come out of the hole, Oil & Gas Glossary

What Does Come Out of the Hole Mean?

Come out of the hole (abbreviated COOH) is the drilling operation of pulling the drill string, completion string, or other tubulars upward from total depth (TD) to surface — removing the bottomhole assembly (BHA), drill pipe, and/or drill collars by successively unscrewing stands and racking them vertically in the derrick or laying them down on pipe racks. The operation is performed to change a dull bit, run wireline logs, run casing, or complete a well. Coming out of the hole is one of the highest-risk operations in drilling, creating hazards including stuck pipe (from differential pressure or mechanical causes), swab-induced wellbore influx, and well control events if the mud system is not properly conditioned before the trip begins.

Key Takeaways

COOH requires careful mud conditioning beforehand — circulating bottoms-up at least once to equalize temperature and pressure, breaking gels, and confirming mud weight and volume — to prevent a swab kick or stuck pipe during the trip.
Swab pressure is the primary pulling hazard: pulling pipe too fast creates a negative pressure surge in the annulus that can draw formation fluids into the wellbore; trip speed is typically limited to 2-5 stands/minute in critical hole sections.
The fill and check procedure — filling the drill string with mud every 5-10 stands and comparing actual fill volume to the theoretical displaced volume — is the primary early-warning indicator for a swab-induced influx during a trip.
A short trip (pulling to a check depth and running back in) is often performed before committing to a full COOH, confirming hole conditions are stable enough to complete the trip safely.
If flow or abnormal fill is detected at any point during the trip, the crew immediately picks up the drill string, attempts to circulate, and activates well-control procedures; the BOP is closed if flow cannot be controlled by circulation.

COOH Procedures and Swab Pressure Management

Before coming out of the hole, the driller circulates the wellbore for at least one complete bottoms-up cycle — long enough to ensure that any gas cut or influx near the bit is circulated to surface and conditioned out of the mud, and that formation pressures are in equilibrium with the hydrostatic mud column. The mud engineer checks mud weight, viscosity, and gel strength: high gel strength increases the surge and swab pressure peaks during initial pipe movement, so gels are broken by slow circulation before pulling begins. Pit volume is recorded as a baseline — any unexplained gain during the trip indicates an influx, and any loss indicates lost circulation.

Once pulling begins, trip speed is governed by swab pressure calculations. Swab pressure is a negative pressure surge created as the pipe is pulled upward, effectively reducing the hydrostatic pressure in the annulus below the bottom of the string. The magnitude depends on pipe OD relative to hole size (annular clearance), mud rheology (plastic viscosity and yield point), and pulling speed. In tight annular clearances — such as 6-in drill collars in an 8.5-in hole — swab pressures at high pulling speeds can exceed 200-300 psi, which in a near-balanced well is enough to cause an underbalanced condition and allow formation fluids to enter. Trip sheets calculated before the trip specify the maximum allowable pulling speed in each hole section, and the driller is responsible for keeping the pipe speed within those limits.

The fill and check procedure provides real-time verification that no influx has occurred. As each stand of pipe is removed from the wellbore, the hole must be filled with mud to replace the steel volume that was pulled out. The mud engineer calculates the theoretical fill volume per stand based on pipe dimensions; if the actual volume pumped is less than expected, it means formation fluids are already occupying that space — a swab kick is in progress. The discrepancy per stand is small but cumulative, so the check is performed every 5-10 stands, with the threshold for investigation typically set at 10-15 barrels of unexplained gain or shortfall.

