What is Directional Solidification?
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What is Directional Solidification?
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Larry Ray Palmer
Edited By: A. Joseph
Last Modified Date: 07 August 2017
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"Directional solidification" is a
It refers to the process of controlled feeding of the molten metal into a temperature-controlled mold to produce a part that is free of hollow spots, called shrink defects.
Directional solidification is also used to refine the metal during the casting process because the impurities found in the molten metal will continue to rise to the surface of the pool, following the path of least resistance as they are pushed up by the solid materials below.
In the directional solidification process, the molten metal at the far end of the mold begins to cool and solidify before the rest of the mold does.
As the metal on the bottom of the mold cools, this line of solidification moves steadily upward toward the molten metal feed.
By controlling the rate of flow for the molten metal feed and introducing thermal variations in the mold, shrink defects can be eliminated, because the liquid metal will naturally run into these dips and vacant areas.
The process of directional solidification is not to be confused with progressive solidification, also called parallel solidification. Although these processes share some similar traits, in progressive solidification, the cooling and solidifying process begins at the walls of the casting and works its way inward.
With directional solidification, the process of solidification begins at the bottom of the casting and works its way to the top.
Parallel solidification in a casting is the underlying cause of defects.
As the molten metal cools too quickly in some areas or remains heated for too long in other areas, it creates defects as a result of solidification,
and contraction.
For example, if molten metal is poured into an L-shaped mold, the metal at the corner of the mold might cool too quickly, causing a bottleneck and trapping an air pocket in the lower leg of the mold.
This air pocket creates a hollow spot in the finished metal part, thus weakening the overall structure.
To control parallel solidification and encourage directional solidification in the casting process, several techniques are employed.
Thermal variations are introduced into the mold by using risers or chills to control hot or cold spots that might create problems with the cast part.
Insulated sleeves also are used to ensure a steady, controlled temperature for the mold.
Finally, the rate of flow and temperature of the molten metal feed are carefully controlled to ensure directional solidification.
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@nony - A directional solidification system makes sense. The question is, in what environments do they use this process? If you are talking about going down to the local home improvement store, I can understand how you can find the stray metal piece that isn’t developed quite right.
I doubt they use directional solidification of steel castings in this context, because it really doesn’t matter for do it yourself projects.
However, if you’re building pieces that are going to be used in aircraft wings, for the purposes of providing support, I’d bet they are using directional solidification for those parts. I’ve heard of wings falling off (or flaps anyway) because of a defect in a ball bearing or some other metal piece.
One of the most frustrating things to deal with from a craftsman’s perspective is using a piece of metal that has been deformed or hollowed out somehow through improper casting.
It doesn’t matter whether you are talking about L shaped pieces like the one mentioned in the article or ball bearings. Most of the time the pieces are useless and it becomes nearly impossible to hammer them back into proper shape, most especially with stainless steel parts.
Be sure to inspect any metal part you buy from a hardware store. I usually find defects if I am buying whole lots. There is usually a bad apple in the bunch.
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Conjecture CorporationFrom Wikipedia, the free encyclopedia
A horizontal directional drill in operation
Screenshot of a structure map generated by
software for an 8500ft (2600 meter) deep gas &
in the Erath field, , . The left-to-right gap, near the top of the
indicates a . This fault line is between the blue/green contour lines and the purple/red/yellow contour lines. The thin red circular contour line in the middle of the map indicates the top of the oil reservoir. Because gas floats above oil, the thin red contour line marks the gas/oil contact zone. Directional drilling would be used to target the gas and .
Directional drilling (or slant drilling) is the practice of drilling non-vertical . It can be broken down into four main groups:
directional drilling, utility installation directional drilling (horizontal directional drilling), , and surface in seam (SIS), which horizontally intersects a vertical well target to extract .
Many prerequisites enabled this suite of technologies to become productive. Probably, the first requirement was the realization that , or , are not necessarily vertical.[] This realization was quite slow, and did not really grasp the attention of the oil industry until the late 1920s when there were several lawsuits alleging that wells drilled from a rig on one property had crossed the boundary and were penetrating a reservoir on an adjacent property.[] Initially, proxy evidence such as production changes in other wells was accepted, but such cases fueled the development of small diameter tools capable of surveying wells during drilling. Horizontal directional
are developing towards large-scale, micro-miniaturization, mechanical automation, hard stratum working, exceeding length and depth oriented monitored drilling.
