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Results
Impact of Reservoir Heterogeneity on Steamflooding, Wafra First Eocene Reservoir, Partitioned Zone (PZ), Saudi Arabia and Kuwait
Meddaugh, W. Scott (Chevron) | Osterloh, W. Terry (Chevron) | Toomey, Niall (Chevron) | Bachtel, Steve (Chevron) | Champenoy, Nicole (Chevron) | Rowan, Dana (Chevron) | Gonzalez, Gregorio (Chevron) | Aziz, Shamsul (Chevron) | Hoadley, S. F. (Chevron) | Brown, J.. (Chevron) | Al-Dhafeeri, F. M. (Chevron) | Deemer, A. R. (Chevron)
Abstract The Paleocene/Eocene age First Eocene dolomite reservoir is estimated to contain than 10 billion barrels of oil of which only a small percentage will be produced during primary development. Consequently, steam flooding is being investigated as an appropriate EOR option. A 1.25-acre, single pattern pilot (SST) and a 40-acre, 16 pattern pilot (LSP) are in progress. The detailed pilot area log, core, and seismic data provide a unique opportunity to assess reservoir heterogeneity. Analysis of temperature and petrophysical logs obtained in a temperature observation well located 35 feet from the SST injector show that a vertical barrier to steam migration exists. Two, relatively thick, very low porosity and very low permeability nodular evaporite-rich zones that were predicted to be the most likely barriers do not appear to be a vertical barrier. Instead, an interval characterized by numerous thin, cycle caps, characterized by muddy, finely crystalline dolomites interpreted to be tidal flat facies may be the vertical barrier. Each of these cycle caps also exhibit signs of subaerial exposure which may also contribute to the generally low porosity and very low permeability of the cycle caps. Detailed studies, including micro-permeameter measurements, quantitative mineralogical studies, and micro-CT scans were used to further characterize this interval. The geological assessments of heterogeneity are supplemented by a history-matched simulation model that suggests the evaporite-rich zones may have acted as short term baffles but that the vertical barrier to steam migration is coincident with the interval with abundant tidal flat cycle caps and exposure surfaces. Geological and other reservoir data obtained from the LSP suggest that similar vertical barriers may exist in the pilot area. Early steamflooding results show a very positive response to steam injection as well as multiple thermal "events" (most likely baffles rather than barriers) in the lowermost flooded zones at the LSP. The LSP data allows inferences to be made regarding the occurrence and distribution of lateral high permeability "connections" between injectors and producers as well as the overall reservoir response to steam injection. While the rapid temperature response observed in a few wells may reflect localized fractures or karst-like zones, numerical simulation using very fine grids (1.25 m cell size) shows that some of the LSP wells may experience very short breakthrough times without the need for fracture or karst-like zones.
- Asia > Middle East > Saudi Arabia (1.00)
- Asia > Middle East > Kuwait (0.69)
- Geology > Sedimentary Geology > Depositional Environment > Transitional Environment > Tidal Flat Environment (0.87)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.69)
- Geophysics > Seismic Surveying (0.68)
- Geophysics > Borehole Geophysics (0.46)
- Asia > Middle East > Saudi Arabia > Saudi Arabia - Kuwait Neutral Zone ("Partitioned Zone") > Arabian Basin > Widyan Basin > Wafra Joint Operations Block > Wafra Field (0.99)
- Asia > Middle East > Kuwait > Saudi Arabia - Kuwait Neutral Zone ("Partitioned Zone") > Arabian Basin > Widyan Basin > Wafra Joint Operations Block > Wafra Field (0.99)
ABSTRACT The offshore Sirt Basin is an underexplored basin with considerable hydrocarbon potential, and the Messinian section is poorly understood. It records a significant evaporitic event, and represents a valuable analogue for understanding evaporite deposition in the geological record. Messinian seismic facies in the Gulf of Sirt have been identified, subdivided and analysed to constrain the relative timing of key depositional and erosional episodes in this complex stratigraphic interval. An enigmatic feature of the interval is ‘palaeo-Lake Sirt’, a marginal evaporitic lacustrine basin containing interbedded evaporite and clastic lithologies subjected to post-Messinian sedimentary deformation. Depositional models have been constructed for the early, mid and late Messinian in the Gulf of Sirt and compared to previous models from other marginal Mediterranean basins. These facies assemblages reflect dramatic changes in climatic, tectonic and sedimentary processes occurring over an extremely short period. It is emphasised that obtaining high quality 3D seismic over a large area is crucial for a sufficient understanding of the depositional systems present in a basin.
