Clay Mineral Diagenesis Research Articles

Late-Stage Diagenesis of Illitic Clay Minerals as Seen by Decomposition of X-Ray Diffraction Patterns: Contrasted Behaviors of Sedimentary Basins with Different Burial Histories

AbstractThe smectite-to-illite diagenetic transformation has been documented in 5 different sedimentary basins using X-ray diffraction (XRD). Intermediate reaction products coexisting because of the effect of kinetics on this reaction have been characterized using decomposition of XRD patterns and comparison with calculated patterns. The nature and relative abundances of the various subpopulations of particles are shown to vary as a function of the geothermal gradient and of the age of the sediment. In all sedimentary basins that experienced a low steady geothermal gradient the physico-chemical characteristics (coherent scattering domain size [CSDS], junction probabilities) of intermediate mixed-layered illite-smectites (I-S) are similar. However, both the relative abundance and the crystallinity of the end-member illite increase as a function of the age of the sediment.In basins that have experienced a higher geothermal gradient, the CSDS of the I-S subpopulation is higher for a given illite content, indicating a slightly different reaction pathway. This difference in the characteristics (peak position and width) of elementary peaks may be used to infer the presence of such a high geothermal gradient when no other data are conclusive. In this case the growth of the illite end-member is favored over the growth of intermediate I-S phases even in young basins. Illitic phases formed from the alteration of kaolin minerals exhibit characteristics similar to the reaction products of the smectite-to-illite diagenetic transformation in the case of a high geothermal gradient. In contrast with what is observed in shale diagenesis, the characteristics of the illitic subpopulations describe a continuum with absolutely no gap in between subpopulations. In sandstone reservoirs, the various subpopulations crystallize simultaneously from a kaolin precursor. As a consequence, no kinship is expected between the various subpopulations.

Clay Mineral Diagenesis in Sedimentary Basins — A Key to the Prediction of Rock Properties. Examples from the North Sea Basin

Clay Mineral Diagenesis in Sedimentary Basins — A Key to the Prediction of Rock Properties. Examples from the North Sea Basin

Lithological and hydrological influences on ground-water composition in a heterogeneous carbonate-clay aquifer system

The influence of clay units on ground-water composition was investigated in a heterogeneous carbonate aquifer system of Miocene age in southwest Florida, known as the Intermediate aquifer system. Regionally, the ground water is recharged inland, flows laterally and to greater depths in the aquifer systems, and is discharged vertically upward at the saltwater interface along the coast. A depth profile of water composition was obtained by sampling ground water from discrete intervals within the permeable carbonate units during coring and by squeezing pore water from a core of the less-permeable clay layers. A normative salt analysis of solute compositions in the water indicated a marine origin for both types of water and an evolutionary pathway for the clay water that involves clay diagenesis. The chemical composition of the ground water in the carbonate bedrock is significantly different from that of the pore water in the clay layers. Dissolution of clays and opaline silica results in high silica concentrations relative to water in other parts of the Intermediate aquifer system. Water enriched in chloride relative to the overlying and underlying ground water recharges the aquifer inland where the confining clay layer is absent, and it dissolves carbonate and silicate minerals and reacts with clays along its flow path, eventually reaching this coastal site and resulting in the high chloride and silica concentrations observed in the middle part of the Intermediate aquifer system. Reaction-path modeling suggests that the recharging surficial water mixes with sulfate-rich water upwelling from the Upper Floridan aquifer, and carbonate mineral dissolution and precipitation, weathering and exchange reactions, clay mineral diagenesis, clay and silica dissolution, organic carbon oxidation, and iron and sulfate reduction result in the observed water compositions.

The Possible Role of Nannobacteria (Dwarf Bacteria) in Clay-Mineral Diagenesis and the Importance of Careful Sample Preparation in High-Magnification SEM Study

ABSTRACT Bacterial textures are present on clay minerals in Oligocene Frio Formation sandstones from the subsurface of the Corpus Christi area, Texas. In shallower samples, beads 0.05-0.1 µm in diameter rim the clay flakes; at greater depths these beads become more abundant and eventually are perched on the ends of clay filaments of the same diameter. We believe that the beads are nannobacteria (dwarf forms) that have precipitated or transformed the clay minerals during burial of the sediments. Rosettes of chlorite also contain, after HCl etching, rows of 0.1 µm bodies. In contrast, kaolinite shows no evidence of bacterial precipitation. We review other examples of bacterially precipitated clay minerals. A danger present in interpretation of our earlier work (and much work of other ) is the development of nannobacteria-looking artifacts caused by gold coating times in excess of one minute; we strongly recommend a 30-second coating time. Bacterial growth of clay minerals may be a very important process both in the surface and subsurface.

