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Thursday 26 January 2023

Comparison between Driller’s method and Wait & weight’s Methods

Comparison between Driller’s method and Wait & weight’s Methods #drilling_manual_lessons Both the Driller’s method and Wait & weight’s Methods provide relative advantages and disadvantages, depending on the general conditions of the area of operation or the specific conditions in the subject well. The choice of kill method is determined through discussions between the Drilling Foreman on location and the Drilling Superintendent. Figures below illustrates a gas kick being circulated to the surface using both the Driller’s and the Wait & weight's Methods. Observing both figures, it is noted that when the gas bubble reaches the casing shoe the Driller’s Method results in a surface casing pressure which is higher than the initial casing pressure, whereas the Wait & weight's Method is less. In the Driller’s Method, the hydrostatic pressure in the annulus is reduced as the gas bubble expands while being circulated out of the well. The bottomhole pressure is being held constant; therefore, the surface casing pressure must increase. Since the hydrostatic pressure above the shoe is the same as it was when the well was initially shut in, as long as the bubble is below the shoe, the pressure at the shoe will be increased an amount equal to the increase in the surface casing pressure plus any circulating friction generated in the annulus above the shoe. This increase in pressure could be sufficient to cause a formation breakdown at the shoe. Consequently, the maximum pressure at the casing shoe occurs when the top of the bubble reaches the shoe if the Driller’s Method is used. Conversely, when the Wait & weight's Method is used, the maximum pressure at the shoe will generally occur when the kill mud reaches the bit. Three exceptions to this are: 1) When the kick volume fills the well above the shoe. 2) When a small kick volume does not increase the casing pressure as it rises into a larger annular area at the top of the collars by the time kill mud reaches the bit. 3) Any time the top of the bubble reaches the shoe before the kill mud reaches the bit. The introduction of kill mud into the annulus through the bit increases the hydrostatic pressure. In order to maintain constant bottomhole pressure, the surface pressure must be reduced; therefore, the pressure at the shoe is reduced. In both methods, once the top of the bubble reaches the shoe, the shoe pressure decreases until the bottom rises above the shoe. Once the bottom portion of the bubble rises above the shoe, the shoe pressure remains constant with the Driller's Method but continues to decline until the kill mud reaches the shoe with the Engineer's Method (provided bottomhole pressure is constant). Therefore, the pressure at the shoe when using the Engineer’s Method will always be less than or equal to the shoe pressure when using the Driller’s Method.
Comparison between Driller’s method and Wait & weight’s Methods

#drilling_manual_lessons

Both the Driller’s method and Wait & weight’s Methods provide relative advantages and disadvantages, depending on the general conditions of the area of operation or the specific conditions in the subject well. The choice of kill method is determined through discussions between the Drilling Foreman on location and the Drilling Superintendent.



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