Optimized Design And Application Study Of Core Drills And Mud Used In The Complex Formation Of The Well-1 Of Songliao Scentific Drilling

With the development of exploration technology, core drilling, scientific exploration engineering and engineering investigation all improve the standards of recovery factor and core quality. This paper, in the light of the ultimate unconsolidated formation and the severely plastic soft formation, conducts optimized design of spacing fluid shape-retained drilling tool sampler and balling-control bit. It also makes researches on the anti-caving water-based drilling mud system in the complex formation based on the Well-1 of Songliao Scientific Drilling. spacing fluidThis paper analyzes the cause of the extremely low recovery factor in the very complex formation, and concludes that when drilling in the ultimate unconsolidated formation, the fluid pressure within the drilling tools should be identically higher than or equal to that of the joint;when drilling in the severely plastic soft formation, the cutter's distribution,cutting discharge space and the waterway structure should be rationally arranged, and at the same time, drilling parameters should be under control, with the view of preventing bit being balled. Therefore, a new method on the optimized design of core drillings in the complex stratum is put forward.Starting with the logic relationship of the interaction between coring drilling tools and hydraulics, the author analyzes the structure intensity of coring drilling tools, decides the design principles of their structural space, and then conducts CFD simulation based on hydraulics. The sillway and the water ring in the rig are the core of this set of drilling tools, which guarantee the core-protection effect. The simulation analysis and the CFD simulation experiment demonstrate that the parameters have good uniformity. The analysis of balling-conrol bit'CFD mould shows that the down-the–hole velocity field distributes evenly with good effect, which prove its scientificness.Through the optimization of structure parameters, such as the thread taper of drill tools, the tooth height, the pitch of screws and the datum distance, etc. , the author has the findings as follows. The thread strength is greatly influenced by the change of rod's partial I.D., i.e., when the I.D. reduces, the whole thread strength rises; the rod strength is greatly influenced by the thread taper, i.e., when the taper is near 1:25, the thread strength is at peak; the relation between the thread strength and the tooth height is very complex. As the pitch of screws increases, the inside pressure on screw thread within the rod is unbalanced, thus, the pressure becomes more concentrated; the thread strength is less influenced by the datum distance.With the fundamental principle and experience of Computational Fluid Dynamics, the author finishes the design and the simulation of spacing fluid shape-retained drilling tool and balling-control bit, gets hold of the distribution pattern of down-the-hole drilling fluid field, and proves that the result is the same as simulation after numerous experiments and tests.Simulation analysis and the CFD simulation experiment both indicate that parameters have good uniformity, but the spillway depth affects the shaft bottom's pressure field and velocity field a lot. The 50mm shaft bottom's velocity field varies a lot, then the shaft bottom would be easy to be affected and its pressure gradient would be also relatively evident; the 70mm spillway has relatively slow velocity, so its core-protecting effect is predicted to be better, but it may affect the drilling rate. Above findings are got from the optimized result of the spacing fluid shape-retained drilling tool. And the optimized result of the balling-control bit demonstrates that the front bevel angel of bit-cutting-edge affects the velocity field structure a lot, but it has little effect on the down-the-hole pressure. The pressure drop of down-the-hole bit becomes the highest when the angle is 30°,which is the best moment to discharge cuttings. 25°bevel takes the second place, and then the 35°. According to the structure parameters of the optimized design, reinforcement theory and the optimized methods, the author designs the core drilling tools used in the Well-1 of Songliao Scientific Drilling., Inner Mongolia and We chuan satiric wells, manufactures the spacing fluid shape-retained drilling tool and the balling-control bit, and , on the basis of engineering practical optimized mud formula, develops the Well-1 of Songliao Scientific Drilling. anti-caving water-based drilling mud system. It has been found that the 2 kinds of drilling rods could highly increase the recovery factor in the relatively complex stratum, meeting the geological needs. The successful application of anti-caving water-based drilling mud, which acts as a good dado in the Well-1 of Songliao Scientific Drilling., proves the feasibility of the theoretical design and the optimized project.