Well Control Procedures2
•The Wait-and-Weight Method
–After the well is shut in, the rig crew “waits”while the drilling fluid in the pits is “weighted”up to the kill-mud weight.
–In order to use this method successfully, sufficient weight material must be on location and the mixing capacity must be sufficient to maintain the kill-mud weight while circulating at the slow pump rate.
–This procedure is more complicated than the Driller’s Method.
–In the Driller’s Method, weighted mud is not pumped into the well until the kick has been circulated out of the well.
–The gas expansion is compensated for by maintaining a constant drill pipe pressure while circulating the kick out.
–When weighted mud is pumped into the well, the casing pressure is held constant until the weighted mud reaches the bit.
–This compensates for the changing hydrostatic pressure in the drill pipe.
•The Wait-and-Weight Method
–In the Wait-and-Weight Method, gas is expanding in the annulus while the hydrostatic pressure is increasing in the drill pipe.
–This requires that the pump pressure needed for maintaining a constant bottom-hole pressure must change as the fluid is circulated.
–A chart of the scheduled pump or drill pipe pressure changes simplifies the kill procedure and reduces the chance of error.
–The pressure schedule or graph determines the pump pressure while the kill mud is being pumped down the drill pipe.
–As the hydrostatic pressure in the drill pipe increases, the pump pressure necessary to maintain the correct bottom-hole pressure is reduced.
–Well-control worksheets for the Wait-and-Weight Method contain a pressure schedule graph.
–The schedule is drawn on standard rectangular coordinates.
–The vertical axis is for the pump pressure and the horizontal axis is for the pump strokes.
–At zero (0) pump strokes, plot the ICP on the pressure scale.
–Plot the surface-to-bit strokes and plot the FCP on the graph.
–Draw a straight line between the two points.
–It is not practical to try to maintain too fine a control on the drill pipe pressure while killing the well.
–Instead, make a chart that shows the pump pressure from the schedule at a selected stroke interval (i.e. 100, 150, 200 etc.).
–The pump pressure is maintained according to this pressure until the selected number of strokes is pumped.
–The pump pressure is then reduced to the next pressure until the stroke interval is pumped.
–This stair step fashion is continued until the kill mud reaches the bit.
–At that time, the pump pressure is held constant until the kill mud is observed at the surface.
•NOTE: The pump pressure will decrease on its own as the kill-mud weight is pumped down the drill pipe.
•This is due to the increase in hydrostatic pressure in the drill pipe.
•As a result, few, if any, choke adjustments are required while pumping kill mud down the drill pipe.
•Some adjustments will be required to account for the changing hydrostatic pressure in the annulus due to the intruding fluid moving up the annulus.
•The Wait-and-Weight Method–Once the kill-weight mud reaches the bit, the pump pressure is held constant at the Final Circulating Pressure (FCP) until the kill mud reaches the surface. –This FCP is calculated with the following equation.
FCP =( RCP x kill-mud weight)/(original mud weight)
–This equation calculates the reduced circulating pressure using the kill-mud weight as the circulating fluid.
–The calculations for pressures through these two sections of the circulating system are based on turbulent pressure losses and energy changes.
–Since the only significant change to the drilling fluid properties used to calculate these pressure losses is the mud density, the circulating pressure is increased by the ratio of the kill-mud weight to the original mud weight.
–The Initial Circulating Pressure (ICP) is calculated the same way as in the Driller’s Method:
ICP = RCP + SIDPP
–The pressure schedule is drawn using the ICP, FCP and the surface to-bit strokes.
–Shut the well in and record the pertinent kick information.
–Calculate the kill-weight mud.
–Begin increasing the mud weight in the surface pits to the kill-weight mud.
–Calculate the ICP.
–Calculate the FCP.
–Calculate the surface-to-bit strokes.
–Construct a pressure schedule.
–Open the adjustable choke and start pumping at the pre-selected slow pump rate.
–Adjust the choke to obtain a pump pressure equal to the ICP.
–Circulate out the kick following the pressure schedule using the adjustable choke.
–Maintain a constant pump rate throughout the
–circulating process.
–Maintain the mud weight in the surface system at the kill-mud weight.
