Fishing (Wellbore): Definition, Tools, and Stuck Pipe Recovery

What Is Fishing in Wellbore Operations?

Fishing encompasses the engineering design and field execution of a downhole intervention to retrieve, mill, or bypass a lost, stuck, or dropped object in the wellbore, using specialized tools deployed on the drill pipe, coiled tubing, or wireline to grip, cut around, or grind the obstructing object so that drilling or production operations can resume. The object being recovered is universally called "the fish," regardless of its size or origin.

How Fishing Operations Work

A fishing operation begins the moment a piece of equipment is lost in the wellbore. The triggering event may be a drill string parting under excess tension or torsional fatigue, a mud motor or BHA becoming irretrievably stuck, a wireline or slickline breaking and leaving sinker bars and jars at depth, a drill pipe tool joint backing off due to improper torque makeup, or simply a hand tool or tong die falling down the hole during surface operations. The object that remains in the wellbore is the "fish," and every decision in the fishing operation flows from an accurate physical description of that fish.

The first tool deployed in almost every fishing operation is the impression block: a short, heavy steel cylinder with a lead face, run to the fish top on the drill string and set down with controlled weight of 5,000 to 15,000 lb (22-67 kN). The lead is soft enough to take an impression of whatever it contacts, and when retrieved to surface, the shape imprinted in the lead tells the fishing engineer the fish's OD or ID, whether it is centered, whether the top is chamfered or squared, and whether there is angular offset from the wellbore axis. This information drives the selection of the primary fishing tool and its inside diameter (for overshots) or outside diameter (for spears and taper taps). Running a fishing tool without an impression block in an unfamiliar fish geometry is a recognized cause of secondary fish creation, where the fishing tool itself becomes stuck.

Fishing string assembly follows a standard order from bottom to top: the fishing tool (overshot, spear, or taper tap), then a bumper sub or safety joint that allows the fishing tool to be released if it becomes stuck, then jars (mechanical or hydraulic), then a jar accelerator, then the drill string itself up to the surface. The jars must be correctly positioned above the expected stuck point so they can fire freely even if the fish holds the bottom of the string. The accelerator stores compressive energy to sharpen the jar impact, increasing the peak force delivered to the fish by 20 to 50% compared to the jar alone. Accurate jar placement requires knowing the free-point depth, which is determined by a free-point indicator tool run on wireline before the fishing assembly is made up.

Fishing Across International Jurisdictions

Canada (Alberta and British Columbia)

In Alberta, the Alberta Energy Regulator (AER) Directive 036 requires operators to report drilling incidents including stuck-pipe and fishing operations that exceed thresholds defined in the directive. Extended fishing operations that require well suspension, abandonment, or a sidetrack must be authorized by the AER through a well suspension or abandonment application under the Oil and Gas Conservation Act (OGCA). The AER's Well Event and Reporting System (WERS) captures fishing NPT as a component of drilling performance data published in AER statistical reports. In British Columbia, the BC Energy Regulator (BCER) administers equivalent requirements under the Drilling and Production Regulation. Montney horizontal wells are the highest-frequency context for fishing operations in western Canada: the long laterals, complex BHA configurations, and high wellbore temperatures in the Montney tight silt create elevated risk of drill string failures and mud motor stator failures that require fishing runs.

United States (Offshore and Onshore)

BSEE administers fishing incident reporting for offshore operations under 30 CFR Part 250. In the Gulf of Mexico (GoM), operators must report any incident that results in significant stuck-pipe or fish left in the wellbore. BSEE requires that an approved drilling program address contingency procedures for stuck pipe and fishing, and any deviation from the approved program during a fishing operation must be reported. GoM deepwater fishing operations are among the most technically demanding in the world: bottom-hole temperatures in the Paleogene Wilcox trend can exceed 300°F (149°C), requiring HPHT-rated fishing tools with temperature-rated elastomers and metal-seal grapples. The American Petroleum Institute (API) publishes Recommended Practice 7G, "Recommended Practice for Drill Stem Design and Operating Limits," which provides guidance on drill pipe fatigue analysis relevant to assessing why a string parted and how to design the fishing assembly. Onshore, the Texas Railroad Commission (RRC) and the Oklahoma Corporation Commission (OCC) require reporting of wells where fish are left in place, which may affect well-spacing, plugging and abandonment (P&A) requirements, and future re-entry permissions.

Australia

NOPSEMA regulates offshore fishing operations in Australian waters under the OPGGS Act 2006. Operators must notify NOPSEMA of incidents resulting in significant NPT or wellbore integrity risk through the incident reporting framework. The Offshore Petroleum (Resource Management and Administration) Regulations 2011 require an approved well operations management plan (WOMP) that addresses contingency procedures, including fishing. Onshore, the relevant authority varies by state: the Department of Energy and Mining (South Australia) and Department of Resources (Queensland) regulate fishing in the Cooper Basin, where Permian Patchawarra Formation sandstones are drilled with a high frequency of fishing incidents due to hard, abrasive formations that cause elevated bit cone and stabilizer wear. The Cooper Basin's remote location and long logistics chain mean that specialized fishing tool inventories must be pre-positioned at the field workshop before spudding, as mobilizing tools from a metropolitan center to an outback location can add three to five days of NPT.

Norway and the North Sea

Ptil (Petroleum Safety Authority Norway) oversees well integrity and drilling incident investigation on the Norwegian Continental Shelf (NCS). The NORSOK D-010 standard, "Well Integrity in Drilling and Well Operations," is the primary technical reference for fishing as a component of well integrity risk management in Norway and is widely adopted across the UK North Sea as well. NORSOK D-010 Section 11 addresses stuck pipe, fishing, and sidetrack procedures with specific requirements for documentation, tool qualification, and risk assessment. Ptil requires operators to include fishing contingency planning in the well program and to investigate and report incidents where fish are left in the wellbore. In the UK sector, NSTA (North Sea Transition Authority) requirements under the Energy Act 2016 include well notification requirements for fishing operations that materially deviate from the approved well program. The Brent and Statfjord fields in the Northern North Sea have extensive fishing histories due to their mature infrastructure and the high frequency of re-entry and workover operations on aging wellstock, generating a significant body of North Sea fishing experience that has contributed to modern fishing tool design standards.

Middle East (Saudi Arabia and UAE)

Saudi Aramco's Well Engineering Manual (WEM) provides detailed procedures for fishing operations in Arab-D carbonate and Khuff Formation clastic and carbonate wells. The WEM specifies mandatory pre-fish characterization steps, approved fishing tool vendors, and escalation protocols if a first fishing run fails. High-pressure, high-temperature (HPHT) conditions in deep Jurassic wells at Ghawar require fishing tools qualified to 350°F (177°C) and 20,000 psi (1,379 bar), which narrows the available tool inventory significantly. Abu Dhabi National Oil Company (ADNOC) applies equivalent standards through its ADNOC-UPST Well Engineering Standards for offshore and onshore fishing in Abu Dhabi. Kuwait Oil Company (KOC) uses its Drilling Engineering Standards Manual for fishing contingencies in the Burgan Field, where unconsolidated Cretaceous Wara sands create a high frequency of sand sloughing and pack-off events that require combined fishing and junk milling approaches.