Petroleum geology
Shadi Mohavel; Golnaz Jozanikohan; Sohaila Aslani
Abstract
The presence of clay minerals of any type, amount or distribution pattern in hydrocarbon wells causes numerous problems in the formation evaluation. In this research, 15 core samples from Asmari Formation in the Maroun Oilfield were selected in order to study the type and distribution pattern of clay ...
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The presence of clay minerals of any type, amount or distribution pattern in hydrocarbon wells causes numerous problems in the formation evaluation. In this research, 15 core samples from Asmari Formation in the Maroun Oilfield were selected in order to study the type and distribution pattern of clay minerals by laboratory investigations. The XRD and microscopic results showed the studied samples consisted mainly of quartz (14.7-72.2%) and carbonate minerals (3.0-65.4%) as main constituent phases; while the plagioclase (0.0-6.7%) and clay minerals (3.3–44.5%) were identified as the main accessory minerals. In some samples, sulfide and ferrous minerals (0.0-2%) were also identified. The calculated percentage of illite in mixed-layer smectite/illite showed the diagenesis has occurred at different depths of reservoir. The SEM/EDX analysis performed on various types of clay minerals showed that kaolinite size varied from 0.7 to 6.5 μm in studied samples. In addition, Illite size ranged in our studied samples from 0.4 to 3.6 μm. Our results indicate that the clays in the Asmari Formation occur in three main patterns as dispersed, pore-bridging and pore-filling with the variation of the total amount of clay minerals, min 3.3% and max 44.5% across the length of Asmari Formation.
Sedimentology
Sh. Erfan; K. Rezaei; R. Lak; S. M. Ale Ali
Abstract
Lake Urmia is the greatest hayper salin Lake in the world. This Lake, located in Azerbaijan area, Northwest of Iran is an intra-continental sedimentary basin. Its area is about 6000 km2 with an average water depth of 6 meter. Evaluation of past climate change in Lake Urmia, according to Clay Minerals, ...
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Lake Urmia is the greatest hayper salin Lake in the world. This Lake, located in Azerbaijan area, Northwest of Iran is an intra-continental sedimentary basin. Its area is about 6000 km2 with an average water depth of 6 meter. Evaluation of past climate change in Lake Urmia, according to Clay Minerals, is the main subject for current study. For mineralogical and sedimentological investigations 18 sediment cores were collected from the east and west of Urmia lake. 96 samples from 18 sediment cores in transect to the center of lake were collected and studied by X-ray diffraction (XRD) technique. The clay minerals include Kaolinite, Illite and Montmorillonite. Kaolinite and Illite are the most important clay minerals in the Coastal plain of urmia lake. Origins of clay minerals in the Coastal plain of urmia lake are generally detrital, occurred by physical weathering and indicate composition of bed rock. The study of surface sediments indicates that amount of clay minerals from margin to center of the lake such as another detrital mineral (Quartz) is decreased. In addition, amount of them towards depth is increased. Therefore, it shows the presence of a high water level and cold - humid climate in the past (late Pleistocene).
M.A Sarparandeh; B Mehrgini; A Mollajan; F Sahabi; G.H Norouzi; G Jozanikohan
Abstract
In evaluating the quality of the reservoir sandstone facies, clay usually has significant effect in reducing reservoir effective porosity, permeability as well as calculation accuracy of formation fluids saturation. There are several methods for identifying and measuring the amount of clay. In sandstone ...
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In evaluating the quality of the reservoir sandstone facies, clay usually has significant effect in reducing reservoir effective porosity, permeability as well as calculation accuracy of formation fluids saturation. There are several methods for identifying and measuring the amount of clay. In sandstone reservoirs, diversity of type and amount of clay minerals may change the capacity of cation exchange (CEC) measured in the reservoir rocks. The last parameter (i.e. CEC) can be an important criterion for zoning of reservoir based on the type of clay minerals. Cation Exchange Capacity (CEC) measurement is used as one of the subsidiary clay typing methods. This parameter is the ability of clay to absorb and release of cations in the surrounding solution, which has a specified range for each clay mineral. In cases of clay mixtures, CEC values tend toward the range of the dominant clay type of sample. In this study, cation exchange capacity of the clay minerals has been calculated in two wells of the Gonbadli Gas Field in the Shurijeh sandstone reservoir. First, CEC of 20 samples has been measured using Bower method and employing intelligent estimator based on neural network as well. Based on the petrophysical logs and laboratory results, an appropriate model was fitted to estimate this parameter in well interval. According to the CEC values of clay minerals, existing data classified into five categories including clean zone and zones of clay containing kaolinite, chlorite-illite, halloysite with two water molecules and montmorillonite. For this purpose Bayesian, Parzn and K- nearest neighbor (KNN) classifiers were used. Finally, the obtained results in comparison with the results of X-ray diffraction experiments (XRD) showed good agreement.
G Jozanikohan; F Sahabi; G.H Norouzi; H Memarian
Abstract
Clay minerals reduce the reservoir quality in different ways. They may cause mechanical problems in drilling and lead to petrophysicalmisinterpretations.Therefore,Clay typing is necessary for upstream petroleum exploration and production industry. In this paper, type, amount and distribution patterns ...