- Geology > Sedimentary Geology > Depositional Environment (1.00)
- Geology > Rock Type > Sedimentary Rock > Evaporite (0.55)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.54)
- Asia > Middle East > Israel > Mediterranean Sea > Levantine Basin (0.99)
- Africa > Middle East > Libya > Sirte District > Sirte Basin (0.99)
- North America > Canada > Alberta > Steve Field > Anadarko 16B Bonnyville 16-4-59-7 Well (0.98)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Sedimentology (0.89)
Several discoveries, such as Tupi, Bem-Te-Vi, Parati, and Guara, have been announced in Santos Basin off the coast of Brazil, mostly in presalt layers. These layers were well imaged by a salt-flood volume in 2003, but distortions in the base of salt (BOS) and presalt layers were still obvious. Therefore, a constant velocity model is not adequate to capture the velocity variation inside the salt bodies, which include mobile salt and evaporites. A depth migration with a complete salt model is necessary to correctly position the reservoir structures. In this paper, we discuss the challenges in building such a velocity model and share the lessons we learned while working on a data set from the deepwater Santos Basin.
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (0.71)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Tupi Well (0.99)
- South America > Brazil > Brazil > South Atlantic Ocean > Santos Basin (0.99)
Nonintrusively monitoring the spread of contaminants in real time with a geophysical method is an important task in hydrogeophysics. We have developed a sandbox experiment showing that the self-potential method can locate both the source of leakage and the front of a contaminant plume. We monitored the leakage of a plume of salty water from a hole at the bottom of a small tank located at the top of a main sandbox. Initially, the sand was saturated by tap water. At a given time, a hole was opened at the bottom of the tank, allowing the salty water to migrate by diffusion and buoyancy-driven flow in the main sandbox. The bottom of the sandbox contained a network of 32 nonpolarizing silver-silver chloride electrodes with amplifiers, connected to a multichannel voltmeter. The self-potential response associated withthe migration of the salt plume in the sandbox was recorded over time. A self-potential anomaly was observed with amplitude varying from a few millivolts at the start of the leak to a few tens of millivolts after a few minutes. The self-potential data were inverted using a time-lapse tomographic algorithm to reconstruct the position of the volumetric source current density over time. A positive volumetric source current density was associated with the position of the leak at the bottom of the leaking tank, whereas a negative volumetric source current density was associated with the salinity front moving down inside the sandbox. These poles were well reproduced by performing a finite-element simulation of the problem. Using this information, we estimated the speed of the salt plume sinking inside the sandbox. Therefore, the self-potential method can be used to track, in real time, the position of the front of a contaminant plume in a porous material.
- Europe (0.68)
- North America > United States > Colorado (0.29)
- Geology > Mineral > Halide > Halite (0.55)
- Geology > Geological Subdiscipline > Environmental Geology > Hydrogeology (0.46)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Solid Waste Management (0.93)
Abstract Layered evaporites have been deposited at many times during the earth's past and occur in many places around the world. Quite often the layered evaporites have been deformed by sediment loading, gravitational stresses, or tectonic processes. Deformation of evaporites typically produces a continuum of structures like salt rollers, salt pillows, and salt diapirs which may further evolve into salt tongues, salt sheets, and salt canopies. There may even be multiple generations of this evolution as seen in the Gulf of Mexico. However, in a large part of the deep water Santos Basin, particularly the area of the Sao Paulo Plateau, something fairly unique is seen. In this area the majority of deformation is contained within the layered evaporites. Updip extension, sediment loading, and gravitational stresses have combined to produce a contractional environment on the Sao Paulo Plateau. Contraction may manifest itself in single isolated folds, simple fold trains, isoclinals folds, asymmetric folds, recumbent folds, or thrusted folds. Multiple detachment zones within the layered evaporite partition strain so that more competent intervals deform disharmonicly. This allows the possibility of stacking different strain styles, such as anticlinal structures over synclinal structures. It also allows for polyharmonic folding patterns. Inflation of salt