–Once the kill mud reaches the bit, maintain the FCP until the kill mud is observed at the surface.
–Stop pumping and shut the well in to check for pressures.
–If shut-in pressures exist, additional mud weight and circulation will be required.
–If no shut-in pressures exist, the well is under control.
–At this time, one or two circulations can be made to condition the mud and increase the mud weight to provide a trip margin.
•The Circulate-and-Weight Method
–The Circulate-and-Weight (Concurrent) Method is used to circulate the kick out of the hole while increasing the density of the drilling fluid gradually to the kill-mud weight.
–The well is shut in only long enough to obtain the pertinent information about the kick situation.
–The calculations and techniques used in the Wait-and-Weight Method are used in the Circulate-and-Weight (Concurrent) Method.
–Start circulating with the initial circulating pressure and begin adding barite to the system until you reach the kill-weight mud.
–This method uses a gradual increase in mud weight as the kick is circulated out.
–The Circulate-and-Weight (Concurrent) Method is more complex than either the Driller’s Method or the Wait-and-Weight Method due to the various densities of drilling fluid in the drill pipe.
–The number of different densities and the volumes of each depends upon the mixing capability and circulating rate of the drilling rig used.
–A complicated pressure schedule is necessary, as is a precise knowledge of when a mud density was achieved and pumped down the drill pipe.
–Excellent communications between the choke operator and the mud pits is required.
–A pressure schedule similar to that of the Wait-and-Weight Method must be developed.
–The difference between the schedules is that the circulating pressure will be plotted vs. the mud weight.
–Use the Y-axis for the pressure and the X-axis for the mud weight.
–Three calculations will be required to complete the schedule:
•Kill-mud weight, ICP and FCP.
–The equations for these are the same as for the Wait-and-Weight Method.
–To construct the schedule, plot the ICP at the original mud weight.
–Then, plot the FCP at the kill-mud weight.
–Use a straight edge to connect the two points.
–Start circulating at the reduced circulating rate.
–Adjust the choke to reach the ICP.
–While circulating, begin increasing the density of the mud in the pits.
–When an increase of 0.1 lb/gal is achieved in the pits, determine the time it will take to reach the bit.
–When this density reaches the bit, decrease the circulating pressure to the value associated with the density on the pressure schedule.
–Maintain this pressure until a new density reaches the bit.
–At this time, reduce the pressure according to the pressure schedule.
–Continue this process until the mud weight at the bit has been increased to the kill-mud weight.
–Maintain the FCP until the kill-mud weight has been observed at the surface.
•The methods outlined in this topic have advantages and disadvantages.
•Knowing the specifics about the well will determine the appropriate method to be successful in circulating the intruding fluid out of the well and circulating the kill-mud into it.
•A brief list of advantages and disadvantages for each method is listed below.
•Wait-and-Weight Method
–Advantages
•Kills the well in one circulation.
•Subjects the casing shoe to the minimum amount of pressure due to additional hydrostatic pressure from the mud weight increase.
–Disadvantages
•The well is shut in for a long period of time with no circulation.
–A gas kick will migrate up the hole, increasing the pressure, unless pressures are monitored constantly.
–Fluids such as saltwater will contaminate the fluid, causing increases in fluid loss. This, in turn, increases the possibility of sticking the drillstring.
–A gas kick in oil-or synthetic-base fluid can strip the barite from the fluid due to the solubility of gas in the base fluid.
–Gas changes phases and acts as a liquid when it solubilizesin the oil-base mud.
–This dilutes the fluid and may reduce the viscosity enough to allow weight material to settle and plug the annulus.
•Requires more calculations than the Driller’s Method.
•Requires sufficient supplies of weight material and a good mixing system to maintain the density as the fluid is circulated.
•Concurrent Method
–Advantages
•Removes the intruding fluid in a minimum amount of time.
•Subjects the casing shoe to a reduced pressure due to increasing hydrostatic pressure.
•Weight-up can be adjusted as weight material supplies allow.
•Concurrent Method
–Advantages
•Removes the intruding fluid in a minimum amount of time.
•Subjects the casing shoe to a reduced pressure due to increasing hydrostatic pressure.
