The tools and techniques used in the horizontal directional drilling (HDD) pilot hole operations are not unlike those involved in drilling a directional oil well. Directional Drilling Training Manual December ATC Version Holder: Confidential This information is confidential and is trade secret property of. PDF | Horizontal directional drilling (HDD) was pioneered in the United States for an innovative road boring contractor who successfully completed a m river.
|Language:||English, Spanish, Dutch|
|Genre:||Politics & Laws|
|Distribution:||Free* [*Registration needed]|
which take part in the development of directional drilling in Russia. The status of. Russian directional drilling was studied and the development directions were. The practice of directional drilling traces its roots to the s, when basic wellbore surveying methods were introduced. These methods alerted drillers to the. Directional drilling is the science of deviating a well bore along a planned course to a subsurface target whose location is a given lateral distance and direction.
Given the North and South Poles, which are approximately the ends of the axis about which the Earth rotates, and the Equator, an imaginary line halfway between the two poles, the parallels of latitude are formed by circles surrounding the Earth and in planes parallel with that of the Equator. If circles are drawn equally spaced along the surface of the sphere, with 90 spaces from the Equator to each pole, each space is called a degree of latitude.
The circles are numbered from 0 at the Equator to 90 North and South at the respective poles. Each degree is subdivided into 60 minutes and each minute into 60 seconds of arc. Meridians of longitude are formed with a series of imaginary lines, all intersecting at both the North and South Poles, and crossing each parallel of latitude at right angles, but striking the Equator at various points.
If the Equator is equally divided into parts, and a meridian passes through each mark, degrees of longitude result. These degrees are also divided into minutes and seconds. While the length of a degree of latitude is always the same on a sphere, the lengths of degrees of longitude vary with the latitude see Figure At the Equator on the sphere, they are the same length as the degree of latitude, but elsewhere they are shorter.
It, thus, becomes necessary to choose arbitrarily one meridian as the starting point, or prime meridian. There have been many prime meridians in the course of history, swayed by national pride and international influence. Eighteenth-century maps of the American colonies often show longitude from London or Philadelphia.
During the 19th century, boundaries of new States were described with longitudes west of a meridian through Washington, D.
In , the International Meridian Conference, meeting in Washington, agreed to adopt the "meridian passing through the center of the transit instrument at the Observatory of Greenwich as the initial meridian for longitude," resolving that "from this meridian longitude shall be counted in two directions up to degrees, east longitude being plus and west longitude minus" Brown, , p. When the map is completed with labels, the meridians are marked with respect to the Greenwich Prime Meridian.
The formulas in this bulletin are arranged so that Greenwich longitude may be used directly. The concept of latitudes and longitudes was originated early in recorded history by Greek and Egyptian scientists, especially the Greek astronomer Hipparchus 2nd century, B.
Claudius Ptolemy further formalized the concept Brown, , p. Because calculations relating latitude and longitude to positions of points on a given map can become quite involved, rectangular grids have been developed for the use of surveyors. In this way, each point may be designated merely by its distance from two perpendicular axes on the flat map.
Specifically, an oblate spheroid is an ellipse rotated about the shorter semi-minor axis. The oblate spheroid is the principal shape used in modeling the surface of the earth. The Earth is not an exact ellipsoid, and deviations from this shape are continually evaluated. For map projections, however, the problem has been confined to selecting constants for the ellipsoidal shape and size and has not generally been extended to incorporating the much smaller deviations from this shape, except that different reference ellipsoids are used for the mapping of different regions of the Earth.
There are over a dozen principal ellipsoids which are used by one or more countries. The different dimensions do not only result from varying accuracy in the geodetic measurements the measurements of locations on the Earth , but the curvature of the Earth's surface is not uniform due to irregularities in the gravity field.
Until recently, ellipsoids were only fitted to the Earth's shape over a particular country or continent. The polar axis of the reference ellipsoid for such a region, therefore, normally does not coincide with the axis of the actual Earth, although it is made parallel.
The discrepancy between centers is usually a few hundred meters at most. Only satellite-determined coordinate systems, such as the WGS 72, are considered geocentric.
They usually consist of the definition of an ellipsoid, a definition of how the ellipsoid is oriented to the earth's surface, a definition for the unit of length, an official name, and region s of the earth's surface for which the datum is intended to be used. The reference ellipsoid is used with an "initial point" of reference on the surface to produce a datum, the name given to a smooth mathematical surface that closely fits the mean sea-level surface throughout the area of interest.
