Clastic Diagenesis Research Articles

Project Based Learning Approach to Shale Diagenesis: A Better Avenue to the Big Picture

This article describes an experimental six-month study that was created to introduce first semester graduate students to geological research in fine-grained rocks. The study was conducted within a graduate-level Clastic Diagenesis course where students examined the mineralogical and chemical variability in shale samples that crop out in regions of different thermal maturity along the Ouachita Mountain Fold Belt. A project-based instructional (PBL) approach was used with a driving question of “what happens to shales during burial diagenesis?” This approach was intended to give students an opportunity early in their graduate studies to participate in authentic geologic research. Each sample was analyzed for the clay-mineralogy using XRD, whole-rock chemistry using XRF, mineralogy of heavy separates, character of the silt-sized quartz and feldspar, and grain size of the non-clay fraction. Qualitative data analyses from student interview transcriptions revealed that based on their experience with the Ouachita project students were able to approach their own thesis topics, regardless of the subject area with a more holistic and experienced scientific perspective. The depth and quality of the research questions they asked in their own subsequent research was influenced by their exposure to the clastic diagenesis problem-based project. Developing competency in the analyses techniques was not the goal of this project but rather developing an overarching understanding of the process used when studying the diagenesis of fine-grained rocks. Evidence that this was achieved is demonstrated in the student's final presentation of the Clastic Diagenesis project at a regional geologic meeting.

Abstract: Clastic Diagenesis and Porosity Prediction in Sedimentary Basins

Abstract: Clastic Diagenesis and Porosity Prediction in Sedimentary Basins

The Role of Organic-Inorganic Interactions in Clastic Diagenesis: ABSTRACTS

The Role of Organic-Inorganic Interactions in Clastic Diagenesis: ABSTRACTS

Mineral surface controls on the diagenetic transport of oxalate and aluminum

The importance of adsorption is virtually unknown at temperatures of > 25°C. This study indicates that interactions between organic acids and mineral surfaces may control Al transport during clastic diagenesis. Oxalate adsorption onto alumina (γ-Al 2O 3) was measured as a function of pH at 25° and 60°C in 0.1 M NaCl solutions. The thermodynamic stability of the surface Al-oxalate complex remains relatively constant with increasing temperature. Decreasing grain size amplifies the degree to which mineral surfaces control Al and oxalate concentrations through oxalate adsorption in fluid-rock systems. Therefore, diagenetic phase changes should be focused at discontinuities in mineral grain diameter. Furthermore, this grain size effect can influence aluminosilicate mineral solubilities and, therefore, may play an important role in determining the distribution and transport of Al and organic acid anions in sedimentary basins.

Burial History Simulations of the Wilcox Group of the Texas Gulf Coast: The Effects of pCO2, Organic Acids, and Organic Acid Anions on Clastic Diagenesis: ABSTRACT

Burial History Simulations of the Wilcox Group of the Texas Gulf Coast: The Effects of pCO2, Organic Acids, and Organic Acid Anions on Clastic Diagenesis: ABSTRACT

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. critical comment

THE ANALYSES of carboxylic acid anions (CAAs) in San Joaquin Basin and Louisiana Gulf Coast formation waters published by MAcGOWAN and SCRDAM (1990) do little to resolve the important question of whether CAAs are of great significance to clastic diagenesis over the temperature range in which they dominate fluid alkalinity, as advocated by these two authors. Comparison of their analyses with analyses of formation waters from the same wells previously published by three independent research groups (HANOR and WORKMAN, 1986; LAND et al., 1988 and LAND and MACPHERSON, 1989; and FISHER and BOLES, 1990), a body of data not discussed in their article, reveals that most of the MAcGOWAN and SURDAM values are grossly inflated relative to the previous analyses (Table 1, Fig. 1). cedures of Llco et al. (1982). While field procedures for CAAs now normally include the addition of a bactericide to the sample, an independent check on the upper limit of total CAAs which could have been present in this water is provided by the results of an alkalinity titration to pH 2.5, also published by HANOR and WORKMAN (1986), which show that the total concentration of weak acid anions (bicarbonate plus CAAs) could not have exceeded approximately 428 mg/1. The alkalinity determinations were done shortly after collection on separate, untreated aliquots stored in gas-tight glass containers. Further details are given in WORKMAN (1985).

