Step 1
Upon indication of kick, calculate shut-in drill pipe pressure constant (SIDPP) and shut-in casing pressure constant (SICP).
Important! If in doubt at any time during the entire procedure, shut in the well, read and record the shut-in drill pipe pressure and the shut-in casing pressure and proceed accordingly.
It is not uncommon for the surface pressures to fluctuate slightly due to temperature, gas migration, or gauge problems. The second statement is extremely important to keep in mind.
When in doubt, shut in the well! It seems that the prevailing impulse is to continue circulating regardless of the consequences. equipment. Also, if the choke starts blocking-off, pressure surges will be less at reduced circulating rates.
Experience has shown that one of the most difficult aspects of any kill procedure is bringing the pump to speed without permitting an additional influx or fracturing the casing shoe. This problem is compounded by attempts to achieve a precise kill rate. There is nothing magic about the kill rate used to circulate out a kick.
In the early days of pressure control, surface facilities were inadequate to bring an influx to the surface at a high pump speed. Therefore, one-half normal speed became the arbitrary rate of choice for circulating the influx to the surface. However, if only one rate such as the one-half speed is acceptable, problems can arise when the pump speed is slightly less or slightly more than the precise one-half speed. The reason for the potential problem is that the circulating pressure at rates other than the kill rate is unknown.
The best procedure is to record and graph several flow rates and corresponding pump pressures as illustrated in Figure.
First Circulation, Step 3
Calculate the Initial Circulating Pressure (ICP) the pressure required on the drill pipe for the first circulation of the well.
Initial Circulating Pressure (psi) = Slow Circulation Rate (psi) + Shut-in Drill Pipe Pressure (psi) 𝐼𝐶𝑃 = 𝑃𝑆𝐶𝑅+ 𝑆𝐼𝐷𝑃𝑃
Step 4
Open choke about one quarter, start pump, and break circulation.
Adjust the choke opening until the choke pressure equals the closed-in annulus pressure plus the overbalance margin. Record the choke pressures throughout the first circulation.
Step 5
Driller brings pump rate up to Kill Rate. Choke operator should operate the choke so as to keep the casing pressure at or near the shut-in casing pressure (SICP) reading. This step should require less than 5 minutes.
Bringing the pump up to speed is one of the most difficult problems in any well control procedure.
Experience has shown that the most practical approach is to keep the casing pressure constant at the shut-in casing pressure while bringing the pump to speed. The initial gas expansion is negligible over the allotted time of five minutes required to bring the pump to speed. It is not important that the initial volume rate of flow be exact. Any rate within 10% of the kill rate is satisfactory. This procedure will establish the correct drill pipe pressure to be used to displace the kick.
Practically, the rate can be lowered or raised at any time during the displacement procedure. Simply read and record the circulating casing pressure and hold that casing pressure constant while adjusting the pumping rate and establishing a new drill pipe pressure. No more than one to two minutes can be allowed for changing the rate when the gas influx is near the surface because the expansion near the surface is quite rapid.
Step 6
After the pump is at satisfactory Kill Rate, Choke operator should transfer his attention to maintain the initial circulating pressure (ICP) reading on the drill pipe pressure gauge. Displace the influx, keeping the recorded drill pipe pressure constant. ICP should be held constant throughout the whole first circulation by adjusting the choke throughout the whole first circulation, until all of the kick fluid has been circulated out of the well. Pump rate is held constant to Kill Rate during first circulation.
Step 7
Once the influx has been displaced, record the casing pressure and compare with the original shut-in drill pipe pressure (SIDPP) recorded in Step 2.It is important to note that, if the influx has been
completely displaced, the casing pressure should be equal to the original shut-in drill pipe pressure (SIDPP).
Consider the U-Tube Model presented in Figure 1 and compare with the U-Tube Model illustrated in Figure 2. If the influx has been properly and completely displaced, the conditions in the annulus side of Figure 1 are exactly the same as the conditions in the drill pipe side of Figure 2. If the frictional pressure losses in the annulus are negligible, the conditions in the annulus side of Figure 1 will be approximately the same as the drill pipe side of Figure 2. Therefore, once the influx is displaced, the circulating annulus pressure should be equal to the initial shut-in drill pipe pressure.
Step 8
If the casing pressure is equal to the original shut-in drill pipe pressure recorded in Step 2, shut in the well by keeping the casing pressure constant while slowing the pumps. If the casing pressure is greater than the original shut-in drill pipe pressure, continue circulating for an additional circulation,
Figure 1
Figure 2
keeping the drill pipe pressure constant and then shut in the well, keeping the casing pressure constant while slowing the pumps.
Step 9
If the shut-in casing pressure is greater than the shut-in drill pipe pressure, repeat Steps 3 through 8.
Step 10
If the kick is out of the hole, shut-in the well and start preparing the kill mud. This assumption is usually made, prior to start of the second circulation.
