Well Drilling Info Tab

The Well Drilling Info tab contains the basic information required to calculate drilling costs and drilling time for a well. Since drilling details would be redundant for secondary completions, this tab is not available in them.

Group: Wells may be added to Well Groups using this pane, either by including them in an existing group (selected from the dropdown list on the left) or by creating it with the Create button. When a group is selected the data is no longer editable in this tab but can be accessed via the corresponding Wells Group node (use the Edit this group link). Conversely, use the Detach button to remove the well from the group and edit its details in this tab.

Rig: Select the rig that will perform the corresponding Well Drilling job. Only if Extended Rig Mode is activated.
Drilling Site: Select a Drilling Site where the wellbore will be drilled. Use the button to load one from the list of already defined sites.
Well Drilling Time: Specify the time it will take the rig to drill this well.
Rig Cost Rate: Cost of rig usage per day.
Drilling Fixed Cost: Fixed expense of the well drilling.
Cost type: Choose between computing drilling costs as CapEx or OpEx. When set to CapEx, the total drilling CapEx = Drilling Fixed Cost + Rig Cost Rate * Well Drilling Time + CapEx of required Resources, with no associated OpEx. When set to OpEx, only resources will have associated CapEx, and all drilling costs will be computed as OpEx.

Choose Cost Category: Choose a category for these costs (see Cost Categories).

Enable Production Lag: (Only for Oil production well Gas production well producers and Water injection well Gas injection well injectors.) Set a lag between completion of the well and start of production.

Since the Enable Production Lag option refers to the time elapsed between completion of a well and start of production, it is available in the Well Drilling Info tab only if drilling and completion for that well have not been separated; otherwise, it will only appear in the Well Completion Info Tab.

Also, if the well belongs to a group for which a production lag has not been enabled, the option will be hidden. (See Well Groups.)

Activities: Activities for the specific job of drilling or completing a well are defined separately in the node for each well. See Activities Pane for a full explanation of how activities work.

Resource Requirements: Resources required for the specific job of drilling or completing a well are defined separately in the node for each well. See Resource Requirements Pane for a full explanation of how resource tracking works.

Learning Curve (Drilling)

Learning curves model the improvement in cost and time gained as a consequence of accumulated experience. The definition of a drilling learning curve will imply a reduction in drilling cost and time as more wells of similar characteristics are drilled.

The default technique for learning to take place consists in grouping wells in Drilling Info Groups. Wells belonging to the a group where a learning curve has been defined will learn from all wells belonging to the same group that have already been drilled.

Alternatively, the Use global experience option may be checked to let wells learn from all other wells already drilled in the project.

Three types of curves are available:

Linear: Defines a linear reduction in well cost and time.
- Fixed Cost Start Well / End Well: Well count when the cost learning curve starts/ends. All previous wells will have the initial cost.
- Drilling Time Start Well / End Well: Well count when the drilling time learning curve starts/ends. All previous wells will have the initial drilling time.
- Fixed Cost % Change: Percentage change from start to end of cost learning curve (note that a negative number must be entered).
- Drilling Time % Change: Percentage change from start to end of drilling time learning curve (note that a negative number must be entered).

Brett-Millheim: Defines a reduction well cost and time based on empirical data. J.F. Brett and K.K. Millheim have developed a drilling performance curve based on actual field data. Their model requires three parameters:
- Final Reduction (c1): Total reduction in drilling time.
- Speed to Final (c2): Rate of learning.
- Minimum Time (c3): Minimum achievable drilling time.

The graph displays drilling days per well vs. well count (Brett and Millheim 1986 Brett, J.F. and K.K. Millheim, “The Drilling Performance Curve: A Yardstick for Judging Drilling Performance”, SPE 15362.).

Brett-Millheim Mearning Curve inputs (drilling)

Logarithmic: Defines a logarithmic reduction in well drilling cost and time.
- Drilling Time Experience Base: Well count when the drilling time learning curve starts. All previous wells will have the initial drilling time.
- Drilling Time Learning Rate: Logarithmic learning slope for drilling time.
- Fixed Cost Experience Base: Well count when the fixed cost learning curve starts. All previous wells will have the initial fixed cost.
- Fixed Cost Learning Rate: Logarithmic learning slope for fixed cost.

The logarithmic learning curve is calculated using the formula c₀∙λ^log₂^(v/v0) where C₀ is the initial value (time or cost), λ is the learning rate, V₀ is the experience base and V is the well number currently being drilled. See further in Understanding Logarithmic Learning.

Logarithmic Learning Curve inputs (drilling)

Departure Curve

Check this box to allow the definition of a table to control the increase (or decrease) in both fixed cost and drilling time as a function of well deviation (distance from facility).

Departure: Surface departure from the center location of a pad or platform as defined by the X-Y coordinates of the well in the Well Details Tab and the X-Y location of the facility in the facility General Tab (Facility).
Fixed Cost Change: The percentage CapEx change as a function of well deviation.
Drilling Cost Change: The percentage drilling time change as a function of well deviation.