Drilling Optimization

WellServ, with the help of its MWD services can help clients adopt effective drilling practices to cut costs and improve performance at your wellsite

By gathering and interpreting critical data acquired from surface and downhole sensors, Wellserv engineers with specialised applications can guide and optimize your drilling program.

Equivalent Circulating Density (ECD) (calculated using annulus pressure) is a powerful optimisation tool and can be used to addresss issues related to

• Restrictions in the Annulus
  • Restrictions to circulation increase the pressure necessary to move the fluid at a specific flow rate
  • Restrictions can be caused by swelling formations, poor hole cleaning, hole collapse, fractured formations or any other formation factor that causes the walls of the borehole to come loose and enter the annulus
• Surge and Swab
  • Surge pressures force the fluid up the annulus with increased velocity, resulting in an increase in ECD
  • Swab pressures force the fluid down the annulus; this subtracts from the pressures felt at the sensor and lowers the ECD
  • Running speed and “tightness” of the hole will dictate the severity of the change in ECD
• Rotation increases ECD
  • Rotation changes the eccentricity of the drillpipe which adds turbulence that requires more pressure to move the fluid; this effect is increased with greater hole inclination and rotation speed
  • Rotation keeps solids suspended, which increases mud weight. The degree of increase is determined by the rate of rotation, mud properties, and the well geometry
• Poor Hole Cleaning
  • Uneven ECD during drilling is an indication of poor hole conditions and varying restrictions to circulation





Applications	Pressure Response	Comments
Monitoring Hole Cleaning	A gradual decrease in ECD while steering indicates poor hole cleaning	This results from cuttings settling out in high angle wellbores
	A steady increase in ECD while rotating indicates poor hole cleaning	This results from settled cuttings being lifted back into suspension
	Short term variations in ECD can indicate poor hole cleaning	This results from restrictions in the wellbore while circulating







• Packoff Pressure Spikes
  • Packoff occurs when enough settled cuttings are present to create a restriction in the annulus which causes a sudden increase in ECD
  • Packoff usually is a result of hole collapse or poor hole cleaning
  • Packoff spikes can be large enough to cause formation fracture