ABSTRACT: Drilling Parameters Are Utilized to Compute Fracture Porosity and In Situ Permeability in a Horizontally Drilled Bakken Well

James R. Lancaster, Asher Atkinson

Drilling parameters, drilling fluid properties, and textural properties of drilled rock are utilized to compute drilling porosity and in situ permeability on vertical wells. Drilling porosity minus sonic porosity quantifies fracture porosity. Sonic delta 'T' and bulk density are utilized to compute total organic carbon in petroliferous shales.

Bakken Shale evaluation of two producing vertical wells results in computations of fracture porosity, total organic carbon, and in situ permeability. From these results, efforts are made to evaluate the Bakken

Shale in a horizontally drilled well. On the horizontal well drilling porosity is computed from drilling parameters, which is converted to fracture porosity.

This data base and pore volume computed from fracture porosity are used to compute in situ permeability. Using Darcy's law, effective in situ permeability is computed to the filtrate advancing into the formation, or to fluid being produced from the formation into the mud system while drilling. In situ permeability of fractures with given width and spacing is determined using an equation for computing flow between parallel plates. With fracture permeability determined, flow rates from the Bakken fractures are calculated to predict well performance.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990