Geometrical instruments – Apparel – Laying out
Reexamination Certificate
2000-12-15
2002-07-16
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Apparel
Laying out
C033S015000, C033S303000, C033S430000
Reexamination Certificate
active
06418630
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a deviation calculation rule used to provide a direct reading of all the necessary parameters and variables for monitoring the drilling path of deviated holes developed in a two dimensional geometric area thereby eliminating the traditional calculations that are done today using modem means of calculation, mainly computers.
Before going into detail about the deviation calculation rule, we will explain what two dimensional (2D) deviated holes are and will define the parameters and concepts the users of this rule will have to use.
HISTORY AND REMINDERS
In the early stages of oil drilling, wells were mostly vertical. Improvements in drilling techniques, the deepening of the pools, the discovery of new off shore oil fields and the cost of “offshore” infrastructures soon made it necessary to implement and improve techniques called deviation techniques. The deviation of a well consists in moving the path of a well away from the vertical line that passes through the wellhead, using a technique adapted thereto. The bottom of the well can therefore be moved by a certain lateral distance (that could be several km) in relation to the vertical line that passes through the wellhead. It then becomes possible to drill a greater number of wells whose paths are divergent from one same above-ground or offshore structure (“cluster” on land, offshore drilling rig or underwater “cluster”). These wells drain the oil from a relatively wide reservoir area compared to the space needed on the surface or at the bottom of the sea to exploit it.
Thus over the last fifty years, we have seen development taking place in a whole typology of deviated wells, among which we can name J wells, S wells, more or less complex horizontal wells, long deflection wells, multiple target wells, multi-lateral wells
Whatever the degree of sophistication of these wells, they all have more or less complex paths that must be located in the space. There are two main classes of paths: two-dimensional paths and three-dimensional paths.
The difference between these two classes of paths is based on the manner in which the inclination and the azimuth move over most of the path. We remind you that the inclination at a given point of a path is the angle that is created, in a vertical plane, by the tangent to the path at this point and the vertical line that passes at this point and that the azimuth of the path at this point is the angle created between the vertical plane that contains the tangent to the path at this point and the geographical vertical plane of reference.
In a 2D path, the variations of the inclination over most of the sections of the well are usually very large compared to the variations of the azimuth. This means that the well remains, for the most part, in the same vertical plane. However, if the variations of the inclination and the azimuth came closer together in absolute values, the inclination and the azimuth would have to progress in completely separate ways, meaning one after the other but never at the same time if the path is to remain 2D.
In a 3D path, the variations of the inclination and the azimuth over most of the sections of the well are much closer in absolute values than in the 2D path. Over substantial portions of the well, the inclination and the azimuth move together in significant way.
This differentiation between the 2D and 3D paths is crucial because the deviation calculation rule that is the object of this invention is only used in cases involving 2D paths. We must however note that this field covers most of the paths that are drilled today.
PATHS AND SECTIONS
There are four different types of sections that constitute 2D paths:
vertical sections in which the value of the inclination is low and close to zero and in which the well's path moves very little laterally, in relation to the vertical line that passes through the wellhead;
curved sections in which the value of the inclination may or may not start at zero and changes significantly compared to the value of the azimuth and in which the path of the well moves laterally in relation to the vertical line that passes through the wellhead in a given direction. These lateral movements generally tend to move the path of the well away from the vertical line that passes through the wellhead, but the opposite is possible and relates precisely to the case of “reverse curved” wells. Among the curved sections, we note positive curved sections in which the value of the inclination increases along the path and negative curved sections in which the value of the inclination decreases along the path. The curved sections may have a constant (arc of circle sections) or variable (catenary sections) curve radius;
straight sections in which the inclination remains constant and equal to a given non null value and in which the path moves laterally in relation to the vertical line that passes through the wellhead in a given direction. As with the curved sections, the straight sections can move the path of the well away from to closer to the vertical line that passes through the wellhead;
sections called navigation or pilot sections, specifically adjusted to the drilling of horizontal drains, in which the inclination changes a lot and tends to follow the dip of the geological beds, in sections, with areas called transition areas; in these sections, the inclination values of the path oscillate around the horizontal position (+ or −90° inclination, in a wide range from 70° to 120°); they consist of successions of curved sections and straight sections.
LOCATING THE 2D PATHS IN SPACE
In order to plan and monitor the 2D paths, they must be located in a two-dimensional space, meaning in a plane that, theoretically, consists of the vertical plane that contains the path. As shown in the enclosed
FIG. 1
, this plane P can be located in a local reference system through its azimuth a, the angle created by the plane P and a vertical reference plane P
1
that contains a fixed geographical landmark located on the surface. The path T, even a 2D type path, rarely develops in a single plane because it presents slight variations of the azimuth. This is why, for the monitoring of the path and the calculations related to it, we will choose as plane P a projection plane on which the path will be projected and this is also why, for the use of the deviation calculation rule, we will consider that the azimuth of the well remains mostly constant, which is an acceptable approximation.
Path T of the well is only known through deviation measurements that are carried out at certain points along the path, in general every drilled 30 m or in certain more critical cases, every drilled 10 m. In the purely 2D field, these are inclination measurements that are linked to drilled lengths in which the drilled lengths correspond for the most part to the cumulated length of the drill rods that are used to drill the well. The drill path is built through calculation, in sections, from these measurement points. In the purely 2D field, we graphically build the path by joining the successive points of measurement M
1
, M
2
. . . with two types of curves: straight sections when the measurement of the inclination remains unchanged between the points of measurement, and arcs of circle when the measurement of the inclination has changed between the two points, whether upward or downward.
The plane P is defined by two orthogonal axes: a horizontal axis directed in the azimuth of the well path and a vertical axis directed downward. On the horizontal axis, for each deviation measurement, we note the cumulated horizontal deflection values DEP of the well, in relation to a geographic referential that can be the geographic position of the wellhead I. The reference is not necessarily the wellhead, it can also be the center of a rig, or any other point that serves as a common reference for a group of wells. For directional calculations we usually work in a local reference and make the origin of the axis coincide with the wellhead.
On the vertical axis, for e
Gutierrez Diego
Pruchnie, Jr. Stanley J.
Total Fina Elf S.A.
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