The tangential method is the simplest calculation among other directional survey calculations.
The tangential method formulas are listed below;
Tangential Method Calculation formula
Aug
15
The Minimum Curvature Method smooths two straight-line segments of the Balanced Tangential Method by using the Ratio Factor (RF).
The formulas for the Minimum Curvature Method are listed below;
β must be in radians
Aug
10
I have some directional calculations that I’ve shared with you. However, some of them are not shared yet so I will try to share all directional drilling formulas that may be helpful for you in the future.
Today, I would like to show you about Balanced Tangential Method Calculation. This calculation method treats half of the measured distance (MD/2) as being tangent to I1 and Az1 and the remainder of the measured distance (MD/2) as being tangent to I2 and Az2.
Jul
5
I created summary page for drilling formulas and calculations (http://www.drillingformulas.com/drilling-formulas-and-calculation-sheets/). I wish these excel sheets would be helpful for you.
Amount of cuttings produced per foot of hole drilled
Annular Pressure Loss
Annular-Capacity
Annular-velocity
Bulk Density Calculation
Buoyancy Factor Oilfield
Convert Pressure to Equivalent Mud Weight
Convert-Specific-Gravity
Cost Per Foot Calculation
Critical RPM
D Exponent Calculation
D Exponent Corrected Calculation
Decrease Oil Water Ratio
Density of Oil Water Mixture
Depth of Washout
Read the rest of this entry »
May
24
We still have the same question as the previous post, Pressure Loss and Equivalent Circulating Density Review, but this case we will do reverser circulation, circulating from annulus to tubing , and see how much pressure and equivalent circulating density at bottom hole.
May
20
This example that I got from my junior member is very simple but it helps you a lot to understand about how to determine pressure loss during normal circulation.
Information given is listed below;
Circulate at 3 bottom up through open end tubing (Down tubing and up annulus) with 12.7 ppg mud.
Pump pressure = 1000 psi
Annulus friction loss = 50 psi
Inside tubing friction loss = 925 psi
Surface line friction loss = 25 psi
May
17
I still have the simple but interesting question about hydrostatic pressure which you can apply this calculation into drilling/cementing operation. The question I got about how much pressure we will see at cement head in case of float shoe fail.
Mar
2
All types of ton-mile service should be calculated and recorded in order to obtain a true picture of the total service received from the rotary drilling line. There are several types of ton miles as follows;
1. Round trip ton-miles
2. Drilling or “connection” ton-miles
3. Coring ton-miles
4. Ton-miles setting casing
5. Short-trip ton-miles
For this time, I will show how to calculate round trip ton-mile.
Round Trip Ton-Miles Calculation
The formula for round trip ton-miles is listed below;
RTTM = (Wp x D x (Lp + D) + (2 x D) x (2 x Wb + Wc)) ÷ (5280 x 2000)
where
RTTM = Round Trip Ton-Miles
Wp = buoyed weight of drill pipe in lb/ft
D = hole measured depth in ft
Lp = Average length per stand of drill pipe in ft
Wb = weight of travelling block in lb
Wc = buoyed weight of BHA (drill collar + heavy weight drill pipe + BHA) in mud minus the buoyed weight of the same length of drill pipe in lb
** If you have BHA (mud motor, MWD, etc) and HWDP, you must add those weight into calculation as well not just only drill collar weight. **
2000 = number of pounds in one ton
5280 = number of feet in one mile
Example: Round trip ton-miles
Mud weight = 10.0 ppg
Average length per stand = 94 ft
Drill pipe weight = 13.3 lb/ft
Hole measure depth = 5500 ft
Drill collar length = 120 ft
Drill collar weight = 85 lb/ft
HWDP length = 49 lb/ft
HWDP weight = 450 ft
BHA weight from directional driller = 8,300 lb
BHA length = 94 ft
Travelling block assembly = 95,000 lb
Solution:
a) Buoyancy factor:
BF = (65.5 – 10.0) ÷ 65.5
BF = 0.847
b) Buoyed weight of drill pipe in mud, lb/ft (Wp):
Wp = 13.3 lb/ft x 0.847
Wp = 11.27 lb/ft
c) buoyed weight of BHA (drill collar + heavy weight drill pipe + BHA) in mud minus the buoyed weight of the same length of drill pipe in lb (Wc):
Wc = {[(120x85) + (49x450) + (8300)] x 0.847} – [(120+450+94) x13.3x 0.847]
Wc = 26,866 lb
Round trip ton-miles = [(11.27 x 5500 x (94+ 5500)) + (2 x 5500) x (2 x 95000 + 26,866)] ÷ (5280 x 2000)
RTTM = 258.75 ton-mile
Please find the excel sheet for round trip ton-miles calculation via click this link.
