Well Control Methods and Procedures Flashcards
Objective of Kill Method
Circulate out any invading fluid (liquid or gas) and circulate a satisfactory weight of kill mud into the well, without allowing further influx into the hole
Constant Bottom-Hole Pressure Kill Methods
Driller’s Method, Wait and Weight Method (Engineer’s Method), Concurrent Method
Driller’s Method
Split into 2 circulations. During the first, the kick fluid is circulated without changing the mud weight; once the influx is out, the mud is weighted up and pumped around the well on the second circulation
Wait and Weight
Kill mud is prepared before starting the kill, and the kick fluid is circulated out while this mud is circulated into the well
Concurrent Method
Kill mud is introduced in stages while circulating.
Three S Procedure (Drilling)
Space out, Shut down pumps, shut-in
Shut-in
Close uppermost applicable BOP when shutting in
Three S Procedure (Tripping)
Stab FOSV, Space out, Shut-in
Total Volume to Weight-Up
Reduce pit volume before weighting up. It takes less time, it requires less barite, and pits may overflow without reducing volume
Barite Required
Volume to Weight up x (15 x Increase in Mud Weight) / (35 - New Mud Weight)
Time for Gas at Surface
Usually seen after pumping 1/2 to 2/3 calculated bototms up strokes
Establishing Circulation
Ensure crew knows responsibilities, eliminate all ignition sources, secure vent lines, line up manifold, and zero stroke counter
DP Pressure Drop / Stroke
(ICP - FCP) / Total DP Strokes, 100 stroke increment is standard
Volumetric Method
Used when unable to circulate (Unoperative pumps, bit plugged, drill pipe above influx, or when pipe is out of hole). A method used to hold CBHP, not kill the well.
Principles of Volumetric Method
Boyle’s Law, Hydrostatic Pressure, and Volume and Height
Boyle’s Law
P1V1 = P2V2, Pressure of a gas is directly related to its volume (neglecting temperature effects)
Volumetric Mud Increment Calculation
Pressure Increment (100 psi) x ACF / (MW x 0.052)
Purpose of Volumetric Method
Permit controlled expansion of the gas bubble as it migrates up the hole.
Volumetric Pressure Increment
The amount of pressure to be used as a working pressure range while performing the Volumetric Control Method.
Volumetric Safety Factor
An increase in the bottomhole pressure which is allowed to occur naturally as gas migrates up the annulus with the well shut in. An appropriate value for the safety factor is 50 - 200 psi.
Volumetric Mud Increment
The volume of mud which is to be bled from the annulus in order to reduce the annular hydrostatic pressure by the amount of the PI.
Volumetric Procedure
- Perform Calculations 2. Allow casing pressure to increase to establish safety factor plus PI 3. Hold casing pressure constant until the mud increment is bled off 4. Wait for the casing pressure to increase as the gas bubble migrates 5. Hold casing pressure constant by bleeding mud from the annulus 6. Alternate holding casing pressure constant and letting gas bubble rise
Gas Rate of Rise (ft/hr)
Change in SICP / (MW x 0.052 x Change in Time)
Volumetric for Subsea
Use ACF at mudline. When KL and CL diverge, begin using ACF of CL.
End of Volumetric Method
When the SICP is stable and not rising. Some gas may be bled off before the SICP stabilizes.
Lubricate and Bleed
Surface pressure is replaced with hydrostatic pressure by pumping mud into the well on top of the gas. The gas and mud are allowed to change places in the hole and a certain amount of the surface pressure is then bled off.
Lubricate and Bleed Procedure
- Perform Calculations 2. Lubricate by slowly pumping a given volume into the well 3. Wait for the gas to migrate back to the surface 4. Bleed gas from the well until the surface pressure is reduced by an amount equal to the hydrostatic pressure of th emud pumped in 5. Repeat steps 2 through4 until all of hte gas has been bled off or a desired surface pressure has been reached
Bullheading
A technique that may be used in certain circumstances during drilling operations to pump an influx back into the formation.
