摘要:

The Orinoco Oil Belt of Venezuela is a very extensive, non‐discrete, crude‐oil producing area located along the southern third of the Maturín (Eastern Venezuela) basin, north of the Orinoco River and the Guayana Shield. It extends due westwards from Puerto Ordaz for 460km; the main producing areas, defined on the basis of productivity and magnitude of crude oil in‐place, cover 13, 600 sq. km. There are no significant surface indications of petroleum anywhere in the Belt. The first well drilled wasLa Canoa‐1in 1936, initiating a stage of exploration which ended in 1967 with publication of a preliminary evaluation of the potential reserves; the Ministry of Energy and Mines, then of Mines and Hydrocarbons, and the State oil companyCorporación Venezolana del Petróleo (CVP) completed a second stage of exploration in 1977; Petróleos de Venezuela and its operating companies then drilled 669 wells in five years (1979–83) totalling 643,000 m with 5.5 MM** m of logs, and shot 15,000 km of seismic lines at a cost of $US 615 MM, an effort conservatively estimated as having taken 2,500 man‐years. The main producing areas are, from east to west, Cerro Negro, Pao, Hamaca, San Diego, Zuata, and Machete. Petroleum characterisation in the Belt is based on the study and analysis of 288 samples. Viscosity (dynamic) of the crude oils at reservoir conditions ranges from 2,000 to 7,000 m Pa.s (cp)†.Production rates average 25 cu. m/d(160 b/d), increasing fourfold after steam stimulation. At the end of 1985, production was 13,000 cu.m/d(80,000b/d)†, from the Cerro Negro and Hamaca main producing areas. Operating costs are similar to those in other heavy‐crude oilfields in the basin. The volume of crude oil in‐place is estimated to be 187.8 B cu. m (1,181 B brls), which makes the Orinoco Oil Belt the largest crude oil accumulation in the world. Proved reserves are 4.161 B cu. m (26.170 B brls). and unproved reserves 14.822 B cu. m (93.230 B brls). Investigative activities are underway, particularly in the Cerro Negro and San Diego producing areas.In subsequent papers of this thematic survey, A. Isea presents a geological synthesis of the Orinoco Oil Belt; G. Don Kiser discusses the exploration results of the Machete area; A. Santos and L. Frontado describes the reservoir geology of the Cerro Negro steam‐injection area; and A. Vega and I. de Rojas summarise exploration re

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00204.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The Orinoco Oil Belt, considered to be the largest hydrocarbon accumulation in the world, is located on the southern border of the Eastern Venezuela basin. The stratigraphic column of the area includes rocks of Pre‐Cambrian to Recent ages, but more than 90% of the crude oils are found in Miocene sediments.Three transgressive‐regressive cycles with wide regional distributions are recognised in the Tertiary system: Cycle 1 includes the La Pascua, Roblecito and Chaguaramas formations of Oligocene age; and Cycles 2 and 3 include the Officina, Upper Chaguaramas and Freites formations of Miocene age. Within the cycles, five lithostratigraphic units are defined, and a sedimento logical model for Units I and III is consequently established, recognizing north‐orientated, wave and tide‐influenced, prograding deltas.Tensional tectonics characterize the area as having two structural provinces, separated by the Hato Viejo fault system: the Eastern Province, characterized by a transgressive sequence overlying the Pre‐Cambrian basement; and the Western Province, where the Tertiary unconformably overlies Cretaceous and Paleozoic sediments. Hydrocarbon accumulations in the Orinoco Oil Belt predominantly occur in stratigraphic traps, but are controlled by regional structures.Four types of crude oils are identified, with density values between 8.5 and 13° API. The volume of oil in‐place in the Orinoco Oil Belt totals 187,897 MM†cu. m(1,181 B brl). The largest accumulations are found in the s

