Petroleum Potential of the Espirito Santo Basin - Term Paper Example

Petroleum Potential of the Espirito Santo Basin (BMS-2 Block) Espirito Santo Basin as identified itself with two fundamental sources of rock systems including the Alagoas Shale and the JiquiaShales. The AlagoasShales are identified with the Aptian age evaporitic environment while the JiquiaShales are found on the upper Neocomian age that is deposited along the continental lagoonal environment (Katz and Mello, 2000; Pg. 182). notably, the open Upper Cretaceous marine tertiary slope sediments that are believed to previously have been potential source of these system rocks; however, the place is currently not regarded as the constitute source sections of these rocks. In should be noted that numerous studies on the oils along the Espirito Santo Basin have indicated that to some degree, the degradation has been the most probable source of these rock systems and they are generated by bacteriological attacks (Ries et al. 2007; Pg. 159). Other source of information concerning oil production along this coastline is the use of gas chromatography and mass spectrometry. These two methods of liquid chemical analyses have provided a means through which oil biomarker information can be retrieved. In fact, the two methods of analyses are usually applied in line with isotopic studies. Inclusively, these methods of chemical analyses provide effective, efficient, and reliable oil/rock and oil/oil correlations. The basin is a source of oil and the main sources of such oil production along Espirito Santo Basin include Alagoas sands that are found below the Aptianevaporites. The other major source within the Espirito Santo Basin is the reservoirs of the tertiary upper cretaceous. The proposed migration of oil geometry from the source systems rocks to the reservoirs of Alagoas usually follows a simple mechanism and this is pegged on the fact that both the reservoir rocks and source rocks have relatively close stratigraphic relationships. The structures provide entrapment at all levels of the anhydrite beds of the Alagoas that in turn provides the seal. Presently, the Alagoas source rocks are considered lie on the generative depressions that are located few kilometers east of (Rio Itaunas, Sao Mateus) oil accumulations sites that are already discovered (Ries et al. 2007; Pg. 176). This distance is considered to be relatively short. In the case of Tertiary-Upper Cretaceous oil accumulations turbiditic reservoirs including FazendaCedro and LagoaParda, Jiquia mature source rocks are usually exposed through erosion especially along the submarine canyons bottoms along with the turbidites deposits. The coalescent, complex, turbiditic sand bodies usually act as the systems of hydrocarbon collection pools that are usually formed through stratigraphic or structural closures. The Cacao offshore field is highly related to the paleogeomorphic closure that is located at the submarine canyon bottom. The oil is usually trapped in the shales slopes in the Upper Cretaceous marine defining the Albian reservoirs capped. This oil formation is best explained by the migration of geometry including the subcrop within the Jiquia mature rock sources found or located below the pre- Alagoas. This collection and attachment of the oil rock sources is defined by high degree of unconformity that is associated with an upward oil migration through into the sandy and permeable sections of Alagoas. This movement of oil is often facilitated with the Alagoas anhydrite absence within this particular section. Finally, it is worth noting that the seafloor topographic burial also leads to occausional but significant formation of structural traps especially within the mass-transport deposits (MTDs) sections. Introduction The government of Brazil created AgênciaNacional do Petróleo (ANP) in the year 1996. This move opened and enlarged the Brazilian upstream market competition. Since the creation of ANP, Brazil has have intense and determined focus on the exploration of renewable energy and has initiated a farm out partnerships alongside long term exploration programs all of which have resulted from bid rounds. Notably, all these initiative resulted to the capital investment of a new exploratory phase that initially concentrated in the eastern part of Brazil including Espirito Santo, Campos, and Santos basins (Ries et al. 2007; Pg. 285). On the other hand, the ANP initiated acquisition of regulated geophysical data that in turn resulted into numerous acquisitions of high quality data that allow modern multiclient seismic surveys. Notably, the Brazilian offshore utilizes the modern 2D and 3D seismic data processing and acquisition technologies. Nonetheless, both the offshore and onshore seismic