Well Bore Stability Technology Using Blocking Drilling Fluid System Suitable for the Deep High Temperature Cracked Strata in Well Songke-2

To solve the problem of drilling in severely cracked hard rock in deep high temperature and high pressure (HTHP) stratum of Well Songke-2, mechanical analysis and physical simulation experiment were used to clarify the factors affecting the thickness of the plugging layer in this study. The sealing effect of high-strength skeleton particles and HT deformable soften particles was verified through HTHP filtration test, and the on-site operation pressure was calculated and controlled. The self-locking mechanical model of the three-particle bridge group skeleton was established, and the anti-destructive ability formula of the single bridge group was derived. Compared with the blank formula, emulsified asphalt, oxidized asphalt and sulfonated asphalt can reduce the HTHP water loss volume by 56%, 44% and 48%, respectively. Particle size and strength, crack width and pressure difference have important influence on the thickness of the plugging layer. A quick blocking effect can be achieved by combining the rigid plugging agent with deformable plugging particles. Based on the above analysis and tests, the drilling pressure in the operation was effectively controlled in conjunction with the on-site technology, and the compaction and anti-collapse effect under moderate positive pressure difference was realized. With the techniques mentioned above, the fifth spud of Well Songke-2 was completed successfully with the open-hole section from 5 910 to 7 018 m.