Calculations And Analysis Of Wellbore Position Uncertainty Based On Gyro Inclinometer

Compared with magnetic inclinometer,gyro inclinometer not only has high measurement accuracy,but also is free from magnetic interference.With the development scale of difficult to exploit oil and gas resources becoming larger and larger,gyro inclinometer technology is more and more used in complex well projects such as large cluster wells and rescue wells.At the same time,the drilling site not only needs a gyro inclinometer with higher measurement accuracy,but also needs to quantitatively describe the spatial position of the real drilling hole trajectory in the formation.Aiming at the problem of gyro inclination measurement and calculation,based on the previous related research,this paper studies the uncertainty of real drilling hole position by using the comprehensive methods of theoretical analysis,numerical simulation and numerical example verification.The gyro inclinometer can have different numbers and types of gyro sensors,and has two inclinometer modes: continuous and static.Firstly,the error sources of different types of gyro inclinometers in different measurement modes are analyzed,and the corresponding models of dual axis compass gyroscope,horizontal rotor gyroscope,dual axis semi continuous gyroscope,dual axis continuous gyroscope,three-axis continuous gyroscope and three-axis compass gyroscope are analyzed;Then,the Matlab tool is used to compile the calculation program of borehole position uncertainty based on gyro inclinometer data.Combined with the field data of accident rescue wells,the basic characteristics of borehole position uncertainty and the influence law of each error source on borehole position uncertainty are calculated and analyzed.A total of 48 error sources are considered in the above six gyro error models.The results show that gyro inclinometer can reduce the uncertainty of borehole position;The calculation results of different gyro inclinometer error models in the vertical well section are basically the same,while the borehole extension direction and high side direction errors calculated by different gyro inclinometer error models in the inclined well section are roughly the same,but the calculation results of lateral errors are quite different.Among them,the calculation error of the biaxial continuous gyro model is the smallest,and the error of the three continuous gyro models is smaller.Among all the error sources,the main error sources that affect the error ellipsoid include MXY3,MXY4,DRF-R,DSF-W,DRF-S and DST-G.the main error sources that affect the error ellipsoid are MXY3,MXY4 and DST-G.at the same time,MXY3 and MXY4 error sources also have a great impact on the eccentricity of the error ellipsoid;Therefore,in the directional drilling project,the gyro inclinometer that can perform continuous measurement should be selected first,and the standard deviation of error sources MXY3 and MXY4 should be controlled within a small range as far as possible.