Clay Mineral Diagenesis and Thermal History of the Thonex Well, Western Swiss Molasse Basin

AbstractResults are presented of a diagenetic study from the 1300 m thick Oligocene Molasse deposits penetrated by the Thônex geothermal exploration well (Geneva, Switzerland). The x-ray diffraction (XRD) studies of fine-grained rocks indicate the following diagenetic changes: a decrease of illite/smectite (US) expandability from approximately 90% to 30% with depth, a decrease of the amount of US in the clay mineral fraction, and the appearance of corrensite at depths >750 m. The transition from random US to ordered I/S occurs at the base of the Thônex well (1200 to 1300 m) and is associated with a coal rank of about 0.7% Rr (mean random vitrinite reflectance) corresponding to paleotemperatures of 110 to 115 °C Corrensite appears at a vitrinite reflectance value of 0.6% Rr and a corresponding paleotemperature of 100 °C. The amount of post-Molasse erosion is estimated to be approximately 2 km. Thermal history modeling of the Thônex well suggests maximum paleotemperatures of 80 to 115°C and an average paleogeothermal gradient of 27 °C/km during Late Miocene maximum burial conditions.

Effects of hydrothermal activity on clay mineral diagenesis in Miocene shales and sandstones from the Ulleung (Tsushima) back-arc basin, East Sea (Sea of Japan), Korea

AbstractClay mineral assemblages in both shales and sandstones of Miocene age have been studied in a well from the Ulleung Basin, a back-arc basin in the East Sea. Samples were examined from burial depths of ~800 to 3000 m. At the shallowest depths the shales contain assemblages dominated by R0 mixed-layer illite-smectite (I-S) together with illite, kaolinite and minor chlorite. The sandstones also contain I-S, but are dominated by large amounts of authigenic kaolinite. In both shales and sandstones I-S becomes R1 ordered at ~ 1000 m depth and at 2000 m depth, and deeper, I-S expandabilities are <20%. At ~ 2400 m depth, kaolinite in the sandstones is replaced by abundant Li-tosudite, indicating that clay mineral diagenesis has been affected by a hydrothermal episode. Furthermore, organic maturity data indicate that much of the succession has experienced considerably higher temperatures in the past. Vitrinite reflectance data are best modelled by a short lived (0.1–0.01 Ma) heating event in the Pliocene. This suggests that the shallow depths over which the smectite to illite reaction is completed and the extensive kaolinitization of the Miocene sandstones may also be related to the hydrothermal event.

Diagenesis and Metamorphism of Clay Minerals in the Helvetic Alps of Eastern Switzerland

AbstractHelvetic sediments from the northern margin of the Alps in eastern Switzerland were studied by clay mineralogical methods. Based on illite “crystallinity” (Kübier index), the study area is divided into diagenetic zone, anchizone and epizone. Data on the regional distribution of the following index minerals are presented: smectite, kaolinite/smectite mixed-layer phase, kaolinite, pyrophyllite, paragonite, chloritoid, glauconite and stilpnomelane. Isograds for kaolinite/pyrophyllite and glauconite/stilpnomelane are consistent with illite “crystallinity” zones. Using the ordering of mixed-layer illite/smectite, the diagenetic zone is subdivided into three zones. The illite domain size distribution was analyzed using the Warren-Averbach technique. The average illite domain size does not change much within the diagenetic zone, but shows a large increase within the anchizone and epizone. The average illite b0 value indicates conditions of an intermediate-pressure facies series.The Helvetic nappes show a general increase in diagenetic/metamorphic grade from north to south, and within the Helvetic nappe pile, grade increases from tectonically higher to lower units. However, a discontinuous inverse diagenetic/metamorphic zonation was observed along the Glarus thrust, indicating 5–10 km of offset after metamorphism. In the study area, incipient metamorphism was a late syn- to post-nappe-forming event.

