Well Stimulation Treatment Glossary

This glossary is intended to provide basic definitions for terms and acronyms used in the WST Disclosure WellSTAR program.

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Term

Acid Fracturing		Back to Top
	A well stimulation treatment, that, in whole or in part, includes the pressurized injection of acid into an underground geologic formation in order to fracture the formation, thereby causing or enhancing the production of oil or gas from a well.
Acid Matrix Stimulation Treatment		Back to Top
	An acid treatment conducted at pressures lower than the applied pressure necessary to fracture the underground geologic formation.
Additive		Back to Top
	A substance or combination of substances added to a base fluid for purposes of preparing well stimulation treatment fluid, including, but not limited to, acid stimulation fluid and hydraulic fracturing fluid. An additive may serve additional purposes beyond the transmission of hydraulic pressure to the geologic formation, including increasing/decreasing viscosity, reducing friction, limiting bacteria, pH control, and decreasing corrosion. An additive may be of any phase and may include proppants. Additives are often given proprietary trade names.
Additive Concentration (%)		Back to Top
	Concentration, by percent, of each additive used during WST.
Additive Supplier		Back to Top
	Supplier of the WST fluid additive.
Analyte		Back to Top
	The chemical constituents detected during testing and analysis of base fluid water source and recovered fluid samples. Analysis of these samples is required for WST disclosure to determine the composition of the water used during WST and the fluids recovered from a well after WST.
Analytical Laboratory		Back to Top
	The firm selected by the operator to analyze base fluid water source and recovered fluid samples for the presence of chemical constituents.
Analytical Laboratory Reports		Back to Top
	Reports prepared by the analytical laboratory to document the process the laboratory uses to analyze the water source and recovered fluids, and report the analytical results. This report is included with the operator’s disclosure form.
Analytical Method		Back to Top
	The standardized analytical technique (approved by the U.S. Environmental Protection Agency [U.S. EPA]) used by the analytical laboratory to determine the concentration of the chemical compounds or elements detected during water source or recovered fluid sample analysis.
Analytical Procedure Name		Back to Top
	The name the analytical laboratory uses to describe an analytical method.
API		Back to Top
	American Petroleum Institute. Oil and gas industry standards organization responsible for creating the numbering scheme for oil and gas wells. The Professional Petroleum Data Management Association (PPDM Association) has been responsible for the API Number standard since 2010.
API Number		Back to Top
	A unique 8-digit numeric identifier assigned to each oil and gas well in the United States.
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Term

Base Fluid		Back to Top
	The continuous phase fluid used in the makeup of a well stimulation treatment fluid. The continuous phase fluid may include, but is not limited to, water, and may be a liquid or a hydrocarbon or nonhydrocarbon gas. A well stimulation treatment may use more than one base fluid.
Base Fluid Suitability		Back to Top
	Designation of whether the base fluid is suitable for irrigation or domestic use.
Base Fluid Water Source		Back to Top
	The water source used as a base fluid supply.
Base Fluid Water Source Sample		Back to Top
	A sample the operator collects at the base fluid water source location.
Baseline/Meridian		Back to Top
	The U.S. Public Land Survey System (U.S. PLSS) is the surveying method used to describe and subdivide land. The baseline runs east-west, and the meridian runs north-south. The baseline and meridian are referenced to a designated initial point, upon which all surveys in a defined area are based.
BBLS		Back to Top
	Barrels. Oil industry unit of measure for oil volume: 1 barrel = 42 gallons.
Bottom of Horizon (TVD)		Back to Top
	The actual vertical depth to the bottom of the rock layer (production horizon) from which hydrocarbons are produced.
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Term

