- Industry: Oil & gas
- Number of terms: 8814
- Number of blossaries: 0
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The temperature of the undisturbed formation at the final depth in a well. The formation cools during drilling and most of the cooling dissipates after about 24 hours of static conditions, although it is theoretically impossible for the temperature to return to undisturbed conditions. This temperature is measured under static conditions after sufficient time has elapsed to negate any effects from circulating fluids. Tables, charts and computer routines are used to predict BHST as functions of depth, geographic area and various time functions. The BHST is generally higher than the bottomhole circulating temperature, and can be an important factor when using temperature-sensitive tools or treatments.
Industry:Oil & gas
The temperature of the circulating fluid (air, mud, cement or water) at the bottom of the wellbore after several hours of circulation. This temperature is lower than the bottomhole static temperature. Therefore, in extremely harsh environments, a component or fluid that would not ordinarily be suitable under bottomhole static conditions may be used with great care in circulating conditions. Similarly, a high-temperature well may be cooled down in an attempt to allow logging tools to function. The BHCT is also important in the design of operations to cement casing because the setting time for cement is temperature-dependent. The BHCT and bottomhole static temperature (BHST) are important parameters when placing large volumes of temperature-sensitive treatment fluids.
Industry:Oil & gas
The temperature at which a solution of a surfactant or glycol starts to form micelles (molecular agglomerates), thus becoming cloudy. This behavior is characteristic of nonionic surfactants, which are often soluble at low temperatures but "cloud out" at some point as the temperature is raised. Glycols demonstrating this behavior are known as "cloud-point glycols" and are used as shale inhibitors. The cloud point is affected by salinity, being generally lower in more saline fluids.
Industry:Oil & gas
The technology focused on maintaining pressure on open formations (that is, exposed to the wellbore) to prevent or direct the flow of formation fluids into the wellbore. This technology encompasses the estimation of formation fluid pressures, the strength of the subsurface formations and the use of casing and mud density to offset those pressures in a predictable fashion. Also included are operational procedures to safely stop a well from flowing should an influx of formation fluid occur. To conduct well-control procedures, large valves are installed at the top of the well to enable wellsite personnel to close the well if necessary.
Industry:Oil & gas
The surface of contact between a water layer and an oil layer.
Industry:Oil & gas
The system of spools, valves and assorted adapters that provide pressure control of a production well.
Industry:Oil & gas
The surface free energy that exists between two immiscible liquid phases, such as oil and water. (Surface tension is the term for the energy barrier between a liquid and air. ) The energy barrier produced by interfacial tension prevents one liquid from becoming emulsified into the other. To form an emulsion, surface free energy must be lowered by adding a third component (an emulsifier) that seeks the interface. Spontaneous emulsification does not typically occur just by adding an emulsifier. Mechanical and heat energy are usually needed to break bulk liquid into droplets. Very low interfacial tension requires less external energy to form a stable emulsion.
Industry:Oil & gas
The surface force per unit area exerted at the top of a wellbore when it is closed at either the Christmas tree or the BOP stack. The pressure may be from the formation or an external and intentional source. The SIP may be zero, indicating that any open formations are effectively balanced by the hydrostatic column of fluid in the well. If the pressure is zero, the well is considered to be dead, and can normally be opened safely to the atmosphere.
Industry:Oil & gas
The supervisor of the rig crew. The driller is responsible for the efficient operation of the rigsite as well as the safety of the crew and typically has many years of rigsite experience. Most drillers have worked their way up from other rigsite jobs. While the driller must know how to perform each of the jobs on the rig, his or her role is to supervise the work and control the major rig systems. The driller operates the pumps, drawworks, and rotary table via the drillers console-a control room of gauges, control levers, rheostats, and other pneumatic, hydraulic and electronic instrumentation. The driller also operates the drawworks brake using a long-handled lever. Hence, the driller is sometimes referred to as the person who is "on the brake. "
Industry:Oil & gas
The stress that must be applied to a material to make it begin to flow (or to yield). Yield stress is a parameter in the Herschel-Bulkley rheological model.
Industry:Oil & gas