Once a datum is adopted, it provides the surface to which ground control measurements are referred. The projection equations of large-scale maps must use the same ellipsoid parameters as those used to define the local datum; otherwise, the projections will be inconsistent with the ground control. Geodetic datums are part scientific and part political.
The most common family of positioning methods is X Y Cartesian coordinates. Ninety nine percent of the earth's wellbores are located by some form of X Y coordinate system. Map projections are defined in a specific unit of length.
They usually have defined coefficients which vary with the location on the surface of the earth.
A worldwide specification of the variable coefficients, called the Universal Transverse Mercator UTM is the most commonly used member of the TM family. The Lambert map projection is also common throughout the world and is currently the most used projection in the U.
The quadrangles formed by the intersection of these lines normally referred to as parallels and meridians, respectively are of different shapes and sizes, which severely complicates the locations of points and the measurement of directions. Polar regions are covered by other, special projections. See Figure Each zone is flattened and a square imposed on it. Thus, its outer edges are curved when drawn on a flat map since they follow the meridian lines on the globe.
Each of the 60 zones is numbered, starting with zone 1 at the th meridian. The areas East and West of the Greenwich Meridian are covered by zones 30 and It is not essential to use the grid sector letter to identify the position of a point on the globe.
To avoid negative values for eastings, the central meridian in any zone is assigned the arbitrary eastings value of ,m. Along the equator a zone is about , meters wide, tapering towards the polar region.
Eastings range in value from approximately , to , For points north of the equator, northings are measured directly in meters, with a value of zero at the equator and increasing toward the north. To avoid negative northing values in the S.
Hemisphere, the equator is arbitrarily assigned a value of 10,, meters and displacements in the southern hemisphere are measured with decreasing, but positive, values as one heads south. Clearly, at the central meridian, Grid North equals True North. Convergence will vary with distance away from the central meridian and with distance away from the equator. Convergence is negative to the East and positive to the West. However, the well surveys will use sensors that reference either Magnetic or True North, and the user must therefor be able to convert from one reference to the other.
Lambert yields the greatest similarity that any plane figure can have with one drawn on the surface of a sphere. Meridiens are equally-spaced radii of the concentric circular arcs representing parallels of latitude; the parallels become further apart as the distance from the central parallels increases.
Straight lines between points approximate great circle arcs for maps of moderate coverage. Two parallels may be made standard or true to scale. In the State Plane Coordinate System SPCS for States using the Lambert projection, the choice of standard parallels has the effect of reducing the scale of the central parallel by an amount which cannot be expressed simply in exact form, while the scale for the central meridien of a map using the Transverse Mercator projection is normally reduced by a simple fraction.
North America is illustrated here to show the change in spacing of the parallels. When used for maps of the conterminous United States or individual States, standard parallels In the U. A Transverse Mercator system was prepared for the remaining States. One or more zones is involved in the system for each State. The U. K National Grid are two common examples. In the State Plane Coordinate System of , NAD27 is the geodetic datum, a foot is the unit of length, three different map projections are used depending upon where in the U.
Coast and Geodetic Survey predecessor at the National Ocean Service to enable surveyors, mappers, and engineers to connect their land or engineering surveys to a common reference system, the North American Datum of The following criteria were applied in the design of the State Plane Coordinate System of It is impossible to map a curved Earth an a flat map using plane-coordinates without distorting angles, azimuths, distances, or area.
Three conformal map projections were used in designing the original State plane coordinate systems, the Lambert conformal conic projection, the transverse Mercator projection, and the oblique Mercator projection. The Lambert projection was used for States that are long in the east-west direction e. The transverse Mercator projection was used for States or zones within States that are long in the north-south direction e.
These same map projections are also often custom designed to provide a coordinate system for a local or regional project. For example, the equations of the oblique Mercator projection produced project coordinates for the Northeast Corridor Rail Improvement project when a narrow coordinate system from Washington, DC, to Boston, MA, was required.
Land survey distance measurements in the s were typically made with a steel tape, or something less precise. Accuracy rarely exceeded one part in 10, Therefore, the designers of the SPCS 27 concluded that a maximum systematic distance scale distortion attributed to the projection of 1: If distances were more accurate than 1: Admittedly, the one in 10, limit was set at an arbitrary level, but it worked well for its intended purpose and was not restrictive on the quality of the survey when grid scale factor was computed and applied.