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. Reply to discussion by P.D. L undegard and L.S. L and

MacGowan and S urdam (1990a) suggested some modifications to the model of Lundegard and Land (1989) to make it more geologically and geochemically reasonable. The predictive power of such a geochemical model is wholly dependent on the species modeled and the constants used; any model that excludes important species or important thermodynamic data, or one that couples certain reactions in an unrealistic way, may produce results which are not geologically or geochemically reasonable (W. K. Harrison, pers. commun., 1988; Y. K. Kharaka, pers. commun., 1991). We have long recognized that, under early-burial diagenetic conditions, aluminosilicate hydrolysis generally controls formation water pH ( Surdam and Eugster, 1976 ; Mariner and Surdam, 1970 ; Taylor and Surdam, 1981 ) and that, during intermediate burial, either aqueous CO 2 or CAA species (in the absence of aqueous S species or other weak conjugate acid-base pairs) will dominate formation water alkalinity and control pH ( Surdam et al., 1989c ). We reassert that the model of Lundegard and Land (1989) does not take into account the relative importance of PCO 2 and of concentrations of both Ca 2+ and CAA and their relative organic metal complexes to carbonate mineral stability in sandstones in the zone of intermediate burial clastic diagenesis (cf. the models of Surdam et al., 1984 and Surdam and Crossey, 1985 ). The usefulness of such models is predicted on the completeness of the model and the use of the best, most accurate thermodynamic data. Also, geologically realistic concentrations of critical species are required for reasonable modeling to be done. Although their model is vigorously defended in the discussion of Lundegard and Land (1989, 1993) , we continue to disagree that their analysis of their model conditions are either geologically or geochemically satisfying. We agree with the fundamental approach and philosophy of Lundegard and Land (1989, 1993) . It is of the utmost importance to determine from experimental, geochemical, petrographic, and geological data what the controls on pH and alkalinity in formation waters are, as well as the exact thermodynamic speciation of aqueous moieties and the stability of detrital and authigenic minerals. Lundegard and Land (1993) raise an additional point about CAA reaction with carbonate minerals in shales, although Fisher and Lewan (1989) , Lewan (1989) and MacGowan and Surdam (1990b) have demonstrated that CAA generated in shale likely migrate in the oil phase along incipient shale microfractures to the sandstone reservoir, and thus are likely to not react much with the shale. Finally, we agree with Lundegard and Land that these areas require much additional experimental and field analysis, and petrographic study.

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. Discussion

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. Discussion

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. Reply to critical comment by J.S. Hanor, L.S. Land and G.L. Macpherson

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis. Reply to critical comment by J.S. Hanor, L.S. Land and G.L. Macpherson

Interrelation between clastic and carbonate diagenesis in the Cambrian rocks in the subsurface of southern Alberta

Interrelation between clastic and carbonate diagenesis in the Cambrian rocks in the subsurface of southern Alberta

Geochemical Modeling of Scale Formation, and Formation Damage during Production from Sulfate and Carbonate Mineral-Bearing Reservoirs

The physical and chemical processes that affect reservoir fluids during production can be modeled by methodologies similar to those used for modeling clastic diagenesis. That these processes may result in formation damage and scale formation make them of interest to production geologists and engineers. Pathway modeling, based upon a series of critical divides, predicts which reactions are likely to occur between formation, production tubing, and reservoir fluids. Thermodynamic equilibria modeling calculates direction and magnitude of possible reactions. Integration of these approaches with observations of patterns of scale formation, production line, and formation damage yield a model capable of predicting the magnitude and direction of reactions that may produce negative impacts on reservoir production. Critical divides characterizing these processes in carbonate and sulfate mineral-bearing reservoirs include: (1) presence or absence of sulfate-bearing minerals within the production volume; (2) presence of iron within production line or formation; (3) ratio of concentration of bicarbonate to hydrogen sulfide; (4) capacity of aqueous and solid phases to buffer formation fluid pH; and (5) magnitude of pressure and temperature drops during production. The model qualitatively predicts: (1) likelihood of sulfide, sulfate, or carbonate mineral precipitation during production; (2) souring of the reservoir; and (3) corrosion ofmore » production tubing. The model has been developed from production histories for Weber Sandstone reservoirs, Colorado and Wyoming, and has been applied to examples of reservoir production from Tensleep and Minnelusa reservoirs in Wyoming.« less

