Fracturing Glossary

How to Use This Glossary

This glossary covers common terms you will encounter when reading about hydraulic fracturing, well completion, and oilfield operations. Terms are listed alphabetically. Each definition is a simplified explanation intended for general understanding, not as a technical specification.

For deeper dives into specific topic areas, explore our dedicated pages on what is hydraulic fracturing, how fracturing works, hydraulic fracturing process step by step, well completion, frac equipment, frac sand, proppant explained, and hydraulic fracturing chemicals explained.

Glossary of Terms

Abandoned Well

A well that has been plugged and abandoned according to regulatory requirements. Surface reclamation may be pending or complete. Abandoned wells require different services than inactive or suspended wells.

Additive

A chemical substance mixed into fracturing fluid in small quantities to serve a specific purpose, such as reducing friction, preventing corrosion, or controlling bacteria. Additives typically represent less than 1% of total fluid volume.

AER (Alberta Energy Regulator)

The provincial regulatory body that oversees oil and gas development in Alberta. The AER publishes well data, issues licences, enforces environmental standards, and manages the regulatory framework for energy resources.

Annular Pressure

The pressure found in the annulus — the space between the casing and the wellbore wall, or between two concentric strings of pipe. Monitoring annular pressure is important for well integrity.

Artificial Lift

Methods used to bring fluids to the surface when reservoir pressure is insufficient for natural flow. Common types include electric submersible pumps (ESPs), rod pumps, gas lift, and progressive cavity pumps.

Ball Sealer

A small spherical device dropped from the surface to divert fluid flow. Ball sealers land on perforations and temporarily block them, forcing subsequent fluid into other perforation clusters within a stage.

Basin

A large geological depression where sediment has accumulated over time. Major oil and gas basins, such as the Permian Basin or the Bakken, contain the rock formations targeted by fracturing operations.

BLEV (Blowout Preventer)

A stack of valve assemblies installed at the surface to control well pressure and prevent uncontrolled releases (blowouts). BOPs are pressure-tested before drilling and completion operations.

BHP (Bottom Hole Pressure)

The pressure measured at the bottom of the well. BHP is a critical parameter during fracturing because it indicates how much force is being applied to the formation.

Blender

A piece of surface equipment used on a frac site to mix proppant (sand) and additives into the fracturing fluid before it is pumped downhole. The blender ensures a consistent slurry.

Bottom Hole Pressure

See BHP. The pressure at the bottom of the wellbore, typically measured near the perforations or target formation depth.

Breakdown Pressure

The surface pressure required to initiate the first fracture in the formation during a frac stage. Breakdown pressure is typically the peak pressure seen during a stage and indicates the rock has failed.

Bridge Plug

A downhole tool set inside the casing to isolate one section of the well from another. Bridge plugs are commonly used during plug-and-perf completions to separate frac stages.

Cluster

A set of perforations within a frac stage that serves as an entry point for fracturing fluid. Multiple clusters are placed within each stage, and cluster efficiency — the percentage that actually take fluid — is a key performance metric.

Casing

Steel pipe installed in a wellbore and cemented in place to line the well, maintain its structural integrity, and isolate different geological zones from each other.

Cement

A slurry pumped between the casing and the wellbore wall to secure the casing in place and create a seal that prevents fluid migration between zones.

Chemical Additive

See Additive. A substance added to fracturing fluid in small amounts to achieve a specific function.

Christmas Tree

The assembly of valves, chokes, and fittings installed at the wellhead after completion. It controls the flow of fluids during production and provides emergency shut-in capability.

Closure Pressure

The pressure at which the formation fracture faces come into contact with the proppant pack, indicating that the fracture has closed onto the proppant. Closure pressure is estimated from pressure decline analysis after a frac stage.

Completion

The process of preparing a drilled well for production. Completion activities may include casing, cementing, perforating, and hydraulic fracturing. See our well completion guide for more detail.

Core Sample

A cylindrical section of rock extracted from the wellbore during drilling. Core samples provide direct data on rock properties, porosity, permeability, fluid content, and fracture characteristics — all of which inform frac design.

Crosslinked Gel

A high-viscosity fracturing fluid created by adding a crosslinking agent to a gelled base fluid (typically guar or hydroxypropyl guar). Crosslinked gel carries more proppant and creates wider fractures than slickwater.

CT (Coiled Tubing)

A long, continuous length of steel pipe wound on a large reel. Coiled tubing can be run into a well under pressure and is used in a variety of well intervention and completion operations.

Data Van

A mobile control room on the frac site where real-time treatment data is monitored. The data van records treating pressure, pump rate, proppant concentration, and other parameters, and displays them for the on-site engineering team.

Decline Curve Analysis (DCA)

A technique that fits mathematical models to production data to forecast future performance and estimate ultimate recovery (EUR). Decline curves are used to evaluate well economics, compare wells, and plan field development.

Displacement

The act of pumping fluid into the wellbore to push the proppant-laden slurry into the formation after the frac treatment has been pumped.

Downhole

Refers to anything located or occurring inside the wellbore, below the surface. Downhole tools, pressures, and conditions are central to fracturing operations.