Regional Tertiary Exhumation in and around the United Kingdom

Abstract Sonic velocities in the Upper and Middle Chalk, the Bunter Sandstone and the Bunter Shale were used independently to quantify apparent exhumation (amount of missing section) in the UK Southern North Sea (SNS). Apparent exhumation results derived from these units are statistically similar. The consistency of results from chalks, shales, and sandstones in the UK SNS, and in other areas (Inner Moray Firth and Celtic Sea/South-Western Approaches), suggests that, at a formation and regional scale, burial-depth is the primary control on velocity (and porosity) in these units, and validates the use of lithologies other than shale in maximum burial-depth determination. The consistency of apparent exhumation results from units of Early Triassic to Late Cretaceous age suggests that Tertiary exhumation was of sufficiently great magnitude to mask any earlier Mesozoic periods of exhumation, and that maximum Mesozoic-Cenozoic burial-depth was attained prior to Tertiary exhumation. The analysis of sonic velocities, apatite fission tracks, vitrinite reflectance, normalized drilling rate and clay mineral diagenesis all suggest that there was a regional component of approximately 1 km of exhumation during Tertiary times, which affected structurally uninverted areas in and around the UK. The widely-recognized inversion-related exhumation is superimposed on regional Tertiary exhumation. Regional Tertiary exhumation need not have been contemporaneous with structural inversion. Further refinement beyond Tertiary age is not possible from the sonic velocity data. Regional exhumation, however, is most likely to be associated with regional Palaeocene or Oligocene/Miocene unconformities. The evidence for regional exhumation implies that there was a pre-exhumational phase of burial (during which the eroded sedimentary rocks were deposited). Exhumation and prior burial associated with the regional Tertiary event need to be incorporated in aspects of basin analysis such as sediment decompaction and diagenetic and maturation modelling, and can, for example, account for the maturity of the Carboniferous of the onshore East Midlands Shelf, and the Lias exposed on the north coast of Somerset. The regional, Tertiary tectonic uplift associated with exhumation must have had a thick-skinned origin, and, in areas where there is no evidence for significant Tertiary igneous activity, a decoupled, two-layer model of lithospheric compression is invoked to account for the subsidence/uplift patterns of both inverted and uninverted areas.

Vitrinite reflectivity and the structure and burial history of the Old Red Sandstone of the Midland Valley of Scotland

Vitrinite reflectivities from Lower Old Red Sandstone (ORS) sediments of the Strathmore region in the Midland Valley of Scotland give values of 1.2% for the Stonehaven Group (Kincardineshire), 0.9% for the Arbuthnott Group (Angus) and 1.3% for the Strathmore Group (Perthshire). These values are corroborated by clay mineral diagenesis studies. The Stonehaven Group reflectivity values are considerably lower than expected under the 9 km thickness of sediments aggregated for the Lower Old Red Sandstone of Kincardineshire and demonstrate a maximum burial of some 3 to 5 km. These results together with detailed vitrinite reflectivity measurements in the Dundee Formation, consideration of post-Devonian burial history and kinetic burial modelling, show that the present level of Lower ORS thermal maturation results from Late Carboniferous maximum burial. This is confirmed by comparison with a vitrinite reflectivity gradient from the Strathclyde Group of Fife. To reconcile the vitrinite reflectivity data with the stratigraphy and structure of the Lower Old Red Sandstone, burial models invoking structural repetition, depocentre migration and structurally assembled stratigraphy are considered. It is concluded that the Lower Old Red Sandstone is a structurally assembled series of basins with the Cowie Formation of the Stonehaven Group being part of a separate depositional succession and structurally juxtaposed into its present position as part of an apparently contiguous sequence.

