Preparation And Property Evaluation Of Pre-formed Particle Gel For Heterogeneous Phase Flooding With Weak Alkali/Surfactant/Polymer

Daqing Oilfield is the biggest continental oilfield for chemical flooding.In the promoted application process for chemical flooding,polymer flooding has come to an end in certain blocks.It is of great urgency to enhance oil recovery factor after polymer flooding.Due to the heterogeneous physical properties of the reservoir,advantageous seepage channels of high permeability are formed during water and polymer flooding,resulting in low or invalid injection for subsequent development.Recovery factor after polymer flooding can be promoted in two ways.One way is to enlarge the sweeping efficiency for middle and low permeability layers.This can be realized by the PPG synthesized in the paper.The other way is to enhance the flooding efficiency for residual oil and this can be realized by ASP flooding.A combination of PPG and ASP flooding is formed in the paper to enhance the recovery factor for layers after polymer flooding.The main contents of the paper are listed below.(1)Synthesis and formulation optimization for PPGAn organic cross-linker,Methylene Bis Acrylamide,MBA,was applied and PPG was obtained by solution polymerization with alkaline hydrolysis.Synthesis parameters,including mass fraction of acrylamide,hydrolysis,content of cross-linker and initiator,varied to see their influences on product properties.The mass fraction for acrylamide was finally set at 25%.By narrowing the parameter scope,the elasticity was proper for PPG.Then an orthogonal experiment was carried out to optimize synthesis parameters.Ultimately,3 optimized formulations for PPGs were synthesized for further property evaluation.(2)Property evaluation for PPGsSeveral properties of optimized PPGs were evaluated in the laboratory.The seepage for optimized PPGs in man-made cores was evaluated by flowexperiments.Results indicated that PPG 3 could effectively block the high permeability core.Injection pressure was promoted and maintained at a high variation level for subsequent water flooding.It was obvious that PPG 3 could migrate into the inner part of the cores and the migration process for PPG 3 was“blocking-crushing-migrating”The interfacial properties for PPGs were evaluated.Results showed that in a relatively wide scope of petroleum sulfonate and Na2CO3 concentrations,ultra-low interfacial tension could be formed.The interfacial tension for PPG and ASP system could maintain at ultra-low level for a relatively long time.The flooding efficiency for PPG and ASP heterogeneous system was evaluated by parallel core flooding experiments.Results indicated that the fluid shunt fraction for the low permeability layers increased obviously.The recovery factor after polymer flooding could be enhanced by 18.86%.(3)Industrialized synthesis for PPGIndustrialized synthesis for PPG was carried out.Property evaluation of lab samples of 5~10Kg indicated good stability and repeatability for synthesis formulation.In the industrialized sample synthesis of 200 Kg and 1000 Kg,by optimizing parameters,properties of the products met the standards for lab products.In this paper,a complete process from lab research to industrialized production has been realized for self-developed PPGs.A pilot test for PPG-ASP heterogeneous flooding is to be carried out.The parameters for industrialized production are going to be adjusted due to the properties and needs of pilot test.PPGs are to be applied in the layers after polymer flooding.It is of great significance for PPGs to enhance the recovery factor for layers after polymer flooding.