There was usually sufficient overlap from one zone to another to accommodate projects or surveys that crossed zone boundaries and still limit the scale distortion to 1: In more recent years, survey accuracy usually exceeded 1: More surveyors became accustomed to correcting distance observations for projection scale distortion by applying the grid scale factor correction.
When the correction is used, zone boundaries become less important, as projects may extend farther into adjacent zones. Some geodesists advocated retaining the design of the existing State plane coordinate system projection type, boundaries, and defining constants and others believed that a system based on a single projection type should be adopted.
The single projection proponents contended that the present SPCS was cumbersome, since three projections involving zones were employed. A study was instituted to decide whether a single system would meet the principal requirements better than SPCS These requirements included ease of understanding, computation, and implementation.
Initially, it appeared that adoption of the Universal Transverse Mercator UTM system would be the best solution because the grid had long been established, to some extent was being used, and the basic formulas were identical in all situations. However, on further examination, it was found that the UTM 6 degree zone widths presented several problems that might impede its overall acceptance by the surveying profession. For example, to accommodate the wider zone width, a grid scale factor of 1: As already discussed, similar grid scale factors on the SPCS rarely exceeded 1: In addition, the "arc-to-chord" correction term that converts observed geodetic angles to grid angles is larger, requiring application more frequently.
And finally, the UTM zone definitions did not coincide with State or county boundaries. These problems were not viewed as critical, but most surveyors and engineers considered the existing SPCS 27 the simpler system and the UTM as unacceptable because of rapidly changing grid scale factors.
This grid met the primary conditions of a single national system. By reducing zone width, the scale factor and the arc-to-chord correction would be no worse than in the SPCS Furthermore, seldom did this cause larger scale factor or arc-to-chord corrections than in the existing SPCS 27, although several of the larger counties would require two zones.
However, the average number of zones per State was increased by this approach. The grids had been in use for more than 40 years and most surveyors and engineers were familiar with the definition and procedures involved in using them. With availability of electronic calculators and computers, little merit was found in reducing the number of zones or projection types.
There was merit in minimizing the number of changes to SPCS legislation.
The project was undertaken because NAD 27 values could no longer provide the quality of horizontal control required by surveyors and engineers without regional recomputations least squares adjustments to repair the existing network.
NAD 83 supplied the following improvements: One hundred and fifty years of geodetic observations approximately 1. Not only does the published geodetic position of each control point change, but the State plane coordinates change for the following reasons: These ellipsoidal parameters are often embedded in the mapping equations and their change produces different plane coordinates. This local system depends upon and has a direct relationship to all the concepts presented thus far in this chapter.
Many assumptions are often made in defining local coordinate systems which are not obvious, but very important. The term Reference Point will be used in this chapter to mean either or both. This reference point has only North and East coordinates defined.
Unless specifically defined otherwise, a Local Coordinate System has each of its axis oriented parallel to the corresponding axis of the "legal" coordinate system in which its Reference Point is defined. Obviously, there must be a defined unit of length, however, this is normally dictated by the customer's preference or governmental regulation. By definition, a Local Coordinate System is a grid system and has to use a Grid North in order to be plotted correctly. Only on a plot drawn using Grid North, can distances and angles be measured directly.
If True North or Magnetic North is used to plot directional survey data, the relationships between lines and points on the plot are not linear and therefore can not be measured directly with a compass or ruler. Quite often, the error distortion is small, but this is not something that is readily apparent and can not be left to individual judgment.
In many cases, governmental reporting requirements are dictating the use of Grid North. Under no circumstances should Anadrill employees prepare or use a well plan based upon a Local Coordinate System which uses anything but Grid North. Requests from a customer to do this should be directed to Senior management and technique and will be evaluated on a case by case basis. Often, it is necessary to convert location data from one local" coordinate system to another.
The slot locations on this drawing are usually defined relative to a drawing local reference system which has its own origin and reference North. It is up to the planner to determine the amount of translation moving the pattern in N, E and rotation moving the pattern around a point required to allow the slots to be located in the DD's local coordinate system.
These reference lines should be referred to as Structure Reference Lines. An analogous discussion can be made for relocating Targets from a geophysical or reservoir based reference system to the Local Coordinate System. Values of magnetic declination change with time and location. As the movement of Magnetic North is constant and predictable, Magnetic declination can be calculated for any given point on the earth at any given time.