Drawdown

The difference between reservoir pressure and flowing bottom-hole pressure. Drawdown is the driving force that causes hydrocarbons to flow from the formation into the wellbore. Higher drawdown increases production rates but may accelerate formation damage or sand production.

Drive Pipe

A large-diameter conductor casing installed at the surface to prevent unconsolidated near-surface soils from caving into the wellbore during drilling. Drive pipe is the first casing string set in a well.

Drill Bit

The cutting tool attached to the bottom of the drill string that grinds and cuts through rock during drilling. Different bit types (roller cone, PDC, hybrid) are selected based on formation hardness and drilling conditions.

Drill Stem Test (DST)

A temporary completion used to evaluate a formation's productive capacity. A DST isolates the target zone, allows fluids to flow to the surface under controlled conditions, and measures formation pressure and permeability.

Drilling Fluid (Mud)

A circulating fluid used during drilling to cool and lubricate the drill bit, carry rock cuttings to the surface, and maintain wellbore pressure. Drilling fluid composition is carefully engineered for each well and formation.

EMS (Emergency Shutdown System)

An automated system that shuts in a well or shuts down equipment in the event of a safety emergency. EMS systems are tested regularly and are a critical safety component on frac sites.

ESG (Environmental, Social, and Governance)

A framework for evaluating a company's performance in environmental stewardship, social responsibility, and corporate governance. ESG considerations are increasingly important in oil and gas operations, including fracturing practices.

ESP (Electric Submersible Pump)

A downhole artificial lift system consisting of an electric motor, gas separator, and multi-stage centrifugal pump. ESPs provide high-volume lift and are common in shale oil wells, though they require electrical infrastructure and are sensitive to gas and solids.

EUR (Estimated Ultimate Recovery)

The total amount of oil or gas expected to be recovered from a well over its productive life. EUR is estimated using decline curve analysis and reservoir simulation.

Flickerwell

A well that cycles between producing and shutting in, often due to liquid loading in gas wells. As liquids accumulate in the wellbore, they suppress gas flow until pressure builds enough to push them out.

Flowback

The fluid that returns to the surface after a frac job once the well is opened for production. Flowback includes a portion of the injected fracturing fluid along with formation fluids. See our how fracturing works page for details on the flowback process.

Flowback Engineer

A specialist who manages the flowback phase after a frac job. Flowback engineers monitor return rates, fluid composition, pressure trends, and clean-up progress to optimize the transition to production.

Fluid Efficiency

The percentage of pumped fracturing fluid that remains in the fracture volume versus the percentage that leaks off into the formation matrix. High fluid efficiency means more of the pumped volume contributes to fracture creation.

Frac

Short for "fracture" or "fracturing." Commonly used as a verb ("to frac a well") or a noun ("the frac job").

Frac Fluid

The mixture of water, proppant, and chemical additives pumped into a well during a hydraulic fracturing treatment. See our how fracturing works page for details on fluid composition.

Frac Fleet

The complete set of equipment deployed for hydraulic fracturing operations at a wellsite, including pump trucks, blender, sand storage, data van, and iron (high-pressure piping). A modern frac fleet can include 15 to 20+ pump trucks.

Frac Gradient

See Fracture Gradient. The pressure per unit of depth required to initiate a fracture in a formation.

Frac Sand

A type of high-quality silica sand used as proppant in hydraulic fracturing. Frac sand grains are round, durable, and resistant to crushing under downhole pressure. Learn more on our frac sand page.

Frac Spread

See Frac Fleet. The entire equipment setup deployed at a wellsite for hydraulic fracturing operations.

Fracture

A crack or break in a rock formation. In hydraulic fracturing, fractures are intentionally created by pumping fluid at high pressure to increase hydrocarbon flow.

Fracture Gradient

The pressure required to create a fracture in a formation, expressed as a function of depth (typically psi/ft or ppg equivalent). Engineers use the fracture gradient to design pump rates and fluid volumes.

Fracture Half-Length (xf)

The distance a fracture extends from the wellbore in one direction. Typical half-lengths range from 200 to 1,500 feet depending on the formation and treatment design. Half-length is a key design parameter in frac engineering.

Fracture Stage

See Stage. A single segment of a horizontal well that is isolated and fractured individually during a multi-stage completion.

Fracture Width

The opening of a fracture, typically measured in fractions of an inch. Width is influenced by fluid viscosity, pump rate, and rock properties. Adequate width is essential for proppant placement and fracture conductivity.

Fracturing Simulator

Software used to model fracture propagation, proppant placement, and treatment outcomes. Fracturing simulators use rock mechanics, fluid dynamics, and historical data to predict fracture geometry and optimize frac design.

Formation Damage

Any impairment to the natural permeability of a reservoir rock caused by drilling, completion, or production activities. Formation damage restricts fluid flow and can significantly reduce well productivity. Stimulation treatments are often designed to bypass or remove damage.

Formation Pressure

The natural pressure of the fluids within the pore spaces of the rock. Formation pressure influences how fluids flow toward the wellbore and affects fracturing treatment design.

