BAKER HUGHES - Drilling Fluids Reference Manual

TABLE OF CONTENTS
Shallow water flows, or pressurized gas zones, can present difficult technical challenges deserving
special focus in the planning and execution phases of deepwater projects. These shallow hazards can
cause such events as lost circulation, hole erosion, poor cement jobs, foundation instability, gas
hydrates, casing buckling and in the worst cases, hole abandonment.
Shallow water flows can occur in zones 500 to 3,500 feet below the sea bed. Shallow gas sands are to
be found at similar depths and require a sealing mechanism. Typically, wells are drilled riserless
through these zones, using seawater and bentonite sweeps. Once a shallow hazard is detected there
are two realistic alternatives: 1) spot a kill fluid and run casing or 2) drill ahead with a weighted fluid.
Baker Hughes Drilling Fluids developed its Dynamic Kill Drilling (DKD) methodology to
facilitate drilling ahead with a weighted fluid to facilitate a “push” of the casing setting depth.
DKD DRILLING
The development of DKD began in 1999 as a tool to address shallow hazards. Since its inception,
continuous and concurrent improvements have been made to all facets of the process. There are
essentially four areas, within the DKD process on which to focus: 1) pre-planning software, 2)
equipment, 3) training and 4) field service.
The DKD process employs a dual gradient concept, consisting of the seawater hydrostatic above the
mud line and the ability to vary the hydrostatic below the mud line through drilling fluid density
variations.
MODU
MODU
4,500’
Water Depth
8.55# Sea Water
3,000’
OH
11.00 x .052 x 7,500
Total PSI
4,290.00 PSI
12.50 x .052 x 3,000
2000.70 PSI
4,290 - 2000.70
2,290.70 PSI
7,500’
11.00# Fluid
2,290.70 /.052 / 3,000 =
14.68 PPG
Figure 13 - 1
DKD Example
The above figure illustrates the dual gradient principle. As can be seen, the hydrostatic pressure on
bottom is a combination of the seawater and drilling fluid columns.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 13-2