data handling have improved quality data acquisition and processing; thus, has reduced the turnaround time in data management as well as improving quality of data (Hilyard,2008; Pg. 414). Some of the improved data handling technologies include extremely long streamers that measure up to eight kilometers in length, higher order normal moveout pre stack time migrations systems, and large data acquisition footprints. These systems have been employed more increasingly in the seismic data handing in regards to oil exploration in the Brazilian oil exploration basins. These application have since led to improved seismic dataset images; hence, helping in effective study and exploration deep water reservoirs including pre-salt rift and salt source rock sections. The main Brazil’s offshore province that produces oil in the deep waters includes Campos Basin that attributes to nearly 70 percent of the Brazilian daily oil output (AAPG Convention, 2000; Pg. 86). However, Brazil also explore oil in its main oil fields that include Roncador, Espadarte, Marlim, Albacora, and Caratinga all of which constitutes to slightly more than 50 percent of the Brazilian proven main oil field reserves. Most of the reservoirs deep water fields are considered turbidites and they range from Upper Cretaceous to Miocene in terms of age (Hilyard, 2008; Pg. 271). Notably, Espirito Santo basins among other offshore basins are the Brazilian known offshore basins producing oil. However, Espirito Santo, Ceará, Santo, South-Bahia, Potiguar, and Sergipe-Alagoasamong other offshore basins only cater for a small percentage of the Brazilian daily oil production. Regional Setting The Espirito Santo to the vitoria high to the south and Abrolhos volcanic complex to the north. The Vitoria High is associated or attached to the Campos basin while Abrolhos volcanic complex is associated with Cumuruxatiba Basin (AAPG Convention; 1994; Pg. 174). The volcanic high region links to the offshore Rio de Janeiro that separates Campos from Santos basin. The Espirito Santo has a total area of 129,429 square kilometers with the onshore area of 12,417.8 square kilometers and offshore area of 117,012.3 square kilometers. Geologic Setting Fig: 1. showing the position of the Espirito Santo among other onshore and offshore basins (Cooper, 1990; Pg. 61) The Espirito Santo basin is a wide coastline that engulfs the Cocao field that is situated along the eastern coast of Brazil. Moreover, to the south the place is found 47km off Sao Mateus City and the 7 km from the coastline. The Espirito Santo basin extends 19 m into the water (Cooper, 1990; Pg. 61). The Espirito Santo basin field comprises an area of nearly 3000 square kilimeters on the onshore and nearly 10,000 square kilometers offshore. These areas are measured within a bathymetric contour of 200m; however, they extend beyond deep waters to the South Atlantic Ocean. The onshore basin oil fields are found on four geologic provinces including the Sao Mateus platform that is located on the northern part of the Espirito Santo basin. It engulfs an area of 1500 square kilometers. The FazendaCedropaleocanyon that engulfs an area of 480 square kilometers; the Regenciapaleocanyon that has an area of nearly 200 square kilimeters, and the Ragencia platform that is surrounded within an area of approximately 900 square kilometers (Cooper, 1990; Pg. 62). The Espirito Santo basin onshore fields aregeologically located for effective and efficient petroleum exploration thereby making the area around the basin a perfect point of gas exploration. Additionally, their area coverageis perfect for the locating and effective movement of machineries. The Espirito Santo basin’s exploration was initiated in the mid-1950s and 825 wells have been drilled on the onshore of the basin with 542 infill wells and developments and 283 exploratory. The basin has since supported exploration of 91 wells on its offshore activities with 10 development wells and 81 exploratory wells. It is worth noting that Petrobra has supported all these development and exploration activities including drilling, seismic, and interpretation services at the Espirito Santo basin (South American handbook, 1924; Pg. 73). Notably, until the present activities at the Espirito Santo basin, 33 hydrocarbon accumulations have been yielded in the onshore points and one on the offshore of the Cacao fields. The Cacao offshore field is located centrally to the Espirito Santo basin such that the upper Cretaceous FazendaCedropaleocanyon forms an outstanding geological feature. The interpretation of the field indicates that it is typically trapped in a paleogaomorphic manner thereby forming paleohigh erosion. This sculpture is a distinct paleocanyon feature of the eastern offshore