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The Machete Area covers 23,610 sq. km (9,116 sq. miles), of the Orinoco Oil Belt in Venezuela. Based on exploration data from 30 old and 74 new wells, the volume of heavy and extra‐heavy crude oil in‐place is estimated to be 40 B cu. m (255 B brl), ** of which 4 B cu.m (22.5 B brl) are in future potentially recoverable; some 62 B cu.m (2.2 T cu. ft) of natural gas may also be recovered. Drill depths to the base of the producing section vary from 518 to 1,220 m. Net oil sand reaches 116 m in thickness for Tertiary reservoirs, and 46 m for Cretaceous ones. The crude oils average 1,022 kg/cu.m (7° API), and have a content of sulphur and various metallic elements typical of similar crudes; viscosities are slightly higher than in the rest of the Belt.Production rates of up to 20 cu. m/d (140 b/d) on pump may be increased ten‐fold by steam injection. Dry natural gas flows of 450 cu.m/d are common. The principal geological factors controlling the Machete accumulations differ from those in adjacent areas, and consist of the subsurface extension of the El Baúl Arch which has controlled sand‐shale facies, pinch‐out lines and structural‐stratigraphic trapping of the heavy crude oils an

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Exploration activity in the Zuata area within the Orinoco Oil Belt in Venezuela has included the drilling of 161 wells and the recording of 3,000 km of seismic lines. Based on these results, a productive area of 9,200 sq. km has been defined, containing 79.3 B cu.m. (499 B brl)† of crude oil in‐place, with densities ranging from 1.021 to 0.934 g/cu.cm (7–20 °API).The principal productive sands are of the Tertiary Officina Formation, deposited during a transgression which occurred in the Miocene. A distinctive feature of the productive formation is its progressive onlap against older rocks (Cretaceous, Paleozoic or Pre‐Cambrian) in a southerly direction which, together with overlying shales, provide the trapping mechanism for the oil which migrated from the north. The productive sands were deposited in a fluvial to coastal plain with deltaic developments. The sands are unconsolidated and fine‐ to very coarse‐grained, with an average porosity of 34% and a permeability of 7μm2(7D). The structure is a monocline dipping 0.5° to 2° to the NE, and the trapping mechanism is principally stratigraphic.In the 134 producers, 300 tests were completed which resulted in an average production of 25 cu.m/d (160 b/d) per well by beam pumping without dilution or heat. Subsequently, a steam cycle of 5,000 metric tons was injected into 16 wells; production increased to some 200 cu.m/d (1,250 b/d) per well.For future development, a Priority Area has been selected: this Area covers 3,500 sq kin, and contains 40.5 B cu.m (255 B brl) of crude oil with a density range of 1.014 to 0.993 g/cu.cm (8–11°API). The oil is at an average depth of 610 m, and the average net oil‐sand thickness is 60 m. The oil‐sand is generally divided into three zones separated by shales, and the gross productive thickness is some 110 m.Similar to Maraven ‘s experience in the oilfields of the Bolivar Coast in Western Venezuela, it may be expected that reservoir compaction will occur, and will be efficiently activated by steam‐soak or “huff and puff’. Based on core compressibility measurements, a recovery factor from compaction drive and solution gas treatments could reach 12 % of the oil in‐place. Under this premise, the Priority Area could have a potential recovery of 4.9 B cu. m. (30.6 B brl), which could support a production of 160,000 cu.m/d(1MM b/d) for 100 years. Any follow‐up steam drive can be assumed to recover at least an additional 10% of the oil in‐place.A Conceptual Development Plan based on clusters, inclined wells (due to the shallow depth) and steam soak has been proposed, and will be validated by a pilot tes

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Several very favourable areas were defined in the Orinoco Oil Belt, after intensive geological, exploration and evaluation studies were conducted between 1970 and 1982.The Cerro Negro project area was selected as the first to be investigated. Subsequently, a small part of this area, covering 5.9 hectares (14.5 acres), and containing about 159,000 cu. m (1 MM** brl) STOIIP of 8 to 11° API, in the objective sand, was chosen in which to initiate the Cerro Negro Steam Injection Project (PIVCN), which is now under development. The Early Miocene Oficina Formation, whose sands constitute the reservoir rock, show a fluvial to deltaic sequence at the base (Morichal Member), a transgressive sequence in the middle section (Yabo‐Jobo Member), and finally a closing prograding sequence (Pilón Member) at the top. Qualitative analyses of the sedimentary section indicate optimum textural, mineralogical and depositional conditions which determined the final configuration of a sequence with excellent reservoir porosity and permeability. The distributary channel facies show the best petmphysical parameters †, (φ35%, φSo:* 30%, Sw: 5%, Vsh:* 6%, K: 50,000md). These values yield an oil content of 2,300 STB/acre‐ft. in the objective sand, namely unit 0–15 of the Morichal Member. Oil entrapment is primarily stratigraphic, and no oil/water contacts or gas caps have been found in the PIVCN project or in the whole of the much larger Cerro

