Start your new year with access to a vast amount of knowledge. C&C Reservoirs’ latest content release includes 82 new and updated Reservoir Evaluation Reports from across the globe. This update includes a wide spread of global oil and gas analogues, including: 29 from Asia-Pacific, 15 from North America, 13 from the Middle East, 12 from Latin America, 7 from Africa, 5 from Russia and the Caspian, and 1 from Europe.
Highlights include:
Ain Zalah Field (Iraq) – Located in the Zagros Mountains, this field has an EUR of 295 MMBO and recovery factor of 20% with the oil trapped in a compressional anticline. Two carbonate reservoirs (Shiranish and Qamchuqa) are separated by a 600 m-thick interval of tight limestones but remain in pressure communication via faults and fractures. Production is mainly through fractures on the crest of the shallower Shiranish reservoir, with the oil pay being recharged from the deeper Qamchuqa. Aquifer influx in the 1969 resulted in rapid rise of the OWC and severed the connection between the two reservoirs resulting in a rapid decline in Shiranish reservoir pressure. Water injection was introduced to counter this decline. Production has been intermittent and by 2021 the field was producing at 3871 BOPD.
Akal Field (Mexico) – Situated on the Campeche Shelf, this is the largest field in the Cantarell Complex. The field has an EUR of 14.6 BBO and recovery factor of 46% with the oil trapped in an overthrusted duplex. The reservoir has a net thickness of 980 m with an oil column of 2200 m and consists of a fracture carbonate dolomitic breccia formed by the impact of the meteorite which created the Chicxulub structure at the end of the Cretaceous. The field was initially produced by solution gas drive with production initially peaking in 1982 at 960 MBOPD from 50 wells. Implementation of infill drilling, facility expansion and nitrogen gas injection led to a secondary plateau of 2001 MBOPD in 2003-05. Afterward, production sharply declined due in large part to a shortage of surface facilities to handle increased water and gas production.
Daqing Field – Xingbei Unit (China) – Onstream since 1966, the unit has a STOIIP of 3947 MMBO and an EUR of 2424 MMBO (61.4% RF), trapped in a heavily faulted inversion anticline. The Cretaceous Saertu-Putaohua-Gaotaizi reservoir comprises lacustrine-deltaic sandstones with an average porosity of 25% and permeability of 368 mD. The light oil is produced by solution gas and weak aquifer drive, supported by water injection from the onset of development. Phased infill drilling, polymer and ASP flooding, acidization, hydraulic fracturing, and artificial lift all contributed to the high recovery factor.
Gudong Field (China) – Onstream since 1985, the field has a STOIIP of 1851 MMBO and an EUR of 686 MMBO (37% RF). Trapped in a broad, faulted, buried-hill draping anticline, the main Miocene Guantao reservoir consists of fluvial channel sandstones with an average porosity of 32% and permeability of 1500 mD. The heavy oil is produced by solution-gas drive, aided by artificial lift and water injection. Step-out, infill, and horizontal drillings have all been implemented here, along with chemical and thermal EOR methods at various scales to improve recovery.
Margarita-Huacaya Field (Bolivia) – Located in the Chaco-Tarija Basin within the Sub-Andean Fold and Thrust Belt, this field has EURs of 3355 BCF and 107 MMBC, for gas and condensate recovery factors of 51% and 22%, respectively. At least five hydrocarbon pools are trapped in a thrust anticline in highly fractured Devonian sandstones with average gross and net pay thicknesses of 160 m and 100 m. Wells are drilled to >5000 m TVD and require high rates to be economic, thus favoring highly deviated wells to maximize contact with the reservoir. A two-year plateau of 636 MMCF/ day and 23,500 BCPD in 2015-16 was achieved with 11 producers. Subsequently offtake began a steady decline and in 2023 production was 424 MMCF/day and 11,200 BCPD.
Okume Complex (Equatorial Guinea) – Hidden in the Rio Muni Basin in water depths of 30-700 m, this group of 5 fields holds a total EUR of 309 MMBO with recovery factor of 24%. Oil pools are stratigraphically trapped in turbidite channel-levee and overbank complexes within two submarine canyons, with over half of the STOIIP in the Elon Field. The Campanian reservoir is highly heterogeneous with connectivity influenced by the degree of vertical channel amalgamation which increases in the more confined upper canyon. Reservoir quality is high, averaging 4 D permeability in channel sands with up to 25 D in some thief zones. Infill drilling has been guided by 3-D/4-D rock physics and AVO inversion. Other techniques used to improve recovery include waterflood and injection of thermally-activated polymers to reduce permeability in thief zones in an attempt to divert injected water into unswept zones in the reservoir. By end-2021 249 MMBO had been produced.