DIAGENESYS STAGE ANALYSIS OF SANDSTONE INTERVAL ON WELL DAR-24, GABUS FORMATION, ANOA FIELD, WEST NATUNA BASIN

KURVATEK ◽  
2018 ◽  
Vol 2 (2) ◽  
pp. 67-76
Author(s):  
Hanindya Ramadhani
Keyword(s):  
Secondary Porosity ◽  
Linear Distribution ◽  
Reservoir Rocks ◽  
Sandstone Diagenesis ◽  
Different Depths ◽  
Calcite Cement ◽  
Primary Porosity ◽  
Stage Analysis ◽  
Pore Lining

Stage of diagenesis of a rock will effect the quality of the rock as a reservoir. Hence, it is a necessary to analyze the diagenesis stage of sandstone at Anoa Field, West Natuna Basin, since the diagenesis stage has not been identified properly. The analysis is carried out using thin section method in five different depths. The product of diagenesis is observed for its cementation level, compaction, recrystallization, dissolution, replacement, and type of porosity wich developed in the rock. The appearance of quartz overgrowth cement and pore filling and pore lining calcite cement show a diagenesis stage which are recrystallization and cementation. The appearance of bent mica mineral and suture grain contact can be a sign of late stage compaction. Dissolution of matrix, cement and grain in the sample show that the rock has come to mesodiagenesis stage. As a result of the observation, the conclusion can be made that the rock has passed the eodiagenesis and mesodigenesis phase. Porosity of the section is both primary porosity (interparticle) and secondary porosity (dissolved) with a range 15%-20% (medium to good). Crossplot depth vs porosity show a linear distribution, which when the depth is increase the porosity will decrease. So it can be concluded that the process of diagenesis is very influential on the quality of reservoir rocks in the study area.Keyword: Gabus Formation, sandstone diagenesis, stage of diagenesis.

GEOLOGICAL CONTROLS ON RESERVOIR QUALITY OF THE NORTHERN PERTH BASIN

1987 ◽  
Vol 27 (1) ◽  
pp. 318 ◽  
Author(s):  
S.L. Bergmark ◽  
P.R Evans
Keyword(s):  
High Energy ◽  
Reservoir Quality ◽  
Gas Field ◽  
Reservoir Rocks ◽  
The North ◽  
Fan Delta ◽  
The Common ◽  
Primary Porosity ◽  
And Control

The major onshore Dongara gas field and a number of adjacent minor gas and oil pools are reservoired in basal Triassic sandstones that are sealed by the overlying Kockatea Shale. Reservoir quality is found to be controlled primarily by the local provenance of the sandstones, by diagenesis and the regional palaeotopography. Sandstones east of Dongara are reworked products of a Late Permian fan delta (Wagina Sandstone) that extended westwards from the basin's eastern, fault controlled margin. Localised high energy streams drained the palaeoslope, depositing thin wedges of mainly fluvial sediments upon and around the flanks of the Permian fan delta during a regional rise in sea level in the Early Triassic. Sandstones to the north of Dongara are localised, low energy offshore bars and strandline deposits derived from Precambrian of the Northampton Block. Diagenetic alterations of the Triassic sandstones, also controlled by the sandstones' provenance, have substantially reduced primary porosity and control permeability. The common presence of the authigenic clay mineral, dickite, is taken as evidence that a fluvial environment of deposition controlled formation of the reservoir rocks.

Diagenetic Control of Porosity and Permeability in Pakawau and Kapuni Group Sandstones, Taranaki Basin, New Zealand

1988 ◽  
Vol 6 (3) ◽  
pp. 263-280 ◽  
Author(s):  
J.D. Collen
Keyword(s):  
New Zealand ◽  
Hydrocarbon Generation ◽  
Burial Diagenesis ◽  
Secondary Porosity ◽  
Calcite Dissolution ◽  
Reservoir Rocks ◽  
Porosity And Permeability ◽  
Reservoir Porosity ◽  
Primary Porosity ◽  
Depth Of Burial