Gas Lift

An artificial lift method where gas is injected into the tubing to reduce the density of the fluid column, allowing reservoir pressure to push the fluid to the surface. Gas lift is versatile and handles varying fluid compositions.

Gondola Trailer

A rail car or truck trailer used to transport and store frac sand at the wellsite. Gondolas are commonly used in sand logistics for large frac operations.

Gravel Pack

A sand control method where sized sand or proppant is placed in the annulus between a screen and the formation to filter formation sand while allowing hydrocarbons to flow. Gravel packs are common in unconsolidated formations.

GSF (Gelled Slickwater Frac)

A hybrid fracturing fluid that combines the high-rate capabilities of slickwater with a small amount of gelling agent to improve proppant transport. GSF offers a middle ground between pure slickwater and crosslinked gel systems.

H2S (Hydrogen Sulfide)

A colorless, toxic gas with a distinctive rotten-egg smell. H2S can be present in some formations and requires special safety precautions on location, including personal gas monitors, wind socks, and H2S-rated equipment.

Head Pressure

The pressure generated by the column of fluid in the wellbore due to gravity. It is a component of the total pressure acting at the bottom of the well.

Heel

The point where the horizontal lateral section of a well meets the curved build section. Fracturing operations typically proceed from the toe (far end) toward the heel.

Horizontal Well

A well that is drilled vertically to a certain depth and then turned to run horizontally through the target formation. Horizontal wells expose a much larger section of the reservoir to the wellbore compared to vertical wells.

Hydraulic Horsepower (HHP)

A measure of the power output of a frac pump, calculated as pressure (psi) multiplied by flow rate (BPM) divided by 40.8. A typical frac pump delivers 2,000 to 3,000 HHP, and a full frac fleet may deploy 30,000 to 50,000+ total HHP.

Inactive Well

A well that is not currently producing but has not been formally suspended or abandoned. Inactive wells may be shut in for economic reasons, awaiting recompletion, or pending regulatory decisions. They often create service opportunities for oilfield companies.

IP (Initial Production)

The production rate measured during the first days or months after completion. IP is a widely cited metric for comparing well performance, though it does not reflect long-term production behavior.

ISIP (Instantaneous Shut-In Pressure)

The pressure recorded immediately after pumping stops at the end of a frac stage. ISIP is used by engineers to estimate formation pressure, evaluate near-wellbore friction, and assess fracture behavior.

Job

A common term for a single fracturing treatment performed on a well. "The job went well" means the frac treatment was completed as planned.

Lateral

The horizontal section of a wellbore that extends through the target formation. Laterals can be one to three miles or more in length. See our what is hydraulic fracturing page for more on horizontal drilling.

Liner

A string of casing that does not extend to the surface but is hung from a previous casing string using a liner hanger. Liners are commonly used in the production section of horizontal wells to reduce cost and casing weight.

Liner Hanger

A mechanical device used to suspend a liner from the bottom of a previous casing string. The liner hanger provides a mechanical and hydraulic seal between the two casing strings.

Linear Gel

A fracturing fluid created by adding a gelling agent (typically guar) to water without crosslinking. Linear gel has moderate viscosity — higher than slickwater but lower than crosslinked gel — and is used in some frac designs for improved proppant transport.

Log (Well Log)

A record of measurements taken along the wellbore to evaluate formation properties. Common logs include gamma ray, resistivity, density, neutron, and sonic logs. Log data informs completion design, frac stage placement, and reservoir evaluation.

Mesh Size

A measurement of proppant particle size, expressed as the number of openings per inch in a screening sieve. Common frac sand mesh sizes include 20/40, 30/50, 40/70, and 100 mesh. Smaller mesh numbers indicate larger particles.

Microseismic Monitoring

A technique that detects tiny seismic events (micro-earthquakes) generated by fracture creation. Microseismic events are located in real time using geophone arrays, providing insight into fracture orientation, height, half-length, and stimulated reservoir volume.

MPD (Managed Pressure Drilling)

A drilling technique that uses automated control of wellbore pressure to maintain a constant bottom-hole pressure within a narrow window. MPD is used in formations with narrow pressure margins or lost circulation risk.

Net Pressure

The pressure inside the fracture above the closure pressure. Net pressure drives fracture propagation and is a key diagnostic parameter. Increasing net pressure during a frac stage may indicate fracture growth, while declining net pressure may indicate fluid leakoff or fracture height growth.

Northern White Sand

A high-quality frac sand mined primarily from the Upper Midwest (Wisconsin, Minnesota, Illinois). Northern White sand is prized for its round grain shape, high silica content (99.5%+), and excellent crush resistance. It is the industry standard for proppant in many North American basins.

Open Hole

A wellbore section that is not lined with casing. In open-hole completions, the production zone is left uncased and exposed directly to the wellbore. Open-hole completions are less common in shale fracturing than cased-hole completions.

Operator

The company that holds the licence for a well and is responsible for its operation, maintenance, and regulatory compliance. Operators are the primary decision-makers for well-related service work.