does occur on the Sao Paulo Plateau. However, typical diapiric structures that occur to the northwest and west are uncommon in this area. Inflation more often occurs where fold structures are stacked or thrusted, building into salt walls generally oriented north-south or northeast- southwest. Allochthonous features also occur but are rare in this data set and seen are only in the most eastern part of these data. Introduction The deep water Santos Basin is the site of numerous recently announced petroleum discoveries such as Jupiter, Tupi, Parati, Carioca, Bem-Te-Vi, Caramba, Guara, Iara, and others. All of these discoveries lie within lease blocks BMS-8-9-10-11-21-24 (Figure 1). These lease blocks and intervening areas are covered by several 3D PSTM and PSDM seismic surveys collectively known as the " Cluster??. The Cluster data was collected beginning in 2001 and covers nearly 23,200 km in water depths of 1,900 m or greater. The western edge of the Cluster is only about 50 km basinward of the shelf margin but the majority of the data lies 100 to 200 km farther out. Tupi was the first pre-salt discovery announced by Petrobras and BM-S-11 block partners BG and Petrogal in 2007. The petroleum industry gave immediate attention to the deep water Santos Basin when the reserves for Tupi were reported as 5-8 billion BOE (Rigzone, 2007). Tupi was quickly followed by a string of additional discoveries made by Petrobras in partnership with various other companies. Although Petrobras has attempted to be reserved, industry analysts have tossed out potential reserves from 33 billion BOE to 70 billion BOE for the trend (Oil Shalegas.com, 2008; UK.reuters.com, 2008). These are staggering numbers and clearly form the basis of the industry's strong interest. Between the sea floor and the pre-salt reservoir lies an interval of Aptian age layered evaporites and Albian to Late Cretaceous or younger sediment overburden. Over much of the Cluster data the evaporites are 2 km thick, although thickness is variable. Also over much of the Cluster data the evaporites are intensely internally deformed. Companies exploring for petroleum in the Gulf of Mexico know well the problems of imaging sub-salt reservoirs. Imaging the reservoir is an even greater issue for development planning. Although it could be argued that seismic data in the Santos Basin image the section below salt better than in the Gulf of Mexico, anything that can interfere with reservoir imaging can affect development costs and reduce the bottom line. Exploration is inherently risky as attested by three recently announced high profile dry holes, Guarani, Corcovado-2, and a third well in BM-S-17(Rigzone, 2009; Rio Times, 2009; Smith, 2009). Thus, an understanding of cause and effect in deformational processes within layered evaporites should improve risk assessment for exploration prospects and contribute to improved seismic imaging of the pre-salt stratigraphy.
- Phanerozoic > Mesozoic > Cretaceous > Lower Cretaceous (0.49)
- Phanerozoic > Mesozoic > Cretaceous > Upper Cretaceous (0.45)
- Geology > Structural Geology > Tectonics > Salt Tectonics (1.00)
- Geology > Rock Type > Sedimentary Rock > Evaporite (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.54)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > South America Government > Brazil Government (0.66)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 (0.99)
- South America > Brazil > Brazil > South Atlantic Ocean > Santos Basin (0.99)
Messinian Salinity Crisis Expression Along North African Margin
Rubino, Jean-Loup (TOTAL (Pau-Paris, Fr)) | Haddadi, Nourredine (TOTAL (Pau-Paris, Fr)) | Camy-Peyret, Jacqueline (TOTAL (Pau-Paris, Fr)) | Clauzon, George (Cerege, Aix en Provence (Fr)) | Suc, Jean-Pierre (Univ de Lyon (Fr)) | Ferry, Serge (Univ de Lyon (Fr)) | Gorini, Christian (UPMC, Paris (Fr))
Abstract The Mediterranean Messinian Salinity Crisis, Hsu et al. (1973) has two main expressions, 1/ very deep subaerial canyons incision on the the hinterland and along basin margins, 2/ deposition of marginal and abyssal evaporites in the basins. Boths are well known everywhere around Mediterranean Sea, but surprisingly the occurence of canyons is poorly documented along North African margin except in Egypt where the Nile canyon is well known from onshore, to offshore, since a long time, Chumakov (1973), Barber (1981), Dalla et al. (1997). More recently messinian canyons have been reported: –In Algeria with the Algiers complex, Rubino et al. (2005), –Offshore and onshore Tunisia, El Euch-El Koundi et al. (2008) –In offshore Libya, Barr et Walker (1978), Ryan & Cita (1978), or onshore in Sirte and Kufrah basins, Grifin (2002), Rubino et al. (2005), Nicolai (2008), Drake et al. (2008), Paillou et al. (2008). –Evidences have been also reported from Morroco, Loget. (2002).