Porosity and permeability of Cretaceous to Oliogocene Pakawau and Kapuni Group sandstones in Taranaki Basin, New Zealand, have been extensively modified by burial diagenesis. Mechanical compaction and the precipitation of silica, carbonate and authigenic clays have caused marked deterioration of potential and actual reservoirs for hydrocarbons. Other authigenic minerals have had less effect. Secondary reservoir porosity and permeability have developed in significant volumes in sandstones at various places, at depths below about 2.5 km. They have formed by dissolution of detrital grains, authigenic cements and authigenic replacement minerals, and by fracturing of rock and grains. The most important process for commercial hydrocarbon accumulation in New Zealand is mesogenetic carbonate (particularly calcite) dissolution. As the most prospective source and reservoir rocks are low in the Cretaceous-Tertiary sequence, the depth of burial necessary for hydrocarbon generation means that most primary porosity has been lost and secondary porosity is essential for a commercial accumulation. Entrapment of hydrocarbons in reservoirs higher in the sequence probably also requires the development of secondary permeability to allow migration.

scholarly journals PETROGRAPHIC CHARACTERIZATION AND DIAGENESIS IN SANDSTONES OUTCROPS OF THE NORTHERN MACEIÓ FORMATION: IMPLICATIONS IN RESERVOIR QUALITY

2021 ◽  
Vol 15 (1-2) ◽  
pp. 37-52
Author(s):  
M. S. C. Tenório ◽  
Z. V. Batista ◽  
G. M. D. Fernandes
Keyword(s):  
Potential Method ◽  
Reservoir Quality ◽  
Petrographic Analysis ◽  
Northern Coast ◽  
Secondary Porosity ◽  
Diagenetic Processes ◽  
Geological Unit ◽  
Northern Portion ◽  
Primary Porosity

The acquisition of geological data is of fundamental importance for the study of areas potentially relevant to the occurrence of petroleum systems. In this context, the development of research in outcropping rock formations has proven to be a potential method to investigate the geology of the geological unit studied in subsurface. One of several examples found in Brazil are the outcrops Barreiras do Boqueirão and Praia de Japaratinga, belonging to the Maceió Formation, located in the northern coast of Alagoas State. The Maceió Formation has the lowest cretaceous sedimentation record within the Alagoas Basin. This sedimentation, present almost in the entire basin, is located mainly in its subsurface. This geological unit is composed of several lithologies, including a turbiditic sequence predominantly formed by shales, sandstones and conglomerates. This environment makes it possible the occurrence of a petroleum system. Our research group chose to investigate this environment because turbiditic sandstones are excellent petroleum reservoirs, and they have a great economic relevance in the Brazilian petroleum scenario. To develop this research, a petrographic characterization of the Maceió Formation sandstones was conducted to help determine the compositional and diagenetic aspects of these rocks and infer the influence of diagenetic processes on the quality of these sandstones as reservoirs. The petrographic analysis showed that the studied sandstones can be classified as arkose and quartzenite, present moderate porosity and good permeability, observed through the predominant presence of floating contacts between the grains. The porosity is predominantly primary intergranular, averaging 15%, but secondary porosity by fracture and dissolution of primary grains also occurs. The sandstones of the Maceió Formation are poorly and moderately selected, with angular, sub-angular and sub-rounded grains, showing low to medium textural maturity, which may also influence the quality of the reservoir, impairing the primary porosity in the samples. The three diagenetic stages were identified as: eodiagenesis, mesodiagenesis, and telodiagenesis. The diagenetic processes found were: mechanical compaction, beginning of chemical compaction, clay infiltration, pyrite cementation, grain dissolution, chlorite cementation, quartz sintaxial growth, and mineral alteration and replacement. Mineral replacement was a phenomenon observed quite expressively in the samples analyzed. This event was evidenced, particularly, by the substitution of muscovite and feldspar for kaolinite, the alteration of biotite was also identified in the samples. Therefore, one can infer that the diagenetic processes had little influence on the reduction of the original porosity in the samples studied. In general, considering all the analyses performed in this research, one can see that the sandstones of the Maceió Formation (northern portion) present a good reservoir quality.

scholarly journals Hydrothermal alteration of aragonitic biocarbonates: assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis

2018 ◽  
Vol 15 (24) ◽  
pp. 7451-7484 ◽  
Author(s):  
Laura A. Casella ◽  
Sixin He ◽  
Erika Griesshaber ◽  
Lourdes Fernández-Díaz ◽  
Martina Greiner ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Structural Changes ◽  
Geochemical Data ◽  
Present Contribution ◽  
Secondary Porosity ◽  
Biogenic Carbonate ◽  
Carbonate Formation ◽  
Hard Tissues ◽  
Primary Porosity ◽  
Carbonate Materials

Abstract. The assessment of diagenetic overprint on microstructural and geochemical data gained from fossil archives is of fundamental importance for understanding palaeoenvironments. The correct reconstruction of past environmental dynamics is only possible when pristine skeletons are unequivocally distinguished from altered skeletal elements. Our previous studies show (i) that replacement of biogenic carbonate by inorganic calcite occurs via an interface-coupled dissolution–reprecipitation mechanism. (ii) A comprehensive understanding of alteration of the biogenic skeleton is only given when structural changes are assessed on both, the micrometre as well as on the nanometre scale.In the present contribution we investigate experimental hydrothermal alteration of six different modern biogenic carbonate materials to (i) assess their potential for withstanding diagenetic overprint and to (ii) find characteristics for the preservation of their microstructure in the fossil record. Experiments were performed at 175 °C with a 100 mM NaCl + 10 mM MgCl2 alteration solution and lasted for up to 35 days. For each type of microstructure we (i) examine the evolution of biogenic carbonate replacement by inorganic calcite, (ii) highlight different stages of inorganic carbonate formation, (iii) explore microstructural changes at different degrees of alteration, and (iv) perform a statistical evaluation of microstructural data to highlight changes in crystallite size between the pristine and the altered skeletons.We find that alteration from biogenic aragonite to inorganic calcite proceeds along pathways where the fluid enters the material. It is fastest in hard tissues with an existing primary porosity and a biopolymer fabric within the skeleton that consists of a network of fibrils. The slowest alteration kinetics occurs when biogenic nacreous aragonite is replaced by inorganic calcite, irrespective of the mode of assembly of nacre tablets. For all investigated biogenic carbonates we distinguish the following intermediate stages of alteration: (i) decomposition of biopolymers and the associated formation of secondary porosity, (ii) homoepitactic overgrowth with preservation of the original phase leading to amalgamation of neighbouring mineral units (i.e. recrystallization by grain growth eliminating grain boundaries), (iii) deletion of the original microstructure, however, at first, under retention of the original mineralogical phase, and (iv) replacement of both, the pristine microstructure and original phase with the newly formed abiogenic product.At the alteration front we find between newly formed calcite and reworked biogenic aragonite the formation of metastable Mg-rich carbonates with a calcite-type structure and compositions ranging from dolomitic to about 80 mol % magnesite. This high-Mg calcite seam shifts with the alteration front when the latter is displaced within the unaltered biogenic aragonite. For all investigated biocarbonate hard tissues we observe the destruction of the microstructure first, and, in a second step, the replacement of the original with the newly formed phase.

scholarly journals Porosity evolution of high-quality reservoirs in deep Palaeogene lacustrine carbonate rocks in the central Bohai Sea

2018 ◽  
Vol 36 (5) ◽  
pp. 1136-1156 ◽  
Author(s):  
Yuanhua Qing ◽  
Zhengxiang Lü ◽  
Xiandong Wang ◽  
Xiuzhang Song ◽  
Shunli Zhang ◽  
...  
Keyword(s):  
Bohai Sea ◽  
Oil And Gas ◽  
Early Stage ◽  
Reservoir Rock ◽  
Secondary Porosity ◽  
Authigenic Minerals ◽  
Porosity Evolution ◽  
Lacustrine Carbonate ◽  
Reservoir Porosity ◽  
Pore Lining

