Exercises Horizontal drilling
1. List five major considerations involved in selecting a particular horizontal well configuration.
Solution
The considerations that enter into selecting a horizontal well configuration include:
- cost
- well spacing and lease restrictions
- conditions of re-entry wells
- reservoir rock characteristics
- production methods
- well objectives
- problem-causing lithologies above the pay zone
- amount of total horizontal departure
- completion methods
- availability of specialized downhole tools
- kick-off depth constraints
- horizontal displacement constraints
2. Define the following horizontal well configurations and list their areas of application:
(a) long radius
(b) medium radius
(c) short radius
(d) ultra-short radius
Solution
(a) Long radius:
- Build rate between 2° and 6° per 100 ft; build radius ranges from approximately 1000 to 3000 ft
- Applications:
- Multiple, extended-reach wells from offshore platforms or other single surface locations.
- Otherwise inaccessible locations.
- Exploratory wells over long intervals.
- Wells that require zone isolation and selective completion/stimulation.
(b) Medium radius
- Build rate between 6° and 35° per 100 ft; build radius ranges from approximately 160 to 1000 ft
- Applications:
- Lease boundary restrictions.
- Re-entry wells.
- Reef reservoirs.
- Fractured reservoirs.
- Reservoirs with potential for gas or water coning.
(c) Short radius:
- Build rate between 5 ° and 10 ° per three ft; build radius 20-40 ft
- Applications:
- Infill drilling in depleted reservoirs
- Shaly intervals or other trouble-prone formations
- Multiple drainholes
- Enhanced oil recovery
(d) Ultra-short radius:
- No bend section
- Applications:
- Soft, unconsolidated formations
- Multiple drainholes from existing vertical wells
3. The inclination angle at the current point is I1=50 deg. The azimuth angle at the current point is A1=30 deg. The required inclination angle at the target point is I2=90 deg. The required azimuth angle at the target point is A2=40 deg. The tool has a deflection capacity of D=33 deg/100 m. The required build rate is B=28 deg/100 m.
Using Guo et. al’s method, find the inclination angle and change in azimuth at the intermediate point, along with the length to drill from the current point to the intermediate point. Find also the tool face angle to set at the intermediate point, the change in azimuth from the intermediate point to point 2, and the total length to drill from the current point to the target point is 143.74 m.
Solution
Calculations are illustrated in Figure 1.
Using Guo et al.’s method, the inclination angle at the intermediate point is calculated to be 76.32 degrees. The change in azimuth from the current point to the intermediate point is 18.5 degrees. The length to drill from the current point to the intermediate point is 94.78 m. The tool face angle to set at the current point is 31.8 degrees. After the intermediate point is reached, the tool face should be re-oriented to the opposite direction in order to hit target at point 2. The tool face angle to set at the intermediate point is -31.8 degrees. The change in azimuth from the intermediate point to point 2 is -8.54 degrees. The total length to drill from the current point to the target point is 143.74 m.
Assessment Horizontal drilling
1. The starting point in planning a horizontal well trajectory is to ____________________.
A .establish the kick-off depth
B .determine the configuration of the build section(s)
C .specify entry depth into the reservoir and the minimum length of the drainhole section.
D .specify the target radius
2. What is the primary reason for installing inflow control devices (ICDs) in horizontal well completions?
A .Zonal isolation
B .Balancing of influx profiles and delay of water or gas intrusion.
C .Sand control
3. Ultra short turn radius drilling is used in __________.
A .soft unconsolidated formations
B .steeply dipping formations
C .side tracking when having stuck pipe problems
D .deep wells
4. How can logging surveys be conducted in a horizontal hole section when wireline methods are impractical?
A .Run logging tools on drill pipe.
B .Use coiled tubing.
C .Use tools with pump-down capability.
D .Use MWD and LWD tools
E .A, B, C and D
F .A, B and D only
5. What horizontal completion type would you choose if zonal isolation and the ability to conduct future workovers was a primary well objective?
A .Open hole
B .Liner with external casing packer
C .Cased, cemented and perforated
D .B or C
6. Which of the following is NOT an advantage of medium radius drilling, when compared with long radius drilling?
A .Torque and drag tendencies less than in long radius wells
B .Vertical portion of the well can be set deeper
C .Attainment of a lateral section with less departure from the vertical
D .Decreased dog-leg severity
7. A medium turn radius well has one section with a build rate angle of:
A .1 to 6° per foot
B .0 to 3 ° per 100 ft
C .6 to 20° per 100 ft
D .20 to 40°per 100 ft
8. The two most common problems that occur while drilling build sections are inability to build hole angle and inability to correct azimuth. These most often result from ________.
A .troublesome formations
B .improper design of the bottomhole assembly
C .poor bit selection
D .A and B
E .A, B and C
9. Which of the following is NOT an area of application for short turn radius drilling?
A .Steam flooding
B .Drilling multiple drainholes from a single wellbore
C .Infill drilling in depleted reservoirs
D .Wells requiring comprehensive formation evaluation programs.
10. Which of the following is NOT a curve design to bring a well from vertical to horizontal?
A .Complex tangent
B .Balanced tangent
C .Simple build
D .Simple tangent
11. Which of these horizontal well configurations does not involve a limit on hole size?
A .Long radius
B .Medium radius
C .Short radius
D .A and B
12. Which of these reservoirs would you be LEAST likely to consider as a candiate for horizontal drilling?
A .Heavy oil reservoir
B .Reservoir with high ratio of horizontal to vertical permeability
C .Reservoir with high ratio of vertical to horizontal permeability
D .Coal bed methane reservoir
13. A short turn radius well may have a radius of curvature as small as _______ feet.
A .5 feet
B .20 feet
C .50 feet
D .100 feet
14. Which of the following is NOT a typical application of long radius drilling?
A .Drilling exploratory wells
B .Wells requiring selective completion
C .Re-entry wells
D .Drilling multiple wells offshore
15. Advantages of long radius drilling include:
A .Relative ease of hole cleaning and cuttings removal
B .Low torque and drag tendencies
C .Ability to expose shallow pay zones
D .Minimal dog-leg severity
16. An artificial lift system that is relatively unaffected by inclination angles is:
A .Sucker rod pumping
B .Electric submersible pumps
C .Reciprocating hydraulic pumps
D .Gas lift
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