edge of Espirito Santo basin (Brazil handbook, 1998; Pg. 97).FazendaCedropaleocanyon onshore portion is also a significant portion of Espirito Santo basin since it has hasturbidite sandstones that interbedded with shale within which one gas field and numerous oil fields have been since discovered. It is also worth noting that these fields are filled up with paleocanyons. Additionally, FazendaCedro supports an oil field that is related to the paleotopography geological features that are similar to those found in the Cocao field. The Tectonic History The exploration Espirito Santo basin started effectively from its offshore in the early 1950s. The activities at the basin started with gravimetric, magnatometric and seismic surveys. These surveys where followed by the 1959 stratigraphic tests that were followed by the first drilling (Deutsche PhysikalischeGesellschaft, 1963; Pg. 131). Nonetheless, the geological factors and the tectonic history greatly influenced the marine and coastal ecosystems on the South America coastline. The Phanerozoic tectonic history of the continent is dominated mainly by its segregation from the continent of Africa. The same history is still influenced by the uplift of mid- Miocene of the Andes. The South America is tectonically divided into two main parts including the Andean chain that is located to the west and the stable vast platform located to the east (Organization for Economic… et al. 2006; Pg. 276). The latter consist of shallow sedimentary rocks and Precambrian rocks that are nearly exposed to the surface. The exposure of these rocks makes exploration easy and convenient. The Espirito Santo basin is part of pacific Andean coastline that is characterized mainly by high relief and relatively narrow shelves that boarder deep trench and a small drainage basin with a rapid vertically moving towards the coast. The coastline is also characterized by low relief, extremely large drainage, broad shelf, and alluvial fans Atlantic coastline. Nearly 93 percent of the today’s drainage system of South America is located to the Caribbean and far from the Andes Atlantic; nonetheless, it provides the perfect example of the contemporary continent scale drainage system that is controlled by the plate tectonics. The main historical element of the South America tectonic is that it broke up from the western Gondwana and led to aborted rifts that characterize the north eastern onshore regions of Brazil. Other features of these drift include numerous rifts that later evolved to form among the largest passive basins in the world including Espirito Santo basins (Organization for Economic… et al. 2006; Pg. 375). Other basins that were formed due to this continental rift evolution include Campos, Pelotas, Santos, and Mucuri among others. These basins especially, Campos, Santos and Espirito Santo basins are mainly characterized be shallow platforms that are filled with tertiary sediments that usually overlap the Precambrian basement specifically to the east of the rift (Price, 1989; Pg. 761). The Espirito Santo basin is also characterized by deep rift trough that is filled with Neocomian and Aptian sediments. At some points, the Espirito Santo basin is characterized with thinner rift sequences that are mainly located on the slope on the boundary formed between oceanic and continental crust that are characterized by sedimentation especially along the continental margin. Fig. 2: Main Brazilian physiographic marginal features(Price, 1989; Pg. 761) Stratigraphy The Espirito Santo basin was mainly filled through two main processes including sedimentation and volcanic processes. Salts tectonics are in the form of thin sub-horizontal layers that are found in the proximal regions next to fault boundaries or hinge lines; these features correspond to the refilling of the rift troughs thereby making them easy for exploration of any kind including exploration of salt and oil as well as gaseous products. For instance, the sedimentation of the Espirito Santo basin troughs on the extensional tectonics and salt extends towards the deep waters and the slope. These elements are noted to dominate the tectonic architecture (Deutsche PhysikalischeGesellschaft, 1963; Pg. 155). The compressional tectonics have ever since the formation of the basins been driven by gravity that pushes nearly every element and resource between oceanic and continental crust towards the boundary. Moreover, the subsidence thermal phase usually leads to thick depocenter in most of the basins including the Espirito Santo basin thereby making drilling process easy and effective. Furthermore, this feature concentrates petroleum, oil and gas in certain areas making exploration easy. However, sedimentation features sometimes lead to abrupt