Method for drilling a borehole from one cased borehole to another cased borehole
AssigneeShell Oil Company
InventorsRobin A. Hartmann, Elvira H. Mulder
Life of this patent
Estimating the term…
Abstract
In a method for drilling adjacent to a cased known first borehole a second borehole in a predetermined direction the following steps are carried out for a number of along hole depths d.sub.i : measuring components of gravity acceleration and magnetic field (earth & casing); determining direction parameters .alpha..sub.i ; deriving magnetic polestrength components, B.sub.p1,i and B.sub.p2,i ; applying B.sub.p1,i /B.sub.p2,i =s.sub.1,i /s.sub.2,i and determining deviations of the predetermined direction; and controlling drilling direction of the second borehole.
Claims16
A method for drilling, relative to a neighbor known first borehole which is provided with magnetized casing portions having polestrengths adapted to be measured, a second borehole into a predetermined direction with regard to the first borehole, the method comprising the steps of:
- a) starting drilling the second borehole from a predetermined position s.sub.0 in a first coordinate system C;
- b) measuring, while drilling the second borehole at and along borehole depth d.sub.i, in a second borehole related coordinate system D, magnetic field components B.sub.D,i of magnetic field vector B and gravity acceleration vector components g.sub.D,i of gravity acceleration vector g;
- c) determining from the B and g components, B.sub.D,i and g.sub.D,i, respectively, direction parameters .alpha..sub.i of the second borehole in the first coordinate system C;
- d) determining from the direction parameters .alpha..sub.i and from magnetic fields Band B.sub.E, B.sub.E being the earth's magnetic field, at least two polestrength components B.sub.p1,i and B.sub.p2,i of a polestrength vector B.sub.p, B.sub.p1,i and B.sub.p2,i being components of B.sub.p at d.sub.i in the first coordinate system C;
- e) applying B.sub.p1,i /B.sub.p2,i =s.sub.1,i s.sub.2,i, wherein s.sub.1,i and s.sub.2,i are position parameters in the first coordinate system C corresponding to the location of the second wellbore with respect to the first wellbore, and determining direction parameter deviations, .DELTA..beta..sub.i with regard to the predetermined direction of the second borehole;
- f) comparing the .DELTA..beta..sub.i with the predetermined direction parameter deviations .DELTA..beta..sub.0i, and, if .DELTA..beta..sub.i is greater than .DELTA..beta..sub.0i, redirecting the second borehole into the predetermined direction;
- and
- g) continuing drilling the second borehole in the predetermined direction and repeating steps b) to f) for a further along borehole depth d.sub.i+1.
A method for verifying direction and position of a second uncased borehole situated near a first borehole having an accurately known position and provided with magnetized casing portions having polestrengths adapted to be measured from the second borehole, the method comprising the steps of:
- a) determining a starting position s.sub.0 of the second uncased borehole in a first coordinate system C;
- b) measuring, the second uncased borehole at and along borehole depth d.sub.i, in the second borehole related coordinate system D, magnetic field components B.sub.D,i of magnetic field vector B and gravity acceleration vector components g.sub.D,i of gravity acceleration vector g;
- c) determining from the Band gcomponents, B.sub.D,i and g.sub.D,i, respectively, direction parameters .alpha..sub.i of the second borehole in the first coordinate system C;
- d) determining from the direction parameters .alpha..sub.i and from magnetic fields B and B.sub.E, B.sub.E being the earth's magnetic field, at least two polestrength components B,.sub.p1,i and B.sub.p,2i of a polestrength vector B.sub.p, B.sub.p1,i and B.sub.p2,i being components of B.sub.p at d.sub.i in the first coordinate system C;
- e) applying B,.sub.p1,i /B.sub.p2,i =s.sub.1,i /s.sub.2,i, wherein s.sub.1,i and s.sub.2,i are position parameters in the first coordinate system C corresponding to the location of the second wellbore with respect to the first wellbore, and differential direction parameter deviations, .DELTA..beta..sub.i ;
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- f) adding .DELTA..beta..sub.i to the known starting positions to verify the direction and position of the second uncased borehole.
Dependencies are inferred from the claim text.