Orphan Well

A well where the licensed operator is no longer responsible — typically due to bankruptcy or licence forfeiture. Orphan wells are managed by industry-funded organizations such as the Orphan Well Association in Alberta.

Pad

The initial volume of fracturing fluid pumped into a well before any proppant is added. The pad creates the initial fractures that the proppant will later fill. Also refers to the surface pad — the prepared area where a wellhead and equipment are located.

Perforation

A hole created through the casing and cement into the surrounding formation, typically using shaped charges fired by a perforating gun. Perforations provide entry points for fracturing fluid.

Perforating Gun

A downhole tool that uses explosive shaped charges to create perforations through the casing and into the formation. Wireline-conveyed perforating guns are the standard method in plug-and-perf completions.

Plug and Perf

A completion method in which bridge plugs are set to isolate individual stages, and then perforations are shot in each stage so it can be fractured one at a time. Plug-and-perf is the most common completion method in North American shale.

PPG (Pounds Per Gallon)

A unit of concentration used to measure proppant loading in fracturing fluid. For example, 4 ppg means four pounds of proppant per gallon of fluid. PPG is also used to express fluid density and equivalent circulating density.

Pressure Pumping

A broad term for high-pressure pumping services used in oil and gas operations, including hydraulic fracturing, cementing, acidizing, and well testing. See our frac pumps page for more on pressure pumping equipment.

Pressure Testing

The process of pressurizing the casing, wellhead, or other equipment to verify mechanical integrity before operations begin. Pressure testing is a critical safety step before fracturing, drilling, or well intervention.

Produced Water

Water that emerges from the formation along with oil and gas during production. Produced water volumes often increase over the life of a well and require management — recycling, treatment, or disposal in approved injection wells.

Proppant

A solid material, typically sand or ceramic beads, that is carried into fractures by the fracturing fluid. When pumping stops, the proppant holds the fractures open so hydrocarbons can flow. Learn about proppant types on our frac sand page.

Proppant Conc.

Short for proppant concentration. See PPG.

Rate

The volume of fluid pumped per unit of time, typically measured in barrels per minute (BPM). Pump rate is a key parameter in frac design and is one of the most closely monitored values during treatment.

Reclamation

The process of restoring a well site to its original or an acceptable condition after well abandonment. Reclamation may involve soil remediation, vegetation restoration, and obtaining regulatory closure.

Refrac (Re-Fracturing)

An additional fracturing treatment performed on a previously fractured well. Refracs are pursued when original completion quality was poor, when depletion has altered the stress field, or when operators want to access bypassed reserves.

Resin-Coated Proppant

Proppant particles coated with a resin layer that cures under downhole temperature and pressure. The resin bonds the proppant grains together, improving crush resistance and preventing proppant flowback. Resin-coated sand is used in higher-stress environments where uncoated sand may fail.

Servo Valve

A precision valve used in well control equipment that responds to electronic or hydraulic signals to regulate pressure or flow. Servo valves are components of managed pressure drilling and automated well control systems.

Service Company

A company that provides specialized equipment, personnel, and expertise to operators for fracturing, wireline, cementing, and other well services.

Shaped Charge

An explosive device used in perforating guns. When detonated, a shaped charge creates a high-velocity jet of metal that penetrates the casing, cement, and into the formation rock. Charge selection depends on casing thickness and desired penetration depth.

Shale Gas

Natural gas produced from shale formations. Shale has extremely low permeability, so hydraulic fracturing is essential for commercial production. Major shale gas plays include the Marcellus, Haynesville, and Montney.

Shale Oil (Tight Oil)

Oil produced from low-permeability shale or tight sandstone formations. Like shale gas, shale oil requires hydraulic fracturing for commercial production. Major shale oil plays include the Permian Basin, Bakken, and Eagle Ford.

Slickwater

A type of fracturing fluid that uses water with a small amount of friction-reducing additive (polymer). Slickwater is the most common fluid type used in shale fracturing because it allows high pump rates at lower friction pressure.

Slurry

The mixture of fracturing fluid and proppant being pumped downhole during a frac treatment.

Slurry Rate

The total volume rate of the proppant-laden fluid being pumped, measured in barrels per minute (BPM). Slurry rate is the surface-measured rate and differs from the downhole rate due to pressure and temperature effects.

Sleeve

A mechanical device in the completion string that can be opened to allow fracturing fluid to enter the formation. Sliding sleeves are an alternative to plug-and-perf for accessing individual frac stages.

Stage

A single segment of a horizontal well that is fractured individually. A typical horizontal well may have 20 to 60 or more stages, each isolated and treated separately.

Stage Spacing

The distance between adjacent frac stages along the lateral. Stage spacing is an important design parameter — closer spacing improves reservoir contact but increases completion cost and may cause stress shadow interactions between stages.

Stress Shadow

The alteration of the local stress field caused by the creation of a hydraulic fracture. When multiple fractures are created in close proximity, the compressive stress from each fracture affects its neighbors, potentially diverting or suppressing fracture growth in adjacent clusters or stages.

