RIGBOOK

DRILLING LOADS
- Forces on the Derrick
Derricks are subjected :
- Weight of the derrick itself
- Wind load
- Stress induced by Floating hull motion
(for floating vessels)
- Horizontal component load of the drill string when racked back
- Hoisting load
The first 3 forces are considered in the structural design of the derrick.
- Calculation of Drilling Loads at Crown Block
Cases
Case 1: Suspended load
The load on the support is equal to the weight being hung.

Case 2a : Static Load
Drilling load is at rest, hoisted by the Drawworks over a single sheave on the Crown Block
The load on the drawworks is equal to the weight being hung from the crown sheave.
The crown supports both the drilling load and drawworks tension, so the force supported is double the weight being hung.

Case 2b : Dynamic Load
Drilling load is in motion, hoisted by the Drawworks over the single sheave on the Crown Block
The load on the drawworks is equal to the weight being hung from
crown sheave PLUS frictions.
The crown block supports both the drilling load and the drawworks tension PLUS frictions, so the force supported in more than the weight being hung.




Case 3: Drilling load is in motion
Drilling load is in motion, hoisted by the Drawworks through a series of sheaves on the Crown and Travelling Blocks
The load supported by the Crown Block is the sum of the load supported by each of the lines.
In this example with 3 lines, the load supported by Crown block is
1500 kg


The load supported by the Drawworks is the drilling load divided by the number of lines on the traveling block.
In this example the force required by the drawworks to hoist a weight of 1000 kg is reduced by by using a travelling block with one sheave.
The series of sheaves in Crown-Travelling Blocks system reduces the load necessary to hoist a weight.

The RAM RIG is a new concept used to hoist the drill string.
The Drawwork and the drilling line are replaced with a system of hydraulic pistons and rams. Ram rigs can be used with singles or stands, depending on the height of the derrick.
They have only recently been developed and are not yet classified within API/ISO Specs

A Mast is a steel framework with square or rectangular cross-section comprised of multiple sections assembled together.
Mast are normally used on land rigs; they are rarely used on offshore rigs.
Most masts have one side open (window side), while others have both the front and rear side open
(full view).
Generally masts are assembled on the ground in horizontal position and are raised using the drawworks. Some masts use telescopic sections and are assembled in vertical (boot strap).
- API Definition
3.16 mast: A structural tower comprised of one or more sections assembled in a horizontal position near the ground and then raised to the operating position.
If the unit contains two or more sections, it may be telescoped or unfolded during the erection procedure.

Mast Types
There are 2 different types of masts for land drilling and service rigs:
- STATIONARY BASE
- WITH GUY LINES

1 CONCEPTUAL DESIGN
- Derricks
Derricks and Masts consist of a steel framework with a square or rectangular cross-section.
Their purpose is to support the hoisting equipment and rack the tubulars while tripping.
The number of joints in a stand (single-double-triple) that the rig can pull is dependent on the height of the derrick.
- Manufacturer Specifications
Derricks are manufactured in accordance with API 4F or related ISO (International Organization for Standardization) 13626 draft.

This specifications covers the design, manufacture, and use of derricks, portable masts, crown block assemblies and substructures.

- Nameplate Information
Derricks built within API/ISO specs must have a specification nameplate attached in a visible place containing the following information:
a. MANUFACTURER’S NAME.
b. PLACE OF CONSTRUCTION.
c. STANDARD ADOPTED (ex. API 4F). d. SERIAL NUMBER.
e. HEIGHT ( ft ).
f. MAXIMUM STATIC HOOK LOAD ( lbs) FOR STATED NUMBER OF LINES TO TRAVELLING BLOCKS. g. MAX. RATED WIND VELOCITY (Knots) WITH RATED CAPACITY OF PIPE RACKED.
h. EDITION OF THE API  SPEC. USED
I.  GUYING DIAGRAM (when applicable)
j. The following note: “CAUTION: ACCELERATION OR IMPACT, ALSO SETBACK AND WIND LOADS WILL REDUCE THE MAXIMUM RATED STATIC HOOK LOAD CAPACITY.”k. LOAD DISTRIBUTION DIAGRAM.
l.  GRAPH PLOTTING MAX. ALLOWABLE STATIC HOOK LOAD VERSUS WIND VELOCITY. m. MAST SETUP DISTANCE FOR MAST WITH GUY LINES.

