Rig volume calculation and capacity are very important to control the well by the mud volume while drilling and different rig operations so, you have to understand the basic concept of volume calculations to achieve this target.
Rectangular Tank Formula
Tank Volume = L X W X H = —- ftᶾ
Where:
L = Length (ft)
W = Width (ft)
H = Hight (ft)
Note: use constant of (5.61) to convert cubic feet to barrels.
It’s used to calculate the mud tank capacity and the mud volume inside it.
A mud tank:
Is an open-top container, typically made of square steel tube and steel plate, to store drilling fluid on a drilling rig. They are also called mud pits.
Mud tanks have different types of shapes depending on clients demands, such as rectangular shape tanks.
Example:
Calculate the tank volume by bbls for the below tank dimension:
L = 15 ft, W = 12 ft, H = 10 ft
Answer:
Volume (bbls)= (L x W x h)/5.61 (const.) = (15 x 12 x 10) / 5.61 = 321 bbls
Volume of cylinder = Area of Base X Hight
= 0.7854 (D/12) ² X H = —- ftᶾ
Where: D = Base Diameter, H= Hight
Volume of cylinder by bbls. = (D² / 1029.4) X H (ft) = — bbls.
To define how many barrels could be held by the cylinder we use the term (Capacity) instead of the term (volume).
It’s used to calculate the Internal capacity for the drill string or the Well capacity. Also, the main purpose of calculating the internal capacities while the operation is to fill up the kill sheet in case you are the one who is considered with killing a detected kick by the Wait and Weight method or Driller’s one.
Annular Capacity = (D²/1029.4) – (d²/1029.4) = — bbls/ft.
Where: D = The hole diameter. & d = drill pipe outer diameter
Metal Displacement:
Metal Displacement = (OD – ID) ²/1029.4 = —- bbls/ft.
In rig mathematics, we calculate the number of barrels needed to fill the hole during the operation to monitor the flow in and flow out of the hole.
According to the annular capacity varieties, we define how many barrels we pump or discharge from the hole to increase or deduct one psi of pressure/foot.
Example:
Calculate the metal displacement of DP of 6 5/8-inch OD and 5.965-inch ID then calculate the total steel displacement for one pipe of 30-foot length.
Answer:
Steel displacement of one foot = (6.6252-5.9652)/1029.4 = 0.0083 bbls/ft
Total displacement for one pipe = 0.00853*30= 0.24 bbls.
Why is the metal displacement calculation important in the rig?
Because we need to calculate the amount of volume of mud in barrels which compensates the metal displacement either in tripping drill equipment in, or pulling them out of the hole.
Lag time Calculations:
Some definition:
Lag Time: is the time in which the mud takes to travel inside the hole between two specified depth points.
Lag In: The time taken between the surface to the bottom of the hole.
“Lag-up” or “Bottoms ‘up”: The time taken between the bottom of the hole to the surface.
Complete cycle: The time taken from the surface to surface.
Measured Depth (M.D): Drilled measured depth.
True Vertical Depth (T.V.D): Drilled True Vertical Depth.
Where: P.O.P = Pump out put, and SPM = Stroke per minute