The oil and gas in the Palaeogene lacustrine carbonate rock reservoirs in the Bohai Sea accumulated during several periods. The reservoir porosity formed during each period affected the degree of accumulation that occurred. In this paper, the percentages of particles, authigenic minerals and pores in the reservoir bed were calculated with the statistical method of microstructure analysis. The formation time was determined with an isotopic analysis of the authigenic carbonate minerals and the homogenization temperature of the gas–liquid inclusions. The percentages of the primary intergranular pores that formed during the different stages were recovered based on the compaction features both before and after the formation of the major authigenic minerals. The evolution of porosity was thus described quantitatively and chronologically, employing the percentages of the residual primary intergranular pores, visceral cavity pores and dissolved pores at the different burial depths. The results indicate that in the initial sediments of the reservoir rock, the primary intergranular porosity was 32.4%. During the early burial stage, the total reservoir porosity increased by up to 46.9%, due to the addition of another type of primary pore, namely visceral cavity pores, which were generated from the decomposition of bioclasts. During the late, deep burial stage, the compaction reduced only 8.2% of the porosity, due to the support of the pore-lining dolomite precipitating during the early stage. Authigenic minerals occupied 12.6% of the porosity, and the dissolution created the secondary porosity by 3.8%. Good preservation of the visceral cavity pores and the growth of the pore-lining dolomites during the early stages are the major factors leading to the high reservoir porosity. The quantitative and chronological characteristics of the reservoir porosity evolution could be described accurately. The prediction of reservoir beds can be better guided than in previously reported methods by applying high resolution microscopic quantitative analysis technology and authigenic mineral timing analysis technology.

scholarly journals Petrophysical Properties and Digenetic Evolution of Shuaiba Formation in Nasiriyah Oil Field, Southern Iraq

2021 ◽  
pp. 4810-4818
Author(s):  
Marwah H. Khudhair
Keyword(s):  
Gamma Ray ◽  
Water Saturation ◽  
Middle Part ◽  
Effective Porosity ◽  
Oil Field ◽  
Neutron Density ◽  
Petrophysical Properties ◽  
Secondary Porosity ◽  
Primary Porosity ◽  
Gamma Ray Log

     Shuaiba Formation is a carbonate succession deposited within Aptian Sequences. This research deals with the petrophysical and reservoir characterizations characteristics of the interval of interest in five wells of the Nasiriyah oil field. The petrophysical properties were determined by using different types of well logs, such as electric logs (LLS, LLD, MFSL), porosity logs (neutron, density, sonic), as well as gamma ray log. The studied sequence was mostly affected by dolomitization, which changed the lithology of the formation to dolostone and enhanced the secondary porosity that replaced the primary porosity. Depending on gamma ray log response and the shale volume, the formation is classified into three zones. These zones are A, B, and C, each can be split into three rock intervals in respect to the bulk porosity measurements. The resulted porosity intervals are: (I) High to medium effective porosity, (II) High to medium inactive porosity, and (III) Low or non-porosity intervals. In relevance to porosity, resistivity, and water saturation points of view, there are two main reservoir horizon intervals within Shuaiba Formation. Both horizons appear in the middle part of the formation, being located within the wells Ns-1, 2, and 3. These intervals are attributed to high to medium effective porosity, low shale content, and high values of the deep resistivity logs. The second horizon appears clearly in Ns-2 well only.

scholarly journals VERTICAL DISTRIBUTION OF DIATOMS ON MOSSES IN WELLS OF BIJELJINA MUNICIPALITY IN BOSNIA AND HERZEGOVINA

2019 ◽  
Vol 1 (20) ◽  
Author(s):  
Milenko Ćurčić ◽  
Dragica Milinković ◽  
Dragana Radivojević ◽  
Dijana Đurić
Keyword(s):  
Relative Humidity ◽  
Vertical Distribution ◽  
Air Temperature ◽  
Relative Number ◽  
Light Climate ◽  
Four Seasons ◽  
Different Depths ◽  
Area Unit ◽  
Number Of Individuals

Vertical distribution of species and infraspecies taxa of diatoms (Bacillariophyta) on well mosses where they live epiphytically, and a relative number of individuals per surface area unit were followed in 8 open wells with shadoof. Researches were conducted during 2015-2016 through four seasons. Sampling of algae material from well mosses that cover interior of the well was conducted on every 50 cm of depth starting from the surface (O cm) to 200 cm. Considering the specificity of substrate on which diatoms live in wells, and those are mosses that are especially expressed to 1,5 m depth of well and whose leafs cover each other and have an effect on light climate of micro habitat with already existing differences in intensity and quality of light, relative humidity of air, temperature of air on different depths, density of populations of certain species Bacillariophyta is in function of such ecological occasions on different well depths. It is concluded that the most abundant populations on mosses of researched wells, during most of the year, develop four aerophilic species of diatoms: Navicula contenta Grunow, N. atomus var. atomus (Kiitzing) Grunow, Achnanthes lanceolata (Brebisson) Grunow ssp. lanceolata var. lanceolata and Amphora normanii Rabenhorst.

