--> The Gunn Graben: Geology, engineering, and the missing key, Geomechanics

AAPG Southwest Section

Datapages, Inc.Print this page

The Gunn Graben: Geology, engineering, and the missing key, Geomechanics


A deep drill test took place in 1989 which discovered an extensive gas charged Pennsylvanian clastic interval on the Matador Arch in north Texas. Unknown at the time, this exploration well stepped off into an elongate, left-lateral, asymmetric graben, where the eventual total vertical depths of these wells reached over 15,000 feet. Rotated fault blocks with several thousand feet of throw to the adjacent fault block, resulted in the development of both positive and negative flower structures where bedding planes dipped upwards to seventy degrees. These fault planes act as the compartmentalization mechanism trapping tight gas within these clastic reservoirs, and therefore reaching the targeted total depth a true drilling challenge. However, by not reaching the targeted total depths, this project left unknown numerous clastic packages undrilled within the Pennsylvanian Bend interval because of mechanical failures within the well bore.

In 2014, Schlumberger proposed a drilling geomechanics solution which involved integrating Schlumberger's Petrel and Stonefish software and Schlumberger's geomechanics expertise from their Petro-Technical Services along with K&M Technology drilling expertise coupled with K&M's torque and drag software to manage these drilling engineering issues. To understand the effect of geomechanics on the well bore, a mechanical earth model (MEM) was constructed via Stonefish which provided a coherent view of the earth stresses and mechanical properties of the rock within the well bore. The MEM was then complimented with a drilling engineering analysis performed by K&M Technology to more fully understand how the well bore was behaving while drilling. By applying these data sets and drilling practices, identifying parameters to increase drilling efficiency, the likelihood of obtaining success within this deep dynamic graben and reaching the targeted total depth becomes greater.