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60 Cards in this Set
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- Back
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hydraulic fracturing |
A stimulation treatment routinely performed on oil and gas wells in low-permeability reservoirs. Specially engineered fluids are pumped at high pressure and rate into the reservoir interval to be treated, causing a vertical fracture to open. The wings of the fracture extend away from the wellbore in opposing directions according to the natural stresses within the formation. Proppant, such as grains of sand of a particular size, is mixed with the treatment fluid to keep the fracture open when the treatment is complete. Hydraulic fracturing creates high-conductivity communication with a large area of formation and bypasses any damage that may exist in the near-wellbore area. |
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hydrofluoric hydrochloric acid
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A mixture of hydrofluoric acid [HF] and hydrochloric acid [HCl] or organic acid used as the main fluid in a sandstone matrixtreatment. Hydrochloric acid or organic acid is mixed with HF to keep the pH low when it spends, thereby preventing detrimental precipitates. The name mud acid was given to these mixtures because they were originally developed to treat damage from siliceous drilling muds.
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holdup depth
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The point or depth at which a tool or drift of a specific size can no longer pass through the wellbore. A higher than expected holdup depth may result from scale, fill, distortion of the wellbore tubulars or formation movement in an openhole completion.
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hot tapping
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The process of drilling a hole through a pressure barrier using special equipment and procedures to ensure that the pressure and fluids are safely contained when access is made. Hot tapping is often used to enable access to the wellbore when wellhead valves jam closed.
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hydraulic packer
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A type of packer used predominantly in production applications. A hydraulic packer typically is set using hydraulic pressure applied through the tubing string rather than mechanical force applied by manipulating the tubing string.
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hydrofluoric-hydrochloric acid
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A mixture of hydrofluoric acid [HF] and hydrochloric acid [HCl] or organic acid used as the main fluid in a sandstone matrixtreatment. Hydrochloric acid or organic acid is mixed with HF to keep the pH low when it spends, thereby preventing detrimental precipitates. The name mud acid was given to these mixtures because they were originally developed to treat damage from siliceous drilling muds.
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hookwall packer
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A type of packer than utilizes an assembly of friction blocks and slips to set and anchor the packer on the casing or liner wall. Hookwall packers generally are run on tubing or drillpipe and typically require some rotation of the packer assembly to activate or set the packer slips. Subsequent application of tension or compression, depending on packer design, will set the packer elements.
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HUD
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The point or depth at which a tool or drift of a specific size can no longer pass through the wellbore. A higher than expected holdupdepth may result from scale, fill, distortion of the wellbore tubulars or formation movement in an openhole completion.
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hydraulic set
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A setting or operating method that uses hydraulic force applied through the tubing or running string to activate a downhole tool. In many cases a drop ball, which lands in a profiled seat, will be used to shift the setting or activation mechanism at predetermined pressures.
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hydrogen sulfide
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An extraordinarily poisonous gas with a molecular formula of H2S. At low concentrations, H2S has the odor of rotten eggs, but at higher, lethal concentrations, it is odorless. H2S is hazardous to workers and a few seconds of exposure at relatively low concentrations can be lethal, but exposure to lower concentrations can also be harmful. The effect of H2S depends on duration, frequency and intensity of exposure as well as the susceptibility of the individual. Hydrogen sulfide is a serious and potentially lethal hazard, so awareness, detection and monitoring of H2S is essential.
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horizontal tree
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A Christmas tree design for subsea applications, configured with the master valves and flow-control equipment on a horizontal axis to minimize the assembly height.
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hydraulic fracture monitoring
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A technique to track the propagation of a hydraulic fracture as it advances through a formation. Microseisms are detected, located, and displayed in time for scientists and engineers to approximate the location and propagation of the hydraulic fracture. Software provides modeling, survey design, microseismic detection and location, uncertainty analysis, data integration, and visualization forinterpretation. Computer imagery is used to monitor the activity in 3D space relative to the location of the fracturing treatment. The monitored activities are animated to show progressive fracture growth and the subsurface response to pumping variations. When displayed in real time, the microseismic activity allows one to make changes to the stimulation design to ensure optimal reservoircontact. Also known as microseismic monitoring, this technique delivers information about the effectiveness of the stimulation of a reservoir that can be used to enhance reservoir development in shale gas completions.
