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Title:
IMPROVED METHOD FOR THE DRILLING OF OIL WELLS
Document Type and Number:
WIPO Patent Application WO/2001/053655
Kind Code:
A1
Abstract:
Method for the drilling of oil wells and for the positioning of the appropriate casings, consisting in drilling the well section of interest and, during the drilling, in maintaining a high degree of hole regularity by the use of automatic verticality and/or curvature control equipment. This method allows the positioning of casings with an almost constant clearance with values of +/- 1.5 inches for the whole well depth (lean profile).

Inventors:
CALDERONI ANGELO (IT)
FERRARIO GUALTIERO (IT)
Application Number:
PCT/EP2000/013370
Publication Date:
July 26, 2001
Filing Date:
December 28, 2000
Export Citation:
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Assignee:
ENI SPA (IT)
CALDERONI ANGELO (IT)
FERRARIO GUALTIERO (IT)
International Classes:
E21B7/04; E21B43/10; E21B44/00; (IPC1-7): E21B43/10; E21B7/06; E21B44/00
Domestic Patent References:
WO2000028188A12000-05-18
WO1999035368A11999-07-15
Foreign References:
US5603386A1997-02-18
US5918674A1999-07-06
Other References:
A. CALDERONI, A. SAVANI, J. TREVIRANUS, J. OPPELT: "Outstanding economic advantages based on new straight-hole drilling device proven in various oilfield locations", SOCIETY OF PETROLEUM ENGINEERS, no. 56444, 3 October 1999 (1999-10-03) - 6 October 1999 (1999-10-06), Houston, XP002166759
A. CALDERONI, A. LIGRONE, C. MOLASCHI: "The lean profile: a step change in drilling performance", SOCIETY OF PETROLEUM ENGINEERS, no. 52788, 9 March 1999 (1999-03-09) - 11 March 1999 (1999-03-11), Amsterdam, XP002166760
J.W. BARKER: "Wellbore design with reduced clearance between casing strings", SOCIETY OF PETROLEUM ENGINEERS, no. 37615, 4 March 1997 (1997-03-04) - 6 March 1997 (1997-03-06), The Hague, XP002166761
P. HEAD, D. TURNER, T. HANSON, S. AL RAWAHI, G. CAMERON: "Slimwells without the pain", SOCIETY OF PETROLEUM ENGINEERS, no. 52795, 9 March 1999 (1999-03-09) - 11 March 1999 (1999-03-11), Amsterdam, XP002166762
Attorney, Agent or Firm:
De Gregori, Antonella (Via Borgonuovo 10, Milan, IT)
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Claims:
CLAIMS
1. A method for the drilling of oil wells and po sitioning. of the appropriate casings, consist ing in drilling the well section of interest and, during the drilling, in maintaining a high degree of hole regularity by the use of automatic verticality and/or curvature control equipment.
2. The method for the drilling of oil wells and positioning of the appropriate casings accord ing to the previous claim, characterized in that the drilling phase is carried out observ ing the following precautions: automatic control of the verticality and/or curvature of the well use of bits equipped with adequate dis tributors and roller reamers use of drilling mud with chemical and rheological characteristics which are such as to minimize any possible well in stability problems constant control of all the drilling pa rameters.
Description:
IMPROVED METHOD FOR THE DRILLING OF OIL WELLS The present invention relates to an improved method for the drilling of oil wells which allows the positioning of lining columns, operating with an almost constant clearance for the whole of the desired well depth and which substantially consists in effecting the drilling, guaranteeing the elimi- nation of any geometrical curvature and irregulari- ties of the hole, whether it be vertical or devi- ated.

During the drilling of oil wells, lining op- erations of the hole (pipe-laying) are effected which comprise the positioning of appropriate cas- ings at pre-established intervals in relation to the depth reached and characteristics of the forma- tions penetrated.

During the pipe-laying, in order to guarantee easy descent of the lining columns into the well,

it is generally necessary to ensure that the dif- ference between the external casing diameter and the hole diameter (clearance) is maintained at suf- ficiently high values.

During conventional technological drilling, the clearance between casing and hole can vary from values of about 6-7 inches (15-16 cm) for the sur- face and/or intermediate phases, to values of al- most an inch for the deeper phases (for example: 26"hole for 20"conductor pipe, 17 1/2"hole for 13 3/8", 12 1/4"hole for 9 5/8"casing, 8 1/2" hole for 7"casing).

The necessity of adopting high clearance val- ues is linked to the high rigidity of pipes with a larger diameter/thickness and the impossibility of drilling perfectly vertical wells and/or with a controlled curvature. In fact, the poor flexibility of pipes together with a certain degree of hole ir- regularity (deviations, curving and/or narrowing) can make the lowering of columns into the well dif- ficult especially during the surface and/or inter- mediate phases.

The necessity, according to the conventional technologies, of producing holes with a considera- bly larger diameter with respect to that of the

casing to guarantee descent to the well bottom dur- ing the surface and intermediate phases, causes the formation of a. large quantity of waste products and a long duration of the plant on the territory with consequent long times and high drilling costs.

The drilling method according to the present invention allows, with the same diameter of the production column, the dimensions of the upper well part (surface and intermediate columns) to be re- duced. This enables a significant reduction in the consumption of materials (mud, cement and steel) and consequently the production of waste products.