ST37 (AER Well Data File)

A dataset published by the Alberta Energy Regulator for Alberta well records. ST37 includes well identification, status fields, operator fields, location fields where available, and well classification details.

Surface Pressure

The pressure measured at the wellhead during pumping. Surface pressure, combined with the hydrostatic pressure of the fluid column, is used to estimate downhole pressure.

Suspended Well

A well where the operator has filed a suspension plan with the regulator. Suspended wells have specific regulatory obligations including fencing, capping, and monitoring requirements.

TCP (Tubing-Conveyed Perforating)

A perforating method where the gun system is conveyed into the well on tubing rather than wireline. TCP allows larger-diameter guns for deeper penetration and can be fired in underbalanced conditions.

Tonne

A metric unit of mass equal to 1,000 kilograms (approximately 2,204 pounds). Proppant volumes are sometimes expressed in tonnes, particularly in Canadian operations.

Tortuosity

The resistance to fluid flow caused by the complex, non-linear path between the wellbore and the main fracture body. Near-wellbore tortuosity increases treating pressure and can contribute to screenout risk. It is caused by misalignment between the perforation direction and the preferred fracture plane.

Treating Pressure

The pressure at which fracturing fluid is being pumped into the formation. Treating pressure must exceed the formation's fracture gradient to create and extend fractures.

Tubing

Pipe installed inside the casing through which fluids are pumped into or produced from the well.

Unconventional Reservoir

A reservoir with rock properties (ultra-low permeability, high clay content, or complex pore structure) that prevent commercial production without stimulation. Shale, tight sandstone, and tight carbonate formations are classified as unconventional. See our what is hydraulic fracturing page for more on unconventional resources.

Viscosity

A measure of a fluid's resistance to flow. In fracturing, fluid viscosity affects proppant transport, fracture width, and pump rate requirements. Slickwater has low viscosity; crosslinked gel has high viscosity.

Watchlist

A saved set of monitoring criteria used to review operators, wells, or regions over time. Watchlists help oilfield service companies repeat research consistently without manually rebuilding the same searches.

Water Management

The planning, sourcing, transport, use, recycling, and disposal of water throughout the fracturing process. Water management is a major logistical and environmental consideration for every frac operation.

Wellbore

The hole created by drilling, including the casing and cement that line it. The wellbore is the conduit through which all fluids flow between the surface and the formation.

Wellhead

The assembly of valves, spools, and fittings at the top of a well that controls the flow of fluids in and out of the wellbore.

Wireline

A cable used to lower tools and equipment into a wellbore. In fracturing, wireline is commonly used to run perforating guns and set bridge plugs during plug-and-perf completions. See our wireline and frac page for more detail.

Wireline Operator

A field technician who operates wireline equipment to run tools into the wellbore. Wireline operators play a key role in perforating and plug-setting operations.

Workover

An operation performed on an existing well to restore or improve production. Workovers may involve re-fracturing, cleaning out the wellbore, or repairing equipment.

Zipper Frac

A technique where two or more parallel horizontal wells are fractured in an alternating, interleaved pattern. By alternating stages between adjacent wells, zipper frac operations can exploit stress changes from the neighboring well to improve fracture complexity and reduce completion time. See our how fracturing works page for more on completion techniques.

100 Mesh Sand

A fine-grain proppant with particle sizes passing through a 100-mesh screen (approximately 0.15 mm or smaller). 100 mesh sand is used in slickwater fracturing to penetrate into narrow, complex fracture networks in shale. Its smaller size allows it to travel further from the wellbore but provides lower conductivity than larger mesh sizes.

20/40 Sand

A coarse-grain proppant with particle sizes between 20-mesh and 40-mesh screens (approximately 0.42 to 0.84 mm). 20/40 sand provides high conductivity and is used in wider fractures or as a tail-in proppant near the wellbore. It requires wider fracture apertures for placement.

40/70 Sand

A medium-grain proppant with particle sizes between 40-mesh and 70-mesh screens (approximately 0.21 to 0.42 mm). 40/70 sand is one of the most common proppant sizes used in North American shale fracturing, offering a balance between transportability and conductivity.

Ceramic Proppant

Synthetic proppant made from sintered bauxite or other ceramic materials. Ceramic proppant has higher crush strength than natural sand, making it suitable for deep, high-closure-stress wells. It is more expensive than sand but maintains conductivity under conditions where sand would fail.

Cleaning Agent

A chemical additive used to break down residual fracturing fluid, emulsions, or scale deposits in the wellbore after completion. Cleaning agents help ensure the well is clean and ready for production.

Equivalent Circulating Density (ECD)

The effective density of the fluid in the wellbore when circulation is occurring, accounting for friction pressure. ECD is important during drilling and fracturing because it affects the pressure exerted on the formation. ECD must remain below the fracture gradient to avoid unintended fracturing.

Extended Reach lateral

A horizontal lateral that extends significantly beyond the typical length for a given basin or formation — often exceeding two to three miles. Extended-reach laterals maximize reservoir contact from a single well pad but require specialized drilling and completion techniques.

