Application of a Gas Kick Simulator to Understanding the Effect of Wellbore Geometry on Kick Control Operations

One of the most important operations during drilling is to control the flow of formation fluids. If a gas kick is taken during drilling, the control of the gas that entered from the formation is critical. The uncontrolled flow of the gas can cause loss of life, drilling equipment, the well, and damage to the environment. In order to regain to control on the reservoir and continue the drilling, the gas kick should be circulated to the surface in a safe way Without fracturing another formation or causing an underground blowout.

Considering the importance of well control operations, many gas kick simulators have been developed for better understanding the mechanics of gas kicks, forecasting the pressure at the surface and the drill pipe, and for training of drilling personnel. These gas kick simulators are capable for computing the pressure distribution in the wellbore. This characteristic of the simulators permits to estimate the pressure at the casing shoe where there is a possibility of fracturing the formation and cause an underground blowout.

The simulator that was used in this study simulates the complete process from the drilling into a permeable zone, through the detection of the gas kick, through the kick killing operation until normal conditions are re-established. The simulator can be used for both oil based and water based mud.

The objective of this report is to undertake a study to understand the effects of wellbore geometry and drilling conditions on the kick control operation and the casing shoe pressure for wells drilled with oil based and water based mud. Three similar wells with different sizes of wellbores were used in this study. The effect of the wellbore geometry on the surface casing pressure and the casing shoe pressure was studied for these wells and oil and water based mud has been compared in each well. The effect of the depth of the gas zone on the casing shoe pressure was studied by changing the depth of the gas reservoir.