Identifying Compartmentalized Sections of Lower Vicksburg Reservoirs and the Potential for Directional Drilling in McAllen Ranch Field, Hidalgo County, Texas
Abstract
Identifying Compartmentalized Sections of Lower Vicksburg
Reservoirs and the Potential for Directional Drilling in McAllen Ranch Field,
Hidalgo County, Texas
Matthew McAllen, Dr. Donald Van Nieuwenhuise, University of
Houston
McAllen Ranch Field has been producing natural gas and condensate for over 50
years. Since 1960, the field has produced over one trillion cubic feet (TCF) from the
Oligocene Vicksburg formation from sandstones with 8-30% porosity, and usually less
than 1 md of permeability. Production from the field is in overall decline, yet the current
operator is undertaking new well locations and drilling programs. The Texas Bureau of
Economic Geology conducted a study of McAllen Ranch Field to model and estimate
the remaining unrecovered reserves trapped behind structural, depositional and
diagenetic low-permeability barriers. The focus of this project was to find untapped,
compartmentalized zones in the reservoirs in the north and south portions of the A.A.
McAllen lease. This was accomplished by first understanding regional and published
work done on McAllen Ranch Field and the Vicksburg formation. The next step was to
identify and correlate well logs to understand the continuity of the stacked, non-
associated gas reservoirs by understanding the typical well log response for the
different depositional facies. After the reservoirs were identified, production data was
examined to assess any potential to produce from isolated reservoir sections. Core
samples were described to understand the depositional and diagenetic low permeability
barriers, which inhibit the drainage radii of gas wells in the field. Results show that the
most potential lies within the depositional and structural trends in the southern portion of
the field that is heavily faulted and may contain isolated incised valley sandstones that
are truncated by faults. The northern portion of the field is less faulted, and has
compartmentalized sections of sand bodies that were deltaic sands that were reworked
by the northern longshore current. This sand body has diagenetic barriers, such as
tightly cemented calcite and chlorite sections. The recommendation for this field is to
partake in a directional drilling program to maximize the recovery from these tight
sandstones.
AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019