Flowback Water

See Flowback. The fluid that returns to the surface after a frac job. Flowback water is tested for chemical composition, salinity, and radioactivity to determine appropriate handling and disposal methods.

Formation Evaluation

The process of analyzing geological, geophysical, and engineering data to characterize a reservoir. Formation evaluation informs completion design, frac design, and production forecasting by providing data on rock properties, fluid content, and reservoir pressure.

Geomechanics

The study of the mechanical behavior of rock formations. In fracturing, geomechanics informs fracture orientation, propagation behavior, stress field analysis, and wellbore stability. Geomechanical models are essential inputs for frac design software.

Leakoff

The loss of fracturing fluid from the fracture into the surrounding formation matrix. Leakoff reduces the volume of fluid available to extend fractures and is controlled by formation permeability, fluid viscosity, and filter cake buildup. Managing leakoff is critical for fracture efficiency.

Limit Entry Technique

A perforation design strategy that restricts the number and size of entry holes to create a uniform pressure drop across all clusters within a stage. By forcing fluid through fewer, smaller entry points, limited entry ensures that all clusters receive fluid rather than allowing preferential flow through the dominant clusters.

Pilot Hole

A smaller-diameter hole drilled before the main wellbore to gather geological data. Pilot hole data — including logs, cores, and formation tests — informs decisions about well placement, casing depth, and completion design.

AAPG (American Association of Petroleum Geologists)

A professional organization advancing the science of geology, including reservoir characterization and unconventional resource evaluation. AAPG publishes research and host conferences relevant to fracturing and completions.

API (American Petroleum Institute)

A U.S. trade association that develops standards for oil and gas equipment, well construction, and operations, including specifications for casing, cement, and pressure-rated frac equipment used in hydraulic fracturing.

Artificial Lift

Methods used to bring fluids to the surface when reservoir pressure is insufficient for natural flow. Common types include electric submersible pumps (ESPs), rod pumps, gas lift, and progressive cavity pumps. See our well completion guide for details.

BOP (Blowout Preventer)

A stack of valve assemblies installed at the surface (or subsea) to control well pressure and prevent uncontrolled releases. BOPs are pressure-tested before drilling and completion operations and are distinct from the frac stack used during pumping.

BPM (Barrels Per Minute)

A unit of pump rate — the volume of fluid pumped per minute. Typical shale frac rates run 60 to 120+ BPM. BPM combined with treating pressure sets the hydraulic horsepower a frac fleet must deliver.

Breakdown Pressure

The surface pressure required to initiate the first fracture in the formation during a frac stage. Breakdown pressure is typically the peak pressure seen during a stage and indicates the rock has failed.

CAPP (Canadian Association of Petroleum Producers)

The primary industry association representing oil and gas producers in Canada. CAPP compiles and reports production statistics for Canadian plays such as the Montney, Duvernay, and Horn River.

Ceramic Proppant

Synthetic proppant made from sintered bauxite or other ceramic materials. Ceramic proppant has higher crush strength than natural sand, making it suitable for deep, high-closure-stress wells. It is more expensive than sand but maintains conductivity where sand would fail. Learn more on our frac sand page.

Chemical Additives

Substances mixed into fracturing fluid in small amounts — usually less than 1% of total volume — to reduce friction, control bacteria, prevent scale, stabilize clays, or adjust pH. Operators disclose additives well-by-well through FracFocus.

Closure Stress

The in-situ stress that presses the fracture faces together once pumping stops, primarily the minimum horizontal stress plus overburden weight. Proppant must resist crushing at this stress; deeper, higher-stress wells use resin-coated or ceramic proppant.

Cluster Efficiency

The percentage of perforation clusters within a stage that actually initiate fractures and receive fluid. Low efficiency wastes stages; it is improved with limited entry perforations, diversion, and engineered phasing. See our how fracturing works page.

Completion Costs

The capital cost of preparing a well for production, including casing, perforating, fracturing, flowback, and surface equipment. In shale wells completion (especially fracturing) often represents 60–70% of total well cost.

Completion Engineering

The discipline of designing how a well is completed — casing, perforations, stimulation, and lift — to maximize recovery. It integrates rock mechanics, petrophysics, and economics, and overlaps with reservoir and production engineering.

Completion Optimization

The iterative process of tuning stage spacing, proppant intensity, and fluid volume using offset well performance, microseismic, and decline curve analysis to improve recovery per dollar spent.

Core Analysis

Laboratory testing of rock core samples to measure porosity, permeability, mechanical properties, and fluid content. Core analysis provides ground-truth data that calibrates petrophysical logs and frac models.

Directional Drilling

Any intentional deviation of the wellbore from vertical. Horizontal drilling is a form of directional drilling; most shale completions use horizontal laterals to maximize contact with thin targets.

Distributed Acoustic Sensing (DAS)

A fiber-optic measurement technique that detects acoustic energy along a cable in or near the wellbore, mapping where fluid enters the formation during pumping. DAS reveals cluster efficiency and fracture growth in real time.

Distributed Temperature Sensing (DTS)

A fiber-optic technique that measures temperature along the wellbore, used during and after pumping to infer fluid entry points and fracture geometry. DTS often complements DAS in modern completions.

