This thesis constrains the distribution of diagenetic alterations and their impact on reservoir-quality and heterogeneity evolution pathways in relation to depositional environments and sequence stratigraphy (systems tracts and key sequence stratigraphic surfaces) of four selected paralic and shallow marine siliciclastic successions. Typical eogenetic alterations encountered include the dissolution and kaolinitization of framework silicates, which are closely associated to shoreface facies of forced regressive systems tract (FRWST), lowstand systems tract (LST), upper part of the highstand systems tract (HST), and below the sequence boundary (SB). These alterations are attributed to incursion of meteoric water owing to rapid and considerable fall in the relative sea level. Extensive carbonate cementation is most evident below marine and maximum flooding surfaces (MFS), whereas dissolution of carbonate cement and detrital dolomite occur in LST, HST and below SB. Parameters controlling the patterns and texture (microcrystalline vs. poikilotopic) of calcite cement have been constrained within sequence stratigraphic framework of the sandstones. Coarse crystalline to poikilotopic calcite textures of meteoric water origin are thus closely linked to the FRWST, LST and upper part of the HST sandstones and occur mainly as stratabound concretions, whereas microcrystalline calcite, which was precipitated from marine porewaters, occurs as continuously cemented layers in the transgressive systems tract (TST) and lower part of the HST sandstones. Eogenetic alterations impose, in turn, profound control on the distribution pattern of mesogenetic alterations, and hence on reservoir quality evolution (destruction vs. preservation) pathways of sandstones. Eogenetic infiltrated clays, which occur in the tidal estuarine TST and HST sandstones, have helped preserving porosity in deeply buried sandstone reservoirs (≈ 5 km) through inhibition of extensive cementation by quartz overgrowths. Other essential findings of this thesis include deciphering the control on the formation of authigenic illite and chlorite by ultra-thin (≤ 1 µm thick), grain-coating clay mineral substrate.

A study of the distribution of diagenetic alterations and their impact on reservoir-quality evolution in four deep-water turbidite successions (Cretaceous to Eocene) from basins in active (foreland) and passive margins revealed the impact of tectonic setting, depositional facies, and changes in the relative sea level. Diagenetic modifications encountered in the turbiditic sandstones from the passive margin basins include dissolution and kaolinitization (kaolin has δ18OV-SMOW = +13.3‰ to +15.2‰; δDV-SMOW = -96.6‰ to -79.6‰) of framework silicates, formation of grain coating chloritic and illitic clays, cementation by carbonates and quartz, as well as the mechanical and chemical compaction of detrital quartz. Kaolinitization, which is most extensive in the lowstand systems tracts, is attributed to meteoric-water flux during major fall in the relative sea level. Preservation of porosity and permeability in sandstones from the passive margin basins (up to 30% and 1 Darcy, respectively) is attributed to the presence of abundant rigid quartz and feldspar grains and to dissolution of carbonate cement as well as mica and feldspars. Diagenetic modifications in turbidites from the foreland basins include carbonate cementation and mechanical compaction of the abundant ductile rock fragments, which were derived from fold-thrust belts. These diagenetic alterations resulted in nearly total elimination of depositional porosity and permeability. The wide range of δ13CV−PDB values of these cements (about -18‰ to +22‰) in passive margin basins is attributed to input of dissolved carbon from various processes of organic matter alterations, including microbial methanogenesis and thermal decarboxylation of kerogen. The narrower range of δ13CV−PDB values of these cements (about -2‰ to +7‰) in the foreland basins suggests the importance of carbon derivation from the dissolution of carbonate grains. The generally wide range of δ18O values (about -17‰ to -1‰) of the carbonate cements reflect the impact of oxygen isotopic composition of the various fluid involved (including marine depositional waters, fluxed meteoric waters, evolved formation waters) and the wide ranges of precipitation temperatures. Results of this study are anticipated to have important implication for hydrocarbon exploration in deep-water turbidites from passive and active margin basins and for pre-drilling assessment of the spatial and temporal distribution of reservoir quality in such deposits.

