Oil Well Completions Concepts and Calculations Part 1

A: Governing principle: Hydrostatic pressure scales linearly with fluid gradient and true vertical depth. Applied here: 9.5 ppg gives ~0.433 × (9.5/8.34) ≈ 0.49 psi/ft; multiplied by 8,000 ft lands near 3,900 psi, making 3,600 psi the closest defensible estimate. Distractor trap: Option B tempts with a round gradient but drifts high when checked against actual brine density.

A: Governing principle: Collapse failure is governed by the maximum differential pressure across the pipe wall. Applied here: A kill with an empty or near-empty tubing string imposes hydrostatic external pressure with minimal internal support, the governing collapse scenario API intends to cover. Distractor trap: Option D appeals to those mixing axial and radial failure modes without checking which one governs collapse.

A: Governing principle: CO2 in the presence of free water drives carbonic acid corrosion in carbon steel. Applied here: Wet gas and chloride brine establish water wetting, making CO2 partial pressure the rate driver rather than sulfide mechanisms. Distractor trap: Option C catches teams over-weighting short-term oxygen exposure while ignoring sustained CO2 chemistry.

A: Governing principle: Zonal isolation relies on physical separation, not intent stated in text. Applied here: A 40 ft standoff versus a 100 ft requirement creates a leakage risk during pressure transients if the drawing is correct. Distractor trap: Option B attracts engineers familiar with tubing stretch but misapplies it to packer-to-perf spacing.

A: Governing principle: Annular volume equals annular area times length, converted to barrels. Applied here: Using typical IDs, the area difference gives ~0.006 bbl/ft, leading to ~6–7 bbl over 1,000 ft. Distractor trap: Option C over-applies the diameter-squared concept without checking actual ID values.

A: Governing principle: Material susceptibility depends on environment and metallurgical condition, not just H2S presence. Applied here: Even in sweet service, hardness and cold work influence cracking risk when chlorides and CO2 drive aggressive corrosion. Distractor trap: Option C pulls from adjacent sour-service logic that doesn’t actually apply to CO2 chemistry.

A: Governing principle: Particle-laden flow removes material by repeated impact when velocity is high. Applied here: Fine sand at elevated rates preferentially erodes screen elements before corrosion mechanisms become limiting. Distractor trap: Option A attracts those who link turbulence to corrosion without accounting for solid particle effects.

A: Governing principle: Fluid gradient is directly tied to density under static conditions. Applied here: Fresh water at standard conditions yields ~0.433 psi/ft, the common field shorthand for fast checks. Distractor trap: Option B reflects a safety instinct but drifts from the physical basis of the gradient.

A: Governing principle: Pressure tests validate integrity at a point in time, while trends signal degradation. Applied here: A marginal pass with worsening behavior suggests a developing leak path that acceptance limits alone won’t catch. Distractor trap: Option A appeals to spec compliance while ignoring operational risk during early life.