Research on borehole deviation in drilling anisotropy formations;

New pitch-resistant theory is known that increasing WOB can arouse drill string buckling,keep drill string eddy,when the well is oblique,it can make drill string produce the axial secondary force,if without borehole deviation,axial additional power disappears.

On the basis of the features of borehole deviation in Well Gong-30,the paper analyses the influence of BHA ,weight on bit,stratum and bit on borehole deviation in drilling,and propose some important technical measures to use PDC bit and Barus bit in drilling in centre Sichuan area.

But well deviation of air drilling is a problem in some place where drilling has no problem with mud.

The formation mainly consists of dolomite and features in complex lithology, which makes it difficult to control well deviation.

Inverted pendulum drill assembly is one kind of new drill assembly for well deviation control, it displays well packed hole character under the small deviation angle and high bit pressure guards.

But the research on borehole deviation control is very few.

This paper briefly mentions the necessity for the development of hole deviation treatment and mapping programs,and details in program structure,processing procedures,their major functions and data format.

Hole deviation is the main technical bottleneck in gas drilling because the negative pressures at the bottom of the hole reduces the apparent strengths of the rocks penetrated,thus in being beneficial to the increase of ROP,on the other hand,a high well angle is easy to be generated in a short time.

Study on correction of well deflection by tomography of cross hole first arrival data and application.;

In view of the difficult drilling problems in east Sichuan such as varied lithologies,interleaved lay- ers of soft and hard rocks,great obliquity of strata easily leading to well deflection,hard rocks difficult to be bro- ken,strata being unfavorable for drilling,high grindability and pressure of strata being difficult to decide etc.

Different sand carrying ratio of gravel filling is used in different well deflection and oilfield.

With the further development of oil-field exploration, the well deviation bring a series harm to the drilling engineering in the drilling process, so the technique of preventing deviation and hole straightening in the drilling process is also caused the oil-field development personnel’s value more and more.

When drilled to MD 6200 m,the interbedded soft and hard fractured formations were encountered,which in combination with high temperature downhole and small hole size made it very hard to control the deviation.