1.1.3 Applications of Directional Drilling
1. Sidetracking: Side-tracking was the original directional drilling technique. Initially,
sidetracks were “blind". The objective was simply to get past a fish. Oriented
sidetracks are most common. They are performed when, for example, there are
unexpected changes in geological configuration (Figure 1-1).
1. Sidetracking: Side-tracking was the original directional drilling technique. Initially,
sidetracks were “blind". The objective was simply to get past a fish. Oriented
sidetracks are most common. They are performed when, for example, there are
unexpected changes in geological configuration (Figure 1-1).
2. Inaccessible Locations: Targets located beneath a city, a river or in environmentally
sensitive areas make it necessary to locate the drilling rig some distance away. A
directional well is drilled to reach the target (Figure 1-2).
sensitive areas make it necessary to locate the drilling rig some distance away. A
directional well is drilled to reach the target (Figure 1-2).
3. Salt Dome Drilling: Salt domes have been found to be natural traps of oil
accumulating in strata beneath the overhanging hard cap. There are severe drilling
problems associated with drilling a well through salt formations. These can be
somewhat alleviated by using a salt-saturated mud. Another solution is to drill a
directional well to reach the reservoir (Figure 1-3), thus avoiding the problem of
drilling through the salt.
accumulating in strata beneath the overhanging hard cap. There are severe drilling
problems associated with drilling a well through salt formations. These can be
somewhat alleviated by using a salt-saturated mud. Another solution is to drill a
directional well to reach the reservoir (Figure 1-3), thus avoiding the problem of
drilling through the salt.
4. Fault Controlling: Crooked holes are common when drilling nominally vertical. This
is often due to faulted sub-surface formations. It is often easier to drill a directional
well into such formations without crossing the fault lines (Figure 1-4).
is often due to faulted sub-surface formations. It is often easier to drill a directional
well into such formations without crossing the fault lines (Figure 1-4).
5. Multiple Exploration Wells from a Single Well-bore: A single well bore can be
plugged back at a certain depth and deviated to make a new well. A single well bore
is sometimes used as a point of departure to drill others (Figure 1-5). It allows
exploration of structural locations without drilling other complete wells.
plugged back at a certain depth and deviated to make a new well. A single well bore
is sometimes used as a point of departure to drill others (Figure 1-5). It allows
exploration of structural locations without drilling other complete wells.
6. Onshore Drilling: Reservoirs located below large bodies of water which are within
drilling reach of land are being tapped by locating the wellheads on land and drilling
directionally underneath the water (Figure 1-6). This saves money-land rigs are much
cheaper
drilling reach of land are being tapped by locating the wellheads on land and drilling
directionally underneath the water (Figure 1-6). This saves money-land rigs are much
cheaper
7. Offshore Multiwell Drilling: Directional drilling from a multiwell offshore platform
is the most economic way to develop offshore oil fields (Figure 1-7). Onshore, a
similar method is used where there are space restrictions e.g. jungle, swamp. Here,
the rig is skidded on a pad and the wells are drilled in “clusters".
is the most economic way to develop offshore oil fields (Figure 1-7). Onshore, a
similar method is used where there are space restrictions e.g. jungle, swamp. Here,
the rig is skidded on a pad and the wells are drilled in “clusters".
8. Multiple Sands from a Single Well-bore: In this application, a well is drilled
directionally to intersect several inclined oil reservoirs (Figure 1-8). This allows
completion of the well using a multiple completion system. The well may have to
enter the targets at a specific angle to ensure maximum penetration of the reservoirs.
directionally to intersect several inclined oil reservoirs (Figure 1-8). This allows
completion of the well using a multiple completion system. The well may have to
enter the targets at a specific angle to ensure maximum penetration of the reservoirs.
9. Relief Well: The objective of a directional relief well is to intercept the bore hole of a
well which is blowing and allow it to be “killed" (Figure 1-9). The bore hole causing
the problem is the size of the target. To locate and intercept the blowing well at a
certain depth, a carefully planned directional well must be drilled with great
precision.
well which is blowing and allow it to be “killed" (Figure 1-9). The bore hole causing
the problem is the size of the target. To locate and intercept the blowing well at a
certain depth, a carefully planned directional well must be drilled with great
precision.
10. Horizontal Wells: Reduced production in a field may be due to many factors,
including gas and water coning or formations with good but vertical permeability.
Engineers can then plan and drill a horizontal drainhole. It is a special type of
directional well (Figure 1-10). Horizontal wells are divided into long, medium and
short-radius designs, based on the buildup rates used. Other applications of
directional drilling are in developing geothermal fields and in mining.
including gas and water coning or formations with good but vertical permeability.
Engineers can then plan and drill a horizontal drainhole. It is a special type of
directional well (Figure 1-10). Horizontal wells are divided into long, medium and
short-radius designs, based on the buildup rates used. Other applications of
directional drilling are in developing geothermal fields and in mining.
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