A small-diameter hydraulic line used to operate downhole completion equipment such as the surface controlled subsurface safety valve (scssv).

Most systems operated by control line operate on a fail-safe basis.

In this mode, the control line remains pressurized at all times. any leak or failure results in loss of control line pressure, acting to close the safety valve and render the well safe.

Abbr.

Coiled tubing.

A type of damage in which formation permeability is reduced because of the alteration of clay equilibrium.

Clay swelling occurs when water-base filtrates from drilling, completion, workover or stimulation fluids enter the formation.

Clay swelling can be caused by ion exchange or changes in salinity.

However, only clays that are directly contacted by the fluid moving in the rock will react; these include authigenic clays, some detrital clays on the pore boundaries and unprotected clay cement.

The nature of the reaction depends on the structure of the clays and their chemical state at the moment of contact.

The most common swelling clays are smectite and smectite mixtures that create an almost impermeable barrier for fluid flow when they are located in the larger pores of a reservoir rock.

In some cases, brines such as potassium chloride [kcl] are used in completion or workover operations to avoid clay swelling.

The elapsed time for mud to circulate from the suction pit, down the wellbore and back to surface.

Circulation time allows the mud engineer to catch “in” and “out” samples that accurately represent the same element of mud in a circulating system.

Circulation time is calculated from the estimated hole volume and pump rate and can be checked by using tracers such as carbide or rice granules.

The complete, circuitous path that the drilling fluid travels.

Starting at the main rig pumps, major components include surface piping, the standpipe, the kelly (rotary) hose, the kelly, the drillpipe, drill collars, bit nozzles, the various annular geometries of the openhole and casing strings, the bell nipple, the flowline, the mud-cleaning equipment, the mud tanks, the centrifugal precharge pumps and, finally, the positive displacement main rig pumps.

The loss of drilling fluid to a formation, usually caused when the hydrostatic head pressure of the column of drilling fluid exceeds the formation pressure.

This loss of fluid may be loosely classified as seepage losses, partial losses or catastrophic losses, each of which is handled differently depending on the risk to the rig and personnel and the economics of the drilling fluid and each possible solution.

A standardized measure of casing-strength properties.

Since most oilfield casing is of approximately the same chemistry (typically steel), and differs only in the heat treatment applied, the grading system provides for standardized strengths of casing to be manufactured and used in wellbores.

The first part of the nomenclature, a letter, refers to the tensile strength.

The second part of the designation, a number, refers to the minimum yield strength of the metal (after heat treatment) at 1000 psi [6895 kpa].

for example, the casing grade j-55 has minimum yield strength of 55,000 psi [379,211 kpa].

The casing grade p-110 designates a higher strength pipe with minimum yield strength of 110,000 psi [758,422 kpa].

since the well designer is concerned about the pipe yielding under various loading conditions, the casing grade is the number that is used in most calculations.

It is also important to note that, in general, the higher the yield strength, the more susceptible the casing is to sulfide stress cracking (h2s-induced cracking).

Therefore, if h2s is anticipated, the well designer may not be able to use tubulars with strength as high as he or she would like.

A remedial cementing operation designed to force cement into leak paths in wellbore tubulars.

The required squeeze pressure is achieved by carefully controlling pump pressure.

Squeeze cementing operations may be performed to repair poor primary cement jobs, isolate perforations or repair damaged casing or liner.

Density separation state of emulsions, often where color variances are noted.

A completion where ct and associated ct-mounted hardware is used as the primary completion flow path.

Abbr.

Cased, cemented and perforated.

A very small string, usually run along the outside of the tubing and banded to the tubing.

Commonly used for hydraulic control of safety valves and sliding sleeves.

May also transmit bottom hole gauge data.

Hydrocarbons which are in the gaseous state under reservoir conditions but which become liquid either in passage up the hole or at the surface.

Pertaining to a colloid, i.e., involving particles so minute (less than 2 microns) that they are not visible through optical microscopes.

Bentonite is an example of a colloidal day.

The change in volume per unit of volume of a liquid caused by a unit change in pressure at constant temperature