When to Bullhead (Drilling)
When a very large influx has been taken, when conventional methods may cause excessive surface pressures, when displacement of the influx would result in an excessive gas volume at surface (MGS limitations), if the influx contains an unacceptable level of H2S, When stripping back to bottom is not feasible, when there is no pipe in the hole, or to reduce surface operations
Factors that Determine Feasibility of Bullheading
The characteristic of the openhole, the rated pressure of the well control equipment and the casing, drill pipe andcasing pressure limits, the type of influx and the relative permeability of the formation, the position of the influx on the hole, the quality of the filter cake at the permeable formation, the consequences of fracturing the openhole, and the possibility of formation damage
Bullheading Procedure
- Calculate surface pressures that would cause fracture 2. Prepare a chart using strokes vs. pumping pressure if heavier mud is used 3. If gas is at surface, used lube and bleed first 4. Bring the pumps up to speed slowly to overcome well pressure 5. Attempt to pump fast enough to exceed gas migration rate 6. As the produced fluids are forced back into the formation, the added hydrostatic should lower pump pressure 7. Stop the pump, shut-in and monitor
What to do after taking a kick off bottom?
- Kill the well off bottom (not recommended) 2. Use volumetric well control if you have migrating gas 3. Strip back to bottom 4. Strip using volumetric well control if you have migrating gas 5. Snub the drill pipe back in the well
Stripping
Tripping pipe through the BOPs when the drill string weight is greater than the net upward force created from the wellbore pressures
Snubbing
Forcing pipe through the BOPs when the drill string weight is not sufficient to overcome the net upward force created by wellbore pressures
Initial Shut-in Considerations (Stripping)
Is the annular in good condition, rig crews should be aware of the responibilities, an IBOP is required for stripping, the annular element can be changed with pipe in the hole by inserting a split element, ram combination stripping is not recommended, surface pressure determines whether annular stripping is possible (due to rating and increased pressure increases wear), field test show good results at 800 psi but unpredictable at 800 psi, reduce the annular pressure to allow drill pipe to be stripped easier, a a surge dampener is usefull to allow tool joints to pass through the annular without increasing annular pressure
Ways to reduce annular pressure to allow stripping
Circulate out the influx if it is above the circulation point, bullhead, or lubricate and bleed if at BOP
Volume Accounting (Stripping)
Bleed off volume equal to the closed end steel displacment
Constant Surface Pressure (Stripping)
Maintaining a constant surface pressure by bleeding fluid through the choke as pipe is run (Most preferred)
Influs Penetration (Stripping)
When the drill string penetrates the influx, the height increases. As the height of the influx increases, hydrostatic pressure decreases and the casing pressure must increase.
Stripping Procedure (Without Volumetric)
- Calculations: bit depth vs. kick depth, pressure increase due to influx penetration, net upward force vs. downward force, determine appropriate safety factor, and calculate theoreticla bleed volume per stand 2. Stab and make up the IBOP on top of te FOSV 3. Regulate annular closing pressure to permit stripping (A small leak is desirable) 4. Strip into the well until you establish the desired safety factor 5. Continue by stripping to the desired depthwhile bleeding of fhte calculated fluid volumeper stand
Stripping Procedure (With Volumetric)
- Calculations: net upwward force vs. downward force, theoreticla bleed volume per stand, determine safety factor, choose PI and MI, bit depth and kick depth, calculate increase in pressure while penetrating bubble 2. Stab and make up IBOP on top of FOSV 3. Regulate annular stripping pressure to permit stripping (A small leak is desirable) 4. Strip into the well until you establish the desired safety factor 5. Continue stripping into the well keeping casing pressure constant 6. When the difference between total fluid bled and pipe displacement equals the MI, strip in while increasing pressure to the next PI step 7. Repeat steps 5 and 6 once the PI has been reached 8. Upon penetrating the bubble: Allow casing pressure to increase by predetermined ammount and adjust step 6 for new MI 9. Repeat steps 5 and 6 until at desired epth
Practical Stripping Considerations
Stripping with volumetric control is complex, eliminate the bubble penetration calculation by adding a safety factor equal to the pressure increase, calculate the MI using the capacity factor around the drill pipe, do not fill the pipe completely to keep track of volumes better, when stripping with volumetric only one step may be achieved before reaching bottom,
Rotating Pipe During Well Control Operations
If rotating pipe is necessary, the pipe should be reciprocated as well. Several incidents have occurred where pipe being rotated has been severed due to steel components that support rubber annular BOP components
Glycol
An inhibiting agent that lowers the temperature at which hydrates would be expected to form
Methanol
Used to dissolve existing hydrate formations