Charts depicting the various declinations and rate of change usually expressed as an annual change are widely used. An Easterly declination is expressed as a Positive value and a Westerly declination is expressed as a Negative value. Although converting from one reference to another appears a simple task, considerable care is needed, depending on the relative directions of convergence and magnetic declination. For example, see Figure Figure Corrections to survey azimuth 3. Any point within a lease can usually be defined in terms of distance from any two adjoining boundaries Figure In this method, lines are surveyed along the irregular edges of the property and the azimuth and length of the lines recorded.
When a well is placed in this type of property, the well location is often described as in the following example See Figure In this case, there are no references defined to a national or international measurement system.
This method has been used for the majority of the wells drilled in Texas. With land wells, the surface location of the well will usually be determined by the factors originally prompting the decision to drill a deviated as opposed to a vertical well. Offshore platforms tend to have between 6 and 60 wells. Adjacent wells may have only 6' feet between centers. Many factors which directly affect installations including water depth, bottom slope, sandy bottom versus coral reef, local currents, etc.
A directional well can have one or more objectives. The most obvious of the objectives is the target. These can be geological structures, geological features such as faults or pinch-outs, other wellbores as in relief well drilling or a combination of these.
In this section, we look at the way in which targets are defined. As we have seen, there are various ways of referring to a surface location UTM, Lambert, Geographic, etc. The same is true for the target location, with the addition of the vertical depth of the target. When planning and drilling a well, it is simpler to use local coordinates when referring to the target. Once the exact location of the local reference point and the target are known, the local coordinates can easily be determined.
They can easily be derived by subtracting the grid coordinates of the surface location from those of the target. For example: Table Rectangular coordinates of a target position. A negative value denotes South or West. Polar coordinates can be derived from the rectangular coordinates. They are expressed as a Distance Departure and a Direction either Quadrant or azimuth. Polar coordinates are derived from the rectangular or Cartesian coordinates as follows: The tan function on most calculations normalizes the answer to a value between 0 and 90 degrees.
Always restore your azimuth to the correct quadrant. From O, there are three axes; to North, to East and "z" vertical down. The distance is SB 3. The distance is B3B2. Usually, the Vertical Section passing through the center of the Target is used for plotting the well profile. In order to ascertain the latest bottom-hole position, it is necessary to perform a survey calculation which includes the three inputs listed above. Projections to the target, etc.
A number of survey calculation methods have been used in directional drilling. Of these, only four have had widespread use: The Tangential Method is the oldest, least sophisticated and most inaccurate method.
This method should never be used. Average Angle and Radius of Curvature methods are in common field use. Average Angle method in particular lends itself easily to a hand-held calculator. Radius of Curvature method is more widely used. However, official survey reports should not use either if the above methods except when demanded by the customer.
Minimum Curvature method should be used for all office calculations and official survey reports. Where possible, it should also be the field calculation method chosen. The DD is advised to have at the well-site a hand-held calculator which is programmed for both Radius of Curvature and Minimum Curvature methods of survey calculation.
The well bore is then assumed to be tangential to these angles. On any curved section of the hole there are flaws in this assumption and this method of survey calculation cannot provide realistic results for anything but a hold section of the well. In a build and hold well, the TVD would be less i. With the well turning to the right in the North East quadrant, one would introduce errors that would result in a position too far to the East, and not far enough to the North.
Effectively, the course length between the two survey points is divided into two, equal length, straight line segments. Thus, if A1 and I1 are the azimuth and inclination respectively at the previous survey point, then: The errors that remain tend to show too great a TVD, and too little displacement during the build section.
Although its accuracy is comparable to the average angle method, this method is not commonly used since the formulae are more complicated. Figure This is then the assumed well path, with a length equal to the actual course length between the two stations.
As such the well bore can be curved in both the vertical and horizontal planes Figure Assuming I and A to be measured in degrees, the radius is: Figure Radius of curvature - horizontal projection In a manner analogous to that for the vertical projection, one can show that: To be more specific, it takes the space vectors defined by the inclination and azimuth at each of the survey points and smooths these onto the well bore by use of a ratio factor which is defined by the curvature of the well bore section.
This curvature is the Dog-leg Figure Figure Minimum curvature - dog leg This method provides one of the more accurate methods for determining the position of the well bore. It is necessary to smooth the straight line segments onto the curve using a Ratio Factor, RF, given by: We can then determine the increments along the three axes, to define the position of the second survey point.