The effectiveness of CO₂ injection in the subsurface for storage and EOR are controlled by reservoir quality variation. This study determines the depositional processes and diagenetic alterations affecting reservoir quality of the Lower Tuscaloosa Formation at Cranfield Field. It also determines the origin, time and processes of the grain-coating chlorite and its impacts on reservoir quality. Moreover, by integrating depositional and diagenetic characteristics and by linking them to sequence stratigraphy, the distribution of reservoir quality, could be predicted within a sequence stratigraphic framework. The studied sandstones are composed of medium to coarse-grained, moderately sorted litharenite to sublitharenite with composition of Q76.1F0.4L23.5. Depositional environment of this formation in the Mississippi Interior Salt Basin is interpreted as incised-valley fluvial fill systems. The cross sections and maps at the field show trend of the sandy intervals within channels with a NW-SE paleocurrent direction. During burial of the sandstones, different digenetic alterations including compaction, dissolution, replacement and cementation by chlorite, quartz, carbonate, kaolinite, titanium oxides, pyrite and iron-oxide modified the porosity and permeability. Among these, formation of chlorite coats plays the most important role in reservoir quality. The well-formed, thick and continuous chlorite coatings in the coarser grain sandstones inhibited formation of quartz overgrowth, resulted in high porosity and permeability after deep burial; whereas the finer grain sandstones with the poorly-formed, thin and discontinuous chlorite coatings have been cemented by quartz. The optimum amount of chlorite to prevent formation of quartz overgrowths is 6% of rock volume. The chlorite coats are composed of two layers including the inner chlorite layer formed by transformation of the Fe-rich clay precursors (odinite) through mixed-layer clays (serpentine-chlorite) during early eodiagenesis and the outer layer formed by direct precipitation from pore waters through dissolution of ferromagnesian rock fragments during late eodiagenesis to early mesodiagenesis. In the context of the reservoir quality prediction within sequence stratigraphic framework, the late LST and early TST are suitable for deposition of chlorite precursor clays, which by progressive burial during diagenesis could be transformed to chlorite, and thus results in preserving original porosity and permeability in deep burial. / text

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-21T12:50:41Z No. of bitstreams: 1 SUELY DE OLIVEIRA PINHEIRO COSTA - DISSERTAÇÃO (PPGRN) 2010.pdf: 8571182 bytes, checksum: 3933b9bf4d5687be8c930b8c044303d3 (MD5) / Made available in DSpace on 2018-09-21T12:50:41Z (GMT). No. of bitstreams: 1 SUELY DE OLIVEIRA PINHEIRO COSTA - DISSERTAÇÃO (PPGRN) 2010.pdf: 8571182 bytes, checksum: 3933b9bf4d5687be8c930b8c044303d3 (MD5) Previous issue date: 2010-05-28 / Este estudo foi desenvolvido com o intuito de diagnosticar os impactos ambientais na área de inserção do reservatório superficial urbano Açude Grande da cidade de Cajazeiras/PB e seu entorno. Entre seus objetivos destaca-se a análise ambiental através da percepção de seus usuários, detectando o nível de informação dos mesmos acerca dos impactos gerados pela ocupação e intervenção antrópica e a caracterização da qualidade da água e seus reflexos na saúde humana, identificando o de interesse dos mesmos em participar de ações para melhorar a qualidade ambiental da área. Para sua realização desenvolveu-se pesquisa bibliográfica da temática, bem como um estudo de campo utilizando os seguintes instrumentos para coleta de dados: Questionário; Associação livre de palavras, Coleta e análise das águas do reservatório superficial Açude Grande. Esta pesquisa revelou que em seu entorno predomina a ocupação por edificações e as poucas áreas claras são desprovidas de mata ciliar e utilizadas para atividade rural (agricultura e criação de animais). Alguns dos entrevistados não apresentam relações afetivas com a área, no que se refere à qualidade ambiental demonstrando desconhecer a importância do reservatório para o ambiente em contrapartida demonstram um apreço por sua função paisagística. Para a caracterização da qualidade da água do açude foi procedida a sua coleta in loco e seqüencialmente a análise físico-química e microbiológica, no período de outubro de 2009 a fevereiro de 2010, respaldando-se na legislação vigente (resolução CONAMA 357/05 e portaria 518/04) onde se constatou que alguns parâmetros encontram-se fora de conformidade para consumo humano. Conclui-se que o açude encontra-se numa área com alto