Formation Fluid Influx and Breakdown Mechanism
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Questions and Answers

Which pressure must be greater than the least principal stress in the formation to initiate a fracture in the borehole wall?

  • The minimum horizontal stress
  • The formation fluid pressure
  • The hydrostatic pressure of the drilling fluid (correct)
  • The formation breakdown pressure

    • What is the direction in which fractures will propagate when the pressure in the borehole exceeds the least of the stresses within the rock structure?

  • Parallel to the maximum horizontal stress
  • Parallel to the vertical stress
  • Perpendicular to the least principal stress (correct)
  • Perpendicular to the maximum horizontal stress

    • What is the primary well control barrier that cannot be achieved if the formation breaks down and mud losses occur?

  • Borehole stability (correct)
  • Hydrostatic pressure
  • Formation fracture pressure
  • Drilling fluid density

    • What is the condition that can lead to formation fluid influx?

    <p>BHP &gt; F.F.P.</p> Signup and view all the answers

    What is the term used to describe the pressure of the drilling fluid column?

    <p>Formation fracture pressure</p> Signup and view all the answers

    What is the consequence of the formation breaking down when the borehole pressure exceeds the least principal stress?

    <p>Mud losses can occur</p> Signup and view all the answers

    What is the main purpose of conducting LOT and FBT tests?

    <p>To identify the weakest part of the wellbore</p> Signup and view all the answers

    When is LOT and FBT testing carried out?

    <p>Immediately after setting and cementing the casing</p> Signup and view all the answers

    What is done to avoid the drillbit getting stuck in the openhole during the LOT and FBT tests?

    <p>Pull the drillbit back into the casing shoe</p> Signup and view all the answers

    What is generally used to close the BOPs during LOT and FBT testing?

    <p>Pipe ram</p> Signup and view all the answers

    Why is pressure applied by pumping a small amount of mud into the well at surface during LOT and FBT testing?

    <p>To measure pressure response in the well</p> Signup and view all the answers

    What is assumed about the weakest part of the wellbore in LOT and FBT tests?

    <p>It is just below the casing shoe</p> Signup and view all the answers

    What is the purpose of calculating the equivalent circulating density (ECD)?

    <p>To get a true representation of the pressure acting against the formation at the bottom of the well</p> Signup and view all the answers

    What contributes to the additional pressure at the bottom of the borehole when the drilling fluid is circulating?

    <p>The frictional pressure required to pump the fluid up the annulus</p> Signup and view all the answers

    In the given example, what was the true vertical depth of the casing shoe?

    <p>5010 ft</p> Signup and view all the answers

    What was the surface pressure at leak off in the given example?

    <p>940 psi</p> Signup and view all the answers

    What is the calculated maximum mud weight for the next section to be drilled in the given example?

    <p>13.3 ppg</p> Signup and view all the answers

    What was the mud weight used to conduct the leak off test in the given example?

    <p>10.2 ppg</p> Signup and view all the answers

    What is the primary purpose of a leak off test (LOT)?

    <p>To determine the maximum pressure the open formation can withstand before fracturing</p> Signup and view all the answers

    When is a leak off test typically conducted?

    <p>After drilling out of a new casing shoe</p> Signup and view all the answers

    How is the leak off pressure determined during a LOT?

    <p>By observing the pressure at which fluid begins to leak into the formation</p> Signup and view all the answers

    What is the primary use of the leak off pressure determined from a LOT?

    <p>To establish the upper limit for the mud weight</p> Signup and view all the answers

    During a LOT, when is the operation typically terminated?

    <p>When the pressure stops increasing linearly</p> Signup and view all the answers

    Which of the following is NOT mentioned as a method to calculate fracture pressure?

    <p>The Bourgoyne and Young Method</p> Signup and view all the answers

    What is the primary purpose of the Formation Integrity Test (FIT)?

    <p>To determine the maximum pressure the formation can withstand</p> Signup and view all the answers

    If fluid begins to leak off into the formation during a FIT, what does it indicate?

    <p>It is not safe to drill the next section with the current parameters</p> Signup and view all the answers

    What is the Leak Off Pressure (LOP) used for?

    <p>To determine the maximum allowable pressure on the formation below the shoe</p> Signup and view all the answers

    What is the Maximum Allowable Annular Surface Pressure (MAASP) calculated from?

    <p>The Leak Off Pressure (LOP)</p> Signup and view all the answers

    How is the maximum allowable mud weight for the next hole section determined?

    <p>From the Leak Off Pressure (LOP) calculations</p> Signup and view all the answers

    What safety factor is typically subtracted from the allowable mud weight?

    <p>0.5 ppg (0.026 psi/ft)</p> Signup and view all the answers

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