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hydraulic-set
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A setting or operating method that uses hydraulic force applied through the tubing or running string to activate a downhole tool. In many cases a drop ball, which lands in a profiled seat, will be used to shift the setting or activation mechanism at predetermined pressures.
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ICD
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Abbreviation for inflow control device, a passive component installed as part of a well completion to help optimize production by equalizing reservoir inflow along the length of the wellbore. Multiple inflow control devices can be installed along the reservoir section of the completion, with each device employing a specific setting to partially choke flow. The resulting arrangement can be used to delay water or gas breakthrough by reducing annular velocity across a selected interval such as the heel of a horizontal well. ICDs are frequently used with sand screens on openhole completions.
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inflow performance relationship
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A mathematical tool used in production engineering to assess well performance by plotting the well production rate against the flowing bottomhole pressure(BHP). The data required to create the IPR are obtained by measuring the production rates under various drawdown pressures. The reservoir fluid composition and behavior of the fluid phases under flowing conditions determine the shape of the curve.
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injection pump
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Any pump used to inject fluid into the reservoir or production system. Injection pumps vary in volume and pressure capacity, from the large injection pumps used in water-injection wells, to much smaller low-volume injection pumps used in continuous scale-inhibitor treatments.
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intermediate casing
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A casing string that is generally set in place after the surface casing and before the production casing. The intermediate casing string provides protection against caving of weak or abnormally pressured formations and enables the use of drilling fluids of different density necessary for the control of lower formations.
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ICV
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Abbreviation for inflow control valve, an active component installed as part of a well completion to partially or completely choke flow into a well. Inflow control valves can be installed along the reservoir section of the completion, with each device typically separated from the next via a packer. Each ICV can be controlled from the surface to maintain flow conformance and, as the reservoir depletes, to stop unwanted fluids from entering the wellbore. A permanent downhole cable provides electric and hydraulic conduits to relay commands from the surface to the ICV.
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inhibitor
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A chemical agent added to a fluid system to retard or prevent an undesirable reaction that occurs within the fluid or with the materials present in the surrounding environment. A range of inhibitors is commonly used in the production and servicing of oil and gas wells, such as corrosion inhibitors used in acidizing treatments to prevent damage to wellbore components and inhibitors used during production to control the effect of hydrogen sulfide [H2S].
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injection well
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A well in which fluids are injected rather than produced, the primary objective typically being to maintain reservoir pressure. Two main types of injection are common: gas and water. Separated gas from production wells or possibly imported gas may be reinjected into the upper gas section of the reservoir. Water-injection wells are common offshore, where filtered and treated seawater is injected into a lower water-bearing section of the reservoir.
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intermittent gas lift
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An artificial-lift method, used in relatively low-productivity wells, in which the gas-lift system is operated on an intermittent basis to enable the buildup of liquids in the wellbore.
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inflatable packer
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A type of packer that uses an inflatable bladder to expand the packer element against the casing or wellbore. In preparation for setting the packer, a drop ball or series of tubing movements are generally required, with the hydraulic pressure required to inflate the packer provided by carefully applying surface pump pressure. Inflatable packers are capable of relatively large expansion ratios, an important factor in through-tubing work where the tubing size or completion components can impose a significant size restriction on devices designed to set in the casing or liner below the tubing.
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injection line
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A small-diameter conduit that is run alongside production tubulars to enable injection of inhibitors or similar treatments during production. Conditions such as high hydrogen sulfide [H2S] concentrations or severe scale deposition can be counteracted by injection of treatment chemicals and inhibitors during production.
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instrument hanger
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A downhole tool on which downhole gauges or instruments that are to be temporarily left in the wellbore are attached. The instrument hanger is run into the wellbore on slickline and set in a completion nipple at the required depth.
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internal pulling tool
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A downhole tool used to pull or retrieve temporary plugs or similar equipment. The internal pulling tool engages on the internal surfaces of the item to be retrieved.