risco de poluição e/ou contaminação devido à crescente urbanização que vem sofrendo, evidenciando a necessidade de intervenções no que concerne a produção de um programa de recuperação da qualidade ambiental da área de seu entorno, que inclui desde a recuperação da mata ciliar até a implantação de programas permanentes de Educação Ambiental, voltada para a busca da consciência ambiental e o exercício de seus direitos como cidadãos. / This study was developed in order to diagnose the environmental impacts in the insertion area of urban surface reservoir Açude Grande in Cajazeiras city / PB and its surroundings. Among its objectives is to highlight environmental analysis through the perception of its users, detecting the level of the same information about the impacts generated by the occupation and anthropic intervention and characterization of water quality and its effects on human health, identifying the interest of them to participate in actions to improve the environmental quality of the area. For its realization was developed a literature search followed by the field study, where worked, using the following instruments for data collection: Questionnaire; free words association, with the terms inducers: Açude Grande, Environment, Collection and analysis of the waters of Açude Grande reservoir surface. This search revealed that around it dominates the occupation of buildings and the few bright areas are devoid of riparian vegetation and used for rural activities (agriculture and animal creation). Some of the interviewed did not have emotional relationships with the area, with regard to environmental quality showing disregard the importance of container to the environment in contrast show an appreciation for your landscape function. To characterize the water quality of the reservoir was performed to collect his loco and sequentially physico-chemical and microbiological, in the period 2009 October to 2010 February, supported in the legislation (CONAMA 357/05 and Decree 518/04) which found that some parameters are out of compliance for human consumption. It is concluded that the dam is in an area with high risk of pollution and / or contamination due to increasing urbanization that has been suffering, highlighting the need for interventions regarding the production of a recovery program of environmental quality in the area of their surroundings, ranging from the recovery of riparian vegetation to the deployment of permanent programs of Environmental Education, rooted in the pursuit of environmental awareness and exercise their rights as citizens.

Magister Scientiae - MSc / Commercial hydrocarbon production relies on porosity and permeability that defines the storage capacity and flow capacity of the resevoir. To assess these parameters, petrographic and petrophysical log analyses has been found as one of the most powerful approach. The approach has become ideal in determining reservoir quality of uncored reservoirs following regression technique. It is upon this background that a need arises to integrate petrographic and petrophysical well data from the study area. Thus, this project gives first hand information about the reservoir quality for hydrocarbon producibility. Five wells (A-J1, A-D1, A-H1, A-K1 and K-A2) were studied within the Orange Basin, Offshore South Africa and thirty five (35) reservoirs were defined on gamma ray log where sandstone thickness is greater than 10m. Eighty three (83) sandstone samples were gathered from these reservoirs for petrographic analyses within Hauterevian to Cenomanian sequences. Thin section analyses of these sediments revealed pore restriction by quartz and feldspar overgrowths and pore filling by siderite, pyrite, kaolinite, illite, chlorite and calcite. These diagenetic minerals occurrence has distructed intergranular pore space to almost no point count porosity in well K-A2 whilst in A-J1, A-D1, A-H1 and A-K1 wells porosity increases at some zones due to secondary porosity. Volume of clay, porosity, permeability, water saturation, storage capacity, flow capacity and hydrocarbon volume were calculated within the pay sand interval. The average volume of clay ranged from 6% to 70.5%. The estimated average effective porosity ranged from 10% to 20%. The average water saturation ranged from 21.7% to 53.4%. Permeability ranged from a negligible value to 411.05mD. Storage capacity ranged from 6.56 scf to 2228.17 scf. Flow capacity ranged from 1.70 mD-ft to 31615.82 mD-ft. Hydrocarbon volume varied from 2397.7 cubic feet to 6215.4 cubic feet. Good to very good reservoir qualities were observed in some zones of well A-J1, A-K1 and A-H1 whereas well A-D1 and K-A2 presented poor qualities.

