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.

Causes of well deviation during gas drilling and its control

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.

Research on borehole deviation in drilling anisotropy formations;

Effects of stress field in bottom hole on borehole deviation during gas drilling

Factors of affecting borehole deviation for air drilling and the technical application

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

Measures to avoid well deflection during gas drilling

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.

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.