Changes

}}

}}

Arecuna field is in the prolific Faja [[heavy oil|heavy-oil]]-producing region of eastern Venezuela,<ref>Audemard, F. E., I. Azpiritxaga, P. Bauman, A. Isea, and M. Latreille, 1985, Marco geologico del Terciario de la Faja Petrolifera del Orinoco de Venezuela: 6th Congreso Geofisica, Venezuela, v. I, p. 70-109.</ref><ref>Burkill, G. C. C., and L. A. Rondon, 1991, Steam soak pilot project in the Zuata area of the Orinoco belt, Venezuela: Fifth U.N. Institute for Training and Research International Conference for the 21st century, v. 2, p. 105-112.</ref> which is in its earliest stages of primary recovery. Defined simply by the limits of the 100-km² Arecuna 3-D seismic survey ([[:File:Methods14ch08f01.jpg|Figure 1]]), Arecuna field contains an estimated 2.8 billion barrels of original oil in place, but to year-end 1996, it had produced only 2.2 million barrels of 7.5-16176.jpg (425 bytes) API oil from 35 producing wells. Initial completions were all from vertical wells, and typical flow rates, which were on the order of 200 barrels of oil per day (BOPD), were subeconomic. Moreover, some of the wells were already producing at 20-40% water cut.

Arecuna field is in the prolific Faja [[heavy oil|heavy-oil]]-producing region of eastern Venezuela,<ref>Audemard, F. E., I. Azpiritxaga, P. Bauman, A. Isea, and M. Latreille, 1985, Marco geologico del Terciario de la Faja Petrolifera del Orinoco de Venezuela: 6th Congreso Geofisica, Venezuela, v. I, p. 70-109.</ref><ref>Burkill, G. C. C., and L. A. Rondon, 1991, Steam soak pilot project in the Zuata area of the Orinoco belt, Venezuela: Fifth U.N. Institute for Training and Research International Conference for the 21st century, v. 2, p. 105-112.</ref> which is in its earliest stages of primary recovery. Defined simply by the limits of the 100-km² Arecuna 3-D seismic survey ([[:File:Methods14ch08f01.jpg|Figure 1]]), Arecuna field contains an estimated 2.8 billion barrels of original oil in place, but to year-end 1996, it had produced only 2.2 million barrels of 7.5-16° API oil from 35 producing wells. Initial completions were all from vertical wells, and typical flow rates, which were on the order of 200 barrels of oil per day (BOPD), were subeconomic. Moreover, some of the wells were already producing at 20-40% water cut.

==Geologic architecture of the Arecuna field==

==Geologic architecture of the Arecuna field==

The sandstone-dominant lithology, broad sandstone distribution ([[:File:Methods14ch08f05.jpg|Figure 5]]), and widespread blocky bedding architecture ([[:File:Methods14ch08f06.jpg|Figure 6]]) provide evidence of river flow that was weakly confined across a broad alluvial plain, although there are well-developed interaxial belts that are sandstone poor. Unconfined bed-load fluvial systems of the Canterbury Plain, New Zealand ([[:File:Methods14ch08f07.jpg|Figure 7]]),<ref>Leckie, D. A., 1994, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0078/0008/1200/1240.htm Canterbury Plains, New Zealand: Implications for sequence stratigraphic models]: AAPG Bulletin, v. 78, no. 8, p. 1240-1256.</ref> perhaps provide the closest modern analog to Merecure Unit A, although these modern systems principally carry boulders, gravel, and very coarse sandstone.

The sandstone-dominant lithology, broad sandstone distribution ([[:File:Methods14ch08f05.jpg|Figure 5]]), and widespread blocky bedding architecture ([[:File:Methods14ch08f06.jpg|Figure 6]]) provide evidence of river flow that was weakly confined across a broad alluvial plain, although there are well-developed interaxial belts that are sandstone poor. Unconfined bed-load fluvial systems of the Canterbury Plain, New Zealand ([[:File:Methods14ch08f07.jpg|Figure 7]]),<ref>Leckie, D. A., 1994, [http://archives.datapages.com/data/bulletns/1994-96/data/pg/0078/0008/1200/1240.htm Canterbury Plains, New Zealand: Implications for sequence stratigraphic models]: AAPG Bulletin, v. 78, no. 8, p. 1240-1256.</ref> perhaps provide the closest modern analog to Merecure Unit A, although these modern systems principally carry boulders, gravel, and very coarse sandstone.

Table 1. Comparison of the stratigraphic nomenclature of this study with existing Corpoven sandstone nomenclature.

'''Table 1.''' Comparison of the stratigraphic nomenclature of this study with existing Corpoven sandstone nomenclature.

====Oficina Unit A====

====Oficina Unit A====

The faulting pattern suggests that there were two main episodes of extension. The north-northwest-south-southeast-oriented fault set appears to be the oldest and was caused by regional extension of the basin (including basement). Bending at the basin rim probably caused the younger east-west fault set, but regional right-lateral strike-slip motion caused by collision of the South American and Caribbean Plates is superimposed on the younger fault set. The large structural low on the south side of the main east-west fault provides evidence of right-lateral shear caused by extensional forces at the fault bend ([[:File:Methods14ch08f14.jpg|Figure 14]]). Several of the small normal faults appear to have been displaced by left-lateral shear, but this apparent displacement is misleading because the dip-slip movement is much greater than the strike-slip motion.

The faulting pattern suggests that there were two main episodes of extension. The north-northwest-south-southeast-oriented fault set appears to be the oldest and was caused by regional extension of the basin (including basement). Bending at the basin rim probably caused the younger east-west fault set, but regional right-lateral strike-slip motion caused by collision of the South American and Caribbean Plates is superimposed on the younger fault set. The large structural low on the south side of the main east-west fault provides evidence of right-lateral shear caused by extensional forces at the fault bend ([[:File:Methods14ch08f14.jpg|Figure 14]]). Several of the small normal faults appear to have been displaced by left-lateral shear, but this apparent displacement is misleading because the dip-slip movement is much greater than the strike-slip motion.

==References==

==References==