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inflow control device
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A passive component installed as part of a well completion to help optimize production by equalizing reservoir inflow along the length of the wellbore. Multiple inflow control devices can be installed along the reservoir section of the completion, with each device employing a specific setting to partially choke flow. The resulting arrangement can be used to delay water or gas breakthrough by reducing annular velocity across a selected interval such as the heel of a horizontal well. Inflow control devices are frequently used with sand screens on openhole completions.
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injection mandrel
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A downhole completion component that enables injection of treatment chemicals or inhibitors into the production conduit. The injection mandrel is equipped with a port- and check-valve system to direct fluid pumped down the annulus or injection line into the production conduit.
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intelligent well
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A well equipped with monitoring equipment and completion components that can be adjusted to optimize production, either automatically or with some operator intervention.
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iron stabilizer
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Also known as a chelating agent, a chemical added to an acid to stabilize iron. In the oil field, acid is used in stimulation treatments and to treat or remove scale or weighting material in reservoir drilling fluids.The injected acid dissolves iron from rust, millscale, iron scales or iron-containing minerals in the formation. Iron can exist as ferric iron [Fe+3] or ferrous iron [Fe+2]. If the iron is not controlled, it will precipitate insoluble products such as ferric hydroxide and, in sour environments, ferrous sulfide [FeS], which will damage the formation. Chelating agents associate with iron [Fe+3 or Fe+2] to form soluble complexes. Citric acid, acetic acid and EDTA are effective chelating agents and can be used at temperatures up to 400oF [204oC].
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inflow control valve
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An active component installed as part of a well completion to partially or completely choke flow into a well. Inflow control valves can be installed along the reservoir section of the completion, with each device typically separated from the next via a packer. Each valve can be controlled from the surface to maintain flow conformance and, as the reservoir depletes, to stop unwanted fluids from entering the wellbore. A permanent downhole cable provides electric and hydraulic conduits to relay commands from the surface to each valve.
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injection pressure
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The pressure at which a treatment or test fluid can be injected into the formation matrix without causing a breakdown, or fracture, of the rock matrix. The injection pressure is commonly described as the surface pump pressure required to achieve injection. However, since the hydrostatic pressure of the fluid column also contributes to the downhole pressure value, the downhole pressure should also be considered.
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J slot
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A type of mechanism commonly used in the setting and unsetting of downhole tools and equipment such as packers. Most conventional downhole tools operate by upward or downward movement, rotation, or a combination of both. The J-slot profile creates the track for an actuating cam or pin that combines rotation and up or down movement to provide a simple yet reliable means of tool activation.
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jar
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A downhole tool that is used to impart a heavy blow or impact load to a downhole tool assembly. Commonly used in fishingoperations to free stuck objects, jars are available in a range of sizes and capacities to deliver upward or downward impact loads. Some slickline tool assemblies use jars to operate tools that contain shear pins or spring profiles in their operating method.
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jet pump
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A type of pump that operates on the principle of a high-pressure fluid jet and the venturi effect it creates. Jet pumps are relatively inefficient but can tolerate a wide range of operating conditions, including easily handling sand-laden or abrasive fluids.
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landing collar
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A component installed near the bottom of the casing string on which the cementplugs land during the primary cementing operation. The internal components of the landing collar are generally fabricated from plastics, cement and other drillable materials.
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lifting sub
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A short drillstring component that is temporarily connected to the top of a tool assembly that is to be lifted vertically, such as when running or retrieving a tool string. The external profile on the upper section of the lifting sub is similar to that of the completion tubing, enabling the rig elevators to lift the assembled tool string safely.
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live oil
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Oil containing dissolved gas in solution that may be released from solution at surface conditions. Live oil must be handled and pumped under closely controlled conditions to avoid the risk of explosion or fire.
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lock mandrel
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Another term for lock, a downhole device, run and retrieved on slickline, that is placed and anchored within the tubing string to provide a setting point for flow-control equipment such as valves, chokes and plugs. The three main types of lock use different means of locating and securing: a slip lock locates and anchors anywhere within the correct size of tubing; the collar lock locates in the space within tubing collars; and the nipple lock locates within completion nipple profiles.
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landing nipple
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A completion component fabricated as a short section of heavy wall tubular with a machined internal surface that provides a sealarea and a locking profile. Landing nipples are included in most completions at predetermined intervals to enable the installation of flow-control devices, such as plugs and chokes. Three basic types of landing nipple are commonly used: no-go nipples, selective-landing nipples and ported or safety-valve nipples.