Origin, Diagenesis, and Petrophysics of Clay Minerals in Sandstones. Sepm Special Publication No. 47 by David W. Houseknecht and Edward D. Pitman, 1992; No. of pages: 282. Price: SEPM members $61.00; non‐members $86.00

Origin, Diagenesis, and Petrophysics of Clay Minerals in Sandstones. Sepm Special Publication No. 47 by David W. Houseknecht and Edward D. Pitman, 1992; No. of pages: 282. Price: SEPM members $61.00; non‐members $86.00

Thermal history of the periphery of the Junggar Basin, Northwestern China

Geochemical analysis of rock core samples show that the basin periphery has experienced low thermal stress; present-day heat flows are in the range of 25–35 mW/m 2 and have not been significantly higher than the worldwide mean of approx. 63 mW/m 2 since the mid-Permian. Present day heat flows were determined from corrected borehole temperatures and rock thermal conductivities. Paleo-heat flows were determined by first-order reaction kinetic modeling of several geochemical paleothermometers (vitrinite reflectance, clay mineral diagenesis and relative proportions of sterane and hopane biological marker diastereomers).

Regional Trends in Water Chemistry, Smackover Formation, Southwest Arkansas: Geochemical and Physical Controls (1)

We present results on regional geochemical analyses of formation waters from Jurassic carbonate strata of the upper Smackover Formation from the southwest Arkansas shelf (Gulf Coast basin). These formation waters have been noted in earlier studies for their exceptional salinities and abnormally Br-rich composition. Our detailed and regionally extensive database shows that chemical heterogeneities occur on a relatively small scale and have spatial relations to faults, which may act as pathways for fluid migration from deeper and hotter portions of the stratigraphic section. One of the most pronounced heterogeneities in water chemistry is an H[2]S-rich anomaly in the center of the shelf. Enrichments in H[2]S are accompanied by large increases in alkali elements (Li, K, and b) and B, which could be produced by higher temperature diagenesis of clay minerals and feldspars in deeper seated siliciclastic strata. Bromide enrichments in all Smackover Formation waters are apparent from relations between Br and Cl contents as well as Br and divalent cation (Carpenter function) values. As suggested by earlier studies of these waters, evaporatively concentrated seawater expelled from associated thick monomineralic evaporite sections may be an important source of Br, Cl, and Na, whereas Ca, Mg, and Sr concentrations have been modified by carbonate mineral recrystallization and dolomitization. Mineral equilibria exert significant controls on concentrations of Ca, Mg, Sr, and SO[4] in these brines. Br enrichment likely was produced by halite recrystallization in fluids already enriched in Br from seawater evaporation. Elevated Cl/Br ratios occur in regional association with lower salinity water near t e South Arkansas fault system, consistent with halite dissolution during meteoric water recharge. Thus, despite relatively uniform reservoir lithology and simple structural setting, processes on small spatial scales have resulted in significant heterogeneity in water chemistry within a small area of the Gulf Coast sedimentary basin. Although movement of fluids along these fault systems is not demonstrated in our study, the regional trends in geochemistry are strongly suggestive of their important role in controlling chemical heterogeneities in Smackover Formation waters.

Diagenesis of Clay Minerals in Sedimentary Basins

Diagenesis of Clay Minerals in Sedimentary Basins

Origin and Diagenesis of Clay Minerals in the Monterey Formation, Santa Maria Basin Area, California

AbstractThe clay mineralogy of the Miocene Monterey Formation was determined for onshore and offshore sequences in the Santa Maria basin area, California. The <0.1-μm fraction of clayey, opal-CT porcelanites, siliceous mudstones, and dolostones from the Pt. Pedernales area consists of mixed-layered illite/smectite (I/S) that contains < 10% illite layers. The underlying Tranquillon Volcanics and Obispo Tuff, the presence of bentonite beds, zeolite minerals, and unaltered volcanic ash beds in the Monterey Formation, and the highly smectitic composition of the I/S suggest that a significant amount of the I/S formed from the alteration of vitreous volcanic ash. The alteration of volcanic glass to smectite coincides with the transformation of biogenic opal-A (mostly diatoms) to opal-CT. Alteration of volcanic glass to smectite may inhibit the opal-A to opal-CT transformation by removing pore-water Mg, promote dolomite precipitation by raising the pH, alter the Sr isotopic composition of the pore waters, and provide an additional source of silica to these predominantly biogenic siliceous rocks. The 0.1- to 2-μm fraction contains mica minerals (discrete illite, biotite, and muscovite) as well as I/S. Clayey, opal-A diatomites from the overlying Sisquoc Formation contain detrital kaolinite and random (R = 0) I/S, but the percent illite layers in the I/S is uncertain.The <0.1-μn fraction of quartz rocks from the Lions Head area and the offshore B-2 well is far more variable, and contains random or ordered (R = 1) I/S, kaolinite, and chlorite. Corrensite was observed at the base of the Lions Head area. The percent illite layers in the I/S increases from 10% to 80% over a stratigraphic depth of 0.8 km that corresponds to a present-day temperature range of 80 to 115°C. Initial illitization of smectite coincides with the opal-CT to quartz transformation. Ordered (R = 1) I/S is associated with abundant diagenetic kaolinite and dolomite in several metabentonite beds. The dominance of sodic plagioclase over K-feldspar, and the absence of kaolinite and chlorite in rocks of equivalent age that have not undergone illitization suggest that limited availability of K results in the alteration of smectite to kaolinite, chlorite, and possibly late dolomite. Minor amounts of clinoptilolite were found in opal-A and opal-CT rocks. Minor to trace amounts of analcime and mordenite were tentatively identified, primarily in quartz rocks.