2 TYPES AND CHARACTERISTICS
There are 3 different types of derricks:
- DERRICK
- MAST
- RAM RIG

- DERRICK
Pyramidal steel framework with square or rectangular cross section assembled as fixed structure.
- API Definition
A semipermanent structure of square or rectangular cross-section having members that are latticed or trussed on all four sides.
This unit must be assembled in the vertical or operation position, as it includes no erection mechanism. It may or may not be guyed.

- Derrick dimensions
Table 1 - Derrick Sizes and General Dimensions

A - The vertical distance from the top of the base plate to the bottom of the Crown Block support
Beam.
B - The distance between heel to heel of adjacent legs.
C - The window opening measured in the clear and parallel to the center line of the derrick side from top of base plate.
D - The smallest clear dimension at the top of the derrick that would restrict passage of crown block.
E - The clearance between the horizontal header of the gin pole and the top of the crown support beam.

Derrick Types
Derrick are normally used on Offshore rigs and can be divided into categories:
- Stationary Derrick
Derrick used on offshore fixed structures
- Dynamic Derrick
Heavyweight derrick used on floating rigs subjected to marine stress.

Installation on offshore floating unit

- SWING UP - PYRAMID
Drawwork lifts the mast, the substructure and the complete rig floor. Only 2 main lifts are required
- 1st lift to pick up mast and part of rig floor


- 2nd lift to pick up draw work and aft part of rig floor.

- SWING LIFT - BRANHAM

- Position of lifting cables
- 1st PHASE: A-frame positioning
- 2nd PHASE : Lifting the Mast
- 3rd PHASE : Lifting the Drawworks
Lifting Cables - Scheme
1st A-frame Positioning - Scheme 2nd Lifting the Mast - Scheme
- SLING SHOT DRECO

Dedicated hydraulic pistons to lift derrick, substructure and complete rig floor.

INSPECTIONS
Periodical inspections
Substructure, derrick and lifting equipment must have periodical inspections, (every six months)
following the builder's instructions and the API regulations: API RP 4G ed API RP 54.
International Organization for Standardization (ISO) ISO 13534.

1.FUNCTION
The substructure has the function of supporting the drawworks, rotary table, stands of DP and derrick. The top side is generally called the rig floor.
Substructure are made following API STD 4E or 4F regulations. There is usually a plate mounted on the substructure identifying its main characteristics

- API Plate
A - NAME OF THE BUILDER
B - ADDRESS
C - API STANDARD (ie API 4F)
D - SERIAL NUMBER
E - HEIGHT (ft)
F - MAXIMUM STATIC LOAD OF ROTARY TABLE G - MAXIMUM SETBACK STATIC LOAD

2 SUBSTRUCTURE LOAD and DIMENSIONS
- Substructure Load
A.Derrick or mast weight
B.Rig Floor and equipment
C.Maximum load of pipe that can be set back in the derrick
D.Maximum hook load
- Dimensions
Substructure dimensions are proportional to the rig power.


3 TYPES AND CHARACTERISTICS
- Substructure Types
Land rigs are made for frequent Rig Up, moving and Rig Down.
This is the main reason why different substructure types have been developed.
Two main types
- Type Box on Box
- Type: High Floor Substructure
- Type Box on Box
Different modules or boxes are positioned to raise the rig floor.
The numbers of boxes depends on the height required to install the wellhead and BOP stack.
- Type: High Floor Substructure
These have been developed to accommodate higher BOP stacks and wellheads.
Although each builder has their own model, they all have the following characteristics:
Enables the drawworks and derrick to be rigged up at ground level, eliminating the need for big cranes; Uses the rig's drawworks to raise the floor and derrick (some models use hydraulic pistons).

Waste pit dimensions must take into account:
- Total mud volume
- Total cuttings volume
- Cuttings treatment (on location or transported)
- Estimated drilling time.
- Weather conditions.