•Weight-up can be adjusted as weight material supplies allow.
–After the well is shut in, the rig crew “waits”while the drilling fluid in the pits is “weighted”up to the kill-mud weight.
–In order to use this method successfully, sufficient weight material must be on location and the mixing capacity must be sufficient to maintain the kill-mud weight while circulating at the slow pump rate.
–This procedure is more complicated than the Driller’s Method.
–In the Driller’s Method, weighted mud is not pumped into the well until the kick has been circulated out of the well.
–The gas expansion is compensated for by maintaining a constant drill pipe pressure while circulating the kick out.
–When weighted mud is pumped into the well, the casing pressure is held constant until the weighted mud reaches the bit.
–This compensates for the changing hydrostatic pressure in the drill pipe.
•The Wait-and-Weight Method
–In the Wait-and-Weight Method, gas is expanding in the annulus while the hydrostatic pressure is increasing in the drill pipe.
–This requires that the pump pressure needed for maintaining a constant bottom-hole pressure must change as the fluid is circulated.
–A chart of the scheduled pump or drill pipe pressure changes simplifies the kill procedure and reduces the chance of error.
–The pressure schedule or graph determines the pump pressure while the kill mud is being pumped down the drill pipe.
–As the hydrostatic pressure in the drill pipe increases, the pump pressure necessary to maintain the correct bottom-hole pressure is reduced.
–Well-control worksheets for the Wait-and-Weight Method contain a pressure schedule graph.
–The schedule is drawn on standard rectangular coordinates.
–The vertical axis is for the pump pressure and the horizontal axis is for the pump strokes.
–At zero (0) pump strokes, plot the ICP on the pressure scale.
–Plot the surface-to-bit strokes and plot the FCP on the graph.
–Draw a straight line between the two points.
–It is not practical to try to maintain too fine a control on the drill pipe pressure while killing the well.
–Instead, make a chart that shows the pump pressure from the schedule at a selected stroke interval (i.e. 100, 150, 200 etc.).
–The pump pressure is maintained according to this pressure until the selected number of strokes is pumped.
–The pump pressure is then reduced to the next pressure until the stroke interval is pumped.
–This stair step fashion is continued until the kill mud reaches the bit.
–At that time, the pump pressure is held constant until the kill mud is observed at the surface.
•NOTE: The pump pressure will decrease on its own as the kill-mud weight is pumped down the drill pipe.
•This is due to the increase in hydrostatic pressure in the drill pipe.
•As a result, few, if any, choke adjustments are required while pumping kill mud down the drill pipe.
•Some adjustments will be required to account for the changing hydrostatic pressure in the annulus due to the intruding fluid moving up the annulus.
•The Wait-and-Weight Method–Once the kill-weight mud reaches the bit, the pump pressure is held constant at the Final Circulating Pressure (FCP) until the kill mud reaches the surface. –This FCP is calculated with the following equation.
FCP =( RCP x kill-mud weight)/(original mud weight)
–This equation calculates the reduced circulating pressure using the kill-mud weight as the circulating fluid.
–The calculations for pressures through these two sections of the circulating system are based on turbulent pressure losses and energy changes.
–Since the only significant change to the drilling fluid properties used to calculate these pressure losses is the mud density, the circulating pressure is increased by the ratio of the kill-mud weight to the original mud weight.
–The Initial Circulating Pressure (ICP) is calculated the same way as in the Driller’s Method:
ICP = RCP + SIDPP
–The pressure schedule is drawn using the ICP, FCP and the surface to-bit strokes.
–Shut the well in and record the pertinent kick information.
–Calculate the kill-weight mud.
–Begin increasing the mud weight in the surface pits to the kill-weight mud.
–Calculate the ICP.
–Calculate the FCP.
–Calculate the surface-to-bit strokes.
–Construct a pressure schedule.
–Open the adjustable choke and start pumping at the pre-selected slow pump rate.
–Adjust the choke to obtain a pump pressure equal to the ICP.
–Circulate out the kick following the pressure schedule using the adjustable choke.
–Maintain a constant pump rate throughout the
–circulating process.
–Maintain the mud weight in the surface system at the kill-mud weight.
