AAPG Bulletin, V. 83, No. 12 (December 1999), P. 1901-1926.
Delaware Mountain Group, West Texas and Southeastern New
Mexico, A Case of Refound Opportunity: Part 1--Brushy Canyon
Scott L. Montgomery,1 John Worrall,2
and Dean Hamilton3
©Copyright 2000. The American Association of Petroleum
Geologists. All rights reserved.
1Petroleum Consultant, 1511 18th Avenue East, Seattle, Washington 98112.
2Scott Exploration Inc., 200 W. First Street, Suite 648, Roswell, New Mexico
88201.
3Consulting Geologist, Midland, Texas.
ABSTRACT
Exploration in Permian (Guadalupian) deep-water sandstones of the
Delaware Mountain Group, west Texas and southeast New Mexico, represents a success story
of the 1990s derived from reevaluation of reservoirs previously deemed uneconomical.
Recent discoveries have concentrated on the Brushy Canyon in New Mexico and, to a lesser
extent, the Cherry Canyon in Texas. Brushy Canyon reservoirs in particular previously were
overlooked due to indications of poor reservoir quality from log and well test data;
however, oil shows observed on mud logs across the northern Delaware basin led to new
completion efforts in the late 1980s and 1990s using gel-sand fracture stimulations.
Productive reservoirs are very fine to fine-grained arkosic to subarkosic sandstones with
porosities of 12-25% and permeabilities typically of 1-5 md. Better reservoir quality is
concentrated in massive channel sandstones variably interpreted as deposited by turbidity
or saline density currents. Significant clay content, lamination, and close interbedding
between oil- and water-bearing units make log analysis and reserve estimates problematic.
As a result, the mud log remains the cheapest, most practical indicator of pay. Reservoir
sandstones can be divided into a series of major productive trends related to
proximal/slope and more distal/basin-floor depositional settings. Well productivity is
variable within each trend, but primary recovery rarely exceeds 10%. Options for enhanced
recovery include pressure maintenance, waterflooding, and carbon dioxide flooding. Early
indications suggest that carbon dioxide flooding may be most appropriate in these
low-permeability, clay-bearing reservoirs.
