Abstract

Portable Technology Puts Real-time Automated Mineralogy on the well Site

Ken Pfau¹, Guy Oliver², Graham Spence², and Lucy Plant²
¹Forest Oil Corporation, Denver, Colorado, USA.
²Fugro Robertson Inc., Houston, Texas, USA

One of the key challenges associated with shale play exploration and production involves understanding the reservoir characterization in order to effectively manage a cost-effective development program.

Historically, core samples and logs have been the method of choice for reservoir characterization. However, the analysis of drill cuttings (the drill bit-induced rock chips) have taken on a new importance not only for reservoir characterization but also for directly determining the nature of the sequence through which the drill bit has penetrated.

This is even more amplified when an operator has no core samples or is limited by the log information. Cuttings thus become the only direct observation of particle size, lithology and reservoir characterization in long and expensive horizontal wells. In this situation, the best option is to extrapolate those observations to millimeter scale observations in the cuttings.

Recently ruggedized and portable scanning electron microscopes with energy dispersive X-ray detectors (SEM/EDS) have become commercially available for rig site deployment specifically aimed at achieving near real time analysis of drills cuttings.

These portable technologies give operators the ability to accurately report rock chemistry, mineralogy, and lithology along with textural information on grain size and shape, rock property information (porosity, specific gravity) and plot the brittleness vs. ductility of the sample in real time, within 30 minutes of a sample arriving at the surface.

Real time access to this detailed reservoir information can benefit the operator by enabling them to more optimally position lateral well bores; more tactically position artificial fracture points based on rock properties; improve well management; and use the measured mineralogical dataset to improve petrophysical log-based calculations.

In a 2011 field test in the Wolf Camp play, Permian Basin West Texas, Forest Oil successfully tested a vertical and lateral well pair using RoqSCAN™. A vertical pilot well and horizontal well were drilled successfully and key formations of the Permian, focusing on the Wolfcamp Shale Formation were sampled and analyzed. Over a 10-week period, more than 600 samples were collected, analyzed and interpreted at the well site in real-time. During drilling of the subsequent lateral well, cuttings data was collected every 10-30 ft. On many occasions, because of a slower rate of penetration (ROP), RoqSCAN was generating mineralogical data 20-30 minutes faster than the measurement while drilling (MWD) tool over the same interval, according to the company.

The real-time RoqFRAC curve analysis, designed to assist operators with mineralogical-based interpretation of these results, generated additional rock properties data on brittleness versus ductility providing Forest Oil with additional mineralogical-based data to assess the artificial fracture capability over the entire length of the lateral target interval. This additional data allows the operator to ‘tactically frac’ the target interval based on mineralogy and, when combined with petrophysical attributes, elastic properties of the rocks. Tactical fracing may lead to a reduction in operating expenses as the number of contributing fracing stations may be reduced.

AAPG Search and Discovery Article #90164©2013 AAPG Southwest Section Meeting, Fredericksburg, Texas, April 6-10, 2013