| After water flowing out of the horizontal well,the water cut rises rapidly,which makes it easy to flood and water channeling.Moreover,after water flowing out,it is difficult to find the water outlet point and effectively block off.In this paper,the improvement of water plugging technology is proposed.Firstly,the wellbore is generally blocked without determining the specific water outlet point.Then,the plugging agent is drilled from the middle to continue the development and production under the condition of semi-plugging.Based on this water blocking technology,a kind of general plugging agent suitable for horizontal wells was developed by combining organic polymer and inorganic rigid reinforcing particles and taking into account the high stiffness and strength of inorganic materials as well as the high toughness of organic materials,the composite of the two at the nanometer scale was achieved,so as to enhance the mechanical properties and stability of the material.In this paper,three kinds of long chain alkylammonium cation intercalation agents and exchangeable cations between montmorillonite layers are used for ion exchange reaction,which can effectively expand the lamellar spacing of montmorillonite,make organic groups cover the surface of montmorillonite lamellar layer,and improve the compatibility between the surface of montmorillonite and organic matrix?The optimal synthesis conditions were determined as:the addition of intercalation agent was 100%of montmorillonite CEC,intercalation time was 1.5 hours,The intercalation temperature was 65??The lamellar spacing of OMMT modified with alkyl ammonium salt was approximately 1.5 times that of unmodified montmorillonite,and the lamellar spacing was about 2.2 nm?The DTG curve shows that the decomposition rate of organic montmorillonite was the highest at 250??450?,but the montmorillonite has no weight loss in this range.UF-OMMT intercalation prepolymer was prepared by traditional 'alkali-acid-alkali'process.The optimal synthesis conditions were determined as:the molar ratio of formaldehyde to urea was 1.7,proportion of urea added in batches is 75:25:5,PVA is added at 0.6%,OMMT modified by cetyl trimethyl ammonium bromide was selected,OMMT is added in the order of the first batch of urea,OMMT is added at 4.0%,reaction temperature 70?,polycondensation pH is 5-5.5.The obtained prepolymer was opalescent,with a viscosity of 20.4 mPa·s,a solid content of 41.31%and a free formaldehyde content of 0.116%.Shearing has little effect on the viscosity of UF-OMMT resin prepolymer,and the prepared resin prepolymer exhibits Bingham fluid flow behavior.The paper prepares high performance plugging materials by adding curing agent and curing regulator and other modifiers to the prepared UF-OMMT resin prepolymer.The concentration of ammonium chloride as the main agent was 0.6%,and that of hexamethylenetetramine as the delay agent was 0.20%.The concentration of the suspending agent APP4 was determined to be 1200 mg/L,the amount of the stabilizer sodium dodecylbenzenesulfonate was 0.3%,the volume adjusting agent phenol was 0.5%,and the prepolymer concentration was 100%.The XRD and SEM results of the plugging agent showed that the montmorillonite layer was distributed in the urea-formaldehyde resin matrix on the nanometer scale to obtain the exfoliated UF-OMMT composite.The morphology of the plugging agent presents a dense morphology with no large pores and gaps in the structure.The conventional properties of the plugging agent were studied.The curing time of the prepolymer was shortened from 6 h to 2.5 h and the curing strength was increased from 8.15 MPa to 11.48 MPa.The salinity had no significant effect on the curing time of UF-OMMT resin and the strength of the plugging agent after curing.The shearing effect has little effect on the curing time of the prepolymer system,but when the shearing time is too long,the urea-formaldehyde resin polymer chain will be destroyed and the solidification strength will be slightly reduced.The solubility of solidified solids in HCl and NaOH is up to 95%,while almost insoluble in simulated formation water and kerosene.The plugging agent has good water resistance and oil resistance.The results of mechanical properties experiment and core flooding model experiment of plugging agent show that the compressive strength of the plugging agent material was 11.45 MPa,the failure compression rate was 21.8%,and the elastic modulus was 25 MPa?The breakthrough pressure gradient of the plugging agent is 86 MPa/m.High plugging strength can meet the requirement of wellbore plugging agent?Combined with the previous SEM results,it can be seen that the plugging agent has a very dense structure,high strength and few pores,which makes the plugging agent have poor permeability and better sealing effect.After the plugging agent was washed by the injected water for 40 h,its plugging pressure was still very high,and the plugging pressure retention rate was 90.9%.After the injection,the plugging pressure remained stable,and the plugging agent system had a strong scouring resistance after curing. |
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