The Cretaceous Nanushuk Formation of northern Alaska records extremely rapid shoreline progradation across the Colville Basin during the Albian-Cenomanian epochs. Additionally, it records a period of tectonic realignment in the region, as the main sediment source began to transition from the Chukotkan orogeny to the west to a more local sediment source of the proximal Brooks Range to the south. Through detailed outcrop characterization and 3-D modeling of three exposed outcrops along the axial trend of the Colville Basin on the North Slope and the Upper section of the Nanushuk, this study clarifies the relative timing of the early Brookian orogenic uplift. Outcrop characterization also allows for a detailed description of spatial and temporal distribution of deltaic facies associations within the Nanushuk Formation. Previously these outcrops were hypothesized to represent dominantly shoreface depositional processes, but field studies indicate the Nanushuk Formation has a complex facies architecture consistent with deltaic environments. This work has important significance for geometry predictions for hydrocarbon exploration and development targeting the Nanushuk sands as a reservoir unit. This new interpretation of both dominant sedimentary process and provenance has implications for 1) reservoir architecture and connectivity, and 2) textural and compositional maturity of Nanushuk sandstones, an emerging hydrocarbon play along the North Slope of Alaska. A detailed mineralogical analysis of 50 samples, coming from the three key outcrops and two additional outcrops from previous studies, using TESCAN Integrated Mineral Analyzer (TIMA), an automated system that utilizes Scanning Electron Microscopy (SEM), shows increased amounts of chromite and biotite associated with key outcrops proximal to the Brooks Range. Chromite mass weight percent ranges from 0.00 % to 0.15 % across five outcrops, with Tuktu Bluff, which is proximal to the Brookian orogenic front having weight percentages that range from 0.01 % to 0.15 % with an average of 0.06 %, in contrast to the other outcrops, which range from 0.00 % to 0.03 % with an average of 0.01 %. In contrast, non-diagnostic elements such as quartz do not show meaningful variance, ranging from 42.66 % to 93.78 % across all outcrops, with proximal outcrop showing an average of 60.64 % while the rest of the outcrops have an average of 64.36 %. Substantial localized enrichment in both chromite and biotite found within outcrops of the Nanushuk Formation at the Tuktu Bluff locality support subaerial exposure of the Brooks Range within the Albian-Cenomanian epochs. The non-uniform distribution of these minerals on both a strike and dip direction show that uplift was non-uniform and suggest specific point sources dominated Brookian input. A better understanding of these patterns will help to focus exploration in areas of best potential reservoir quality. Measured sections and 3-d models were created to better understand the depositional architecture and how the deltaic influence in this highly progradational system affects the reservoir geometries. In all three outcrops of interest along the axial trend and higher up in the Nanushuk section, we observed current ripples, lensoidal geometries, low angle trough cross bedding, scoured bases, and wood chunks and pebble lags at channel basses, all of which, are consistent with fluvial dominated deltas. Deltaic deposition complicates predicting the geometry of the reservoir away from outcrop control with lateral avulsions of the delta system and laterally changing distributary channels. At Ninuluk, Kanayut, and Rooftop Ridge, distributary and interdistributary channels comprise approximately 19.5 %, 23.5 % and 20.36 % of the outcrop, respectively. Overall, net to gross sand ratios of 38.69 %, 66.54 % and 55.47 % were calculates at Ninuluk, Kanayut, and Rooftop Ridge, respectively. If assuming the sands in the net to gross are the reservoir rock, then approximately half of the reservoir rocks at each outcrop are in distributary channel settings which adds to the complexity of facies prediction away from the control outcrops.