Measuring the inclination of a
(its deviation from the vertical) is comparatively simple, requiring only a pendulum. Measuring the
(direction with respect to the geographic grid in which the wellbore was running from the vertical), however, was more difficult. In certain circumstances, magnetic fields could be used, but would be influenced by metalwork used inside wellbores, as well as the metalwork used in drilling equipment. The next advance was in the modification of small gyroscopic compasses by the , which was making similar compasses for aeronautical navigation. Sperry did this under contract to
(which was involved in a lawsuit as described above), and a spin-off company "" was formed, which brand continues to this day,[][] absorbed into . Three components are measured at any given point in a wellbore in order to determine its position: the depth of the point along the course of the borehole (measured depth), the inclination at the point, and the magnetic azimuth at the point. These three components combined are referred to as a "survey". A series of consecutive surveys are needed to track the progress and location of a wellbore.
Prior experience with rotary drilling had established several principles for the configuration of drilling equipment down hole ("Bottom Hole Assembly" or "BHA") that would be prone to "drilling crooked hole" (i.e., initial accidental deviations from the vertical would be increased). Counter-experience had also given early directional drillers ("DD's") principles of BHA design and drilling practice that would help bring a crooked hole nearer the vertical.[]
In 1934, H. John Eastman & Roman W. Hines of , became pioneers in directional drilling when they and George Failing of , saved the , . Failing had recently patented a portable drilling truck. He had started his company in 1931 when he mated a drilling rig to a truck and a power take-off assembly. The innovation allowed rapid drilling of a series of slanted wells. This capacity to quickly drill multiple relief wells and relieve the enormous gas pressure was critical to extinguishing the Conroe fire. In a May, 1934,
article, it was stated that "Only a handful of men in the world have the strange power to make a bit, rotating a mile below ground at the end of a steel drill pipe, snake its way in a curve or around a dog-leg angle, to reach a desired objective." Eastman Whipstock, Inc., would become the world's largest directional company in 1973.[]
Combined, these survey tools and BHA designs made directional drilling possible, but it was perceived as arcane. The next major advance was in the 1970s, when
drilling motors (aka , driven by the hydraulic power of drilling mud circulated down the drill string) became common. These allowed the drill bit to continue rotating at the cutting face at the bottom of the hole, while most of the drill pipe was held stationary. A piece of bent pipe (a "bent sub") between the stationary drill pipe and the top of the motor allowed the direction of the wellbore to be changed without needing to pull all the drill pipe out and place another whipstock. Coupled with the development of
tools (using ,
telemetry, which allows tools down hole to send directional data back to the surface without disturbing drilling operations), directional drilling became easier.
Certain profiles cannot be drilled while the drill pipe is rotating. Drilling directionally with a downhole motor requires occasionally stopping rotation of the drill pipe and "sliding" the pipe through the channel as the motor cuts a curved path. "Sliding" can be difficult in some formations, and it is almost always slower and therefore more expensive than drilling while the pipe is rotating, so the ability to steer the bit while the drill pipe is rotating is desirable. Several companies have developed tools which allow directional control while rotating. These tools are referred to as
(RSS). RSS technology has made access and directional control possible in previously inaccessible or uncontrollable formations.
Wells are drilled directionally for several purposes:
Increasing the exposed section length through the reservoir by drilling through the reservoir at an angle
Drilling into the reservoir where vertical access is difficult or not possible. For instance an oilfield under a town, under a lake, or underneath a difficult-to-drill formation
Allowing more
to be grouped together on one surface location can allow fewer rig moves, less surface area disturbance, and make it easier and cheaper to complete and produce the wells. For instance, on an
or jacket offshore, 40 or more wells can be grouped together. The wells will fan out from the platform into the reservoir(s) below. This concept is being applied to land wells, allowing multiple subsurface locations to be reached from one pad, reducing costs.
Drilling along the underside of a reservoir-constraining fault allows multiple productive sands to be completed at the highest stratigraphic points.