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Clay minerals reduce the reservoir quality in different ways. They may cause mechanical problems in drilling and lead to petrophysicalmisinterpretations.Therefore,Clay typing is necessary for upstream petroleum exploration and production industry. In this paper, type, amount and distribution patterns of different clay minerals in 76 core samples from two producing and non- producing wells inthe ShurijehFormation, aging early cretaceous,were identifiedby six different instrumental analytical methods such as X-Ray diffraction (XRD), X- Ray fluorescence, thin section studies, thermal analysis (DTA-TGA), scanning electron microscopy (SEM) and measuring the cation exchange capacity (CEC). The results proved that the dominant clay minerals are illite, magnesium rich chlorite andkaolinite. The minor clays are glauconite (in the both wells), montmorillonite (in producing well) and mixed layers of illite-montmorillonite and chlorite-montmorillonite. The average amount of each clay minerals in non-producing well is more than producing one. Then clay minerals were classified on the percentage basis into five classes (less than 10%, 10-15%, 15-20%, 20-25% and more than 25%).According to quantityof samples in each class, the producing and non-producing wells were recognized as clean and shaly sand respectively. An increase in glauconite and Illite amounts and also an increase in illite and chlorite layers of mixed-layered clayswith increasing burial depth and temperature is an obvious sign of burial diagenesis in this formation. The best correlation was observed between percentages of clay minerals and iron, aluminum, potassium and magnesium.The clay minerals in the ShurijehFormation are diagenetic alteration of rock fragments, plagioclase and alkali feldspar in origin and in some cases they originate from outside with layered distribution. Distribution pattern of the autogenic clays are pore filling, pore coating and pore bridging, which cause the porosity and permeability reduction in this formation.
L Abdi; H Rahimpour-Bonab
Abstract
The Meyghan Playa is an inland closed basin, which is located in center of the aquifer Arak plain. This playa is a seasonal lake and from hydrological point of view acts as erosional base level of region and is appropriate site for precipitation clastic and chemical deposits. For mineralogical and sedimentological ...
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The Meyghan Playa is an inland closed basin, which is located in center of the aquifer Arak plain. This playa is a seasonal lake and from hydrological point of view acts as erosional base level of region and is appropriate site for precipitation clastic and chemical deposits. For mineralogical and sedimentological investigations 94 sediment samples were collected from the playa. 19 samples from surface sediments in transect to the center of playa and 31 specimens from 7 cores were systematically collected and studied by X-ray diffraction (XRD) technique. The clay minerals include Illite, Chlorite, Kaolinite,Vermiculite and Smectite. Illite and Chlorite are the most important clay minerals in the playa. Origins of clay minerals in the Meyghan playa are generally detrital, occurred by physical weathering and indicate composition of bed rock. The study of surface sediments indicate that amount of clay minerals from margin to center of the playa such as another detrital mineral (Quartz) is decreased. In addition, amount of them towards depth is increased. Therefore it shows the presence of a high water level and cold - humid climate in the past (late Pleistocene).
M. Hosseini-Barzi; M. Houshyar; H. Ghalavand
Abstract
Field study, calcimetery and petrography of thin sections from Gurpi type section and petrography of cuttings from Ziloee oil field (well No. 5 and well No. 8) represent two carbonate members and two hybrid (mostly marl and in a few samples clay marl) members in these deposits. Microfacies analysis of ...
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Field study, calcimetery and petrography of thin sections from Gurpi type section and petrography of cuttings from Ziloee oil field (well No. 5 and well No. 8) represent two carbonate members and two hybrid (mostly marl and in a few samples clay marl) members in these deposits. Microfacies analysis of the carbonate members implies 2 microfacies belong to open sea of a carbonate ramp model. Moreover, authigenic glauconite and phosphate and framboidal pyrite propose deposition of these sediments in an anoxic condition. XRD and SEM analysis of marl members provide existence of illite and chlorite as clay minerals by certain detrital source and smectite by digenetic and probability detrial source in the upper marl member and existence of quartz in lower member. Coexistence of these minerals proposes a temperate climate during deposition of the upper marl member. Semi-quantitative analysis of XRD data represents descending trend for relative amounts of illite and ascending trend for smectite during deposition of upper marl member of Gurpi Formation which implies deepening of the sedimentary basin and relative climate warming. The digenetic processes in these deep marine deposits are limited to cementation, illitization, hematization and fracturing. Moreover, studying SEM images evident autogenetic origin of smectite in two samples from upper cretaceous (under K/T boundary) which can form during fluid exchange with mafic minerals and/or detrial clay minerals such as detrial smectite, illite. The absence of digenetic smectite in two samples from Paleocene (over K/T boundary) can be related to change in basin condition in Zagros basin, this period of time. Also, studying relative abundance of K and Th in NGS logs of well number 8 in Ziloee oil field shows that clay minerals in this formation are illite and montmorillonite.
