IWCF Level 1 flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Well control definition
- The management of pressure in a wellbore to prevent formation fluids from entering it unintentionally, and to circulate out any influx safely while protecting personnel, the rig, the well and the reservoir.
- Pore pressure
- The pressure of fluids contained in the pore spaces of a formation. When it exceeds the normal hydrostatic gradient for the area it is called abnormal pressure and requires a heavier mud weight.
- Fracture pressure
- The pressure at which a formation begins to crack and accept fluid. It forms the upper limit of the safe mud weight window, above which losses and formation damage occur.
- Hydrostatic pressure formula
- Ph = 0.052 x mud weight in ppg x true vertical depth in feet, giving psi. In metric units Ph = mud weight in kg/m3 x TVD in metres x 0.00981.
- True vertical depth
- The vertical distance from the rotary table or datum to the point of interest. Hydrostatic pressure depends on TVD, not measured depth, so deviated wells use TVD for all pressure calculations.
- Overbalance
- A condition where hydrostatic pressure in the wellbore is greater than formation pore pressure. It is the normal drilling state and prevents influx, but excessive overbalance can cause losses and stuck pipe.
- Underbalance
- A condition where formation pore pressure exceeds the hydrostatic pressure exerted by the wellbore fluid column. If a permeable zone is exposed, formation fluid will flow into the well and form a kick.
- Primary well control
- Prevention of influx using the hydrostatic pressure of the drilling fluid column. It is maintained by keeping mud weight, mud level and equivalent circulating density within the safe pressure window.
- Secondary well control
- The use of blowout prevention equipment and agreed procedures to close in and circulate out an influx when primary control has been lost. It includes the BOP stack, choke manifold and kill line.
- Kick
- An unintended entry of formation fluid into the wellbore caused by pore pressure exceeding hydrostatic pressure. It must be detected early, the well shut in, and the influx circulated out under controlled conditions.
- Blowout
- An uncontrolled flow of formation fluids from a well. It occurs when a kick is not detected or not controlled, and it may discharge at surface or underground into another permeable formation.
- Underground blowout
- Flow of formation fluid from a high-pressure zone into a lower-pressure formation downhole, often through a casing shoe or a poor cement seal. Surface flow may be absent, so pit and pressure data are the main indicators.
- Gain in pit volume
- An increase in the total volume of mud in the surface system that is not explained by a deliberate addition. With pumps off and the well static, a gain indicates an influx is entering the wellbore.
- Flow with pumps off
- Continued mud flow from the annulus after the pumps are stopped. In a static well this is a positive kick indicator because the only driving force is formation pressure exceeding hydrostatic pressure.
- Short fill on trip
- When running pipe back in the hole, the volume of mud displaced should match the steel volume. A fill volume less than calculated means fluid has left the well, indicating an influx during the trip.
- Trip margin
- Extra mud weight added before tripping to offset the loss of equivalent circulating density when pumps stop and to cover swabbing effects. It keeps the well overbalanced during pipe movement.
- Trip tank
- A small, calibrated tank used to measure precisely the mud volume going into or out of the well during trips. Its level is the primary instrument for detecting gains or losses while the pumps are off.
- Swabbing
- A reduction in bottomhole pressure caused by pulling pipe upward, which can draw formation fluid into the well. It is most likely with a fast trip, a balled-up string or high-viscosity mud.
- Surge pressure
- An increase in bottomhole pressure caused by running pipe into the hole or by starting pumps. Excessive surge can fracture the formation and cause losses, which may later lead to a kick.
- Equivalent circulating density
- The effective mud weight at a given depth while circulating, equal to hydrostatic pressure plus annular friction loss. It is always higher than the static mud weight and sets the upper limit during drilling.
- Kick tolerance
- The maximum influx volume that can be taken and still circulated out without fracturing the weakest exposed formation. It depends on pore pressure, fracture pressure, mud weight and well geometry.
- Shut-in drill pipe pressure
- The stabilised pressure read on the drill pipe gauge after the well is closed in. It reflects the difference between formation pressure and hydrostatic pressure in the drill string and is used to calculate kill mud weight.
- Shut-in casing pressure
- The stabilised pressure on the casing gauge after shut-in. It includes the drill pipe pressure plus the hydrostatic effect of the influx in the annulus, so it is normally higher than SIDPP.
- Kill mud weight
- The mud weight required to balance formation pressure, calculated as current mud weight plus SIDPP divided by 0.052 times TVD. It is circulated according to the chosen well control method.
- Slow circulating rate
- A reduced pump rate used for well killing and for recording circulating pressures. It keeps annular friction losses low so that pressures measured while circulating can be related to static pressures.
- Formation integrity test
- A test that pressurises the formation below the casing shoe to confirm it can withstand the planned mud weight. Results give the maximum allowable annular surface pressure and the fracture gradient.
- Leak-off test
- A formation integrity test taken to the point where pressure deviates from the straight line, indicating the formation is starting to take fluid. The pressure at that point is the leak-off pressure.
- Maximum allowable annular surface pressure
- The surface pressure limit that, when added to hydrostatic pressure in the annulus, equals the formation fracture pressure at the casing shoe. It must not be exceeded while circulating out a kick.
- Positive kick indicator
- A sign that an influx has definitely entered the well, such as a pit gain with pumps off, flow from the annulus with pumps stopped, or a short fill during a trip.
- Gas cut mud
- Mud contaminated by formation gas, which reduces its density and gives a false high gas reading at surface. A small gas cut usually has little effect on bottomhole pressure.
- Kick while tripping
- An influx that enters during pipe movement, usually through swabbing or because the hole is not kept full. It is detected by comparing actual fill volume with calculated steel displacement.
- Well control awareness
- Understanding the pressure balance in a well, recognising kick indicators early, and knowing the correct immediate action, which is to stop operations, shut the well in and inform the supervisor.