Rock Fragmentation Mechanism And Bit Adaptability Evaluation Of Hard And Brittle Formations In The Songliao Basin

In recent years,with the continuous deepening of oil and gas resources exploitation in my country,the drilling depth has increased accordingly,and the proportion of hard and brittle formations encountered in deep well drilling has increased year by year,while conventional PDC bits are prone to cutting when drilling into hard and brittle formations.Tooth chipping or damage will lead to a decrease in the drilling speed of the drill bit,prolong the drilling cycle,and seriously affect the production efficiency.How to efficiently drill into hard and brittle formations with drill bits has become an urgent problem to be solved in my country’s oil and gas drilling.In order to solve the above problems,this paper starts with the anti-drilling characteristics of the formation rocks in the Rang 70 block of the Songliao Basin,and measures the rock mineral components,rock hardness,rock drillability,compressive strength and other parameters of the block through experiments.According to the experimental results,it can be seen that the rocks in this block have high hardness and brittle nature,and some rocks have high shale content.The drillability of the rocks in this block is poor,and the drillability grade of most rocks exceeds 10,which belongs to the difficult-to-drill formation,and it is difficult for the PDC bit to effectively break the rock.Based on the experimental data and logging data,a correlation model between the anti-drilling characteristics and the acoustic time difference was established,and the anti-drilling characteristic profile of the block was formed,and the drill bit was preselected according to the anti-drilling characteristic prediction profile of the Rang 70 block formation.In this way,a reliable basis can be provided for the selection of drill bits in Block 70.In order to improve the penetration ability of the PDC bit in the hard and brittle formation,thereby increasing the ROP,the force of the drill bit composite is analyzed according to the interaction process between the PDC bit and the formation rock,and the mechanical model of the bit breaking the rock is established..On this basis,the process of PDC slices being pressed into the cutting rock under load is studied,and the rock-breaking efficiency of PDC slices under different cutting angles is analyzed.The drill bit is optimized according to the anti-drilling characteristic profile of Rang 70 block in Songliao Basin combined with the virtual strength index.During the field construction,it was found that the drill teeth of the preferred drill bit were severely worn when drilling into hard and brittle formations,and mud balls frequently appeared,which indicated that the existing drill bit had unreasonable design.In order to solve the existing defects of the existing drill bit,the single-tooth rock breaking and the jet flow of different nozzle sizes were analyzed through numerical simulation,and a drill bit optimization scheme suitable for the hard and brittle formation in the Songliao Basin was proposed based on the characteristics of the formation.The optimized drill has the advantages of impact resistance,super wear resistance,reverse taper milling,and efficient chip removal.The research results of this paper have certain guiding significance and use value for improving the rock-breaking efficiency of PDC bit in hard and brittle formations and ensuring the smooth progress of on-site drilling construction.