CAS Number		Back to Top
	See: Chemical Abstract Service Number.
CCR		Back to Top
	California Code of Regulations. Well stimulation treatment (WST) is regulated under CCR Title 14, Sections 1751 through 1789.
Chemical Abstracts Service Number		Back to Top
	A unique identification number assigned by the Chemical Abstracts Service (CAS) for every chemical compound or mixture of chemical compounds described in scientific literature.
Chemical Constituent (Chemical Name)		Back to Top
	Name of the chemical compounds contained within the WST fluid additives.
Chemical Constituent Concentration (% mass)		Back to Top
	Concentration of each chemical constituent of the WST fluid. The total (or total of each stage) should sum to 100%.
Chemical ID if no CAS No.		Back to Top
	A unique identification number selected by the operator if no CAS number exists for the chemical constituent.
Class II Injection Well		Back to Top
	Class II wells are used for the injection of fluids brought to the surface in connection with oil or gas production, for enhanced recovery of oil or gas, or for storage of liquid hydrocarbons. (See 40 C.F.R. § 144.6(b).) The Class II well designation was established by the U.S. EPA for the purpose of regulating injection wells under the Safe Drinking Water Act of 1974.
Confidential Well		Back to Top
	The designation given to a well in accordance with Public Resources Code (PRC) section 3234, that protects certain information regarding the well from public disclosure for a limited period of time.
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Term

Directional Drilling		Back to Top
	An oil or gas well drilling technique in which drilling tools are used to control the direction and inclination of a wellbore.
District Code		Back to Top
	The numerical code used by the Geologic Energy Management Division (CalGEM, formerly DOGGR) to identify the geographic management district where the well is located. The code for each district is as follows: 01. Cypress 02. Ventura 03. Orcutt 04. Bakersfield 05. Coalinga 06. Sacramento
Division		Back to Top
	The Geologic Energy Management Division, also referred to as CalGEM, (formerly DOGGR), which is the division in the Department of Conservation responsible for regulating the oil, gas, and geothermal industry.
DOGGR		Back to Top
	The former Division of Oil, Gas and Geothermal Resources is the Geologic Energy Management Division (as of January 1, 2020) in the Department of Conservation responsible for regulating the oil, gas and geothermal industry.
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Term

EPA		Back to Top
	Environmental Protection Agency. A Federal agency whose mission is to protect human health and the environment.
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Term

Field Name		Back to Top
	The name given to the geographic extent of the underground accumulation of oil and gas.
Formation Name, Bottom of Horizon		Back to Top
	The name of the geologic formation at the bottom of the oil and gas production zone (horizon).
Formation Name, Top of Horizon		Back to Top
	The name of the geologic formation at the top of the oil and gas production zone (horizon).
Fracture Azimuth		Back to Top
	Axial direction of modeled well stimulation induced fractures in degrees (e.g., 0 = true north, 90 = east, 180 = south, 270 = west).
Fracture Height		Back to Top
	Extent, in feet, of modeled well stimulation induced fractures parallel to the orientation of the wellbore.
Fracture Length		Back to Top
	Extent, in feet, of modeled well stimulation induced fractures perpendicular to the orientation of the wellbore.
Ft.		Back to Top
	Feet. A linear unit of measurement equal to 12 inches.
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Term

GeoTracker		Back to Top
	The Water Boards’ data management system for managing sites that impact groundwater, especially those that require groundwater cleanup (Underground Storage Tanks [UST], Department of Defense, Site Cleanup Program) as well as permitted facilities such as operating USTs and land disposal sites: http://geotracker.waterboards.ca.gov
Groundwater Monitoring Plan (GWMP)		Back to Top
	A document approved by the State Water Resources Control Board (SWRCB) that outlines the program to monitor the possible impact of WST to local groundwater where water quality is sufficient to be considered a resource for drinking water or agricultural use.
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Term

Horizontal Well		Back to Top
	A directionally drilled well that is drilled vertically then turns to become near parallel (horizontal) with the ground surface.
Hydraulic Fracturing		Back to Top
	A well stimulation treatment that, in whole or in part, includes the pressurized injection of one or more base fluids mixed with physical and chemical additives into an underground geologic formation in order to fracture the formation, thereby causing or enhancing the production of oil or gas from a well.
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Term