This technique also avoids the necessity of produc- ing holes with a diameter which is too large with respect to the diameter of the columns to be low- ered, which generally implies the possibility of effecting holes with a smaller diameter compared to the conventional technique. All of this positively influences the advancement rate of the bit there- fore allowing the production times of the holes to be reduced, with a consequent decrease in the costs. The technique according to the present in- vention also enables a significant reduction in the operating costs, as the verticality and/or regular curvature of the well facilitates all workover and

well intervention operations.

This method comprises a drilling and pipe- laying technique which allows the positioning of the lining columns operating with an almost con- stant clearance with values of more or less 1.5 inches (3-4 cm) for the whole well depth (from the top to the bottom), or in any case for the whole of the desired well depth. The fact that a reduced clearance is adopted, allows, with the same number of columns and final diameter of the production casing, the dimensions of the upper part of the well to be greatly reduced.

This solution is mainly suitable for applica- tions in deep, vertical or deviated wells, also in the presence of formations with a low drilling ca- pacity and/or difficulty in controlling the trajec- tory. In these cases the use of the technique ac- cording to the invention allows considerable time saving and reduction in the drilling costs.

An object of the present invention therefore relates to an improved method for the drilling of oil wells and for the contemporaneous positioning of appropriate casings, characterized in that the clearance is kept almost constant for the whole of the desired well depth, consisting in drilling the

well section of interest, maintaining a high degree of hole regularity by the use of automatic verti- cality and/or curvature control equipment.

In particular, the method according to the following invention comprises effecting the drill- ing phase according to the following procedures: -automatic control of the verticality and/or curvature of the well; use of bits equipped with adequate distribu- tors and roller reamers, in order to guarantee hole regularity and calibration; use of drilling mud with chemical and rheological characteristics which are such as to minimize any possible problems of hole in- stability; -constant control of all the drilling parame- ters in order to maintain a curvature (BUR/DO) of 0.7 degrees every 30 m, with a maximum slope of 1.5 degrees in the vertical sections.

For the automatic control of the well verti- cality, the use of the device called"Straight Hole Drilling Device (SDD)", a drilling instrument pro- duced by the Applicant in collaboration with Baker Hughes, has proved to be particularly advantageous.

This device, contrary to the conventional systems,

automatically effects a continuous correction of the verticality and is based on a retro-activated control which ensures the absolute verticality of holes, even in formations which have a strong ten- dency to cause the bit trajectory to deviate from the vertical.

The use of a device called Autotrak, a drill- ing instrument produced by the Applicant, again in collaboration with Baker Hughes, has proved to be advantageous for the automatic control of the cur- vature. This device effects a continuous correction of the curvature which guarantees an optimum geome- try in the deviated sections.

A preview of both apparatuses produced in col- laboration with Baker was provided in the paper SPE 50379 of November 1998.

Various alternatives are available on the mar- ket both for the automatic verticality control and curvature control, such as: -RDS of Camco ; -AGS of Cambridge Automation -Well Director of Well Done As an illustrative but non-limiting example of the method according to the present invention, the pipe-laying procedure is effected as follows.

After producing a perfectly vertical and well calibrated hole the lining columns can be lowered into the well. In order to facilitate the passage of the casing into the hole calibrated with a re- duced clearance, the following precautions should be observed: Use threaded connections of the flush or near- flush type. The integral connection called"A- SFC" (Agip Semi Flush Connection) described in patent application 5934 filed on 19/02/1999 by the same Applicant, can be advantageously used. This connection has a limited clearance (external diameter 2.5% higher than the exter- nal pipe diameter) and is characterized by a significant improvement in the compression and torque strength/efficiency, with respect to existing connections of the same category. The joint is also equipped with a double metal to metal seal which makes it suitable for appli- cations in deep wells and/or in the presence of high pressures.

Check the perfect rectilinearity of the pipes.

The tolerances admitted by the API regulation in terms of residual manufacturing deforma- tions are not acceptable in effecting the Lean

technique. The rectilinearity must therefore be accurately checked before beginning the piping operations.

Limit the use of centralizers (if necessary use an Integral Blade Centralizer).

During the pipe laying, limit the descent rate of the column to avoid forcing and the crea- tion of dangerous ramming linked to the re- duced ring dimensions.

Use cementation shoes of the centralized type (Stabilizer Shoe) equipped with an auto fill- up device.

During the cementation special malts with a high fluidity and mechanical resistance are used.

In the case of possible deviated sections, in addition to the following precautions, curvature should be planned in relation to the flexibility of the casings to be used.

Operating as described above, it was possible to lower a casing with an external diameter slightly less than that of the hole (about 1.5 inches) into the well, creating a narrower pipe- laying profile (Lean), with the advantages de- scribed above and without jeopardizing the diameter

of the production column.

Figure 1 compares the conventional pipe-laying program with the"Lean"program. The data in said figure were obtained in the Monte Enoc 9 well ef- fected in the Field of Val D'Agri in Basilicata. It is evident how with the"Lean"solution, starting from a lower diameter of the surface and intermedi- ate columns, a production column is obtained with the same diameter as that produced with the conven- tional solution.

Figure 2 describes a further two examples of Lean pipe-laying, which can provide a valid alter- native to the previous scheme, above all in contin- gency situations.

Figure 3 schematically represents a comparison between the hole sections.