tilting of the rift of the blocks to shelf edges or to the oceanic crust defined by deep water regions (Roberts and Bally, 2012; Pg. 178). Each drift has its own disadvantages and advantages to oil and gas exploration. The Espirito Santo basin’s tectonic history is also associated with volcanic activities thereby forming its additional Espirito Santo basin’s refilling mode. For instance, the Cumuruxatiba and Espirito Santo basins especially on the westward are characterized by prolonged volcanic features especially in their oceanic crust. Notably, the volcanic complexes including the Royal Charlotte and Abrolhos are indication that these basins have larger portions of Tertiary basaltic rocks (Norsk Petroleum Sforening, Doré, and Sinding-Larsen, 1996; Pg. 671). These features among others are clear indication of concentration of oil and gas among other valuable natural resources including salt to locations that makes them easy to explore due to the structure and nature of the underlying rocks. Additionally, the refilling of these basins especially the Espirito Santo basin makes it effective for the exposure of the oil and gas to the upper level of the crust; thus, making the same easy to explore. Petroleum Elements within the Espirito Santo Basin Petroleum system usually engulfs series of elements including active pod of source rock with all other gas and oil related elements including oil and gas accumulation. Nonetheless, the fundamental elements indicating the presence of petroleum in the basin include reservoir rock, source rock, overburden rock, and seal rock. Nonetheless, all these elements must be place in space (basin) and time within which the extraction processes are required for the petroleum accumulation (Sinding-Larsen, and Wellmer, 2010; Pg. 251). Therefore, in the case the Espirito Santo Basin, the availability of the sediment rock reservoir is a clear indication that the basin is a petroleum reservoir. Additionally, some early investigation indicated the presence of hydrocarbon that accumulated within the basin (Roberts and Bally, 2012; Pg. 678). Notably, regardless of the amount of the hydrocarbon in reservoir, such presence indicates the presence of petroleum in such basins. Therefore, the presence of hydrocarbon in the Espirito Santo Basin is a clear indication of oil and gas in the basin. Moreover, the seal rocks at the basin are horizontally placed. Notably, sedimentary basin is not the only source rock, the availability seals and reservoirs; however, the entire sedimentary column place a vital decisive and active role in the entrapment, genesis, and conservation of oil and gas in the Espirito Santo Basin. Finally, it is worth noting that these sedimentary columns within the basin forms potential oil and gas traps with the Espirito Santo Basin (Glover and Economides, 2010; Pg. 95). It should be noted the source rocks, seal intervals, and reservoir are all indicated within the seismic data obtained from the Espirito Santo Basin. Fig. 3: showing the total sedimentary thickness within the basin (Ramberg, Koyi, and Mancktelow, 2000; Pg. 147). Burial and Thermal History of the Espirito Santo Basin The full temperature and pressure as well as petroleum expulsion, generation, and migration models have since been put in place to help in understanding the thermal activities of the Espirito Santo Basin among other basins including Santos and Campos basins (Peters, et al., 2005; Pg. 254). This model was collectively referred to the Greater Campos Basin. It is approximately 1200km by 200km in size and it incorporates a well formulated salt restoration with full maturity and temperature calibration with data extracted from the basins ’data base (Roberts and Bally, 2012; Pg. 971). Among the vital information embedded in the model include hydrocarbon composition and PVT conditions that uses cracking kinetics and multicomponent generation in the thermal analyses of these basins. Nonetheless, the historic temperature simulation of the Greater Campos Basin that includes Espirito Santo Basin indicates that the basin is highly thermally complex with great explosions that usually range from the historic Albian period to the contemporary time. However, the increased burial due to increased thermal effect of Espirito Santo Basin have been reported to never be keeping pace with the effects of the post rift decay. This is suspected to be attributed for by heal flow and salt diapirsmimpacts (Danforth, et al., 2013; Pg. 252). These effects are known to be the perfect elements explaining the thermal history of Espirito Santo Basin especially from the pre salt layers. Additionally, these shifts in thermal stability in the Espirito Santo Basin also explain the steady decrease in the temperature especially