Diagenesis of quartz in the Upper Proterozoic Kaimur Sandstones, Son Valley, central India

The Upper Proterozoic Kaimur Sandstones in central India are quartz-, sublithic- and lithic-arenites cemented by quartz, illite and hematite. Diagenetic quartz occurs in five modes: syntaxial overgrowths, fracture healings, aggregates of small euhedral crystals, quartz resulting from the alteration of detrital silicates and from the recrystallization of quartz. Intergranular pressure dissolution is suggested as the main source of silica with smaller contribution from other sources, such as silica dissolved in meteoric waters, stylolitization, clay-mineral diagenesis, and the alteration of detrital silicates. Studies on the fluid inclusions and oxygen isotopes of diagenetic quartz suggest that meteoric water modified by diagenetic reactions has mediated the quartz cementation.

Diagenesis of Clay Minerals in Sedimentary Basins: A Symposium Third Goldschmidt Conference Reston, Virginia May 8–10, 1992

Diagenesis of Clay Minerals in Sedimentary Basins: A Symposium Third Goldschmidt Conference Reston, Virginia May 8–10, 1992

Clay mineral and zeolite diagenesis in the Toa Baja Well, Puerto Rico

Several diagenetic reactions typical of volcaniclastic sediments have been identified in the Toa Baja well. The zeolites heulandite and (less commonly) analcite, present in the upper half of the drilled section, give way to laumontite at depth. A decrease with depth in the expandability of mixed layer chlorite/smectite was observed. Corrensite was detected over the depth range 1676–2286 m. Temperatures implied by the depth ranges of diagenetic and indicator minerals are consistent with a paleothermal gradient of about 30–50°C/km, assuming little or no erosion of section.

Clay Mineral Diagenesis in Core KM-3 of Searles Lake, California

AbstractCore KM-3 at Searles Lake, California, comprises 693.4 m of lacustrine sediments deposited over the past 3.2 m.y. The lake water evolved from moderately saline, slightly alkaline, and dominated by Na, Ca, Cl, SO4, and HCO3 + CO3 to a highly alkaline brine dominated by Na and CO, ions. Sediments are chiefly muds and evaporites. Montmorillonite and illite are the principal detrital clay minerals supplied to Searles Lake at present and probably during the late Pliocene and Pleistocene.The drill core is divided into three diagenetic zones on the basis of clay-mineral reactions. The upper zone (0-291.1 m) contains authigenic Fe-illite, Mg-smectite, K-feldspar, and analcime, which average 60–70% of the <2-μm silicate fraction of mud samples. The principal silicate reactants are detrital montmorillonite and kaolinite, which have been largely consumed. The middle zone (291.1–541.6 m) also contains authigenic Fe-illite, Mg-smectite, K-feldspar, and analcime, but they form only 20 to 30% of the <2-μm silicate fraction, and considerable detrital montmorillonite and kaolinite remain unaltered. In muds of the lower zone (541.6–693.4 m), a small amount of clinoptilolite is the only authigenic silicate mineral identified, although authigenic montmorillonite probably coexists here as well. Vitric ash is the silicate reactant, and detrital clay minerals apparently remain unaltered in the lower zone.Diagenetic zoning reflects the pore-water chemistry, in which pH may have been the most important parameter. Sediments of the upper zone were deposited in highly alkaline lakes of variable salinity, and sinking brines with a pH of 9.0–10.0 have saturated all sediments. Sediments of the middle zone were deposited in lakes of moderate to high salinity. The pH was overall lower than in the upper zone, although it probably exceeded 9.0, at least locally, during silicate diagenesis. Moderate salinity and a slightly alkaline pH (~ 7.5–8.0) are inferred for both the lake and pore water of the lower zone.Oxygen-isotope values of authigenic Fe-illite, Mg-smectite, and K-feldspar, and phillipsite in the upper diagenetic zone reflect a high degree of evaporative concentration and presumably of salinity. Equilibrium water values calculated for 22°C from the oxygen-isotopic composition of authigenic phyllosilicates range from −3.5 to +1.9%, averaging −1.2% (SMOW). Higher salinities are suggested for K-feldspar, for which water values range from +1.8 to +4.8%, averaging +3.4‰ The water value for phillipsite is +0.3‰ By comparison, rainfall at Searles Lake has an average δ18O value of about −9.8%, and a brine sample has a value of +4.0‰Mud samples of the middle and upper diagenetic zones tend to be rich in Fe-illite or Mg-smectite, but not in both, indicating that the two minerals are favored to some extent by different environments. Fe-illite seems to be generally favored by oxidizing conditions and probably by a playa environment, and Mg-smectite seems to be favored by reducing conditions and an open-water environment. One strati-graphic unit of the upper zone does not fit this pattern and contains abundant Fe-illite in sediments of a deep perennial lake.

