A Research Of Tarim Oilfield,North Tarim Block Drilling Speed

With the development of the world energy pattern and China's energy demand,tarim oilfield,as the main area of China's energy development,has been continuously strengthened in exploration and development in recent years,and the deep-well and ultra-deep-well drilling has been started and rich oil and gas exploration achievements have been obtained.As the main upper production block of tarim oilfield,the average design well depth of the north tarim block is about 6,800 meters,the formation is deep and the downhole safety risk is high,which brings great challenges to drilling and affects the major breakthrough and exploration process of oil and gas exploration to a great extent.Therefore,it is of great significance to carry out research and application on the speed-up technology of deep well drilling in this area,so as to reduce the drilling cost and improve the comprehensive drilling benefits in the north tarim block.The analysis of engineering geological data in the north area of tarim indicates that there are great tectonic differences,complicated geological conditions and high drilling difficulty in this area.In the course of drilling,it is necessary to cross many sets of strata from neogene to ordovician,and the bottom temperature of the middle completion and completion Wells is up to 145 ?-160 ?.There is a layer of paste salt in the paleogene gidique formation,and the first short trip after drilling is of great tension and long time.Two open open hole about 5000 m long and the same open hole section there are two or more different pressure system,various kinds of lithology are frequent,basalt,tuff and so on special lithology,strong due to formation rock mechanics properties,caused low rate of penetration,bit type selection is difficult,and frequent tripping bit change,reduce monthly drilling speed.In addition,the borehole wall stability in this area is poor,Triassic system is prone to collapse,Permian system is prone to leakage,for Permian leakage layer,the existing technical means can not fully improve the pressure capacity to meet the purpose of drilling through the lower formation and no longer occur leakage,once there is a slight change may occur a malignant accident;There is high pressure brine in some ordovician sangtamu formation,which brings great challenges to the well control work,stuck work and drilling fluid performance adjustment.The reservoir in the seam and hole system leads to the strong heterogeneity of the target bed,the great difference in formation pressure,the difficulty in selecting drilling fluid density,the frequent occurrence of abnormal high pressure or the loss of regurgitation with the depth below 1000 m,which is very easy to cause well leakage or blowout.From the perspective of well trajectory control,due to the large dip Angle of the lower formation and the change of azimuth in the second quadrant,conventional drilling methods cannot effectively control the change of bottom-hole displacement,and the straight section is easy to miss in the later period.At present,the average drilling period of vertical Wells is about 85 days,and the average drilling period of inclined Wells is about 115 days.In view of the above problems,this paper analyzes and researches the drill bit selection,acceleration tool selection,orientation technology and drilling fluid technology on the basis of summarizing and sorting out the status quo of deep well drilling in China and the difficulties existing in the north tarim block.In the aspect of bit selection,the optimization of PDC bit and hybrid bit is mainly carried out.In the aspect of speed-up tools,the working principle of screw,torque impactor and impactor is expounded,and the characteristics of its application are analyzed.In the aspect of directional technology,combining with the difficulty of orienting in the long open hole segment,the analysis is carried out on the straight well segment and directional segment,and the application of hydraulic oscillator is mainly introduced.In the aspect of drilling fluid,drilling fluid optimization is carried out according to the formation characteristics of the vertical and directional sections.Through this study and field application experiment,improve the block the use of new tools and the exploration of the new technology,forming a set of suitable for northern area fast optimal drilling technology,and solve the trip more frequently in the process of drilling,mechanical speed low,reduce or eliminate the complex accident rate,at the same time of shortening drilling cycle,reduce the cost of drilling,have achieved good economic and social benefits,the tarim oilfield construction "30 million tons of tarim construction" and "to ensure the safety of national energy strategy" has important strategic significance.