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

In petroleum geology, the widespread practice of mapping lateral variations of lithology within the confines of general formations instead of time‐zones inevitably provokes differences of opinion over the scope and definition of stratigraphy. These differences can be traced back to a blending together of the separate concepts of two founders of geology, William Smith and Abraham Gottlob Werner. Werner originated alithologicdefinition of rock formations; also, he taught the concept that the relative ages of formations could be determined by fossils. Smith contributed to the development of stratigraphy with his invention of the term ‘stratigraphical’, which referred to the occurrence of specific fossils and rock types within units ofstrata.The outcome of reconciling these different concepts has been that geologists have used Smith's basic terminology, the principle of superposition, and the formational units of stratigraphy, but have redefined them to accord with Werner's theory of Earth history. These changes in definition have confused the concept of stratigraphy, because they misrepresent its spatial form evident from ‘regularity in stratal order’. This general law was accepted by William Smith as the basis for his stratigraphical arrangement of rocks and fossils, which in the practice of correlating rocks by superposition led to a stratigraphic system of strata and the economy of a single stratigrap

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The Bejuco area (4,200 sq. km) is in Eastern Mexico, south of the Tampico District. Ammonites, gumma‐neutron logs, and lithologic samples of 65 exploratory wells were studied in order to construct structural maps at several levels within the Neocomian and Upper Jurassic. The purpose of this work was to study the stratigraphy, paleogeography, erosional unconformities, and also the occurrences of hydrocarbons of Late Jurassic‐Neocomian age.In most of the area, the Huasteca series of Middle‐Late Jurassic age lies discordantly on rocks of continental facies. In a few places in the NW, south, SE and centre, the Huasteca overlies intrusive rocks, and in the NW, the Huasteca also overlies metamorphic rocks in a few localities.Marine sedimentation commenced at the beginning of middle Callovian time in the eastern part of the region. Several successive periods of transgression took place: (1) during the early Kimmeridgian (central and western area); (2) the late Tithonian (north); and (3) the late Hauterivian (southern part).An important geological phenomenon is the submarine erosional unconformity which represents the Neocomian‐Eocene time‐interval. The area underlain by this unconformity has a delta shape and extends from the SW to the east. This is the precise area of the Bejuco paleocanyon. The unconformity today lies at a depth of between 1,200 and 2,900 m.The presence of hydrocarbons in either Tithonian or Neocomian rocks is controlled by structural traps, and in some places by combinat

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Reflectance values were determined for selected huminite (eu‐ulminite, eugelinite and phlobaphinite) and liptinite (cutinite and resinite) samples from a 560—m thick unit of lignitic‐sub‐bituminous coals in the Hat Creek coal deposit of British Columbia.The objective of this study was to determine: (a) the reflectance differences between macerals, especially those of the humocollinite subgroup, and to determine the possibility of the use of the reflectance of the humocollinite maceral as an indicator of rank; (b) the trend of reflectance of humocollinite macerals (kerogen Type III) with depth; and (c) comparison of the reflectance trends of resinite and cutinite (kerogen Type II) with that of the humocollinite macerals (kerogen Type III).Two types of corpohuminite were found in the same coal: Type 1 phlobaphinite with reflectance lower than eu‐ulminite, and Type 2 phlobaphinite with reflectance higher than eu‐ulminite. Reflectance of eugelinite was higher than corpohuminite and eu‐ulminite.Kerogen Type III (huminite) in these coals consists of: a) low‐reflecting hydrogen‐rich phlobaphinite Type 1; b) phlobaphinite Type 2 and eu‐ulminite B. with intermediate reflectance and hydrogen content; c) relatively high‐reflecting and perhaps hydrogen‐poor eugelinite. The reflectance of all these macera

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00212.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0141-6421    

DOI:10.1111/j.1747-5457.1987.tb00213.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY