- Industry: Oil & gas
- Number of terms: 8814
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The leakage of the liquid phase of drilling fluid, slurry or treatment fluid containing solid particles into the formation matrix. The resulting buildup of solid material or filter cake may be undesirable, as may the penetration of filtrate through the formation. Fluid-loss additives are used to control the process and avoid potential reservoir damage.
Industry:Oil & gas
The last cement system pumped during primary cementing. The tail cement covers the lower sections of the well, especially planned completion intervals, and is typically more dense than the lead slurry that precedes it.
Industry:Oil & gas
The large-diameter metal pipe that connects the bell nipple under the rotary table to the possum belly at the mud tanks. The flowline is simply an inclined, gravity-flow conduit to direct mud coming out the top of the wellbore to the mud surface-treating equipment. When drilling certain highly reactive clays, called "gumbo," the flowline may become plugged and require considerable effort by the rig crew to keep it open and flowing. In addition, the flowline is usually fitted with a crude paddle-type flow-measuring device commonly called a "flow show" that may give the driller the first indication that the well is flowing.
Industry:Oil & gas
The ion of potassium, K<sup>+</sup>. There are tests used to monitor high (>5000 mg/L) or low (<5000 mg/L) potassium ion (K<sup>+</sup>) concentration in water-base muds. The test for high<br>concentration, as specified by the API, is based on the insolubility of potassium perchlorate. A volume of mud filtrate is mixed with an excess of NaClO<sub>4</sub> in a centrifuge tube. White KClO<sub>4</sub> is precipitated by the reaction. After the<br>tube has spun in a centrifuge to settle the white sediment in the tube, the amount of precipitate is read and compared to a calibration chart that relates sediment to concentration of K<sup>+</sup> in the filtrate sample. The test to monitor low<br>potassium ion (K<sup>+</sup>) concentration in water-base muds, as prescribed by API, is a titration procedure using quaternary ammonium salt solution (QAS) as reagent. Potassium ion is first precipitated as the tetraphenylborate (TPB) salt by adding an<br>excess of sodium tetraphenylborate. After filtering out the solid, the amount of TPB not reacted with K<sup>+</sup> ion is titrated with a standard QAS solution. The endpoint is purple-to-light blue color change. </p><p>The test for high potassium ion<br>concentration was first applied to drilling fluids by Ron Steiger at Exxon Production Research Co. And has proven to be a reliable way to measure K<sup>+</sup> ion concentration in a mud at the wellsite, which allows the mud engineer to maintain the<br>proper level when drilling through hydratable shales. Before a direct test for K<sup>+</sup> ion was available, KCl in a mud was monitored by chloride analysis. Although simple to perform, this analysis was misleading and counterproductive because after<br>drilling shale with a new KCl mud for awhile, the beneficial K<sup>+</sup> ion was consumed by the clays but the Cl<sup>-</sup> ion remained in the mud. Eventually, the wellbore shales hydrated, fell into the hole and created severe mud and drilling<br>problems. As a result of improper analytical methods, early potassium muds earned an undeservedly negative reputation. </p><p>For optimal shale stability, K<sup>+</sup> ion must be continually maintained by adding KCl (or some other K salt) as fast as it<br>is consumed. The advent of a direct field-worthy method for K<sup>+</sup> analysis, the result of Dr. Steiger's efforts, was a breakthrough in the use of water mud for drilling troublesome shale. <br>Reference:<br>Steiger RP: "Fundamentals and Use<br>of Potassium/Polymer Drilling Fluids to Minimize Drilling and Completion Problems Associated with Hydratable Clays," Journal of Petroleum Technology 34, no. 8 (August 1982): 1661-1670.
Industry:Oil & gas
The intentional pumping of wellbore fluids down the annulus and back up through the drillpipe. This is the opposite of the normal direction of fluid circulation in a wellbore. Since the inside volume of the drillpipe is considerably less than the volume of the annulus outside of the drillpipe, reverse circulation can bring bottomhole fluids to the surface faster than normal circulation for a given flow rate. Two potential hazards of reverse circulation include lifting cuttings and other junk into the drillstring and the rapid flow of reservoir fluids to the surface in a kick situation.
Industry:Oil & gas
The intentional directional control of a well based on the results of downhole geological logging measurements rather than three-dimensional targets in space, usually to keep a directional wellbore within a pay zone. In mature areas, geosteering may be used to keep a wellbore in a particular section of a reservoir to minimize gas or water breakthrough and maximize economic production from the well.
Industry:Oil & gas
The intentional deviation of a wellbore from the path it would naturally take. This is accomplished through the use of whipstocks, bottomhole assembly (BHA) configurations, instruments to measure the path of the wellbore in three-dimensional space, data links to communicate measurements taken downhole to the surface, mud motors and special BHA components and drill bits, including rotary steerable systems, and drill bits. The directional driller also exploits drilling parameters such as weight on bit and rotary speed to deflect the bit away from the axis of the existing wellbore. In some cases, such as drilling steeply dipping formations or unpredictable deviation in conventional drilling operations, directional-drilling techniques may be employed to ensure that the hole is drilled vertically. While many techniques can accomplish this, the general concept is simple: point the bit in the direction that one wants to drill. The most common way is through the use of a bend near the bit in a downhole steerable mud motor. The bend points the bit in a direction different from the axis of the wellbore when the entire drillstring is not rotating. By pumping mud through the mud motor, the bit turns while the drillstring does not rotate, allowing the bit to drill in the direction it points. When a particular wellbore direction is achieved, that direction may be maintained by rotating the entire drillstring (including the bent section) so that the bit does not drill in a single direction off the wellbore axis, but instead sweeps around and its net direction coincides with the existing wellbore. Rotary steerable tools allow steering while rotating, usually with higher rates of penetration and ultimately smoother boreholes. <br><br>Directional drilling is common in shale reservoirs because it allows drillers to place the borehole in contact with the most productive reservoir rock.
Industry:Oil & gas
The instrument used to measure viscosity and gel strength of drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument, also known as a V-G meter. Two speeds of rotation, 300 and 600 rpm, are available in all instruments, but some are 6- or variable-speed. It is called "direct-indicating" because at a given speed, the dial reading is a true centipoise viscosity. For example, at 300 rpm, the dial reading (511 sec<sup>-1</sup>) is a true viscosity. Bingham plastic rheological parameters are easily calculated from direct-indicating viscometer readings: PV (in units of cp) = 600 dial - 300 dial and YP (in units of lb/100 ft<sup>2</sup>) = 300 dial - PV. Gel strength is also directly read as dial readings in oilfield units of lb/100 ft<sup>2</sup>.
Industry:Oil & gas
The instantaneous volume (spurt) of liquid that passes through a filter medium prior to deposition of a competent and controlling filter cake. In static filtration, the spurt volume can be a disproportionately large percentage of the total 30-minute filtrate in an API-type test. This indicates that filter cake is slow in being deposited compared to a similar mud with lower spurt loss. To avoid uncertainties of spurt-loss volume, relative filtrate volume is used in static tests.
Industry:Oil & gas
The industry-standard document that provides guidelines for testing methods for cements and cement formulations for use in well cementing. These recommended procedures are commonly modified to address the specific conditions of a particular well.
Industry:Oil & gas
