Slug is heavy drilling mud that is used to pump when you want to pull pipe dry. However, excessive volume of slug in the well can create higher mud weight and cause the problem. Today I would like to share my experience regarding slug in the well.
The situation happened on the drilling rig like this.
The well was TD with 13.0 ppg mud and circulation was conducted until the shale shakers. After that we pull 10 stands wet and pumped 40 bbl of 15.0 ppg slug and came out of hole without any problem. Then we run the logging and we got stuck. We picked the fishing gear and grabbed the fish. We pulled out 10 stands wet and hole was taking proper fill. We pumped same amount of slug 40 bbl of 15.0 ppg and came out of hole. The decision was made by town to trip in hole to do the wiper trip.
Tripping was done with caution and break circulation was conducted every 3000 ft to break the gel. Prior to TD 100 ft, we made up top drive and slowly washed down to TD. While we were circulating, the mud weight out was varied from 13.2 ppg to 14.2 ppg. Additionally, we start losing mud while circulating.
Do you know what went wrong?
The two slugs in the well cause us trouble.
If you would like to learn about drilling engineering, this book, Applied Drilling Engineering – Spe Textbook Series, is my recommendation. The book contains various topics regarding drilling engineering.
What will you learn from this book?
Rotary drilling – basic of drilling rigs, rig power system, hoisting system, circulating system, etc.
Drilling fluids – Mud test, pilot test, water based mud and oil based mud.
Cements – composition of cement, cement testing, cement additives, and cement placement techniques used in the drilling field.
Drilling hydraulics – Hydrostatic pressure, annular pressure during well control operation, buoyancy factor, non static well condition, flow through jet bits, rheology models, laminar and turbulent flow, surge/swab pressure and particle slip velocity.
This is the second up date of drilling formula spread sheet, Drilling Formula Excel Sheet Version 1.2.
Drillingformulas.com distributed the first version of drilling formula spread sheet on 28 March 2011 and another update on 18 May 2011. The calculation sheet has been downloaded over 8,300 times around the world since the fist distribution.
Today, the lasted up date of drilling formula spread sheet, Drilling Formula Excel Sheet Version 1.2 is available for you to download. It is still totally FREE !!!.
Click here to get the drilling formulas spread sheet.
What new drilling formulas are added into this version?
Cutting Slip Velocity Method#1
Cutting Slip Velocity Method#2
Surge and Swab Pressure Method#1
Surge and Swab Pressure Method#2
Total Flow Area Table
Calculate Influx Height
Hydrostatic Pressure Loss Due to Gas Cut Mud
Kill Weight Mud
Maximum pit gain from gas kick in water based mud
Maximum Surface Pressure from Gas Influx in Water Based Mud
How many total useful drilling formulas in this version?
There are a total of 75 formulas which are divided into 7 categories (Applied Drilling Formulas, Basic Drilling Formulas, Directional Drilling Calculation, Drilling Fluid Formulas, Engineering Formulas, Hydraulic Formulas and Well Control Formulas).
How much will it cost?
Nothing. The spread sheet is totally FREE for everybody.
This is another method to determine cutting slip velocity. The process of calculation is quite different from the first method however it is still straight forward calculation. It still gives you the following answers: annular velocity, cutting slip velocity and net velocity.
Let’s get started with this calculation method.
1. Determine n
n is the power law exponent.
Θ600 is a value at 600 viscometer dial reading.
Θ300 is a value at 300 viscometer dial reading.
Cutting slip velocity is velocity of cutting that naturally falls down due to its density. In order to effectively clean the hole, effect of mud flow upward direction and mud properties must be greater than cutting slip velocity (settling tendency of cuttings). Otherwise, cutting will fall down and create cutting bed.
You can learn more detail about it via this topic -> Cutting Slip Velocity
This calculation will show annular velocity, cutting slip velocity and net velocity so you can use as a reference for you hole cleaning indication.
There are 2 calculation methods and I will show the first method via this topic.