Carboxylic acid anions in formation waters, San Joaquin Basin and Louisiana Gulf Coast, U.S.A.—Implications for clastic diagenesis

Carboxylic acid anions (CAA) in formation waters are of interest to studies of clastic diagenesis because of their ability to buffer formation water Eh and pH (and thus substantially contribute to controls on carbonate mineral stability), and their ability to complex and transport Al and Si from the site of aluminosilicate mineral dissolution during diagenesis. Carboxylic acid anions are also extremely important to the aqueous geochemistry of Ca, Fe, Mn, Pb and Zn. Some formation waters from sedimentary basins contain high concentrations of CAAs. The analyses of 20 formation waters from the San Joaquin Basin, California and 20 formation waters from the Louisiana Gulf Coast Basin presented in this study, show concentrations as high as 8100 ppm monofunctional and 370 ppm difunctional CCA; by comparison, previously reported analyses indicate monofunctional CAA occir in concentrations up to 10,000 ppm and difunctional CAA may occur in concentrations up to 2610 ppm. Analyses of drilling muds and scale soaps presented in this study show that few if any difunctional CAA in the study area can be attributed to contamination from these sources. Additionally, aqueous extracts of crude oils contain both mono- and difunctional acid anions, as do the aqueous and petroleum phases of hydrous pyrolysates. Previously unreported dissolution experiments, equilibrium computer simulations, and hydrous pyrolysis experiments support those already published and suggest that CAA are generated during thermal maturation of kerogen and expelled from the shale along oil-wet microfractures. Upon entering the water-wet sandstone pore, the hydrophilic CAA partition into the aqueous phase. Organic-inorganic reactions may occur which from CAA-metal complexes. Because the complexes are hydrophobic, they partition in the petroleum phase, where present. Carboxylic acid anions are of great importance to clastic diagenesis over the temperature range in which they dominate fluid alkalinity; certainly, no other viable mechanism has been advanced which adequately explains the observed aluminosilicate mineral dissolution with subsequent mass transfer of A1, as well as the carbonate mineral diagenetic successions observed in sand-shale systems world-wide. The utility of modeling these observations of organic-inorganic diagenesis is limited only by the ability to model the concentration and distribution of CAA through space and time.

Kinetic Control on Clastic Diagenesis in the Los Angeles Basin as Determined by Apatite Fission Track Analysis: ABSTRACT

The relationship between diagenesis and thermal history in Miocene-Pliocene sediments of the Los Angeles basin were determined from analysis of illite/smectite ratios, apatite fission tracks, extent of feldspar dissolution, and carbonate cementation in argillaceous sediments and sandstones from subsurface and outcrop samples. The extent of the smectite-to-illite transformation and feldspar dissolution as a function of depth can be spatially related to principal faults and fault-bounded structural elements of the basin. The rate of smectite illitization and of feldspar dissolution increases near principal fault zones. Major cementation of sandstones by calcite and baroque dolomite cements is largely restricted to areas located along major fault zones; however, less extensive calcite cementation is found in the deeper parts of the basin central syncline. Time-temperature histories based upon track length histograms of fission tracks in apatite grains indicate that the more tectonically active flanks of the basin had higher thermal gradients during the latest Miocene to latest Pliocene compared to the central-basin structural block. For example, in the Brea Olinda field located along the Whittier fault zone, thermal gradients of 35{degree}C/km are interpreted since deposition of latest Miocene sediments whereas thermal gradients affecting a well 9 mi from the Whittier fault zone were muchmore » lower until 1-2 Ma, when the gradient increased to 35{degree}C/km. Taken together, these data indicate that the diagenesis of clastic sediments in the Los Angeles basin is strongly controlled by reaction kinetics and that the temperatures associated with structural domains in the basin have exerted the dominant control on reaction extent.« less

Evaluation of Clastic Diagenesis Using Coupled Kinetic and Equilibrium Models: ABSTRACT

Evaluation of Clastic Diagenesis Using Coupled Kinetic and Equilibrium Models: ABSTRACT