Drilling a "" to relieve the pressure of a well producing without restraint (a ""). In this scenario, another well could be drilled starting at a safe distance away from the blowout, but intersecting the troubled wellbore. Then, heavy fluid (kill fluid) is pumped into the relief wellbore to suppress the high pressure in the original wellbore causing the blowout.
Most directional drillers are given a blue well path to follow that is predetermined by engineers and geologists before the drilling commences. When the directional driller starts the drilling process, periodic surveys are taken with a downhole instrument to provide survey data (inclination and azimuth) of the well bore. These pictures are typically taken at intervals between 10–150 meters (30–500 feet), with 30 meters (90 feet) common during active changes of angle or direction, and distances of 60–100 meters (200–300 feet) being typical while "drilling ahead" (not making active changes to angle and direction). During critical angle and direction changes, especially while using a downhole motor, an MWD () tool will be added to the
to provide continuously updated measurements that may be used for (near) real-time adjustments.
These data indicate if the well is following the planned path and whether the orientation of the drilling assembly is causing the well to deviate as planned. Corrections are regularly made by techniques as simple as adjusting rotation speed or the drill string weight (weight on bottom) and stiffness, as well as more complicated and time-consuming methods, such as introducing a downhole motor. Such pictures, or surveys, are plotted and maintained as an engineering and legal record describing the path of the well bore. The survey pictures taken while drilling are typically confirmed by a later survey in full of the borehole, typically using a "multi-shot camera" device.
The multi-shot camera advances the film at time intervals so that by dropping the camera instrument in a sealed tubular housing inside the drilling string (down to just above the drilling bit) and then withdrawing the drill string at time intervals, the well may be fully surveyed at regular depth intervals (approximately every 30 meters (90 feet) being common, the typical length of 2 or 3 joints of drill pipe, known as a stand, since most drilling rigs "stand back" the pipe withdrawn from the hole at such increments, known as "stands").
Drilling to targets far laterally from the surface location requires careful planning and design. The current record holders manage wells over 10 km (6.2 mi) away from the surface location at a true vertical depth (TVD) of only 1,600–2,600 m (5,200–8,500 ft).
This form of drilling can also reduce the environmental cost and scarring of the landscape. Previously, long lengths of landscape where required to be removed from the surface which is no longer required with this form of drilling.
Until the arrival of modern downhole motors and better tools to measure inclination and azimuth of the hole, directional drilling and horizontal drilling was much slower than vertical drilling due to the need to stop regularly and take time-consuming surveys, and due to slower progress in drilling itself (lower rate of penetration). These disadvantages have shrunk over time as downhole motors became more efficient and semi-continuous surveying became possible.
What remains is a difference in operating costs: for wells with an inclination of less than 40 degrees, tools to carry out adjustments or repair work can be lowered by gravity on cable into the hole. For higher inclinations, more expensive equipment has to be mobilized to push tools down the hole.
Another disadvantage of wells with a high inclination was that prevention of sand influx into the well was less reliable and needed higher effort. Again, this disadvantage has diminished such that, provided sand control is adequately planned, it is possible to carry it out reliably.
of stealing Iraq's oil through slant drilling. The
redrew the border after the , which ended the seven-month
of Kuwait. As part of the reconstruction, 11 new oil wells were placed among the existing 600. Some farms and an old naval base that used to be in the Iraqi side became part of Kuwait.
In the mid-twentieth century, a slant-drilling scandal occurred in the huge .
Between 1985 and 1993, NCEL (now the ) of Pt Hueneme, California developed controllable horizontal drilling technologies. These technologies are capable of reaching 10 000–15 000 ft ( m) and may reach 25 000 ft (;m) when used under favorable conditions.
. . 6 June 2013.[]
. American Oil & Gas Historical Society.
. The . 21 May 2008. Archived from
on 14 February .
. Ministry of Foreign Affairs of Japan 2014.
4 September .
Julia Cauble Smith (). . Handbook of Texas Online. Texas State Historical Association.
Wikimedia Commons has media related to .
Popular Science, May 1934, early article on the drilling technology
American Oil & Gas Historical Society
A video depicting horizontal shale drilling can be seen .
Popular Science, June 1942, pp. 94–95.
21 July 2012
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