Oil and Gas Terms Beginning with “C” — Page 7

What Is Chrome Lignosulfonate? Chrome lignosulfonate (CLS) is a thermally stable water-based drilling fluid additive produced by sulfonating kraft lignin — a byproduct of the paper pulp industry — and crosslinking the… Read more →

Tubing manufactured from an alloy containing a high proportion of chrome, typically greater than 13%. Chrome tubing is classified as a corrosion-resistant alloy (CRA) and is used where the wellbore conditions or… Read more →

Pertaining to a mud additive (usually lignosulfonate or lignite) that does not contain any chromium compounds. Read more →

A salt of chromium in which chromium atoms are in the plus-3 valence state, such as chromic chloride, CrCl3. Chromic compounds are considered less harmful to the environment than chromates (plus-6 valence) because they… Read more →

What Is a Chronostratigraphic Chart? Chronostratigraphic chart (also called a Wheeler diagram or time-space diagram) is a geological display that plots geological time on the vertical axis against lateral distance along… Read more →

What Is Chronostratigraphy? Chronostratigraphy is the branch of stratigraphy concerned with establishing the age and time relationships of rock bodies — assigning absolute or relative ages to stratigraphic units and… Read more →

What Is Churn Flow? Churn flow (also called churning flow or transitional flow) is a chaotic, unstable multiphase flow regime occurring in vertical and near-vertical pipes at intermediate gas-liquid ratios — positioned… Read more →

A technique for marine seismic acquisition around salt domes or other circular features in which the acquisition vessel travels in a spiral path above the feature. Circle shooting can also be performed to increase… Read more →

To pump fluid through the whole active fluid system, including the borehole and all the surface tanks that constitute the primary system. Read more →

What Does Circulate Out Mean? Circulate out (also called circulating out a kick or kill circulation) is the well control procedure of pumping the influx — gas, oil, or salt water that entered the wellbore during a kick… Read more →

(noun) The continuous flow of drilling fluid from the surface mud system, down through the drillstring, out through the bit nozzles, up the annulus carrying cuttings, and back to the surface for solids removal and… Read more →

What Is a Circulation Device? Circulation device (also called a circulating sub, crossover sub, or circulating valve) is a downhole tool run in a drill string or workover string that allows drilling or treatment fluid… Read more →

What Is Circulation Loss? Circulation loss (also called lost circulation or lost returns) is the uncontrolled flow of drilling fluid from the wellbore into the formation — a condition in which drilling mud pumped down… Read more →

What Is a Circulation Sub? Circulation sub (also called a circulating sub, bypass sub, or side-port sub) is a downhole BHA component containing a side-port or valve mechanism that can be opened by surface pressure… Read more →

The complete, circuitous path that the drilling fluid travels. Starting at the main rig pumps, major components include surface piping, the standpipe, the kelly hose (rotary), the kelly, the drillpipe, drill collars,… Read more →

A downhole device that enables circulation through the tubing string and associated annulus. As a completion accessory, a circulation valve is included to circulate fluid for well kill or kickoff. Circulation valves… Read more →

What Is Citric Acid in Oilfield Operations? Citric acid (chemical formula C6H8O7; also known as 2-hydroxypropane-1,2,3-tricarboxylic acid) is a weak triprotic organic acid used in oilfield stimulation and completion… Read more →

A conventional method of mapping reservoir parameters in two dimensions, x and y. The resulting map set usually includes the top and bottom structure map derived from seismic and well data and that are used to generate… Read more →

What Is Clastic Sediment? Clastic sediment (from the Greek klastós, meaning "broken") is sediment composed of fragments (clasts) of pre-existing rocks and minerals that were mechanically weathered, eroded, transported… Read more →

What Is Clay in Reservoir Rocks? Clay in oil and gas reservoirs refers to fine-grained phyllosilicate minerals — primarily kaolinite, illite, chlorite, smectite (montmorillonite), and mixed-layer clays — that occur in… Read more →

What Is a Clay Extender? Clay extender (also called a bentonite extender or polymer extender) is a high-molecular-weight polymer additive used in water-based drilling fluids to increase the viscosity yield of bentonite… Read more →

What Is a Clay Stabilizer? Clay stabilizer (also called a shale stabilizer or formation clay inhibitor) is a chemical additive used in drilling, completion, and workover fluids to prevent reactive formation clays —… Read more →

What Is Clay Swelling? Clay swelling is the volumetric expansion of clay minerals — particularly smectite (montmorillonite) and mixed-layer illite-smectite clays — when they absorb water or other polar fluids, driven by… Read more →

What Is Clay-Water Interaction? Clay-water interaction (also called clay hydration or clay reactivity) is the physico-chemical process by which water molecules and dissolved ions contact clay minerals in shales and… Read more →

What Is Clay-Bound Water? Clay-bound water (CBW) is a component of the total pore water in a reservoir rock that is electrostatically held on the surface of clay mineral particles — firmly attached to the clay platelets… Read more →

An all-inclusive term to describe various progressive interactions between clay minerals and water. In the dry state, clay packets exist in face-to-face stacks like a deck of playing cards, but clay packets begin to… Read more →

Pertaining to a sedimentary rock, such as sandstone or limestone, that contains only minimal amounts of clay minerals. Clean reservoir rocks typically have better porosity and permeability than dirty rocks whose pores… Read more →

The removal of wellbore-fill material, such as sand, scale or organic materials, and other debris from the wellbore. Many reservoirs produce some sand or fines that may not be carried to surface in the produced fluid.… Read more →

A period of controlled production, generally following a stimulation treatment, during which time treatment fluids return from the reservoir formation. Depending on the treatment, the cleanup period can be relatively… Read more →

What Is Clear Water Drilling? Clear water drilling (also called plain water drilling or water-only drilling) is a drilling technique using plain water — or water with minimal additives such as a pH modifier or oxygen… Read more →