It is the Anadrill method of choice. It combines the tangential and balanced tangential calculation methods, and takes into account the length of the survey tool STL. It treats the portion of the course over the length of the survey tool as a straight line i.
Compared to the "actual" TVD of The actual well bore may behave very differently. In addition, this comparison does not include any turn, so reasonable amounts of caution should be used when comparing on method to another. However, it is fairly reasonable to assume that methods which compare badly in a single plane situation will almost certainly behave worse in a three dimensional case. It is usually expressed in degrees per feet or degrees per 10 or 30 metres of course length.
Several formulae are available to compute the total effects when there is a change in both inclination and direction between survey points.
In the following formulae: It makes no assumptions about the well path, and is therefore independent of survey calculation methods. For the Tangential Method gives an approximation only: Each directional well is unique in the sense that it has specific objectives. Care has to be exercised at the planning stage to ensure that all aspects of the well are tailored to meet those objectives. Drilling a directional well basically involves drilling a hole from one point in space the surface location to another point in space the target in such a way that the hole can then be used for its intended purpose.
To be able to do this we must first define the surface and target locations. Location The first thing to do is to define a local coordinate system See Chapter 3.
In many land wells, this will be the surface location. The target location is then converted to this local coordinate system, if necessary. Target Size During the drilling phase of a directional well, the trajectory of the wellbore in relation to the target is constantly monitored. Often, costly decisions have to be made in order to ensure that the objectives of the well are met. A well defined target is essential in making these decisions. The technology available today allows us to drill extremely accurate wells.
The cost of drilling the well is largely dependent on the accuracy required so the acceptable limits of the target must be well defined before the well is commenced.
Cost versus Accuracy is the key consideration here. In many cases, operator companies adopt an arbitrary in-house target size or radius of tolerance , particularly in multi-well projects. The size of the target radius often reflects the convention rather than the actual geological requirements of the well. It is common for specific restrictions or hard lines to be specified only when they depict critical features such as fault lines, pinch outs or legal restrictions such as leaseline boundaries.
Many directional wells have been unnecessarily corrected or sidetracked in order to hit a target radius which in fact did not represent the actual objective of the well. Good communication with the relevant department Geology or Exploration before beginning the well can help to avert this kind of error.
This is particularly true when a correction run is being contemplated. The first step of any plan to correct the azimuth of a well should always be consultation with the Geology Department. Wellbore Profile Knowing the position of the surface location and given the location of the Target, its TVD and rectangular coordinates, it is possible to determine the best geometric well profile from surface to the bottom-hole target. In general, Directional wells can be either: Once the profile has been selected, the well can be planned.
From a Directional Drilling point of view, this involves choosing the following: The selection of the Kick-off point is made by considering the geometrical well-path and the geological characteristics.
The optimum inclination of the well is a function of the maximum permissible build rate and drop rate if applicable and the location of the target. This can be a severe limiting factor in deeper wells.
Higher build rates are often not possible to achieve in soft formations. Once the desired build rate and inclination have been established, the kick-off point can be determined.
There is usually some flexibility in order to accommodate casing points. From a mathematical point of view the two well types must be further broken down into those where the radius of build, or sum of the radii of build is greater or lesser than the total displacement of the well. This is especially true when adjacent wells are producing and a collision could result in an extremely dangerous situation. Anti-collision planning begins with accurate surveys of the position of the subject well and all existing wells in its vicinity as well as a complete set of proposed well plans for future wells to be drilled in the vicinity.
The surveys and well plans are used to carefully map the relationship of the proposed new well to all existing wells and any proposed future wells. The Spider-plots are normally small scale to provide an overall view of the field Figure 3- 23 , and large scale to permit careful analysis of a given part of the field, such as the surface location Figure The Spider-plot can be used for tracing a planned trajectory and visually analyzing the threat of collision with other wells.
Analysis by manual calculation is not practical due to the large number of survey stations involved. One of the more commonly used types of proximity analysis is known as a Traveling Cylinder. Traveling Cylinder analysis seeFigure involves imagining a cylinder with a given radius enclosing the wellbore from one depth to another, the zone of interest. Any well entering this cylinder i. The traveling cylinder analysis is a useful planning tool, enabling the planner to test various trajectories and select the one which is most suitable.