- Africa > Middle East > Libya (0.69)
- Africa > Middle East > Egypt > Nile Delta (0.29)
- Geology > Geological Subdiscipline (1.00)
- Geology > Sedimentary Geology > Depositional Environment > Marine Environment (0.49)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.31)
- North America > Canada > British Columbia > Western Canada Sedimentary Basin > Alberta Basin > Deep Basin (0.99)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Deep Basin (0.99)
- Asia > Middle East > Turkey > Mediterranean Sea > Mediterranean Basin > Cilicia Basin (0.99)
- (2 more...)
Abstract Triassic anhydrite and gypsum rocks are widespread in the Southern Alps. Two case studies from Lombardy are presented. The former is characterised by a thick lens of gypsum and anhydrite covered by dolostones and with many underground cavities generating subsidence. Indiscriminate urbanization led to build in risky areas. At the second site, gypsum and anhydrite were quarried with a room and pillar technique. At present, lower levels are completely flooded and groundwater flowing contributes to dissolution of pillars. Uniaxial, triaxial and splitting tensile tests have been performed on intact cores of anhydrite and gypsum. The effect of anisotropy on UCS was investigated. Samples have been degraded under a constant water flux and specimen have been measured, weighted and tested for UCS at regular intervals. The compressive strength of degraded samples is reduced dramatically in the earlier stages of degradation. X-ray diffraction and SEM/EDS analyses, both on intact and degraded samples show that the outer border of anhydrite cores transforms to gypsum during the water flux.
- North America > United States (0.49)
- Europe > Italy > Lombardy (0.35)
- Geology > Mineral > Sulfate > Gypsum (1.00)
- Geology > Mineral > Sulfate > Anhydrite (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.36)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (22 more...)
Abstract In the beginning of exploration of the Brazilian Continental Shelf, Petrobras focused its exploratory efforts on deltaic sequences and a discovery was done in the offshore extension of the Sergipe-Alagoas Basin. The important discoveries in turbidites in Campos Basin in the middle 1970's, pointed out these siliciclastic reservoirs as the main exploratory targets in the Brazilian continental margin. Applying well defined geological models, along with true seismic amplitude and in-house wavelet processing, Petrobras advanced into Campos Basin deep waters in the middle 1980's. Production in such scenery of deep waters and heavy oil was the great challenge to overcome at that time. In the 1990's, the deep water petroleum province in Campos Basin consolidated the Petrobras expertise in Exploration and Production in turbidite reservoirs in the deep and ultra-deep realms. The development of technologies integrating oil and reservoir characterization, drilling systems, artificial lifting and flow technologies were carried out to overcome the challenge of producing from turbidites in deep waters. New geodynamic and geotectonic concepts of rifting have defined new strategies for deep and ultra-deep water areas in Brazilian offshore basins. In Santos basin, these concepts together with seven years of work where the exploratory process was followed according to innovative procedures and adjusted to the geological challenges of the area, Petrobras obtained a tremendous exploratory success and a world-class petroleum province was found. This province is located in the central portion of Santos basin, in ultra deepwater, ranging from 2,000 to less than 3,000 meters water depth and situated about 200 km from the Brazilian coast line. It represents a prominent regional feature covered by a continuous evaporitic sequence, thicker than 2,000 meters. The pre-salt targets comprise a thick carbonate section in depths ranging from 5,000 to 6,500 meters. With the results a paradigm was broken, pointing for the great potential of carbonate rocks in the deep/ultra-deep waters in the Brazilian Continental Margin. New exploratory models and production technologies will be necessary to overcome the challenges that Petrobras will face in near future. Introduction Brazilian petroleum exploration commenced onshore in the Reconcavo Basin in 1948. By the mid 1950s, several small fields had been discovered in the Neocomian/Barremian rift section and by the beginning of the 1960s, exploration of the same rift section led to the discovery of the first onshore Brazilian giant oil field, in the Sergipe Basin. By the mid 1970s, several medium-size fields were found on the continental shelf area of this basin. As an outcome of first oil crisis the exploration of the Brazilian continental margin basins accelerated and by the end of the 1970s, several offshore fields were discovered in the continental shelf of Campos Basin. Intense exploration had then started in Brazil. Petrobras, a government controlled company, rapidly gained experience and developed sedimentological and stratigraphic models for the Brazilian passive continental margin, and its exploration activities moved toward deep water regions. The 1980s were punctuated by the discovery of giant deep water fields in the continental slope region of the Campos Basin (e.g., the Marlim, Albacora, and Caratinga Fields). Very innovative technology was developed to produce from marine siliciclastic reservoirs in this region. The oil-bearing reservoirs are turbidite systems of hyperpicnal origin, deposited in prodelta and deep marine settings. Production from these fields, together with the other Brazilian continental margin fields placed Petrobras as the 9th largest energy company in the world.