Fast Facts: Come Out of the Hole (COOH)

Abbreviation: COOH (opposite of RIH — run in the hole)
Primary hazard: Swab pressure-induced wellbore influx (swab kick)
Typical trip speed limit: 2-5 stands/minute in critical sections
Fill check interval: Every 5-10 stands; compare actual vs. theoretical fill volume
Pre-trip conditioning: Minimum one bottoms-up circulation before pulling
Short trip depth: Typically to the shoe of the previous casing string
Swab pressure factors: Pipe OD, hole size, mud rheology, pulling speed
Last-resort action: Close BOP and initiate well kill if flow is uncontrolled

Drilling Operations Tip:

In wells with high gel-strength mud or extended static periods (e.g., after a wireline logging run), break circulation slowly before beginning COOH — apply weight on the pump gradually while monitoring for pressure spikes or sudden losses. High gels that are broken abruptly can generate a surge pressure sufficient to fracture the formation at a weak zone, causing lost circulation that then accelerates the swab effect on the trip out. A slow, staged gel-breaking circulation takes 15-30 minutes but can prevent hours of lost-circulation treatment and stuck pipe remediation.

Come out of the hole is also referred to as:

tripping out — the most common field shorthand; "tripping" refers to the entire pipe-movement operation, with direction specified by "out" or "in"
pulling out of the hole (POOH) — used interchangeably with COOH in most drilling contexts; POOH is slightly more common in North American usage, COOH in international operations
making a trip — general term for the round-trip operation of pulling to surface and running back in; used when both COOH and RIH are implied
wet trip — a specific COOH variant where the pipe is circulated while being pulled (pumping and pulling simultaneously) to reduce swab effect and keep the annulus swept clean

Frequently Asked Questions About Coming Out of the Hole

What is the difference between a short trip and a full COOH?

A short trip involves pulling the drill string only partway out — typically to above a zone of interest, a problematic formation, or to the shoe of the last casing string — and then running back in (RIH) without fully removing the string from the wellbore. Short trips are used to check hole conditions (verify the hole is stable and not packing off), to work through tight spots before committing to a full pull, or to verify fill volumes are consistent with a clean wellbore. A full COOH pulls the entire string to surface, which is required for bit changes, logging runs that need a clean wellbore, or casing and liner runs.

Why does coming out of the hole take so long?

Each stand of drill pipe must be physically unscrewed from the string, hoisted by the traveling block, and set back in the derrick (racked) or laid down to the pipe deck. A typical stand is two to three joints of pipe, or 60-90 ft. In a 15,000-ft well, the crew may pull 200 or more stands, each requiring connection breaks on the drill floor, spinning out, and racking. At an efficient pace of 3-4 stands per minute, a full trip out still takes 50-70 minutes of continuous pipe handling — before accounting for fill-and-check stops, any tight spots, and mud conditioning. Deep wells, deviated holes, or problematic formations can extend a single COOH to 12-24 hours of continuous operations.

What does it mean when the well "swabs in" during a trip?

A swab-in, or swab kick, occurs when the negative pressure surge created by pulling the pipe reduces the effective hydrostatic head below formation pressure, allowing formation fluids — gas, oil, or water — to enter the wellbore. The crew detects it through a gain in the pit volume, a short fill (less mud was needed to fill the hole than expected), or, in severe cases, visible flow at the bell nipple. Once a swab kick is confirmed, the string is slowed or stopped, the well is observed for flow, and if flow is present, the BOP is closed and the kick is circulated out using the driller's method or wait-and-weight procedure. Swab kicks are one of the most common precursors to well control incidents.

Why COOH Matters in Oil and Gas

Every bit change, logging run, casing job, and completion operation in a drilled well requires at least one trip out of the hole, making COOH one of the most frequently executed and time-critical operations in the drilling phase of a well. Trip time is non-productive time from a pure penetration standpoint, so reducing trip frequency — through extended drill bit runs, logging while drilling (LWD), and motor optimization — is a key efficiency focus for drilling engineers. At the same time, a poorly executed trip remains one of the most common pathways to a well control incident: the statistics on kicks show that a disproportionate share occur during trips rather than while drilling ahead. Mastery of COOH procedures, swab pressure management, and the fill-and-check discipline is therefore central to drilling safety and one of the core competencies of any experienced driller.

Come Out of the Hole: Definition, Drilling Operations, and Trip Procedures