Laboratory		Back to Top
	The name of the laboratory, displayed as an abbreviation, where fluid analysis was conducted. Information for all abbreviations is provided on the Analytical Laboratory Abbreviations list.
Latitude		Back to Top
	A geographic coordinate that specifies the distance the well is located north or south of the equator. Measured in terms of the 360 degrees of a circle.
Lease Name		Back to Top
	The name of the mineral rights lease associated with the well. In some cases, there is no lease name and this field will be blank.
Letter of Concurrence (LOC)		Back to Top
	A document from the State Water Resources Control Board (SWRCB) agreeing with the operator's assertion that there is no groundwater resource in the vicinity of the wells undergoing WST.
Longitude		Back to Top
	A geographic coordinate that specifies the distance the well east or west of the prime meridian in Greenwich, England. Measured in terms of the 360 degrees of a circle.
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Term

MD		Back to Top
	See: Measured Depth.
MDL		Back to Top
	See: Method Detection Limit.
Measured Depth		Back to Top
	Depth measured along the wellbore. As the wellbore may be at an angle from vertical this number may not match true vertical depth measurements.
Method Detection Limit		Back to Top
	The minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero. The method detection limit is laboratory-specific and is established by the analytical laboratory for each analytical method and each piece of analytical equipment.
MG/L		Back to Top
	Milligrams per Liter. Unit of measurement for water sample concentration, equal to one milligram of a substance dissolved in one liter of water.
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Term

N/A		Back to Top
	Not Applicable.
Nature of Recovered Fluid		Back to Top
	The physical form of the recovered fluid, which is typically water-based.
ND		Back to Top
	Not Detected. The analyzed compound or analyte was not detected in the sample at or above the reporting limit.
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Term

Offshore		Back to Top
	A well where the wellbore is completed below the seabed.
Onshore		Back to Top
	A well where the wellbore is completed below lands that are not submerged under ocean waters or inland bays during mean high tide.
Operator		Back to Top
	A person who, by virtue of ownership, or under the authority of a lease or any other agreement, has the right to drill, operate, maintain, or control a well or production facility.
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Term

PPB		Back to Top
	Parts per Billion. A unit of measurement of the chemical concentration determined by comparing the mass of each constituent with the total mass of the sample. (1/1,000,000,000).
PPM		Back to Top
	Parts per Million. A unit of measurement of the chemical concentration determined by comparing the mass of each constituent with the total mass of the sample. (1/1,000,000).
PCI/L		Back to Top
	Picocuries per Liter. A unit of measurement for levels of radioactive compounds or elements, such as radon gas.
PLSS		Back to Top
	Public Land Survey System. The system used by the Federal Government to survey, subdivide and describe land.
PRC		Back to Top
	Public Resource Code. The California PRC was codified in 1939 to consolidate and revise the laws relating to natural resources (e.g., mines and mining, oil and gas, forestry).
Produced Water		Back to Top
	Water extracted from the ground during oil production processes. Produced water is often, but not always, highly saline (briny) and usually contains some hydrocarbons.
PQL		Back to Top
	Practical Quantitation Limit. The lowest concentration that can be reliably measured with precision and accuracy for a specific laboratory analytical method.
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Term

Radioactive Constituent		Back to Top
	Name of the radioactive element or constituent detected in the recovered fluid. Radioactive elements may be naturally occurring in the rock formations.
Radiological Component or Tracer		Back to Top
	A radioactive compound used to track the movement of WST fluid through the formation.
Radiological Recovery Method		Back to Top
	The method used to recover the radiological component or tracer.
Range		Back to Top
	Used in the U.S. PLSS, the range is a measure of distance east or west from a referenced principal meridian, in units of six miles.
RDL		Back to Top
	See: Reported Detection Limit.
Recovered Fluid		Back to Top
	The fluids recovered following WST, either from flowing to the wellhead under pressure, or produced from the well.
Recovered Fluid Disposal Method		Back to Top
	Disposal method of fluids recovered from the well following WST. Recovered fluids are often injected into Class II injection wells.
Recovered Fluid Sample		Back to Top
	A sample the operator collects of the fluids recovered following WST.
Reported Detection Limit		Back to Top
	The lowest concentration at which an analyte can be detected in a sample, and its concentration reported, with a reasonable degree of accuracy and precision. This is a laboratory-specific number.
Result Qualifier		Back to Top
	The code identifying the qualifier of an analytical result (e.g., greater than, equal, etc.).
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Term