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean (1.00)
- South America > Brazil > Sergipe > South Atlantic Ocean (0.75)
- South America > Brazil > Alagoas > South Atlantic Ocean (0.75)
- Geology > Structural Geology > Tectonics > Plate Tectonics (1.00)
- Geology > Sedimentary Geology > Depositional Environment > Marine Environment > Deep Water Marine Environment (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (1.00)
- Government > Regional Government > South America Government > Brazil Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Merluza Field > Juréia Formation (0.99)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 > Tupi Field > Lula Formation (0.99)
- South America > Brazil > Rio de Janeiro > South Atlantic Ocean > Santos Basin > Block BM-S-11 > Tupi Field > Guaratiba Formation (0.99)
- (18 more...)
Repeated high-precision gravity measurements using an automated gravimeter and analysis of time series of samples allowed gravity measurements to be made with an accuracy of or better. Nonlinear instrument drift was removed using a new empirical staircase function built from multiple station loops. The new technique was developed between March 1999 and September 2000 in a pilot study conducted in the southern Salt Lake Valley along an east-west profile of eight stations from the Wasatch Mountains to the Jordan River. Gravity changes at eight profile stations were referenced to a set of five stations in the northern Salt Lake Valley, which showed residual signals of in amplitude, assuming a reference station near the Great Salt Lake to be stable. Referenced changes showed maximum amplitudes of through at profile stations, with minima in summer 1999, maxima in winter 1999–2000, and some decrease through summer 2000. Gravity signals were likely a composite of production-induced changes monitored by well-water levels, elevation changes, precipitation-induced vadose-zone changes, and local irrigation effects for which magnitudes were estimated quantitatively.
- Asia (0.66)
- North America > United States > Utah (0.48)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Renewable > Geothermal > Geothermal Resource (0.46)
Velocity-model determination during seismic data processing is crucial for any kind of depth imaging. We compared two approaches of grid tomography: prestack stereotomography and normal-incidence-point (NIP) wave tomography. Whereas NIP wave tomography is based on wavefield attributes obtained during the common reflection surface stack and thus on the underlying hyperbolic second-order traveltime approximation, prestack stereotomography describes traveltimes by local slopes (i.e., linearly) in the prestack data domain. To analyze the impact of the different traveltime approximations and the different input-data domains on velocity model building, we applied two implementations of these techniques to two profiles of a field marine data set from the Levante Basin, eastern Mediterranean. Because ofthe presence of a thick, tabular mobile unit of the Messinian evaporites, strong vertical and lateral velocity contrasts had been expected. The velocity models revealed the reconstruction of high-velocity contrasts by grid tomographic methods is limited because of the smooth description of the velocity distribution. The lateral resolution of velocities obtained from prestack stereotomography appears to be better than those from NIP wave tomography, which is related to the difference in the approximation of traveltimes, the determination of input data, and the description of the velocity distribution. Other differences are caused mainly by different implementations of the inversion schemes. Nevertheless, both algorithms provide suitable models for high-quality depth imaging, whereas most of the reflections are fairly flat in CIGs.
- Europe > Germany (0.28)
- Asia > Middle East > Israel (0.28)
- North America > United States > Illinois > Madison County (0.24)
- Geology > Structural Geology (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (0.93)
- Geology > Rock Type > Sedimentary Rock > Evaporite (0.63)
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (1.00)