GB/T 28911-2012Vocabulary of drilling engineering for the petroleum and natural gas (English PDF)

2.1 Basic concept of well

2.1.1 Well

The cylindrical hole which is of certain depth and is drilled in formation for the purpose of exploration and development of petroleum, natural gas and other underground resources.

2.1.2 Wellhead

The top opening end of well.

2.1.3 Well bottom

The bottom of well.

2.1.4 Well wall

The cylindrical inner wall of well bore.

2.1.5 Well bore

The entirety of a well.

2.1.6 Well section

A certain section of the well bore.

2.1.7 Open hole

The well section which is not sealed and separated with sleeve, screen casing or other measures.

2.1.8 Measured depth

The measured length of hole axis from the rotary table surface (reference point) to a certain measuring point in well.

2.1.9 True vertical depth

The distance from a certain point on hole axis to the horizontal plane on which the wellhead is located.

2.1.9.1 Deep well

The vertical well with true vertical depth neither less than 4,500m nor larger than 6,000m.

2.1.9.2 Ultra-deep well

The vertical well with true vertical depth no less than 6,000m.

2.1.10 Well diameter

The diameter of well bore.

2.1.11 Annulus

The annular columnar space between well wall and casing string or between casing strings when there is casing string set in well.

2.1.12 Hole axis

The center line of well bore.

2.1.13 Casing program

The number of casing layers of a well, the setting depth, the diameter of casing at each layer, the well bore diameter of corresponding well section, the depth of open hole and the top depth of cement ring outside the casing.

2.2 Well type

2.2.1 Well type

The classification of well according to the purpose of drilling, which is generally classified into exploratory well and development well.

2.2.1.1 Exploratory well

The general term of wells drilled during exploration phase of oil and gas field, which generally is classified into regional exploratory well, blue sky exploratory well and appraisal well. Regional exploratory well and blue sky exploratory well are drilled for the purpose of looking for oil and gas pool; appraisal well is drilled for the purpose of ascertaining the edge of oil and gas pool, and determining the depth of oil and gas pool, the thickness variation of oil and gas zone, the oil and gas bearing condition, etc.

2.2.1.2 Development well

Various producing wells and injection wells drilled for the purpose of developing petroleum, natural gas or other resources as well as the observation well, information well, inspection well and the like drilled for the purpose of maintaining certain output and also researching the variation in underground condition during development.

2.2.2 Well type

The classification of well according to the shape of well trajectory, which is generally classified into vertical well and directional well.

2.2.2.1 Vertical well

The well of which the hole axis is designed into a plumb line.

2.2.2.2 Directional well

The well of which the designed target point and the wellhead are not on the same plumb line.

2.3 Drilling method