In the Permian Basin, strata of Leonardian age typically consist of interbedded carbonates and siliciclastics interpreted to be turbidite deposits. Happy Spraberry Field produces from a 100-foot thick carbonate section in the Lower Clear Fork Formation (Lower Leonardian) on the Eastern Shelf of the Midland Basin. Reservoir facies include oolitic- to-skeletal grainstones and packstones, rudstones and in situ Tubiphytes bindstones. Depositional environments vary from open marine reefs to shallow marine oolitic shoal mounds. Best reservoir rocks are found in the oolitic-skeletal packstones. Diagenesis occurred in several phases and includes (1) micritization, (2) stabilization of skeletal fragments, (3) recrystallization of lime mud, (4) intense and selective dissolution, (5) precipitation of four different stages of calcite cement, (6) mechanical compaction, (7) late formation of anhydrite and (8) saddle dolomite and (9) replacement by chalcedony. Oomoldic porosity is the dominant pore type in oolitic grainstones and packstones. Incomplete dissolution of some ooids left ring-shaped structures that indicate ooids were originally bi-mineralic. Bacterial sulfate reduction is suggested by the presence of (1) dissolved anhydrite, (2) saddle dolomite, (3) late-stage coarse-calcite cement and (4) small clusters of pyrite. Diagenetic overprinting on depositional porosity is clearly evident in all reservoir facies and is especially important in the less-cemented parts of the oolitic grainstones where partially-dissolved ooids were subjected to mechanical compaction resulting in "eggshell" remnants. Pore filling by late anhydrite is most extensive in zones where dissolution and compaction were intense. Finally, a porosity-permeability model was constructed to present variations in oolitic packstone- rudstone-bindstone reservoir rocks. The poroperm model could not be applied to oolitic grainstone intervals because no consistent trends in the spatial distribution of porosity and permeability were identified. Routine core analysis did not produce any reliable value of water saturation (Sw). An attempt to take advantage of wireline log data indicates that the saturation exponent (n) may be variable in this reservoir.

Linking diagenesis to depositional facies and sequence stratigraphy enables better prediction of spatial and temporal distribution of diagenetic alterations, and thus of evolution of reservoir quality in sandstones. This thesis demonstrates that employing this approach is possible because depositional facies and sequence stratigraphy can provide useful information on parameters controlling the near-surface diagenesis, such as changes in: (i) pore-water chemistry, (ii) residence time of sediments under certain geochemical conditions, (iii) detrital composition and proportion of extra- and intra-basinal grains, and (iv) types and amounts of organic matter. Evidence from four case studies enabled the development of conceptual models for distribution of diagenetic alterations and of their impact on evolution of reservoir quality in sandstones deposited in paralic, shallow marine and fluvio-lacustrine environments. Diagenetic alterations that have been constrained within the context of depositional facies and sequence stratigraphy include: (i) carbonate cement (microcrystalline and equant calcite spars dolomite over poikilotopic calcite), pyrite and glaucony are most abundant in progradational braid-delta fan sequences, particularly along the topsets (i.e. maxiumum flooding surface, MFS) and along parasequences boundaries in the deltaic facies of the early highstand systems tract HST, (ii) cementation by coarse spar calcite, dolomite, and the formation of moldic porosity by the dissolution of framework carbonate grains are most abundant in the aggradational fan deltas sequences, (iii) eogenetic kaolinitization of framework silicates is largely restricted to the fluvial and paralic HST sandstones, whereas telogenetic kaolinite may occur in the transgressive systems tract TST sandstones too, (iv) formation of goethite ooids in the TST sediments, (v) formation of glaucony, siderite spherules, and extensive grain-coatings, grain-replacing and ooidal berthierine, more in the TST than in the HST sediments, particularly below the transgressive surface TS and MFS, (vi) cementation by calcite with (δ18OV-PDB = -11.5‰ to -5.4‰) and Fe-dolomite/ankerite (δ18OV-PDB = -10.8‰ to -9.6‰) occurs in both TST and HST sandstones, (vii) syntaxial quartz overgrowths are most extensive in the HST sandstones owing to the presence of incomplete grain-coating berthierine/chlorite, (viii) greater amounts of micro-porosity in the TST sandstones than in the HST sandstones are related to the greater amounts of berthierine/chlorite in the former sandstones, and (ix) chlorite rims around quartz grains retarded the precipitation of quartz overgrowths, and hence prevented a greater loss of primary intergranular porosity in fluvio-lacustrine sandstones. Therefore, constraining the distribution of diagenetic alterations in the contexts of depositional facies and sequence stratigraphic context is a powerful approach to be used in hydrocarbon exploration.

