- Industri: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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A type of electrode device that is able to measure resistivity in different directions around the sonde. In most laterologs, the electrodes are cylinders that average the resistivity azimuthally around the sonde. In azimuthal laterologs, the electrode is segmented radially in several portions, each of which responds to the resistivity in the direction it is facing.
Industry:Oil & gas
A type of drillstem testing conducted with the drillstring in the hole and the surface valve closed to create a closed chamber of known volume into which the reservoir fluid can flow. The drillstring is sometimes filled with nitrogen at a relatively low pressure prior to testing. When the well begins to flow, the nitrogen or air is compressed and the volume of fluid inflow can be calculated as a function of time by monitoring the surface pressure in the drillstring. The bottomhole valve is closed to halt flow when the surface pressure reaches a value calculated prior to testing. This ensures that a precisely known amount of production has taken place.
Industry:Oil & gas
A type of downhole packer that is activated or set by applying compressive force to the packer assembly. In most cases, this is achieved with set-down weight from the running string, which is controlled by the driller or operator observing the weight indicator on the rig or coiled tubing unit.
Industry:Oil & gas
A type of downhole isolation tool that may be unset and retrieved from the wellbore after use, such as may be required following treatment of an isolated zone. A retrievable bridge plug is frequently used in combination with a packer to enable accurate placement and injection of stimulation or treatment fluids.
Industry:Oil & gas
A type of deliverability test conducted in gas wells to generate a stabilized gas deliverability curve (IPR). In a flow-after-flow test, a well flows under a constant rate until it reaches stabilized conditions (pseudosteady state). After the stabilized rate and pressure are recorded, the rate is changed and the well flows until pressure stabilizes again. The same procedure is repeated three or four times. The stabilization requirement is an important limitation of this type of test, especially in low-permeability formations, which require longer stabilization times. This test is also known as a backpressure or four-point test.
Industry:Oil & gas
A type of damage in which the formation wettability is modified, generating a change in relative permeability that eventually affects well productivity. <br><br>Surfactants or other additives in drilling fluids, especially oil-base mud, or other injected fluids can change formation wettability. A naturally water-wet formation could be changed into an oil-wet formation with consequent production impairment caused by reduction of oil relative permeability. <br><br>Wettability change is normally treated with mutual solvents to remove the rock-oil coating (asphaltene or paraffin precipitation), followed by a strong water-wet surfactant to reduce the tendency of further hydrocarbon precipitation.
Industry:Oil & gas
A type of damage in which heavy hydrocarbons precipitate when temperature or pressure is reduced. These deposits are commonly located in the tubing, gravel pack and perforations, or inside the formation. The injection of cold treating fluids promotes the formation of organic deposits. <br><br>Organic deposits such as paraffins or asphaltenes are resolubilized using aromatic organic solvents such as toluene or xylene. Small amounts of alcohol help to further dissolve asphaltenes.
Industry:Oil & gas
A type of damage in which formation permeability is reduced because of the alteration of clay equilibrium. <br><br>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. <br><br>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.
Industry:Oil & gas
A type of damage in which foreign particles injected during normal well operations, such as drilling, completion, workover, stimulation or enhanced recovery, block the near-wellbore formation, reducing well productivity. <br><br>Potentially damaging particles in drilling fluids include clays, cuttings, weighting agents and fluid-loss control materials. In workover and stimulation fluids, suspended solids include bacteria and polymer residues. Foreign plugging particles can also be introduced as a result of poor water-handling practices. These foreign particles include debris from tanks and tubing.
Industry:Oil & gas
A type of corrosion produced when easily removed scales (such as iron carbonate) that were initially protecting the metals in the pipe are eroded and the underlying metals are corroded. <br><br>Erosion-corrosion is a common cause of failure in oilfield equipment. The attack is normally localized at changes of pipe sections, bends or elbows where there is high velocity or turbulent flow.
Industry:Oil & gas
