Oil and Gas Terms Beginning with “X”

A technique for imaging a core by moving a source of X-rays along a core and recording the attenuated X-rays on the other side on a suitable photographic film.

A technique for the semiquantitative mineralogical analysis of a sample of rock by measuring the diffraction peaks in X-rays diffracted by the sample. The position of the diffraction peaks is a measure of the distance between discrete crystallographic diffracting planes within minerals, while their intensity indicates the quantity of the mineral. The technique is only semiquantitative because the size and shape of the diffraction peak are strongly influenced by the geometry of the measurement, for example orientation of the minerals, and sample preparation. Fine particles such as clays must be separated from larger particles and measured separately if they are to be detected properly. To reduce errors associated with preferred orientation of minerals, samples are most commonly ground to a powder before analysis, a technique known as powder X-ray diffraction.

A technique for elemental analysis of samples based on the characteristic fluorescence given off by different elements subjected to X-rays. In core analysis, X-ray fluorescence often is used to help determine mineral content. The elemental volumes are inverted to mineral volumes by assuming certain standard formulae for mineral composition.

The reactive (X) signal, or that part of the alternating signal at the receiver of an inductionlogging tool that is out of phase with the transmitter current. This signal, also known as the quadrature signal, is less sensitive to formationconductivity and must be separated from the R-signal, which is the main or, in older tools, the only source of the induction log. In a simple two-coil array, a large component of the X-signal is caused by direct coupling between transmitter and receiver coils. This direct signal is largely eliminated by use of a bucking coil. The X-signal provides a first-order correction to the skin effect of the R-signal.

A polysaccharide secreted by the bacteria genus Xanthomonas campestris, also known as xanthan gum. XC in water muds provides non-Newtonian mudrheology, highly desirable because of the flat velocity profile it produces in annular flow, which is required for efficient cuttings lifting in lower density muds. XC polymer is anionic, with tolerance for salinity and fair tolerance for hardness ions. XC is a finely powdered material that can vary in the amount of residual bacteria debris and the ease with which it disperses into water. Temperature tolerance varies with water-phase components, but starts to degrade around 200 to 250°F [93 to 121°C]. Extreme pH or hardness are not well-tolerated by XC polymer and it is susceptible to bacterial attack.

An aromatic hydrocarbon molecule containing a benzene ring with two methyl side chains, formula C6H4(CH3)2. Xylene is an excellent solvent, especially for aromatic solids such as asphaltic materials. It is used as a solvent and emulsionbreaker in workover operations to clean up reservoirs. In drilling mud testing, a 50/50 xylene/isopropanol (IPA) mixture had been used to break oil-mud emulsions prior to titrations to measure alkalinity, chloride and calcium. However, the xylene mixture has been replaced by a single material, propylene glycol normal propyl ether (PNP), to break oil mud emulsions.