During the drilling process, the trajectory of the well can be extrapolated and analyzed to ensure that unsafe proximity to adjacent wells is avoided.
Some systems are more accurate than others, but they are all prone to some degree of inherent error. In addition to the accuracy of the measuring device, the survey may also be subject to errors resulting from downhole changes in the magnetic field, Magnetic Interference, which may not be detected at the surface.
They proposed an ellipse actually an ellipsoid since it is a 3-D body that represents the envelope of the likely position of a given well survey point based on the error associated with the components of a survey measurement. They quantified systematic errors associated with either a magnetic or gyro compass, and those due to misalignment of the tool in the hole, depth measurement, and inclination.
By quantifying these errors for different tools it is possible to estimate the total range of error on the position given by a survey - and hence define the ellipsoid of certainty see Figure Figure Ellipsoid of certainty 3. This tendency can vary from negligible to severe and is the reason for most directional corrections. The problem with walking tendencies is that they are very often difficult to predict. The conventional solution to walking problems is the "Lead Angle" where the tendency is anticipated using past experience in the same or similar areas, and built into the initial directional orientation of the well.
Directional drilling databases are useful tools for quantifying walking tendencies. The use of steerable systems, while more costly, removes a lot of the guesswork and allow a straighter, more accurate hole to be drilled. If the direction is not critical, then the lead angle can be estimated and put to test. This is used to plot the progress of the well while it is being drilled. The map is plotted on gridded paper so that the survey points can be entered manually and is presented as a Vertical projection and a Horizontal projection.
The vertical projection of the actual well is plotted using the TVD and Vertical Section values from the survey calculations. Some are designed to run on small, hand-held calculators while others require powerful computers. The key factor in selection is need. If the program is needed to calculate surveys and plan wells, then a small hand held calculator is sufficient, if the program is needed to drive a large plotter and generate well plan maps, store bulk survey data and run a sophisticated BHA database, then obviously something larger and more powerful is called for.
Anadrill has its own software packages; e. The survey calculation output is important and should allow the user to specify the required format. Minimum Curvature is the Anadrill preferred method and is the industry standard.
Well planning often calls for unconventional well profiles, so the planning program should allow the user as much freedom as possible to specify the requirements of the well. In addition to Build-and Hold, and "S" Type wells, the user may wish to plan wells with several targets, several build rates or planned sums, and horizontal wells with inclinations above 90 degrees.
The quality and format of the output can make this tool easier to understand and use. This is particularly important when drilling horizontal wells where target intersection is critical. Interpolation allows more accurate plotting of Geological features. DD tools and technology have evolved tremendously in the past 20 years. Today, there is a broad range of PDMs for different applications. The various methods used to deflect a wellbore are described in this chapter.
Orientation is covered separately in Chapter The DD must be familiar with all the DD tools at the rig-site and in the workshop. The remaining DD tools are briefly described here. More detailed information is available from the manufacturers.
Most of the DD tools are straightforward to operate. While a directional drilling simulator is a useful aid in the teaching of DD concepts, the only way to fully understand how a wellbore is deflected and how the various DD tools are used is to get some on-the-job training.
This chapter should provide a lot of the background knowledge required. Objectives of this Chapter On completing this chapter the directional driller should be able to do the following exercises 1. Describe the use of an open-hole whip-stock. Explain how deflection is achieved using the jetting kickoff technique.
Describe the uses and applications of: They are used at the bottom of a BHA to provide weight on bit and rigidity. Flush or spiral drill collars are available. In directional drilling, spiral drill collars are preferable Figure The chances of differential sticking are greatly reduced. Spiral drill collars usually have slip and elevator recesses.
Stress-relief groove pins and bore back boxes are optional. The drill collars various sizes are normally owned by the drilling contractor. Short drill collars may be manufactured or a steel drill collar may be cut to make two or more short collars. SDCs of various lengths e. They are manufactured from high-quality, corrosion-resistant, austenitic stainless steel.
Survey instruments are isolated from magnetic disturbance caused by steel components in the BHA and drillpipe. It is also used in locked BHAs, particularly where the borehole's inclination and direction give rise to high magnetic interference.
It is often run above a mud motor. In conventional rotary BHAs, a float valve is inserted either in the bit sub in the case of a pendulum BHA or in the bored-out near-bit stabilizer. Poppet and flapper designs of float valve are available.