In the Permian Basin, strata of Leonardian age typically consist of interbedded carbonates and siliciclastics interpreted to be turbidite deposits. Happy Spraberry Field produces from a 100-foot thick carbonate section in the Lower Clear Fork Formation (Lower Leonardian) on the Eastern Shelf of the Midland Basin. Reservoir facies include oolitic- to-skeletal grainstones and packstones, rudstones and in situ Tubiphytes bindstones. Depositional environments vary from open marine reefs to shallow marine oolitic shoal mounds. Best reservoir rocks are found in the oolitic-skeletal packstones. Diagenesis occurred in several phases and includes (1) micritization, (2) stabilization of skeletal fragments, (3) recrystallization of lime mud, (4) intense and selective dissolution, (5) precipitation of four different stages of calcite cement, (6) mechanical compaction, (7) late formation of anhydrite and (8) saddle dolomite and (9) replacement by chalcedony. Oomoldic porosity is the dominant pore type in oolitic grainstones and packstones. Incomplete dissolution of some ooids left ring-shaped structures that indicate ooids were originally bi-mineralic. Bacterial sulfate reduction is suggested by the presence of (1) dissolved anhydrite, (2) saddle dolomite, (3) late-stage coarse-calcite cement and (4) small clusters of pyrite. Diagenetic overprinting on depositional porosity is clearly evident in all reservoir facies and is especially important in the less-cemented parts of the oolitic grainstones where partially-dissolved ooids were subjected to mechanical compaction resulting in "eggshell" remnants. Pore filling by late anhydrite is most extensive in zones where dissolution and compaction were intense. Finally, a porosity-permeability model was constructed to present variations in oolitic packstone- rudstone-bindstone reservoir rocks. The poroperm model could not be applied to oolitic grainstone intervals because no consistent trends in the spatial distribution of porosity and permeability were identified. Routine core analysis did not produce any reliable value of water saturation (Sw). An attempt to take advantage of wireline log data indicates that the saturation exponent (n) may be variable in this reservoir.

For decades the Upper Cretaceous Lower Tuscaloosa Formation of the U.S. Gulf Coast has been considered an onshore hydrocarbon play with no equivalent offshore deposits. A better understanding of the Lower Tuscaloosa sequence stratigraphic and paleogeographic framework, source-to-sink depositional environments, magnitude of fluvial systems, regional trends in reservoir quality, and structural influences on its deposition along with newly acquired data from offshore wells has changed this decades-long paradigm of the Lower Tuscaloosa as simply an onshore play. The mid-Cenomanian unconformity, underlying the Lower Tuscaloosa, formed an extensive regional network of incised valleys. This incision and accompanying low accommodation allowed for sediment bypass and deposition of over 330 m thick gravity-driven sand-rich deposits over 400 km from their equivalent shelf edge. Subsequently a transgressive systems tract comprised of four fluvial sequences in the Lower Tuscaloosa Massive sand and an overlying estuarine sequence (Stringer sand) filled the incised valleys. Both wave- and tide-dominated deltaic facies of the Lower Tuscaloosa are located at the mouths of incised valleys proximal to the shelf edge. Deltaic and estuarine depositional environments were interpreted from impoverished trace fossil suites of the Cruziana Ichnofacies and detailed sedimentological observations. The location and trend of valleys are controlled by basement structures. Lower Tuscaloosa rivers were 3.8m – 7.8m deep and 145m – 721m wide comparable to the Siwalik Group outcrop and the modern Missouri River. These systems were capable of transporting large amounts of sediment indicating the Lower Tuscaloosa was capable of transporting large amounts of sediments to the shelf edge for resedimentation into the deep offshore. Anomalously high porosity (>25%) and permeability (>1200md) in the Lower Tuscaloosa at stratigraphic depths below 20,000 ft. are influenced by chlorite coating the detrital grains. Chlorite coatings block quartz nucleation sites inhibiting quartz cementation. Chlorite coats in the Lower Tuscaloosa are controlled by the presence and abundance of volcanic rock fragments supplying the ions needed for the formation of chlorite. Chlorite decrease to the east in sediments derived from the Appalachian Mountains. An increase in chlorite in westward samples correlates with an increase of volcanic rock fragments derived from the Ouachita Mountains. / text