Research Of Weak Gel Profile Modification In Caoshe Oilfield

Taizhou formation in Caoshe oilfield is characterized with high temperature, high salinity, and strong heterogeneity. The waterflooding effect was bad and carbon dioxide drive was used afterward.But the purpose to produce stably and enhance recovery wasn't achieved, because heterogeneity wasn't beneficial to carbon dioxide drive.After analysed,it is concluded that weak gel profile-modifying deeply is fit for Caoshe oilfield.On the basis of searching a number of documents, the theory is generalized which includes weak gel component, the gelation mechanism, the seepage character in porous medium, and the oil displacement mechanism, etc. Through simulating the condition in Caoshe oilfield, weak gel system is selected, and its performance is evaluated.Finally, the plan is given for weak gel profile-modifying. In this paper, the main recognition can be concluded as follows:1. Weak gel, a kind of weak gelation system with three-dimensional structure, is composed with low concentration polymer and cross-lingking agent, in which the intermolecular cross lingking is mostly and the intramolecular cross linking is secondary.It is an important technique in TOR,because it has dual effects that are profile control and oil displacement.2. Weak gel has a unique seepage character in porous medium.It is ease for it to enter into high permeability zones with high capacity channel,while it is hard for it to enter into low permeability layers,which indicates that weak gel can enter into heterogeneous lays selectively and have a seepage nature. Weak gel can also greatly reduce the permeability of water under the condition of residual oil saturation, but it has little effect on the permeability of oil in the condition of irreducible water.3. The weak gel system is choosed out for caoshe oilfield: polymer(1630s) 2000～3000mg/L,and organic aldehyde 2000～3000mg/L.The system has good gelation performances, and the greater the system concentration is, the higher the gelation viscosity is.4. It has also researched the saline and thermal stability, injection property, ageing stability, resistance factor, residual resistance factor, and so on. Experimential results indicate that weak gel has caused apparent sealing effect on high permeability core after gelatinating, which finally realises the purpose of profile control.So it can meet requires of Caoshe oilfield.5. The analysis of reservoir sensitivity and permeability distribution provides a criterion for selecting well and matching technologic measures of weak gel.The next step is to ascertain the thickness of sharp water takeup lays, the permeability, the crossflow zones, and its orientation, the correspondent injection-production relationship, and the tracer detecting technology between wells. On the basis above, it has given a detailed plan of weak gel profile-modifying which is quite fit for this reservoir.