Enhanced Recovery

Methods to increase the hydrocarbon recovery factor beyond primary depletion, including waterflooding, gas injection, and (in tight rock) optimized fracturing and refracs. Not to be confused with primary stimulation like the initial frac.

Field Development

The planning and sequencing of multiple wells across a lease or unit — including parent/child spacing, pad design, and facility layout — to maximize recovery while managing cost and interference such as frac hits.

Flushing Stage

The clean, proppant-free fluid pumped at the end of a frac stage to displace the remaining slurry out of the casing and into the formation. Accurate flush volume prevents proppant left in the casing and avoids pushing proppant too far out.

Foam Fracturing

A fracturing method using a nitrogen- or CO2-based foam as the carrying fluid, often with minimal water. Used in water-sensitive, low-pressure, or cold formations where cleanup and reduced water use matter; common in tight gas and coalbed methane.

Frac Design

The engineering plan for a fracturing treatment — stage count, fluid type and volume, proppant type and ramp, pump rate, and schedule — built from geology, logs, and offset data, then calibrated against real-time pressure.

Frac Economics

The analysis of completion CAPEX and OPEX against expected revenue from production, expressed through metrics like ROI, EUR, and break-even price. Frac economics drive decisions on stage count and proppant intensity.

Frac Hits

Unintended fracture communication between a new well and an adjacent existing well, which can damage the offset well's production or integrity. Managed through spacing, sequencing, and real-time monitoring.

Frac Monitoring

The real-time observation of a frac job — treating pressure, pump rate, proppant concentration, plus microseismic, DAS, and DTS — to verify the design is behaving as expected and to respond to anomalies.

Frac Software

Specialized applications running in the data van that log job parameters, control equipment, and model fracture propagation. Frac software compares actual to designed values and supports post-job analysis.

Frac Stack

The surface pressure-control assembly — a frac tree plus high-pressure iron — that contains the well during pumping and connects the missile manifold to the wellhead. It is rated for the maximum treating pressure.

Horizontal Wells

Wells drilled vertically then turned to run horizontally through the target formation. Horizontals expose far more reservoir than vertical wells and are completed with 20–60+ frac stages. See our what is hydraulic fracturing page.

Hydraulic Fracturing Process

The sequence of drilling, casing, perforating, pumping a pad, ramping proppant in the slurry, flushing, and repeating per stage, followed by flowback and production. The full step-by-step is on our how fracturing works page.

Hybrid Frac

A design that begins with a slickwater pad to build fracture complexity, then transitions to crosslinked or linear gel to place higher proppant concentrations. Hybrid fracs aim to optimize both geometry and conductivity.

In-Situ Stress

The natural stress state in the rock before any disturbance, comprising overburden, maximum horizontal stress, and minimum horizontal stress. Fractures open perpendicular to the minimum horizontal stress; in-situ stress drives fracture geometry.

Lateral Length

The length of the horizontal section of a wellbore, typically one to three miles in shale. Longer laterals expose more reservoir and improve the recovery factor, though they raise drilling and completion cost.

Maximum Horizontal Stress

The larger of the two horizontal principal stresses. Fractures tend to propagate in the plane perpendicular to the minimum horizontal stress, so the maximum horizontal stress influences fracture orientation and height growth.

Measured Depth (MD)

The actual length of wellbore drilled from the surface. MD is used for casing, cement, and proppant volume calculations, while pressure and fracture-gradient calculations use true vertical depth (TVD).

Microseismic

Tiny seismic events generated as fractures propagate, detected by geophone arrays to map fracture location, orientation, and stimulated reservoir volume. Microseismic is a primary method for evaluating frac effectiveness.

Missile (Manifold)

The high-pressure manifold that distributes blended fluid from the blender to each frac pump and to the wellhead. The missile is part of the iron and is pressure-tested before pumping.

NPT (Non-Productive Time)

Any period when pumping stops due to equipment failure, weather, or operational issues. Low NPT signals reliable equipment and crews and directly improves well economics.

Nitrogen Frac

A fracturing treatment using nitrogen gas — often as a foam — to reduce water use and improve cleanup in low-pressure or water-sensitive formations. Common in tight gas and coalbed methane completions.

Offset Well

A nearby well used as a reference for geology, pressure, and performance, and a potential victim of frac hits. Offset well data is a key input to frac design and field development planning.

Parent Wells

The first wells drilled and completed in a spacing unit. Their depletion and stress shadow affect later child wells, so operators manage parent/child sequencing and may refrac parents.

Perforation Clusters

Groups of shaped-charge perforations within a stage that act as entry points for fracturing fluid. Cluster count, spacing, and phasing are designed to promote uniform fracture initiation across the stage.

Petrophysics

The study of the physical and chemical properties of rocks and their contained fluids, derived from logs and core analysis. Petrophysics provides porosity, permeability, and water saturation used in frac design.

Poisson Ratio

A rock elastic property describing the lateral strain per unit axial strain under stress. Along with Young's Modulus, Poisson ratio influences fracture height growth and is an input to geomechanical frac models.

