Research And Performance Evaluation Of High-Strength Slow-Settling Plugging Agent For Water Shutoff In Horizontal Wells

This dissertation mainly focuses on the chemical water shutoff system with cement as the main agent.Firstly,through the selection and performance optimization of additives for different plugging agent systems,a high-strength slow-settling plugging agent system for horizontal wells was obtained;Then the solidification and slow-settlement mechanism of the plugging agent system was studied.Finally,the comprehensive performance and process application conditions of the plugging agent system are analyzed to provide a basis for the application of the plugging agent system in the field.Through the selection and performance evaluation of the main agent and additives of the plugging agent system,the formula of high strength and slow settling plugging agent system for chemical water plugging in horizontal wells is obtained.The formula is that G grade Portland oil well cement(water cement ratio 0.4)+6%suspension agent xfj-1+8%fluid loss reducer lsj-1+5%reinforcer PS-1+2%dispersant/retarder JSJ.The suspension time of the system is more than 6h,and the compressive strength after curing is more than 30MPa.The system has excellent slow settling property and high curing strength.The solidification and slow-settlement mechanism of the high-strength slow-settling plugging agent system was studied through TG-DSC,infrared spectrum analysis,XRD analysis and other means.The study on the curing enhancement mechanism of the plugging agent system showed that the XRD pattern of the plugging agent system with polymer PS-1 did not find the Ca(OH)₂ peak 8 hours before hydration.It shows that the addition of PS-1 will delay the hydration reaction in the early stage of the plugging agent system;From the scanning electron microscope and FTIR results after the plugging agent system is cured,it can be seen that the white film association structure formed by the reaction between PS-1 and the cement main agent can be attached to the surface of the hydration product or filled in the gap of the hydration product,making the structure of the plugging agent system more compact after curing,and the strength of the plugging agent system be enhanced.The slow sedimentation and dispersion mechanism of the plugging agent system shows that the Zeta potential of the blocking agent system added with JSJ is negative,and the absolute value of the potential value is greater than the blank sample,it shows that the electrical properties of the plugging agent system are changed,and the particles have a repulsive electrostatic effect,which makes the cement particles dispersed;The comprehensive performance and process adaptability of the plugging agent system are studied by combining the oilfield field process application conditions and laboratory tests.The results show that the slow-sinking time of the plugging agent system can reach more than 6hours,and the curing compressive strength can reach 32.2MPa.From the results of the sand-packed pipe physical model experiment,it can be seen that the maximum breakthrough pressure can reach 0.9 MPa·cm^-1 and the plugging rate can reach 99.2%when the plugging agent system is cured at 90?for 7 days under 1PV injection volume.In summary,the plugging agent system obtained in the dissertation research is compared with the currently used horizontal well plugging agent system,which has a longer slow down time and higher curing strength,it can be used as a new type of horizontal well chemical plugging agent system for field application.