.05mm. Therange of clay content is wide from8%to40%. Siltstone has generally good sorting,rounded relatively poor. With the increase of surfactant concentration, the temperaturehas to be gradually increased in order to resolve the surfactants, especially a hightemperature for multi-alkyl phenyl sulfonate and petroleum sulfonate. As a nonionicsurfactant, the binary surfactants give a lower temperature than anionic surfactants.3. The composite and properties of flooding oil systems were studied. The results ofindoor artificial experiment indicate that, the oil recovery of the core flooding can befurther enhanced up to22.5%~20.9%for alkali ternary system, comparing to thewater-drive flooding; and even up to25.9%~24.4%for base free system, whichindicate that we have achieved good results on the improvement of the displacementefficiency in the binary complex system; on the other hand, the oil recovery of thecore flooding can be further enhanced up to22.7%~22.8%for the weak base ternarysystem; and up to25.8%~26.4%for polymeric surfactant of JBJ Ⅲ system. Theseresults indicate that binary complex and polymeric surfactant of JBJ Ⅲ systems canimprove the oil recovery significantly.4. Indoor natural core flooding experimental results show that, comparing to thewater-drive flooding, the oil recovery can be further improved up to15%or more forthe ternary system containing strong base; and up to20%or more for binary complexsystem, and to13.1%for the weak base ternary system; the oil recovery can be further enhanced up to10.0%for polymeric surfactant of JBJ Ⅲ system. Therefore, thebinary complex system can further improve the most oil recovery comparing to thewater-drive flooding.5. According to the above results, it has been shown that in order to improve the oilrecovery, surfactants of binary complex system can be chosen to use for PⅠ1-4-2oillayers, and weak base ternary systems and polymeric surfactants can be used for S Ⅱ7-8A oil layers, and strong base ternary systems for S Ⅱ7-8-B oil layers, and then itis binary complex system with strong base is suitable for Gaotaizi oil layers.