Mud Related Drilling Problems Stuck Pipe

•The drill string can be stuck for many reasons including poor hole cleaning due to inadequate mud carrying capacity, sloughing shale, key seating and/or differential pressure sticking.
•Bridges can be caused by poor cleaning or by sloughing of the walls into the wellbore.
–The key to a muds lifting capacity is indicated by the appearance of formation solids coming over the shale shaker.
–An unusually large amount of shale indicates that the hole is washing out.
–Rounded edges on large cuttings show that these pieces have been tumbling in the hole for a long time and are not being lifted out effectively.
–Long splinters or fissured shale may indicate that the shale is "popping" into the wellbore, indicative of overpressuredshale.
–At times large amounts of material can remain in the hole without any surface indication that a hole cleaning problem exists.
•Large pieces of rock, which are not removed from the hole often, become lodged between stabilizers or reamers and the hole.
–If this occurs while drilling, the torque required to rotate the drill string will increase rapidly.
–If pieces of rock become lodged while making a connection or during a trip, the additional pull of the hook will appear as a drag.
–A sudden increase in pump pressure can sometimes be observed, as bridges form and restrict mud flow up the annulus
•Prevention of stuck pipe is often the best remedy


•Methods of preventing stuck pipe due to sloughing shale or inadequate hole cleaning may include the following:
–Increase the viscosity and particularly the Yield Point of the mud.
•There is no exact yield value that can be specified, as every situation is unique, but generally an upper Yield Point of ±30 lb/100ft2should clean most cuttings or cavingsfrom the wellbore.
•Again watch the shale shaker closely to determine the characteristics of cuttings.
–If possible annular hydraulics should be improved, to provide faster cuttings transport.
•Pump liners may have to be changed or larger bit nozzles utilized so that more fluid may be circulated without excessive pump pressure buildup.
•Critical velocities should be calculated to avoid turbulent flow that could increase shale problems by tearing up or eroding the hole.
–Use viscous pills to sweep the hole when drilling. This is a common and effective practice when drilling
–Increasing the mud density may be beneficial in some cases to balance the pore pressure of the shale, and to help hold formations in place to stabilize the wellbore.
–Reducing the water loss may help to minimize the hydration of shales and wetting along bedding planes with could disperse and slough into the wellbore.
–The drill string itself should be evaluated to minimize flexure of the string against the sides of the wellbore, which might tend to physically knock shale from the walls of the borehole.
–Keep the hole full at all times.
•Avoid excessive surge or swab pressures by tripping slowly, especially if a float is utilized in the string.
–Use invert mud or inhibitive water base mud.