Emerging technology for quantifying minimal anisotropy
C. Barrientos, E. Wielemaker, T.J. Plona, J.B.U. Haldorsen, P. Saldungaray and L. Arroyo Franco
Journal name: First Break
Issue: Vol 24, No 9, September 2006
Info: Article, PDF ( 4.25Mb )
Price: € 30
Until recently, reliable measurement of anisotropy magnitude and orientation was possible only when the velocity anisotropy was greater than 5%. Carlos Barrientos, Erik Wielemaker, Thomas Plona, Jakob Haldorsen, and Pablo Saldungaray (Schlumberger) and Jose Luis Arroyo Franco (Pemex) show how quantification of anisotropy of less than 5% is possible by means of improved transmitters and additional receivers (both axial and azimuthal). Quantification of anisotropy as small as 1% is now not only possible but can be achieved through the use of either sonic or seismic methods. Such information is crucial in determining stress direction for well placement and for application of oriented perforating techniques. The ability to detect minimum anisotropy also aids in identification of in-field drilling opportunities in mature fields and to maximize fracture treatments. The Pemex Cuitlahuac field in the Tertiary Burgos Basin in the northeastern corner of Mexico was selected to demonstrate the mechanisms of anisotropy detection because of its formations in which the targets are tight and laminated gas sands deposited in a flu-vio-deltaic environment. Evidence of weak acoustic anisotropy using data acquired with a new modular sonic tool as well as borehole seismic data generated by shear vibrators is presented. Also, two different mechanisms of anisotropy, differing in magnitude and direction, are described.