Water-Mineral-Organic Matter Interactions during Clastic Diagenesis of Cretaceous Heavy Oil Reservoirs, Cold Lake Area, Alberta: ABSTRACT

Water-Mineral-Organic Matter Interactions during Clastic Diagenesis of Cretaceous Heavy Oil Reservoirs, Cold Lake Area, Alberta: ABSTRACT

Sandstone diagenesis and porosity modification during basin evolution

The properties of sandstones as potential reservoirs and shales as source rocks depend on primary facies relationships and diagenesis. Porostiy loss due to mechanical compation and pressure solution is essentially a function of grain parameters (sorting, packing and composition) and net overburden stress. The porosity loss can be predicted to a certain extent. The importance of secondary porosity caused by dissolution of framework grains and cements has been fully recognized. The discussion has focused on the processes causing such dissolution and to what extent it can cause net increase in porosity. The most critical factor in clastic diagenesis is the nature of porewater flow and the degree of mass transfer taking place as a result of this. In the North Sea reservoir rocks, petrographic and geochemical evidence suggest that most of the leaching of feldspar and mica resulting in the formation of kaolinite occurred early during fresh wather flushing. Recent calculations indicate that »acids« derived from source rocks are inadequate to explain the secondary porosity observed in reservoir rocks. Mathematical modelling suggests that thermal convection is of limited importance in sedimentary basins, except where there are high lateral changes in geothermal gradients. Evidence from porewater geochemistry suggests that porewaters in sedimentary basins are often stratified or compartmentalized in a way which is inconsistent with large scale convection or compactional flow, making it necessary to assume that diagenetic reactions are relatively isochemical during deeper burial. A better understanding of the diagenetic reactions will help us to improve our predictions about porosity/depth relations, pore size, and pore geometry distribution in reservoir rocks. Porosity depth trends from offshore Norway and published data from other basins are discussed. Empirical linear best fit lines are found to illustrate the relationship quite well for depths between one and five km. Within a specific region, the linear porosity gradient is a function of mineral composition and of temperature and pressure gradients. Primary porosity tends to be best preserved in sandstones with high proportions of stable grains (e. g. in quartz arenites) down to about 3 or 4 km. At greater depth, porosity loss is accelerated due to increased pressure solution. Secondary and primary porosity adjacent to feldspar grains then tends to be selectively preserved relative to primary pores between quartz grains.

Salt-Dome-Related Diagenesis of Miocene Sediment, Black Bayou Field, Cameron Parish, Louisiana: ABSTRACT

ABSTRACT The Black Bayou Field is associated with a salt dome which pierces Miocene sediment and rises to within 900 ft of the surface. The Louisiana Gulf Coast regional geothermal gradient is locally affected by the salt dome. The gradient increases to values greater than the regional gradient, 1.26°F/100 ft (23°C/km), near the dome. Local effects of the salt dome on clastic diagenesis have been determined by studying sandstone samples adjacent to and away from the salt dome within Miocene sediment. Sample depths range from 4155 to 6145 ft. Distances of samples from the edge of the dome range from 82 to 820 ft. During the late Oligocene a widespread regression exposed the top of the dome. It was subsequently buried, and throughout Miocene time the salt dome probably remained at shallow depths. Upward movement of the dome occurred contemporaneously with deposition of Miocene sediment. Diagenesis of Miocene sediment began with formation of quartz overgrowths. This was followed by precipitation of calcite and pyrite by meteoric water at shallow depths. Today, secondary porosity is abundant near the dome. Dissolution of calcite and framework grains has occurred. Precipitation of kaolinite, in primary and secondary pore spaces, followed this dissolution. Kaolinite is absent at distances greater than 325 ft from the edge of the dome. Analysis of clays reveals that alteration of smectite to illite has not occurred. Although higher-than-regional thermal gradients and possible Na-rich pore fluids exist near the dome, plagioclase grains have not been albitized; burial temperatures are less than 175°F (80°C). Present fluid circulation patterns around the east flank of the dome are controlled by both density- and pressure-induced flow. Meteoric water, with density enhanced by dissolved salts, migrates down along the east flank of the dome, and warm, geopressured fluids, originating in Oligocene shales, flow up along the flank into Miocene sediment. These vertically migrating fluids are acidic which may result from sulfate reduction of salt-dome associated minerals. Also, deep-heated fluids could contain organic acids originating in the shaley interval below the base of the Miocene section.