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liner
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Any string of casing in which the top does not extend to the surface but instead is suspended from inside the previous casing string. Many conventional well designs include a production liner set across the reservoir interval. This reduces the cost of completing the well and allows some flexibility in the design of the completion in the upper wellbore, such as when the fluid characteristics make it beneficial to increase the diameter of the conduit and components
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lock
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A downhole device, run and retrieved on slickline, that is placed and anchored within the tubing string to provide a setting point for flow-control equipment such as valves, chokes and plugs. The three main types of lock use different means of locating and securing: a slip lock locates and anchors anywhere within the correct size of tubing; the collar lock locates in the space within tubing collars; and the nipple lock locates within completion nipple profiles.
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lubricator valve
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The topmost valve on a Christmas tree that provides vertical access to the wellbore.
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life of the well
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The period of time during which economically sustainable production levels may be expected from a well. The anticipated well life and the characteristics of the reservoir fluid are the two main factors in specifying the completion system components.
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liner hanger
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A device used to attach or hang liners from the internal wall of a previous casing string. Liner hangers are available in a range of sizes and specifications to suit a variety of completion conditions.
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make up
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To connect tools or tubulars by assembling the threaded connections incorporated at either end of every tool and tubular. The threaded tool joints must be correctly identified and then torqued to the correct value to ensure a secure tool string without damaging the tool or tubular body.
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master valve
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A valve located on the Christmas tree that controls all flow from the wellbore. A correctly functioning master valve is so important that two master valves are fitted to most Christmas trees. The upper master valve is used on a routine basis, with the lower master valve providing backup or contingency function in the event that the normal service valve is leaking and needs replacement.
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microannulus
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A small gap that can form between the casing or liner and the surrounding cement sheath, most commonly formed by variations in temperature or pressure during or after the cementing process. Such variations cause small movement of the steel casing, breaking the cement bond and creating a microannulus that is typically partial. However, in severe cases the microannulus may encircle the entire casing circumference. A microannulus can jeopardize the hydraulic efficiency of a primary cementing operation, allowing communication between zones if it is severe and connected.
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mud acid
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A mixture of hydrofluoric acid [HF] and hydrochloric acid [HCl] or organic acid used as the main fluid in a sandstone matrixtreatment. Hydrochloric acid or organic acid is mixed with HF to keep the pH low when it spends, thereby preventing detrimental precipitates. The name mud acid was given to these mixtures because they were originally developed to treat damage from siliceous drilling muds. Mud acid is also called hydrofluoric-hydrochloric acid.
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mandrel
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A bar, shaft or spindle around which other components are arranged or assembled. The term has been extended in oil and gas wellterminology to include specialized tubular components that are key parts of an assembly or system, such as gas-lift mandrel orpacker mandrel.
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matrix acidizing
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"The treatment of a reservoir formation with a stimulation fluid containing a reactive acid. In sandstone formations, the acid reacts with the soluble substances in the formation matrix to enlarge the pore spaces. In carbonate formations, the acid dissolves the entire formation matrix. In each case, the matrix acidizing treatment improves the formation permeability to enable enhanced production of reservoir fluids. Matrix acidizing operations are ideally performed at high rate, but at treatment pressures below the fracture pressure of the formation. This enables the acid to penetrate the formation and extend the depth of treatment while avoiding damage to the reservoir formation.
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microseismic monitoring
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A technique to track the propagation of a hydraulic fracture as it advances through a formation. Microseisms are detected, located, and displayed in time for scientists and engineers to approximate the location and propagation of the hydraulic fracture. Software provides modeling, survey design, microseismic detection and location, uncertaintyanalysis, data integration, and visualization for interpretation. Computer imagery is used to monitor the activity in 3D space relative to the location of the fracturing treatment. The monitored activities are animated to show progressive fracture growth and the subsurface response to pumping variations. When displayed in real time, the microseismic activity allows one to make changes to the stimulation design to ensure optimal reservoir contact. Also known ashydraulic fracture monitoring, this technique delivers information about the effectiveness of the stimulation of a reservoir that can be used to enhance reservoir development in shale gas completions.