Note that some clients may not allow the use of a float valve because of kick-control problems. The DD should check the client's regulations on arrival at the rig. The float sub is usually provided by the DD company. The float valve is usually provided by the drilling contractor. It is bored out to take a float valve. Various sizes of bit sub are normally provided by the drilling contractor.
A "skirt" is fitted to the lower part of the body, around the necked-down portion, forming a basket for junk to settle in Figure The junk sub is run directly above the bit. It catches pieces of junk which are too heavy to circulate out.
Bleed holes in the skirt allow the mud to return to the system. The junk sub is provided by the drilling contractor. Figure Junk sub 5. A float sub can be used as an extension sub. The extension sub is usually provided by the DD company. Its heavy wall tube is attached to special extra-length tool joints. These provide ample space for recutting the connections and reduce the rate of wear on the OD. The OD of the tube is also protected from abrasive wear by a centre wear pad Figure Tool joints and wear pad are hard-banded.
Some HWDP have two wear pads. All dimensions are given in inches, unless otherwise stated. Chances of differential sticking are reduced.
Its three-point wall contact feature solves two serious problems in directional drilling. It permits high-RPM drilling with reduced torque. HWDP can be run through hole angle and direction changes with less connection and fatigue problems. For normal directional jobs, 30 joints of HWDP should be sufficient.
They are usually bored out to accept a float valve.
Most stabilizers have a right-hand spiral. For directional control, wall coverage in plan view is recommended. By conventional directional drilling, the wells could only achieve a maximum reach of about ft. To accommodate an MWD tool an 8-in. OD non-magnetic drill collar has to be bored out from 3-in. ID to 3. By how much will this reduce the stiffness of the collar? In a deviated well the proposed BHA calls for 8" x 3" drill collars run beneath 5", Calculate the effects of bending for this configuration, and suggest an alternative to reduce bending.
A pendulum assembly is made up of a number of 8-in. Calculate the side force on the bit. Explain how the tendency for a bottom hole assembly to build or drop angle can be affected by changing the position of the lowermost stabilizer. A correction run is to be made using a positive displacement motor and a bent sub that is expected to make a total change in angle of 2.
Calculate the new direction at the end of the correction run. Check your results by drawing a Ragland diagram. Draw a Ragland diagram to calculate a the toolface which will give the maximum turn to the right,. Check your results by applying the appropriate equations. Moore, Oil and Gas Journal, 5 March Brumley and J. McCollum, Drilling, June Cox and W. Bruha, a. Lowen and G. Gradeen, P. Drilling Data Book, I. Editions Technip.
Keene and D. Use the following survey data to determine the trajectory coordinates for tangential method? Average angle Or Angle Averaging Method: Determine the trajectory coordinates for the corrected survey points given below:. Measured depth ft inclination angle deg direction angle 0 0 Radius of In addition, these doglegs can cause key seating problems. Most operators place a limit on the amount of angle change allowable over a ft segment.
The limit is deg per ft. Directional Sensor Hardware The figure above shows the basic configuration of the Directional Sensor probe. The nominal length of the sub is 30 feet. The nonmagnetic collar is usually referred to as Monel. Inclination temperature Direction weight on bit tool-face angle torque on bit gamma ray sonic velocity Resistivity.
A lower cost MWD tool can be used if only directional drilling information is required. It was a widely used technique several years ago. It involved the use of a large bit jet and two smaller jets.
After washing ft rotary was used to drill the rest of the joint. Whip stock is a very simple device used to kick off the well. Separated into 2 categories: Open hole whip stocks ii. Casing whip stocks. Bent subs: For this reason, it z The survey tool is not far is normal practice to jet behind the bit. Movie 1 bottom trip W. Movie 2 section milling 3.
Movie 3 section milling 4. Movie 4 retrieving a W. Movie 5 cement type W. Movie 6 Casing W. Rabia, univ. J Adams, pennwell books, Tulsa, Oklahoma. B, Dec D Thanks for your attention. Flag for inappropriate content.
Related titles. Jump to Page. Search inside document. D z Definition: D Design a directional well with the following restrictions: D Ans. The minimum curvature method uses the angles at A1 and A2 and assumes a curved well bore over the course length not a straight line. Inclination temperature Direction weight on bit tool-face angle torque on bit gamma ray sonic velocity Resistivity z Inclination, direction, and tool-face angle are of particular interest in directional drilling.
After washing ft rotary was used to drill the rest of the joint 2.