Changes

==Percussion sidewall coring==

==Percussion sidewall coring==

Most sidewall cores are obtained by percussion sidewall coring systems (Figure 1). These tools shoot hollow, retrievable, cylindrical bullets 1 in. wide by 1.75 in. long into the borehole wall. The tool (gun) can be combined in multiples of approximately 30 bullets with 120 shots a general maximum. The gun is lowered to the desired depth, then individual bullets are electrically fired from the surface. The bullets remain connected to the gun by wires, and movement of the gun pulls the bullets from the borehole wall.

[[file:sidewall-coring_fig1.png|thumb|left|{{figure number|1}}Percussion sidewall coring system. Copyright: Halliburton Logging Services, Inc.]]

[[file:sidewall-coring_fig1.png|thumb|{{figure number|1}}Percussion sidewall coring system. Copyright: Halliburton Logging Services, Inc.]]

Most sidewall cores are obtained by percussion sidewall coring systems ([[:file:sidewall-coring_fig1.png|Figure 1]]). These tools shoot hollow, retrievable, cylindrical bullets 1 in. wide by 1.75 in. long into the borehole wall. The tool (gun) can be combined in multiples of approximately 30 bullets with 120 shots a general maximum. The gun is lowered to the desired depth, then individual bullets are electrically fired from the surface. The bullets remain connected to the gun by wires, and movement of the gun pulls the bullets from the borehole wall.

Different bullet “core barrel” designs are available for unconsolidated, soft, and medium to hard formations. Therefore, it is wise to have more than one type of core barrel on location until acceptable core recovery can be demonstrated. Figure 1 illustrates a typical percussion sidewall coring tool.

 

Different bullet “core barrel” designs are available for unconsolidated, soft, and medium to hard formations. Therefore, it is wise to have more than one type of core barrel on location until acceptable core recovery can be demonstrated. [[:file:sidewall-coring_fig1.png|Figure 1]] illustrates a typical percussion sidewall coring tool.

The advantages of this coring system are speed, low cost, and the precise ability to sample zones of interest after open hole logs have been run. The disadvantage is that the bullet usually alters the formation by shattering harder rock or compressing softer sediments, thereby reducing the quantitative value of the sidewall core analysis data. Also, percussion sidewall core recovery tends to be low in very hard or fractured rock.

The advantages of this coring system are speed, low cost, and the precise ability to sample zones of interest after open hole logs have been run. The disadvantage is that the bullet usually alters the formation by shattering harder rock or compressing softer sediments, thereby reducing the quantitative value of the sidewall core analysis data. Also, percussion sidewall core recovery tends to be low in very hard or fractured rock.

The rotary, or drilled sidewall coring tool, was developed to recover sidewall core samples without the shattering impact of the percussion system. Suitable for hard to friable rock, the rotary sidewall corer uses a diamond-tipped drill to cut individual plugs from the sidewall. The samples are broken off and pulled from the sidewall by the core drill. The drill is then retracted into the body of the tool where the samples are deposited. The tool is moved to a new sample location after depositing each sample. A “gun” of 30 samples, each 0.9375 in. wide by 1.75 in. long, can be taken during one trip.

The rotary, or drilled sidewall coring tool, was developed to recover sidewall core samples without the shattering impact of the percussion system. Suitable for hard to friable rock, the rotary sidewall corer uses a diamond-tipped drill to cut individual plugs from the sidewall. The samples are broken off and pulled from the sidewall by the core drill. The drill is then retracted into the body of the tool where the samples are deposited. The tool is moved to a new sample location after depositing each sample. A “gun” of 30 samples, each 0.9375 in. wide by 1.75 in. long, can be taken during one trip.

The advantage of the rotary sidewall coring system is that it produces samples suitable for quantitative core analysis. The disadvantages are high cost per sample and longer time per recovered core. Rotary sidewall core recovery is low in unconsolidated formations. Figure 2 shows how a rotary sidewall coring tool operates.

The advantage of the rotary sidewall coring system is that it produces samples suitable for quantitative core analysis. The disadvantages are high cost per sample and longer time per recovered core. Rotary sidewall core recovery is low in unconsolidated formations. [[:file:sidewall-coring_fig2.png|Figure 2]] shows how a rotary sidewall coring tool operates.

[[file:sidewall-coring_fig2.png|thumb|{{figure number|2}}Rotary sidewall coring tool. Copyright: Halliburton Logging Services, Inc.]]

[[file:sidewall-coring_fig3.png|thumb|{{figure number|3}}Process of Sidetrak Coring System®. Copyright: Foothills Diamond Coring, Calgary, Canada.]]

==Sidetrak coring system==

==Sidetrak coring system==

A new Sidetrak Coring System® is just coming on the market and merits discussion for two reasons. First, the system is designed to acquire a larger, more continuous core sample from a drilled and logged wellbore than is possible with existing sidewall coring tools. Second, the emergence of a new tool confirms there is still room for improvement in the area of acquiring high quality, low cost core samples.

A new Sidetrak Coring System® is just coming on the market and merits discussion for two reasons. First, the system is designed to acquire a larger, more continuous core sample from a drilled and logged wellbore than is possible with existing sidewall coring tools. Second, the emergence of a new tool confirms there is still room for improvement in the area of acquiring high quality, low cost core samples.

A very close cousin to a conventional core barrel, the Sidetrak Coring System is designed to cut up to [[length::10 ft]] of 2.5-in. core. The tool is attached to a conventional drill string and is lowered into the zone of interest. An integral arm pushes the core barrel against one side of the wellbore, resulting in a slightly sidetracked core. This tool is still in the development stage, but it shows promise and should be available in the future. Figure 3 shows a prototype of the new Sidetrak Coring System.

A very close cousin to a conventional core barrel, the Sidetrak Coring System is designed to cut up to [[length::10 ft]] of 2.5-in. core. The tool is attached to a conventional drill string and is lowered into the zone of interest. An integral arm pushes the core barrel against one side of the wellbore, resulting in a slightly sidetracked core. This tool is still in the development stage, but it shows promise and should be available in the future. [[:file:sidewall-coring_fig3.png|Figure 3]] shows a prototype of the new Sidetrak Coring System.

 

[[file:sidewall-coring_fig3.png|thumb|{{figure number|3}}Process of Sidetrak Coring System®. Copyright: Foothills Diamond Coring, Calgary, Canada.]]

==Wellsite handling of sidewall cores==

==Wellsite handling of sidewall cores==