𝐾𝑖𝑙𝑙 𝑀𝑢𝑑 𝑊𝑒𝑖𝑔𝑡 = 𝑂𝑟𝑖𝑔𝑛𝑎𝑙 𝑀𝑢𝑑 𝑊𝑒𝑖𝑔𝑡 + 𝑆𝐼𝐷𝑃𝑃 𝑇𝑉𝐷 ∗ 0.052
SIDP, SICP = 0 The well is dead and the mud density is sufficient to balance the well.
SIDP, SICP both are equal and > 0 The mud weight must be increase to balance the formation pressure.
SIDP > SICP There is still influx from the annulus has occurred during the initial circulation.
Second Circulation, Step 11
Prepare Kill Mud. Raise the mud weight in the suction pit to the density determined in step 10
.
Step 12Determine the number of strokes to the bit by dividing the capacity of the drill string in barrels by the capacity of the pump in barrels per stroke.
𝑉𝑜𝑙𝑢𝑚𝑒 (𝑃𝑖𝑝𝑒) = 𝐿𝑒𝑛𝑔𝑡 ∗ 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐹𝑎𝑐𝑡𝑜𝑟 (𝐷𝑃, 𝐻𝑊𝐷𝑃, 𝐷𝐶) 𝑉𝑜𝑙𝑢𝑚𝑒 𝐴𝑛𝑛𝑢𝑙𝑢𝑠 = 𝐿𝑒𝑛𝑔𝑡 ∗ 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝐹𝑎𝑐𝑡𝑜𝑟 𝐶𝑎𝑠𝑖𝑛𝑔, 𝑂𝑝𝑒𝑛 𝑜𝑙𝑒
𝑃𝑢𝑚𝑝 𝑆𝑡𝑟𝑜𝑘𝑒𝑠 = 𝑉𝑜𝑙𝑢𝑚𝑒 𝑃𝑢𝑚𝑝 𝐷𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
𝑇𝑖𝑚𝑒 = 𝑃𝑢𝑚𝑝 𝑆𝑡𝑟𝑜𝑘𝑒𝑠 𝑆𝑙𝑜𝑤 𝑃𝑢𝑚𝑝 𝑅𝑎𝑡𝑒 Step 13
Open the choke about one quarter, start the pump and break circulatio
n.
Step 14
Bring the pump to the Kill Rate. As Driller’s is bringing the pump up, Choke operator should maintain the casing pressure to a value at or near to shut-in casing pressure (SICP) reading.
Warning!Once the pump rate has been established, no further adjustments to the choke should be required. The casing pressure should remain constant at the initial shut-in drillpipe pressure. If the casing pressure begins to rise, the procedure should be terminated and the well shut in.
Again, consider the U-Tube Model in Figure 1. While the kill weight mud is being displaced to the bit on the drill pipe side, under dynamic conditions no changes are occurring in any of the conditions on the annulus side. Therefore, once the pump rate has been established, the casing pressure should not change and it should not be necessary to adjust the choke to maintain the constant drill pipe pressure. If the casing pressure does begin to increase, with everything else being constant, in all probability there is some gas in the annulus. If there is gas in the annulus, this procedure must be terminated. Since the density of the mud at the surface has been increased to the kill, the proper procedure under these conditions would be the Wait and Weight Method. Therefore, the Wait and Weight Method would be used to circulate the gas in the annulus to the surface and control the well.
Step 15
After pumping the number of strokes required for the kill mud to reach the bit, read and record the drill pipe pressure.
Step 16
When Drill Pipe is filled with mud then two options are applied for constant BHP,
Casing pressure is held constant while pumping kill mud from surface to bit and drill pipe pressure is held constant thereafter until kill mud is observed returning to the surface.
Alternately, during second circulation, a drill pipe pressure schedule can be calculated and followed while pumping kill mud from surface to bit, and drill pipe pressure is held constant thereafter. Usually a graph is made from ICP to FCP for checking how the drill pipe pressure drop, as Kill Mud moves down to bit, without the choke being moved. As Kill Mud is added into the pipe, it moves down toward bit. As it reaches bit (bottom), the drill pipe pressure is just that require circulating the Kill Mud around the well. The drill pipe pressure starts dropping below the initial circulating pressure, as the kill mud starts down the drill pipe, reaching the final circulating pressure when the kill mud reaches the bit. Thereafter the drill pipe pressure is held at the final circulating pressure by controlled opening the choke, as the kill mud moves up the annulus. This FCP value is equal to SCR pressure and increase slightly for the addition of Kill Mud.
𝐹𝐶𝑃 = 𝑃𝑠𝑐𝑟 + 𝐾𝑖𝑙𝑙 𝑀𝑢𝑑 𝑊𝑒𝑖𝑔𝑡 𝑂𝑟𝑖𝑔𝑛𝑎𝑙 𝑀𝑢𝑑 𝑊𝑒𝑖𝑔𝑡 Step 17
Once Kill Mud reaches surface through bit, stop pumping, shut-in the well and confirm that it is dead. Shut in the well by keeping the casing pressure constant while slowing the pumps. Read and record the shut-in drill pipe pressure and the shut-in casing pressure. Both pressures should be 0.Open the well and check for flow. If the well is flowing, repeat the procedure. If no flow is observed, raise the mud weight to include the desired trip margin and circulate until the desired mud weight is attained throughout the system.