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multiphase fluid
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A fluid, generally a liquid, comprising more than one phase, such as water- or oil-based liquids, solid material or gas. Multiphase fluids and their behavior are of concern in two main areas, the flow of multiphase fluids and the separation of the various phases at surface.
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manifold
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An arrangement of piping or valves designed to control, distribute and often monitor fluid flow. Manifolds are often configured for specific functions, such as a choke manifold used in well-control operations and a squeeze manifoldused in squeeze-cementing work. In each case, the functional requirements of the operation have been addressed in the configuration of the manifold and the degree of control and instrumentation required.
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matrix stimulation
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A treatment designed to treat the near-wellbore reservoir formation rather than other areas of the productionconduit, such as the casing across the production interval, production tubulars or the perforations. Matrix stimulation treatments include acid, solvent and chemical treatments to improve the permeability of the near-wellbore formation, enhancing the productivity of a well. Matrix stimulation is a process of injecting a fluid into the formation, either an acid or solvent at pressures below the fracturing pressure, to improve the production or injection flow capacity of a well. The goal of a matrix treatment is different in sandstones than in carbonates. In sandstones, matrix treatments restore or improve the natural formation permeability around the wellbore by removing formation damage, by dissolving material plugging the pores or by enlarging the pore spaces. In carbonates, matrix stimulation creates new, highly conductive channels (wormholes) that bypass damage. Because of these differences, the selection criteria for the treating fluid are also distinct. For sandstone treatments, knowledge of the extent, type of damage, location, origin, reservoir mineralogy (petrographic study) and compatibility of the treating fluid with the formation are especially important. In carbonate treatments, reservoir temperature, pumping rate and fluid type become more significant because these parameters directly affect the reactivity of the treating fluid with the reservoir rock. A sandstone matrix stimulation treatment is generally composed of a hydrochloric acid [HCl] preflush, a main treating fluid (HCl-HF mixtures) and an overflush (weak acid solution or brine). The treating fluid is maintained under pressure inside the reservoir for a period of time, after which the well is swabbed and returned to production. In carbonate reservoirs, HCl is the most common fluid used. Organic acids such as formic and acetic acid are used in either sandstone or carbonate acidizing, mainly in retarded-acid systems or in high-temperature applications. Matrix stimulation is also called matrix treatment or matrix acidizing.
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minimum restriction
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The smallest diameter present in a wellbore through which a tool string must pass to enable access to the operating depth or zone of interest. The minimum restriction determines the maximum tool string outside diameter and may influence the configuration of the assembled tools or equipment. The minimum restriction should be considered in both running and retrieving modes if any increase in tool string outside diameter is likely, such as when perforating or when using inflatable packers.
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multiphase fluid flow
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The commingled flow of different phase fluids, such as water, oil and gas. Multiphase fluid flow is a complex factor, important in understanding and optimizing production hydraulics in both oil and gas wells. Four multiphase fluid flow regimes are recognized when describing flow in oil and gas wells, bubble flow, slug flow, transition flow and mist flow.
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marginal well
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A well that, for reasons of depletion or natural low productivity, is nearing the limits of viable production and profitability.
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mechanical skin
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The reduction in permeability in the near-wellbore area resulting from mechanical factors such as the displacementof debris that plugs the perforations or formation matrix. Such damage in the near-wellbore area can have a significant effect on the productivity of a well. |
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mist flow
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A multiphase fluid-flow regime characterized by the gas phase being distributed as bubbles through the liquid phase. In a producing wellbore where the bubbles are uniformly distributed, there is little relative motion between the phases. Where the bubbles congregate and combine to form a less uniform distribution of the gas phase, some slippage will occur between the phases with the gas tending to cut through the liquid phase. |
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multiple completion
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A single wellbore having tubulars and equipment that enable production from two or more reservoir zones. In most cases, at least two tubing strings will be used to provide the necessary level of control and safety for production fluids. However, in some simple dual completions, the second or upper zone is produced up the tubing-casingannulus. The wellhead and surface flow-control facilities required for multiple completions can be complex and costly; hence, multiple completions are relatively uncommon. |
