Studies On Synthesis Andapplication Of Pre-Formed Particle Gel For EOR

At present there is a strong demand in Shengli Oilfield to improve the oil recovery in thereservoirs under post-polymer flooding stage,(the) reservoirs with high temperature and highsalinity, and/or the heavy heterogeneous reservoirs.Consequently, there is an urgent need forEOR chemicals that are heat resistance and salt tolerable as well as exhibiting excellentperformance on profile control. Thus B-PPG (Branched Preformed Particle Gel) with aspecial structure which has its partial long chain branching connected to its partial3Dcross-linked network.It was designed and developed by applying dimethylaminoethylmethacrylate (DMAEMA) as a functional monomer to assist potassium persulphate-sodiumbisulfite as redox initiator. The branched points and branched chains of B-PPG were provenby1H NMR. The application performances in EOR of B-PPG were evaluated. B-PPG showsexcellent results in both the rheological properties and the migration ability as well as anoutstanding fluid diversion since it can play in situ profile control dynamically during itspenetration along porous media in the reservoir through repeating the piling up-plug-pressurerising-extending and deforming to pass proceeding at porous throats. The design thought ofHeterogeneous Combination System which co-exist both in the viscoelastic body phase andthe liquid phase was proposed according to micro displacement characteristic of polymerflooding, surfactant-polymer flooding and B-PPG flooding, consisting of B-PPG, surfactantsand polymer. Heterogeneous combination system for a post-polymer flooding reservoir atZhongyi Block, Gudao Oilfield was designed based on the interaction between the chemicals.It shows that the percolation paths are blocked alternately thus resulting in dynamic in-situfluid diversion to displace more oil during micro displacement experiment of HeterogeneousCombination System. In conclusion, the Heterogeneous Combination System shows biggerincrements of injected pressure rising, water cut decline and oil recovery improving comparedwith polymer flooding and SP flooding as a result of B-PPG’s outstanding performance onfluid diversion thus adjusting the inhomogeneity of the reservoir formations and formationswith relatively medium or lower permeability are activated sequentially at macro displacement experiments. A pilot site was screened at Zhongyi Block in Gudao Oilfield andwas followed by a field test. So far, obvious water cut decreases and oil production increaseswere achieved in the pilot.There are6production wells show oil rate response among10production wells in the central area of the pilot, with average daily oil production of a singlewell from2.0t/d to5.9t/d, and the overall water reduced from96.3%to88.9%. Theapplication results showed that Heterogeneous Combination System is initially successfullyand has good potential in post-polymer flooding reservoirs.