Origin and Diagenesis of Clay Minerals in Relation to Sandstone Paragenesis: An Example in Eolian Dune Reservoirs and Associated Rocks, Permian Upper Part of the Minnelusa Formation, Powder River Basin, Wyoming

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in the diagenetic evolution of these sandstones. Allogenic clay minerals are present in shaly rock fragments and laminae. Early infiltration of clays into porous sabkha sands commonly form characteristic menisei or bridges between framework grains or, when more extensive, form coatings or rims on grain surfaces. Authigenic clays include nearly pure smectite, mixed-layer illite/smectite (I/S), and late diagenetic illite and corrensite; these clay minerals are present as pore-lining cements. In addition to the deposition and neoformation of clay minerals throughout sandstone paragenesis, the conversion of smectite to illite occurred as temperatures increased with progressive burial. A temperature of 103C is calculated at a present depth of 3,200 m using a geothermal gradient of 30C/km and a mean annual surface temperature of 7C. After correction for uplift and erosion (250 m), the maximum calculated temperature for the conversion of all random I/Smore » to ordered I/S is 100C. This calculated temperature is in excellent agreement with temperatures of 100-110C implied from I/S geothermometry.« less

Aux Vases Sandstone Diagenesis: Implications for Hydrocarbon Recovery from Southern Illinois Reservoirs

The Aux Vases Sandstone (Mississippian) is a problematic yet productive reservoir in the Illinois basin. The Aux Vases Formation was deposited in a mixed siliciclastic-carbonate offshore environment. Hydrocarbon reservoirs are dominantly elongate sandstone bodies interpreted as subtidal facies within a prograding tidally influenced deposystem. Oil saturated zones, in most cases, are composed of fine-grained, cross-bedded, friable, feldspathic quartz sandstone. Resistivity logs, even from productive wells, are typically characterized by unusually low resistivities (2-4 ohms) that lead to high calculated water saturations. X-ray diffraction, SEM/EDS, and thin section studies were used to analyze diagenetic processes that may affect hydrocarbon production in several Aux Vases reservoirs. Diagenetic processes common to the field studied include: (1) early calcite cementation occluding primary porosity and inhibiting compaction, (2) dissolution of feldspar grains to form authigenic clay, (3) dissolution of early calcite cement, (4) diagenesis of detrital clay minerals into new authigenic clay minerals, and (5) multiple stages of quartz overgrowths that reduce porosity. Commonly used drilling and completion practices may adversely affect reservoir quality by reacting with diagenetic products. Loosening of the fine mineral fraction that causes migration of fines and swelling of expandable clay minerals are examples of this type of damage. Knowledge ofmore » reservoir mineralogy and diagenesis may influence drilling and completion practices and affect selection of secondary and tertiary recovery methods.« less