Significantly increased volumes of proppants have been placed in carbonate reservoirs such as the San Andres formation in the Howard Glasscock field in Howard County, Texas. The treatments that have been performed were accomplished using significantly smaller volumes of liquid. The treatment placement success can be attributed to the incorporation of recent advances in wireline inputs, perforating techniques, and computer design capabilities using accurate reservoir data. New blending equipment capable of computer interaction has also contributed to the ability to accurately schedule and place the higher proppant concentrations.
The use of the previously mentioned components have resulted in controlled fracture heights while taking advantage of in-situ stress barriers. The greater created fracture conductivity will allow for increased production of fluids once this waterflood has been completely implemented.
The Howard Glasscock San Andres field is located in Howard, Glasscock, Sterling, and Mitchell Counties in the Permian Basin of West Texas. It was discovered and has been producing since 1925. Structurally, the reservoir is an anticline trending generally in a easterly to westerly direction. Anomalies form small, localized traps in the younger beds. Reservoir rock consists of a fine, crystalline dolomite with anhydrite and shale stringers. The rock structure exhibits a heterogeneous pattern with layers of low to medium porosity. The drive mechanism is solution gas with a small quantity of water which is found mostly along the western slopes of the field. General properties of the reservoir are:
Oil............. 31.7 API gravity at 60F Water.................... Rw 0.09 at 75F Porosity................... Average 10.5% Permeability............... 0.1 md - 5 md
The completion of the latest infill drilling program has yielded wells with an average initial production potential of 34 BOPD and 30 BWPD. The majority of the most recently completed wells lack injection support thus the lower current production levels of 7 BOPD and 6 BWPD. The injection support for these producers was implemented in August and September, 1987. Anticipated waterflood performance is approximately 9 to 12 months. Previously undertaken waterflood operations have indicated that once injection support has reached its anticipated and calculated level of performance, the production levels in affected wells have been 30+- BOPD with 40+- BWPD.