SOUTH COWDEN FIELD:GRAYBURG FORMATION HIGH-FREQUENCY CYCLE CORRELATION MOSS UNIT: DIP SECTION W E Sun Moss # 157 3,700 ' Unocal Moss Unit # 9-17 2,700 ' Unocal Moss Unit # 16-14 3,500 ' Unocal Moss Unit # 8-12 3,400 ' Unocal Moss Unit # 6-16 2,300 ' Unocal Moss Unit # 6-20 4400 Queen 1 Queen Formation Sun Paul Moss #157 E 4200 E 4200' Grayburg 4500' 4B 4500 4500' F 4500 4250' 4600 Grayburg Fo 4A 4550' F 4500 4500 4550' F0 F1 4300 Grayburg 4300' 3 4600' F2 F3 F1 4600 Hdgrnd G 4600' 4600 4350' F2 4650' 4700 Grayburg 2 4600 F3 4600 4650' 4400 4400' H 4700' 4700 G Grayburg 1 4700' 4700 4800 Guadalupian 4700 13 San Andres 4750' Formation South Cowden Grayburg Field: Dip Section H Interpretation by S. C. Ruppel Amoco Midland Regional Farms Unit South Cowden Field See Ruppel and Bebout (2001) for more complete details. 40 Constructed by Milton Kwong and Mike Ye Sequence Framework of 41 UNOCAL 42 Moss Grayburg Unit Texaco North Cowden 37 Overview: South Cowden Grayburg Field is developed at the edge of the Glorieta terminal platform margin over a middle San Andres, 5 38 4 basin-restricted, progradational wedge. The structural axis of the field coincides with the southeast-trending axis of this wedge; Grayburg 44 facies patterns indicate that deposition was also controlled by this feature. This cross-section, presented at a standard 5”=100’, extends 43 from the updip, interior part of the field near the ancestral Glorieta margin, along the structural axis and then downdip to the east. Well- EXPLANATION A' Amoco 3-D 48 4 displayed in this section are (1) the overall proximal to distal thickening of the Grayburg section, (2) four high frequency sequences that are Grid 47 part of a longer term transgressive-regressive event, and (3) major basinward facies offset at the base of the Queen Formation. 5 Explanation Midland A Lower San Andres 6 FINA Stratigraphic Units: Although not readily apparent in outcrop, four distinct high frequency sequences are delineated in South Cowden Production Amoco North Colbert 1 Unit Field and along the eastern margin of the Central Basin Platform (CBP). Cowden 9 2 FINA 60 Emmons Basin 8 Mudstone Guadalupian 14A HFS (Grayburg 1): Two cores in the field demonstrate that the basal Grayburg consists of thin backstepping middle Grayburg OXY Rhodes 7 Unit platform facies, which are locally capped by tidal flats, that build into a thick sheet cracked, pisolitic tidal flat complex at the top of the first Production Cowden 12 6 sequence updip. Tepee tidal flat complexes such as this are most commonly developed during long term sea level rise due to major 11 1 40 increases in accommodation. Thin siltstone cycles at the base of the section suggest remobilization of clastics accumulated during Goldsmith 17 Tidal Flat lowstand. 10 Grayburg and San Andres OXY Johnson 18 M Ft Outer Ramp and Basin Unit 13 4 V.E. = 12.5 X Guadalupian 14B HFS (Grayburg 2): Grayburg 2 documents continued backstepping and flooding of the platform reflected by fusulinid 1 20 facies overlying the top of Grayburg 1 tidal flat complex. The aggradational ooid-peloid grainstone complex at the top of this sequence is Arco/Conoco Siltstone/Sandstone N. Foster Phillips Core extensive over the structural axis and is capped by tidal flat facies updip. Both the grainstones and the fusulinid facies are locally South Cowden Peloid-Ooid Grain-Dominated Packstone-Grainstone Grayburg/San Unit productive (predominantly along the downdip margin of the field) where sulfate has been leached. Andres Platform Odessa 0 0 Guadalupian 15A HFS (Grayburg 3): Maximum flooding of the platform is represented by high frequency, laterally continuous, siltstone- Amoco Clear Fork San Andres/Grayburg based fusulinid wackestone cycles at the base of Grayburg 3. This flooding event is recognizable across much of the Permian Basin. The Cross-section South Foster presence of siltstones in this part of the section again supports their interpretation as remobilized eolian clastics. Fusulinid cycles at the Lines Platform Margin Depositional Axis base of Grayburg 3 exhibit relatively low permeability and act as a flow baffle across much of the reservoir. Reservoir-scale Ft core-based Unocal Fusulinid Wackestone Harper 3D Guadalupian 15B HFS (Grayburg 4): Aggradational highstand deposits of Grayburg 4 consist of well-developed high-frequency cycles of Regional log-based 0 1000 2000 F Correlation Markers pelloidal wackestones to grainstones. Cycles generally contain mud-dominated bases and grain-dominated tops but display lateral changes in texture consistent with basinward progradation. Much of the production from the Grayburg is associated with zones of Peloid Wackestone-Packstone Sequence Boundary carbonate alteration and sulfate dissolution in this sequence. Highest permeability is in many cases associated with mud-dominated facies, 3-D Grid Bureau the grain-dominated rocks remaining tightly cemented. Unocal/Fina/ 0 300 600 High-frequency Cycles Phillips S. Cowden of N Intraclast Packstone-Grainstone Guadalupian 16, 17 HFS (Queen): The base of the Queen is marked by a major basinward offset in facies to sandstone-based and tidal Economic flat capped inner platform cycles. Reservoir potential is limited to downdip where cycles bases become more carbonate-rich. Meters Penwell Geology 0 5 miles.