000			02517nab a2200217 4500
005			20260520004418.0
008			260224s2013 xxu ing
041			_aInglés
245	0	0	_aExplicit Calculation of Expansion Factors for Collision Avoidance Between Two Coplanar Survey-Error Ellipses
260			_a _b _cmar. 2013
270			_a03/05/2013 ; 03/05/2013
300			_a10 p. ; 75-85
520			_aTraducción del resúmen del autor: The positional uncertainty about a point on a wellbore is commonly represented as an ellipsoid. The ellipsoid also accounts for the dimensions of the casing or open hole. With the use of this model, at any time the resulting uncertainty about a wellbore along its trajectory is a curved, continuous cone. To a good approximation, the intersection of the plane normal to a reference well with these cones can be represented as ellipses. This simple geometrical model has been adopted by standards organizations to define minimal acceptable separation distances between wellbores (e.g., the Norwegian NORSOK D-10 Standard and Oil and Gas UK Well Integrity Guidelines). Because of mathematical difficulties, the existing methods for calculating the resulting separation factors are only approximations and may be either too optimistic or too conservative, particularly for ellipses with high eccentricities. This paper presents explicit equations for determining the exact condition in which the ellipses touch, expressing the result as an expansion scale factor. Methods are presented for the expansion of either ellipse or both, together with implementation notes and other associated tools. The new algorithms are only marginally less efficient than the existing approximation methods, and they can be used to increase the allowable proximity of two adjacent wells while satisfying the geometrical and probabilistic constraints. The examples included in the paper illustrate this. The proposed calculation method is consistent with existing industry wellbore uncertainty models. Because the determination of the osculating condition is exact, the calculation is neither too optimistic nor too conservative. This paper is a response to discussions held at the SPE Wellbore Positioning Technical Section meeting on 3 November 2011.
581			_a1
773	0		_tSPE Drilling & Completion _g28
942			_cARTICULO
100	1		_aSawaryn, S.J. _919947
100	1		_ajamieson, A.L. _953080
100	1		_aMcGregor, A.E. _953081
999			_c187646 _d187646