for the last 80 Ma thereby leading to vulnerability and complexity of the historic thermal model of the Espirito Santo Basin among other basins with Greater Campos Basin. Notably, these thermal changes relates to fundamental risks in numerous parts of the basin for both post and pre salt layers thereby leading to sever biodegradation and extensive hydrocarbon reservoir thermal cracking. Discussion The exploration research on the viability of Espirito Santo Basin for the petroleum products started in the year 1957. In the year 1969, petroleum was discovered with the production starting in the year 1973. The first construction of oil pipelines started in the year 1981 (Norsk Petroleum Sforening, Doré, and Sinding-Larsen, 1996). These pipeline connected Vitoria and Sao Mateus. They also provided the oil for the AracruzCelulose and since 1982 that the oil was supplied in these areas; there has never been disruption of the supply. However, it should be noted that until 1988, there was no gas association with these productions but on the same year, the viability of gas in that drilled oil was discovered offshore of Rio Doce River (Danforth, et al., 2013; Pg. 279). Additionally, another gas fields were discovered around the same areas in the year 1996. These discoveries lead to the industrial development of these gas and oil field areas. The future exploration of the Espirito Santo Basin for petroleum is still bright since the oil and gas of the area cannot be overexploited since Brazil has numerous oil and gas fields with the Greater Campos Basin among other areas. For instance, there are have been recent discovery of new oil and gas field around São Rafael Farm that has been approximately to have increased nearly all the Brazilian petroleum reserves by 30 percent (Danforth, et al., 2013; Pg. 88). Currently, the Espirito Santo Basin is projected to produce natural gas at rate of 500 million m3 /d. however, these figures are not confirmed; therefore, there are needs for close data that gives the exact statistics on the amount of natural resources being exploited from the Espirito Santo Basin. On the other hand, it is also noted that the consumers nearly demand natural gas at a rate of 600 million m3 /d. this may call for increased exploitation of the natural gas from Espirito Santo Basin (Danforth, et al., 2013; Pg. 109). However, they may opt to supply the difference or a certain amount from other areas to meet there consumer supply demands. The largest uncertainty that the above data can also help in resolving is the future of petroleum production in the Espirito Santo Basin. It should be noted that in the year 2011, numerous petroleum fields were discovered at the Espirito Santo Basin; however, there are no certainty of the future of these petroleum deposits (Meadows, 1997). It should be noted that Espirito Santo Basin is based north of other petroleum active sites located south of the basin. Additionally, the Espirito Santo Basin is recorded to have a complex and uncertain thermal activities and this may interfere with petroleum reservoirs around Espirito Santo Basin. Therefore, there are need for accurate data to help in predicting the sustainability of the petroleum reservoirs despite these underlying geological conditions and activities respectively. Espirito Santo Basin is currently viable for petroleum exploration activities. However, it appears that slim geological and geochemistry studies have been conducted on the Espirito Santo Basin active and inactive sites since its initial exploration in the late 1950s. Hence, the Espirito Santo Basin fields need for additional and extra petroleum viability studies on top of the 2011 discoveries (Roberts and Bally, 2012; Pg. 121). Moreover, it would be vital for the management of the Espirito Santo Basin petroleum exploration and the Espirito Santo government to work on the actual threats of the Espirito Santo Basin’s petroleum products in the future. Most of Greater Campos Basin petroleum explorations are increasingly taking place in the south of Espirito Santo Basin, and due to geological location of Espirito Santo Basin oil and gas reservoirs, there are acute and dire possibilities that the Espirito Santo Basin research may dry up by oil and gas moving to the south (Ramberg, Koyi, and Mancktelow, 2000; Pg. 226). Therefore, these concerned Espirito Santo Basin’s management organs must commit to serious and effective research work that may give them appropriate solution to the concerns of the switching location of their oil and gas reservoirs. References (1924). South American handbook. Bath, Eng. [etc.], Footprint Handbooks, Ltd. [etc.]. (1998). Brazil handbook. Bath, England, Footprint Handbooks. 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