CIRCULATION & WELL CONTROL

WILD WELL CONTROL

 Learning Objectives

You will learn:

 The importance of pump rates and pressures during well control operations
 Pressure relationships
 Basic calculations necessary in well control for:
 Capacity

 Volume

 Strokes

WILD WELL CONTROL

 Overview

• Pumps are one of the basic tools used in well control.

• Used to circulate kick fluids out
• Used to circulate kill fluid throughout well.
• Used to pump cement, pills, plugs, etc.
• Usually measured in strokes per minute and output, bbls/min.
• Small changes in pump rate can greatly affect pressures throughout well.
• So, in well control, to keep bottom hole pressure in a specified range, pump
rate needs to be carefully controlled.

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WILD WELL CONTROL
 Circulation and Well Control

Overview
• Pumps are one of the basic tools used in well control.
• Used to circulate kick fluids out.
• Used to circulate kill fluid throughout well.
• Used to pump cement, pills, plugs, etc.
• Usually measured in strokes per minute and output, bbls/min.
• Small changes in pump rate can greatly affect pressures
throughout well.
• So, in well control, to keep bottom hole pressure in a specified range,
pump rate needs to be carefully controlled.

WILD WELL CONTROL

 Kill Rate

 Pump speed is critical because it affects pump pressure.

• Any change in speed may drastically affect circulating pressure!
 Usually taken at 1/4, 1/3 and 1/2 normal circulating rate.
• Often 20, 30 and 40 stk/min are used.
• Sometimes based on rate to reach a certain pressure.
• Sometimes based on bbls/min (e.g., 2 – 5 bbls/min).

WILD WELL CONTROL

 Kill Rate Pressure

 Kill rate pressure is the circulating pressure at the kill rate pump speed.
 Kill rate pressures should be taken when:
• There is a change in fluid density or fluid flow (rhelogical) characteristics.
• There is a change in bit and bit nozzles.
• BHA, downhole tools and string changes.
• When 500 or more feet of new hole is drilled.
• Each tour.
• After pump repair.

WILD WELL CONTROL

 Kill Rate Pressure

 Ideally, kill rate pressures should be taken through the kill manifold and choke.
• Have to flush kill manifold and choke.
• Usually taken with BOP stack open instead.
 A small change in rate can affect circulating pressure greatly.
 This can be mathematically calculated.
• A pump pressure and rate must be known.
• Fluid properties have to be the same.
• Much better to get actual pressures than calculated.
P2 = P1 X (SPM22  SPM12)
Where:
P2 = original pump pressure at SPM1, psi
P1 = reduced or changed pump pressure at SPM2, psi
SPM1 = original pump rate, stks/min
SPM2 = reduced or changed pump rate, stks/min

WILD WELL CONTROL

 Initial Circulating Pressure

 Initial circulating pressure (ICP) - the combination of shut-in drill pipe pressure plus the pressure
needed to circulate fluid at a given rate.

ICP = KRP + SIDPP

Where:
ICP = initial circulating pressure, psi
KRP = kill rate pressure, psi
SIDPP = shut in drill pipe pressure, psi

WILD WELL CONTROL

 Initial Circulating Pressure

 ICP is the circulating pressure used once the pump is at kill rate speed.
• If no kill fluid is pumped, then this is the circulating pressure necessary to maintain BHP constant at or
slightly above FP.
• If kill fluid is pumped, ICP must be allowed to drop as the kill fluid fills the string increasing hydrostatic
killing the pressure deficit.

WILD WELL CONTROL

 Final Circulating Pressure

 Once kill fluid fills the string the circulating pressure is commonly referred to as
Final Circulating Pressure (FCP).
This change in circulating pressure can be calculated by:

FCP = KRP X (KWM  OMW)

Where:
FCP = final circulating pressure, psi
KRP = kill rate pressure, psi
KWM = kill weight mud (fluid), ppg
OMW = old mud weight, ppg

WILD WELL CONTROL

 Surface to Bit, Pump Strokes and Time

 The number of strokes to pump a fluid, such as a kill fluid, from the surface to the end of the
string is critical for successful well control and maintaining BHP constant.
 Also, the time to pump from the surface to the end of the string is important.

 The volume within the string must be calculated. This is the combined total of:
• Volume of tubing or drill pipe.
• Volume of BHA.
• Additionally, the amount of strokes/time to clear the surface equipment should be known.

WILD WELL CONTROL

 Surface to Bit, Pump Strokes and Time

 To calculate a pipe/string volume:

Volumebbls = Capacity bbl/ft X Length ft

This is calculated for each section of the string (i.e. pipe, HWDP, BHA)
 The volumes are totaled for the entire string.

 To calculate the amount of strokes to displace the string volume:

Strokes = Total String Volume bbls  Pump Output bbl/stk

Note: Capacity of pipe may be looked up in charts and tables.

WILD WELL CONTROL

 Surface to Bit, Pump Strokes and Time

 If lookup tables are not available, the following formula can be used to calculate the capacity of a
cylindrical object such as an open hole, casing, tubing, drill pipe, BHA or choke/kill lines in bbls/ft :

Capacity bbls/ft = Diameter2  1029.4

WILD WELL CONTROL

 Annular Volumes

 The calculation for annular volume is similar to that of capacity, but subtracting out the
displacement of the tubulars in the well.
 There may be several different bbl/ft annulus capacity sections:
• Based on well bore geometry and where different pipes are located.
• Each section must be calculated individually:
- Tubing/DP in casing, liner, open hole and/or riser.
- Hevi wate in casing, liner, open hole and/or riser.
- BHA/DC in casing, open hole and/or riser.

WILD WELL CONTROL

 Annular Volumes

 If lookup tables are not available, the capacity for each section can be calculated by:
Capacity bbls/ft = (OD2 - ID2)  1029.4
Where:
ID = ID of open or cased hole, inches
OD = OD of tubular in section, inches
Note: 1029.4 is the conversion factor between cylindrical area and volume

 Once the capacities are known, the volumes for each section and total volume can be calculated.

 Strokes to surface and time to surface for bottoms up can then be easily calculated.

WILD WELL CONTROL

 Total Circulating Strokes and Time

 Simply by adding the volumes for each section, a total volume, strokes and circulating time down
the string and back to surface can be calculated.
• By adding separate volumes from surface, or the bottom of the string we can also calculate volume,
strokes and time to circulate for:
- End of string or bit to casing shoe
- Choke and kill line
- Any individual or combined lengths and sections

WILD WELL CONTROL

 Circulation and Well Control

Learning Objectives
 You learned the importance of pump rates and
pressures during well control operations.
 You learned pressure relationships.
 You learned basic calculations necessary in
well control for:
• Capacity
• Volume
• Strokes

WILD WELL CONTROL