impact of cuttings concentration on ECD

1. A PROJECT REPORT PRESENTATION ON
IMPACT OF CUTTINGS CONCENTRATION ON EQUIVALENT
CIRCULATION DENSITY
PRESENTED BY-
PRATIK KUMAR
DEPARTMENT OF PETROLEUM ENGINEERING
NIMS INSTITUTE OF ENGINEERING & TECHNOLOGY
NIMS UNIVERSITY RAJASTHAN, JAIPUR
2018

2. CONTENTS
• INTRODUCTION
• DEFINITIONS
• OBJECTIVES
• SYMPTOMS OF THE INADEQUATE HOLE CLEANING
• ECD CALCULATION
• CUTTINGS CONCENTRATION PROFILE AT VARIABLE FLOW RATES
• ECD AT BOTTOM WITH/WITHOUT CUTTINGS
• ECD AT BOTTOM VS. FLOW RATE AT VARIABLE ROPS
• CONCLUSION

3. INTRODUCTION
 Cuttings concentration vary throughout the wellbore which depends on the ROP,
pump rate, rheology and viscosity and amount of cuttings created.
The effective density exerted by a circulating fluid against the formation that takes into
account the pressure drop in the annulus above the point being considered.
 Drilling problem that may result includes:
High torque and drag
Reduction in rate of penetration
Faster bit wear
Losing control of the bottom hole pressure
Stuck pipe

4. DEFINITIONS :
CUTTINGS CONCENTRATION - The cuttings concentration is the volume fraction of
cuttings in the annulus fluid.
EQIVALENT CIRCULATION DENSITY (ECD)- ECD is the effective density that combines
current mud density and annular pressure drop.
HYDROSTATIC PRESSURE- The pressure exerted by the drilling fluid at equilibrium at a
given point within the fluid, due to force of gravity.
SLIP VELOCITY-The difference between the average velocities of two different fluids
flowing together in a pipe.
PLASTIC VISCOSITY – PV is the slope of the shear stress/shear rate line above the yield
point.
YIELD POINT- YP is used to evaluate the ability of a mud to lift cuttings out of the annulus

5. OBJECTIVES
 Cuttings concentration will affect the pressure and ECD in annulus.
Increasing flow rate or decreasing annulus cross section area will
always increase hole cleaning.
Cuttings density and mud density directly affects the ECD when
considering cuttings concentration.

6. SYMPTOMS OF INADEQUATE HOLE CLEANING
Small volume of cuttings at the shaker as compared to the volume of
the hole cleaning
Large amount of fill after trips
Increasing drag
Increasing torque
Reground (small and rounded) cuttings
Increased ECD as measured by the PWD tool

7. ECD CALCULATION
ECD= P/0.052*TVD

8. Cuttings concentration profile at variable flow rates
Flow rate
(gpm)
Cuttings concentration (%)
Interval 1 Interval 2 Interval 3
78 10.74 8.03 2.44
94 4.89 3.96 1.76
120 2.28 2.02 1.21
286 0.48 0.47 0.40
400 0.31 0.30 0.27
800 0.14 0.14 0.13
Interval 1: 0 – 6,500 ft; Interval 2: 6,500 – 9,500 ft; Interval 3: 9,500 – 10,000 ft

9. ECD AT BOTTOM WITH/WITHOUT CUTTINGS
Flow rate (gpm) ECD at bottom (ppg)
ROP: 0 (ft/hr) ROP: 20 (ft/hr)
78 10.72 11.72
94 10.72 11.19
120 10.73 10.95
286 10.78 10.82
400 10.84 10.87
800 11.42 11.44

11. ECD AT BOTTOM VS. FLOW RATE AT VARIABLE ROPS
At the same flow rate, the higher the drilling rate, the higher the
ECD at bottom.

12. CONCLUSION
cuttings concentration will affect the pressure and ECD in annulus. At
design stage, cuttings concentration should be calculated to predict the
actual ECD at bottom to prevent the loss of circulation, differential sticking
and other hazard damage of the wellbore.
Increasing flow rate or decreasing annulus cross section area will always
increase hole cleaning.
Cuttings density and mud density directly affects the ECD.
Actual ECD prediction is more important for those wells with a narrow
margin between the pore and fracture pressure gradient.