Clastic Facies and Diagenesis, Lewis-Evans Interval in Black Warrior Basin: ABSTRACT

Clastic Facies and Diagenesis, Lewis-Evans Interval in Black Warrior Basin: ABSTRACT

Oxygen-isotope studies of clastic diagenesis in the Lower Cretaceous Viking Formation, Alberta: implications for the role of meteoric water

Summary The oxygen-isotope compositions and paragenetic sequence of diagenetic minerals from the Lower Cretaceous Viking sandstone and conglomerate from south-central Alberta, Canada have been used to identify changes in porewater composition during diagenesis and to relate these changes to major geological events within the western Canada sedimentary basin. Large-scale influx of meteoric water has played an important role in diagenesis of this unit, especially following uplift of the basin in early Eocene time. Diagenetic phases include early kaolinite ( δ 18 O SMOW = + 24.9 to +28.2 ‰), siderite ( δ 18 O SMOW = + 22.0 to + 23.9 ‰; δ 13 C PDB = −6.3 to −1.3 ‰), calcite ( δ 18 O SMOW = + 26.0 ‰; δ 13 C PDB = −0.4 ‰) and chlorite ( δ 18 O SMOW = + 10.7 − + 13.4 ‰), followed in order by dolomite ( δ 18 O SMOW = + 19.3 − + 22.1 ‰; δ 13 C PDB = −5.9 to −2.6 ‰), calcite ( δ 18 O SMOW = + 13.9 − + 15.9 ‰; δ 13 C PDB = −8.4 to −6.1 ‰), ankerite ( δ 18 O SMOW = + 16.3 − + 17.9 ‰; δ 13 C PDB = −12.4 to −3.5 ‰), kaolin group minerals ( δ 18 O SMOW = + 12.0 − + 15.7 ‰), and illite ( δ 18 O SMOW = + 14.2 − + 15.7 ‰) and illite/smectite ( δ 18 O SMOW = + 13.8 − + 16.5 ‰). Quartz overgrowths ( δ 18 O SMOW = + 16.2 − + 27.4 ‰) began crystallizing relatively early during burial diagenesis and continued to form at least up to the onset of late diagenetic formation of clay minerals. The interpretation of these results is that shallow diagenesis, early in the burial history (glauconite, pyrite, calcite, chlorite), occurred largely in the presence of seawater-derived fluids, although a freshwater influence is indicated where siderite and(or) early kaolinite cements are abundant. As compaction and burial diagenesis proceeded (diagenetic chlorite, quartz overgrowths, dolomite), the porewaters became enriched in 18 O due to water/rock interaction. Burial diagenesis was terminated in the early Eocene by uplift related to the major Laramide Orogeny. Recharge of the basin by low 18 O meteoric water occurred at this time. The meteoric water then became involved in the formation of diagenetic quartz, calcite and ankerite (and the dissolution and albitization of feldspar) at or near maximum burial temperatures, and in the crystallization at lower temperatures of kaolin group minerals, illite and illite/smectite as the post-Eocene erosion progressed.

Formation of secondary porosity in sandstones by quartz framework grain dissolution

An understanding of the nature and origin of porosity in sandstones is crucial to the evaluation of their potential as hydrocarbon reservoirs. Primary porosity is normally destroyed by cementation, compaction and pressure solution during burial, but it has recently been recognized that significant secondary porosity can develop at depth1–3. This discovery has been called “the most significant advance in the study of clastic diagenesis in the past decade”4. Several genetic types of secondary porosity have been identified ; these include porosity formed by: (1) fracturing; (2) shrinkage; (3) dissolution of sedimentary grains and matrix; (4) dissolution of authigenic cements; and (5) dissolution of authigenic replacive minerals5. Formation of secondary porosity by framework grain dissolution has been thought mainly to involve decomposition of feldspars and lithic grains6,7.We demonstrate here that significant secondary porosity can also develop by dissolution of quartz framework grains if the rocks are exposed to alkaline pore fluids during deep burial and/or uplift.