Title: A folded wedge model for determination of true stratigraphic thickness in directional wells

Authors: Shunshan Xu, A.F. Nieto-Samaniego, J.M. Grajales-Nishimura, L.G. Velasquillo-Martinez, G. Murillo-Muneton, J. Garcia-Hernandez

Addresses: Universidad Nacional Autonoma de Mexico, Centro de Geociencias, Apartado Postal 1-742, Queretaro, Qro., 76001, Mexico. ' Universidad Nacional Autonoma de Mexico, Centro de Geociencias, Apartado Postal 1-742, Queretaro, Qro., 76001, Mexico. ' Instituto Mexicano del Petroleo, No.152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico, D.F., Mexico. ' Instituto Mexicano del Petroleo, No.152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico, D.F., Mexico. ' Instituto Mexicano del Petroleo, No.152, Col. San Bartolo Atepehuacan, C.P. 07730, Mexico, D.F., Mexico. ' Petroleos Mexicanos Exploracion y Produccion Region Marina NE, Activo Cantarell (PEP-RMNE), Mexico

Abstract: For exploration and development the geologists and engineers try to know the true stratigraphic thickness (t). The monoclinal and folded bed models are published methods for t calculation. Both models assume parallel beds which can lead to significant deviations. In order to calculate the values of t considering the effects of both folding and stratigraphic variation we propose the |folded wedge model|. Three are considered: β1, the bed dip at the point where the well enters; β2, the bed dip at the point where the well leaves; and α, the deviated angle of borehole (angle between vertical and borehole). Three values of t can be obtained: the value measured normal to top (t6); the value measured normal to bottom (t7); the average value measured normal to bottom and top (t8). The folded wedge model is applied to the Cantarell oil field complex obtaining more reasonable values of t than using the existing methods. [Received: August 16, 2009; Accepted: February 10, 2010]

Keywords: true stratigraphic thickness; wedging bed modelling; folded wedge model; absolute deviation; directional wells; oil fields; folding variation; stratigraphic variation.

DOI: 10.1504/IJOGCT.2010.035374

International Journal of Oil, Gas and Coal Technology, 2010 Vol.3 No.3, pp.245 - 268

Published online: 26 Sep 2010 *

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