–Once the kill mud reaches the bit, maintain the FCP until the kill mud is observed at the surface.
–Stop pumping and shut the well in to check for pressures.
–If shut-in pressures exist, additional mud weight and circulation will be required.
–If no shut-in pressures exist, the well is under control.
–At this time, one or two circulations can be made to condition the mud and increase the mud weight to provide a trip margin.
•The Circulate-and-Weight Method
–The Circulate-and-Weight (Concurrent) Method is used to circulate the kick out of the hole while increasing the density of the drilling fluid gradually to the kill-mud weight.
–The well is shut in only long enough to obtain the pertinent information about the kick situation.
–The calculations and techniques used in the Wait-and-Weight Method are used in the Circulate-and-Weight (Concurrent) Method.
–Start circulating with the initial circulating pressure and begin adding barite to the system until you reach the kill-weight mud.
–This method uses a gradual increase in mud weight as the kick is circulated out.
–The Circulate-and-Weight (Concurrent) Method is more complex than either the Driller’s Method or the Wait-and-Weight Method due to the various densities of drilling fluid in the drill pipe.
–The number of different densities and the volumes of each depends upon the mixing capability and circulating rate of the drilling rig used.
–A complicated pressure schedule is necessary, as is a precise knowledge of when a mud density was achieved and pumped down the drill pipe.
–Excellent communications between the choke operator and the mud pits is required.
–A pressure schedule similar to that of the Wait-and-Weight Method must be developed.
–The difference between the schedules is that the circulating pressure will be plotted vs. the mud weight.
–Use the Y-axis for the pressure and the X-axis for the mud weight.
–Three calculations will be required to complete the schedule:
•Kill-mud weight, ICP and FCP.
–The equations for these are the same as for the Wait-and-Weight Method.
–To construct the schedule, plot the ICP at the original mud weight.
–Then, plot the FCP at the kill-mud weight.
–Use a straight edge to connect the two points.
–Start circulating at the reduced circulating rate.
–Adjust the choke to reach the ICP.
–While circulating, begin increasing the density of the mud in the pits.
–When an increase of 0.1 lb/gal is achieved in the pits, determine the time it will take to reach the bit.
–When this density reaches the bit, decrease the circulating pressure to the value associated with the density on the pressure schedule.
–Maintain this pressure until a new density reaches the bit.
–At this time, reduce the pressure according to the pressure schedule.
–Continue this process until the mud weight at the bit has been increased to the kill-mud weight.
–Maintain the FCP until the kill-mud weight has been observed at the surface.
•The methods outlined in this topic have advantages and disadvantages.
•Knowing the specifics about the well will determine the appropriate method to be successful in circulating the intruding fluid out of the well and circulating the kill-mud into it.
•A brief list of advantages and disadvantages for each method is listed below.
•Wait-and-Weight Method
–Advantages
•Kills the well in one circulation.
•Subjects the casing shoe to the minimum amount of pressure due to additional hydrostatic pressure from the mud weight increase.
–Disadvantages
•The well is shut in for a long period of time with no circulation.
–A gas kick will migrate up the hole, increasing the pressure, unless pressures are monitored constantly.
–Fluids such as saltwater will contaminate the fluid, causing increases in fluid loss. This, in turn, increases the possibility of sticking the drillstring.
–A gas kick in oil-or synthetic-base fluid can strip the barite from the fluid due to the solubility of gas in the base fluid.
–Gas changes phases and acts as a liquid when it solubilizesin the oil-base mud.
–This dilutes the fluid and may reduce the viscosity enough to allow weight material to settle and plug the annulus.
•Requires more calculations than the Driller’s Method.
•Requires sufficient supplies of weight material and a good mixing system to maintain the density as the fluid is circulated.
•Concurrent Method
–Advantages
•Removes the intruding fluid in a minimum amount of time.
•Subjects the casing shoe to a reduced pressure due to increasing hydrostatic pressure.
•Weight-up can be adjusted as weight material supplies allow.
•Concurrent Method
–Advantages
•Removes the intruding fluid in a minimum amount of time.
•Subjects the casing shoe to a reduced pressure due to increasing hydrostatic pressure.
•Weight-up can be adjusted as weight material supplies allow.
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