A Study And Application Of Weak Gel Profile Modification Agent Of Phenol Formaldehyde Resin Crosslinked Polyacrylamide

Weak gel profile controlling and driving is a kind of recently developed new technique integrating profile controlling and oil driving. It has strong practicability. Weak gel is used as deep liquid turning agent with particular capability to amend heterogeneity in the deep of high or super high water bearing reservoir, improve water-injecting exploitation effect and gets succeed oil field applications in recent years. Then this technique gets more and more people attention.Weak gel is a kind of gelatin system formed by low concentration polymer and cross-linking agent. The polymer concentration is higher than that of polymer driving liquid and add little cross-linking agent. This kind of gel has definite viscosity, good elasticity or tenacity and relatively low strength. Its sweeping effect in stratum is dynamic. It can enlarge sweep volume and improve oil-driving efficiency in greater range.We make synthetical water dissolved phenol-formaldehyde resin cross-linked with PAM. Using ultraviolet spectrometry and viscosity means, the lowest polymer concentration of 600mg/L can be get in weak gel system. To Weak gel system, dynamic viscosity can distinguish strength of gel. When elastic modulus G' >0.1 Pa, can use dynamic surging means to measure gel strength.Research on the prescriptions of phenol-formaldehyde resin/PAM prescription, and choose out the best prescription is: PAM 0.3%, phenol 1.1%, cross-linking agent 1.2%, regulator 0.4%. To study on the affecting factors of prescription, gel strength is getting greater and gel-growing time is getting shorter with temperature. Salinity can improve gel strength. The influence of 2 valences caution is greater than that of 1 valence caution. Gel system grows to be gel, maintain it different marinating medium with different pH and salinity, will not appear gal-breaking phenomena. It was shown that the weak gel system has preferable stability.Porous medium has shear effect to weak gel. When viscosity is sheared to 25% of the primary, it will not continue to drop. When shear stops, the viscosity can gets back to over 85% of the primary. Double pipe driving tests show that weak gel has dual effect of profile controlling and driving. It can come into high osmotic large pores firstly. The weak gel not only can resolve the portrait conflict in thick stratum, but also can resolve the plane conflict, enlarge sweeping volume and improve driving efficiency. Weak gel has determinate selectivity to cores with different permeability. Its selectivity has relation with permeability level difference of double core groups and also is decided by permeability.In order to improve plugging capability of weak gel profile controlling agent to high osmotic cores, commonly add some solid grains into it. When the diameter ratio of pore and grain is 7.5 to 14, grains have relative better plugging capability to cores. In order to assure steadily injecting, wesuggest that solid grains adding quantity should be over 8%.Concluded out 5 kinds of oil-driving mechanism of Weak gel: the weak gel can selectively come into high osmotic large pores firstly; weak gel can make latter liquid turning; weak gel can overcome Jamin's effect to drive oil; after gel transited mainstream channel quickly, it can produce a negative pressure region, ambient remaining oil can be aspirated and join into oil stream; oil drops before driving front gather and form oil wall.On-spot tests show that take profile controlling before injecting polymer can get better effect, improve polymer-injecting exploiting effect. Mathematical model and on-spot tests show that profile controlling can improve oil recovery by 3%.