| BBZQ is a bottom water oilfield in a certain area of Kazakhstan,with reservoir porosity ranging from 25% to 35%,permeability ranging from 1.02 to 11100 × 10-3 ? m2,loose cementation and strong interlayer heterogeneity.At present,the biggest problem in oilfield development is serious water channeling and low water flooding recovery.Therefore,polymer+pre-cross-linked gel particles are used to drive oil.In practice,it is found that the effect of pre-cross-linked gel particles in use is unstable,and the application type,dosage,application concentration and technological process can not be well determined for the formation.Understanding the migration and blockage mechanism of pre-cross-linked gel particles is the basis to solve these problems.Based on the understanding of pore structure in the study area,this paper first evaluates the main properties of gel particles in the study area,and then studies the migration and sealing mechanism and influencing factors of pre-gel particles in the study area through microscopic model,quartz sand proppant sand filling pipe model and sand filling model in the study area,and obtains the following main understandings and research results:1.KJ-06 pre-crosslinked gel particles have good water swelling,temperature resistance and salt resistance,which meet the requirements of reservoir development in the study area.309#pre-crosslinked gel particles have poor water swelling and salt resistance,while Z-1#pre-crosslinked gel particles have poor temperature resistance.The larger the particle size of pre-cross-linked gel particles,the greater the change multiple of average particle size after water absorption and swelling;2.The compressive strength and elastic modulus of gel particles can be measured quickly and accurately by image method,and the elastic modulus measured by image method can reflect the deformation ability of pre-crosslinked gel particles more accurately;3.The migration modes of pre-crosslinked gel particles in porous media can be divided into direct passage,extrusion deformation passage,extrusion crushing passage,surface adsorption and release.The plugging modes can be divided into complete plugging and stacking/bridging plugging.The migration patterns of pre-gel particles with different properties in porous media are different,which are obviously related to the elastic modulus and compressive strength of pre-gel particles:(1)Pre-gel particles with large elastic modulus are mainly crushed through extrusion,bridging/stacking plugging,showing good injectability,weak plugging ability and erosion resistance;(2)Pre-gel particles with small elastic modulus are mainly extrusion deformation passing,shear crushing passing,adsorption and release,large particle plugging,stacking/bridging plugging,which show good injectivity,relatively uneven migration distribution in porous media and good plugging property;(3)Pre-gel particles with high compressive strength are mainly extrusion deformation,blocking by large particles,bridging/stacking blocking,showing poor injectivity,uneven migration and distribution of porous media,good blocking property and easy to completely block the pore throat;4.The plugging rate of 309# pre-gel particles ranged from 49.1% to 63.6%,with an average of 56.4%,showing good injectivity.The plugging rate of KJ-06 pre-gel particles ranged from35.3% to 93.9%,with an average of 59.8%,showing good injectability.The plugging rate of Z-1# particles ranges from 93.9% to 98.0%,with an average of 95.95%.The plugging rate is relatively high,showing poor injectivity;5.Pre-crosslinked gel particles with low elastic modulus have better plugging effect at low injection rate,while pre-crosslinked gel particles with high elastic modulus and high compression resistance have better plugging effect at high injection rate.Compared with the core pore throat size,the pre-cross-linked gel particles are too large or too small,which can not effectively block the reservoir.The matching pre-cross-linked gel particle size should be selected according to the reservoir core pore throat size;The best matching factors of 309# particles are0.632-0.759,KJ-06 particles are 0.644-0.789,and Z-1# particles are 0.742-0.891.The larger the mass concentration is,the stronger the plugging ability is,and the injection problem exists when it is too high;6.KJ-06 particles should be selected for deep profile control in BBZQ reservoir,with particle size of 140-170 mesh,mass concentration of 2300mg/L and injection pressure gradient of 0.025MPa/cm;309# particle is suitable for profile control and flooding in shallow layer,with particle size of 100-140 mesh and mass concentration of 3000 mg/L;The Z-1# particle should be plugged at the shallow part or closed mouth,with the particle size of 170-200 mesh,the mass concentration of 3000mg/L and the injection pressure gradient of 0.051MPa/cm.The research results of this paper laid a theoretical foundation for the use of pre-crosslinked gel particles in the study area. |
PDF Full Text Request