Geological structure of J2/1 layer of the Surgut arch in order to clarify the prospects of oil potential and justify geological exploration

2021 ◽  
pp. 30-39
Author(s):  
A. V. Turabaeva ◽  
V. A. Belkina
Keyword(s):  
Industrial Development ◽  
Geological Structure ◽  
Geological Exploration ◽  
Complex Objects ◽  
Reservoir Rocks ◽  
Oil Reserves ◽  
Geophysical Information ◽  
Low Efficiency ◽  
High Degree

Due to the high degree of production of oil reserves in Western Siberia, geological exploration has been carried out mainly on complex objects for the last 10 to 15 years. The complexity of the task increases because of the fact that the predictive properties of seismic data on such objects are not high. All this leads to low efficiency of geological exploration.In order to increase the efficiency of geological exploration of complex objects, we have proposed a methodology, in which, based on the results of a comprehensive analysis of diverse geological and geophysical information, a model of the quality of hydrocarbon reserves has been built. The ranking of the zones of the quality map of reserves will justify the most effective strategy of geological exploration, that is, the strategy with the least risks. In proposed methodology, special attention is paid to assessing the economic impact of involving reserves in industrial development. Testing of the methodology on reservoir rocks of the J2/1 layer within the Surgut arch has showed its rather high forecast properties.

Hydrodynamic conceptual model of groundwater in the headwater of the Rio de Oro, Santander (Colombia) by geochemical and isotope tools

2020 ◽  
Vol 20 (4) ◽  
pp. 1567-1579
Author(s):  
M. Cetina ◽  
J-D. Taupin ◽  
S. Gómez ◽  
N. Patris
Keyword(s):  
Isotopic Composition ◽  
Conceptual Model ◽  
Temporal Variations ◽  
High Mountain ◽  
Secondary Porosity ◽  
Water Geochemistry ◽  
Carbonate Formation ◽  
Mountain System ◽  
Geological Formation ◽  
Primary Porosity

Abstract Metamorphic, igneous and sedimentary rocks, with low to no primary porosity, outcrop in the La Moza micro-basin stream (headwater of the Rio de Oro). In this high mountain system, water isotopic composition of rainwater, water isotopes and geochemistry of groundwater (springs) and surface water were determined. Groundwater flows are associated to phreatic aquifers in relationship with secondary porosity generated by fracturing, which is increased by dissolution processes in case of carbonate formation producing karstic systems and by the weathering phenomenon mainly affecting granodioritic rocks. Water geochemistry shows low to medium electrical conductivity (EC) depending on the geological formation, but a unique calcium bicarbonate facies. Spring water EC shows limited temporal variations. The isotopic composition of spring indicates a meteoric origin, local infiltration and groundwater flows with low residence time. A conceptual model of the recharge zone is proposed that crosses the surface watershed and covers part of the adjacent Rio Jordán basin, where the Berlin Paramo is located.

PROSPECTIVITY AND EXPLORATION HISTORY OF THE BARROW SUB-BASIN, WESTERN AUSTRALIA

1997 ◽  
Vol 37 (1) ◽  
pp. 117 ◽  
Author(s):  
P.W. Baillie ◽  
E.P. Jacobson
Keyword(s):  
Lower Cretaceous ◽  
Source Rocks ◽  
Reservoir Quality ◽  
Liquid Hydrocarbons ◽  
Reservoir Rocks ◽  
Long Period ◽  
Porosity And Permeability ◽  
History Of ◽  
Hydrocarbon Reserves

The Carnarvon Basin is Australia's leading producer of both liquid hydrocarbons and gas. Most oil production to date has come from the Barrow Sub-basin. The success of the Sub-basin is due to a fortuitous combination of good Mesozoic source rocks which have been generating over a long period of time, Lower Cretaceous reservoir rocks with excellent porosity and permeability, and a thick and effective regional seal.A feature of Barrow Sub-basin fields is that they generally produce far more petroleum than is initially estimated and booked, a result of the excellent reservoir quality of the principal producing reservoirs.Structural traps immediately below the regional seal (the 'top Barrow play') have been the most successful play to date. Analysis of 'new' and 'old' play concepts show that the Sub-basin has potential for significant additional hydrocarbon reserves.

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