Ref book: 
Formulas and Calculations for Drilling, Production and Workover, Second Edition
Dec
14
For subsea applications, hydrostatic pressure exerted by the hydraulic fluid must be accounted for calculation.
In this case, we assume water depth at 1500 ft, therefore hydrostatic pressure exerted by hydraulic fluid (hydraulic fluid pressure gradient = 0.445 psi/ft) = 0.445×1500 = 668 psi. Besides of that, the concept for calculation is as same as surface accumulator. So please take a look about how to calculate usable volume per bottle as following steps.
Step 1 Adjust all pressures for the hydrostatic pressure of the hydraulic fluid:
Pre-charge pressure = 1000 psi + 668 psi = 1668 psi
Minimum system pressure = 1200 psi + 668 psi = 1868 psi
Operating pressure = 3000 psi + 668 psi = 3668 psi
Step 2 Determine hydraulic fluid required to increase pressure from pre-charge pressure to minimum system pressure:
Boyle’s Law for ideal gase: P1 V1 = P2 V2
1668 psi x 10 = 1868 x V2
16,680 ÷1,868 = V2
V2 = 8.93 gal
It means that N2 will be compressed from 10 gal to 8.93 gal in order to reach minimum operating pressure. Therefore, 1.07 gal (10.0 – 8.93 = 1.07 gal) of hydraulic fluid is used for compressing to minimum system pressure.
Step 3 Determine hydraulic required increasing pressure from pre-charge to operating pressure:
P1 V1 = P2 V2
1668 psi x 10 gal = 3668 psi x V2
16,680 ÷ 3668 = V2
V2 = 4.55 gal
It means that N2 will be compressed from 10 gal to 4.55 gal in order to reach operating pressure. Therefore, 5.45 gal (10.0 – 4.55 = 5.45 gal) of hydraulic fluid is used for compressing to operating pressure.
Step 4 Determine usable fluid volume per bottle:
Usable volume per bottle = Total hydraulic fluid/bottle – Dead hydraulic fluid/bottle
Usable volume per bottle = 5.45 – 1.07
Usable volume per bottle = 4.38 gallons
Well Control Book Ref book: 
Formulas and Calculations for Drilling, Production and Workover, Second Edition
Dec
9
Accumulator (Koomey) is a unit used to hydraulically operate Rams BOP, Annular BOP, HCR and some hydraulic equipment. There are several of high pressure cylinders that store gas (in bladders) and hydraulic fluid or water under pressure for hydraulic activated systems. The primary purpose of this unit is to supply hydraulic power to the BOP stack in order to close/open BOP stack for both normal operational and emergency situation. Stored hydraulic in the system can provide hydraulic power to close BOP’s in well control operation, therefore, kick volume will be minimize. Accumulators should have sufficient volume to close/open all preventers and accumulator pressure must be maintained all time.
This post you will learn how to calculate usable volume per bottle by applying Boyle’s gas law:
Use following information as guideline for calculation:
Volume per bottle = 10 gal
Pre-charge pressure = 1000 psi
Operating pressure = 3000 psi
Minimum system pressure = 1200 psi
Pressure gradient of hydraulic fluid = 0.445 psi/ft
For surface application
Step 1 Determine hydraulic fluid required to increase pressure from pre-charge pressure to minimum:
Boyle’s Law for ideal gase: P1 V1 = P2 V2
P1 V1 = P2 V2
1000 psi x 10 gal = 1200 psi x V2
10,000 ÷ 1200 = V2
V2 = 8.3 gal
It means that N2 will be compressed from 10 gal to 8.3 gal in order to reach minimum operating pressure. Therefore, 1.7 gal (10.0 – 8.3 = 1.7 gal) of hydraulic fluid is used for compressing to minimum system pressure.
Step 2 Determine hydraulic required increasing pressure from pre-charge to operating pressure:
P1 V1 = P2 V2
1000 psi x 10 gals = 3000 psi x V2
10,000 ÷3000 = V2
V2= 3.3 gal
It means that N2 will be compressed from 10 gal to 3.3 gal. Therefore, 6.7 gal (10.0 – 3.3 = 6.7 gal) of hydraulic fluid is used for compressing to operating pressure.
Step 3 Determine usable fluid volume per bottle:
Usable volume per bottle = Hydraulic used to compress fluid to operating pressure – hydraulic volume used to compress fluid to minimum pressure
Usable volume per bottle = 6.7 – 1.7
Usable volume per bottle = 5.0 gallons
Ref book: Formulas and Calculations for Drilling, Production and Workover, Second Edition