Sample ID		Back to Top
	The name the well operator gives to the fluid sample.
SB 4		Back to Top
	Senate Bill 4 for WST (2013) was enacted into law on January 1, 2014 under the PRC, Sections 3000 through 3161.
Section		Back to Top
	Used in the U.S. PLSS, a section is approximately one-square-mile block of land. There are 36 sections in a survey township.
Slurry Volume		Back to Top
	Volume in barrels of fluid, including base fluid, proppant, and additives used during WST.
Stage		Back to Top
	A specific perforation interval in a WST that is isolated from other perforation intervals when undergoing a treatment process that is specific to that interval.
Stage Number		Back to Top
	WST stage number as identified by the operator.
Stage Bottom (MD)		Back to Top
	Depth, in feet, to the bottom of the perforated interval of each well stimulation stage, measured along the wellbore.
Stage Bottom (TVD)		Back to Top
	True vertical depth, in feet, to the bottom of the perforated interval of each well stimulation stage.
Stage Top (MD)		Back to Top
	Depth, in feet, to the top of the perforated interval of each well stimulation stage, measured along the wellbore.
Stage Top (TVD)		Back to Top
	True vertical depth, in feet, to the top of the perforated interval of each well stimulation stage.
SWRCB		Back to Top
	State Water Resources Control Board. A department in the California Environmental Protection Agency responsible for protecting public health, the environment and water resources through the regulation of water quality.
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Term

TD		Back to Top
	See: Total Depth.
Top of Horizon (MD-Feet)		Back to Top
	Depth to the top of the production horizon, in feet, measured along the wellbore.
Top of Horizon (TVD-Feet)		Back to Top
	True vertical depth, in feet, to the top of the production horizon.
Total Depth (TD)		Back to Top
	The total depth of an oil or gas well, measured in feet, as measured depth (MD) or true vertical depth (TVD.)
Township		Back to Top
	Used in the U.S. PLSS, a township is a square parcel containing 36 square miles of land, or a measure of distance north or south from a referenced baseline, in units of six miles.
Trade Name		Back to Top
	Product name given by the manufacturer to an additive contained within the WST fluid.
Trade Secret Protection		Back to Top
	Classification that protects certain information regarding WST additives from public disclosure. ((See Pub. Resources Code, § 3160, subd. (j).)
True Vertical Depth (TVD)		Back to Top
	Depth of an oil or gas well measured vertically from ground surface without reference to the wellbore path.
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Term

UG/L		Back to Top
	Micrograms per Liter. Unit of measurement for water sample concentration, equal to one microgram of a substance dissolved in one liter of water.
UIC		Back to Top
	Underground Injection Control. A Division program approved by the U.S. EPA pursuant to the federal Safe Drinking Water Act to regulate Class II injection wells.
UIC Project Number		Back to Top
	A unique 8-digit code used by the Division to identify a project within the Class II Underground Injection Control program.
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Term

Valid Value List		Back to Top
	The list that provides standardized terms (usually abbreviated) for certain fields (e.g., analytical methods, chemical constituents, analytical laboratories, units). The analytical laboratory abbreviation list used for the SB 4 program is based on the valid values list used by the SWRCB for data submitted to their Geotracker website. http://geotracker.waterboards.ca.gov/
Volume Prior to Sampling		Back to Top
	Volume, in barrels, of fluids recovered following well stimulation at the time of initial sampling (greater than 1 well volume, less than 3 well volumes).
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Term

Water Supplier		Back to Top
	The private individual, agent, or company that provided the base fluid water.
Well Designation		Back to Top
	Well identifier used by the Division that consists of a combination of the lease name and the well ID.
Well ID		Back to Top
	Well number designated by the well operator that appears within Division records.
Well Stimulation Treatment (WST)		Back to Top
	A treatment of a well designed to enhance oil and gas production or recovery by increasing the permeability of the formation.
WST Permit Number		Back to Top
	Number assigned by the Division to an approved WST permit.
WST Start Date		Back to Top
	Date WST was initiated.
WST End Date		Back to Top
	Date WST was terminated.
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