Pressure Control

The discipline of maintaining well control during operations using BOPs, wellheads, frac stacks, and monitored pressures. Pressure control is essential before, during, and after pumping.

Production Engineering

The discipline of managing a well through its productive life — artificial lift selection, rate management, and workovers — to maximize recovery and economic value. It follows completion and fracturing.

Production Forecasting

Estimating future production and EUR using decline curve analysis, type curves, and reservoir simulation. Forecasting guides investment and field development decisions.

Proppant Concentration

The mass of proppant per unit fluid volume, expressed in pounds per gallon (PPG). Typical frac designs ramp from 0.5–1.0 ppg to 4–8+ ppg, balancing conductivity against screenout risk. See our frac sand page.

Proppant Transport

The ability of the fracturing fluid to carry proppant into the fracture without settling out. Transport depends on fluid viscosity, pump rate, and proppant size; slickwater transports less proppant than gel at a given concentration.

Real-Time Data

Live measurements from the frac job — pressure, rate, proppant concentration, volumes — plus DAS/DTS, displayed in the data van and used to adjust the treatment and ensure safety. For equipment context see our frac equipment page.

Reservoir Characterization

The integration of geology, geophysics, petrophysics, and engineering to build a model of the target reservoir. Good characterization guides landing depth, stage placement, and fluid selection.

Reservoir Engineering

The discipline of estimating recoverable hydrocarbons, designing stimulation, and forecasting performance using material balance and reservoir simulation. It closely supports completion and fracturing decisions.

Reservoir Simulation

Numerical modeling of fluid flow in the reservoir, including fracture interaction, used to forecast EUR and optimize well spacing and completion design. Simulation complements decline curve analysis.

Rock Mechanics

The study of how rock deforms and fails under stress. In fracturing, rock mechanics — via Young's Modulus, Poisson ratio, and in-situ stress — predicts fracture initiation, propagation, and geometry.

Sand King

Personnel or systems on a frac site that manage proppant delivery from storage to the blender, matching sand supply to the pumping schedule. Consistent feed prevents screenouts and holds the designed ramp.

Screenout

An event where proppant bridges in the fracture or near the wellbore, stopping further placement and causing a rapid pressure rise. Screenouts can be planned (tip screenout) or unplanned events requiring response.

Shaped Charge

An explosive device used in perforating guns. When detonated, a shaped charge creates a high-velocity jet of metal that penetrates the casing, cement, and into the formation rock. Charge selection depends on casing thickness and desired penetration depth.

Sliding Sleeve

A mechanical device in the completion string opened sequentially (by balls or shifting tools) to allow fracturing fluid into the formation without wireline perforating. Sleeves can reduce completion time versus plug-and-perf.

Stage Spacing

The distance between adjacent frac stages along the lateral. Closer spacing improves reservoir contact but increases cost and stress shadow interaction; optimized using offset data and economics.

Stimulated Reservoir Volume (SRV)

The volume of rock connected to the wellbore by the induced fracture network. Larger SRV generally correlates with higher production and is estimated via microseismic, fiber optics, and production analysis.

Stress Shadow

The alteration of the local stress field caused by an existing hydraulic fracture, which can suppress or divert growth in adjacent clusters or stages. Managed through spacing, limited entry, and diversion.

Surface Equipment

The full set of pumps, blenders, sand systems, iron, missile, and data van deployed at the surface for a frac job. Most surface equipment is described on our frac equipment page.

Tight Gas

Natural gas from low-permeability sandstone or carbonate that requires hydraulic fracturing to produce commercially. Major tight gas plays include the Montney, Horn River, and parts of the Anadarko Basin.

Tight Oil

Oil from low-permeability formations requiring stimulation. Tight oil plays include the Bakken, Eagle Ford, and parts of the Permian Basin. Also called shale oil when produced from shale.

Toe

The far end of the horizontal lateral, opposite the heel where the lateral meets the build section. Fracturing typically proceeds from the toe toward the heel in plug-and-perf completions.

True Vertical Depth (TVD)

The vertical distance from the surface to a point in the well. TVD is used for pressure and fracture-gradient calculations, while measured depth is used for volumetric and casing counts.

Vertical Wells

Wells drilled straight down with no horizontal section. Verticals contact only the formation thickness and are fractured in a limited interval; they produce far less from shale than horizontal wells.

Well Completion

The process of preparing a drilled well for production — casing, cementing, perforating, fracturing, flowback, and installing production equipment. See our well completion guide for detail.

Well Stimulation

Any treatment that improves the flow capacity of a well, including hydraulic fracturing, acidizing, and matrix stimulation. Fracturing is the dominant stimulation for unconventional reservoirs.

Wireline

A cable used to lower tools into a wellbore. In fracturing, wireline runs perforating guns and sets bridge plugs during plug-and-perf completions. See our wireline and frac page for more.

Young's Modulus

A rock elastic property measuring stiffness (stress per unit strain). Higher Young's Modulus generally favors wider, more conductive fractures and is a key input to geomechanical frac models alongside Poisson ratio.