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Effective porosity
About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.
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TL;DR: In this paper, the most significant sandstone reservoir in Iraq is represented by the Zubair Formation, which is divided into three lithofacies: the upper unit is composed mostly of shale layers, the middle unit is consisting of sandstone rocks and the lower ones are consisting mainly of Shale with less sandstone layers.
Abstract: The Barremian succession in the present study is represented by the Zubair Formation which the most significant sandstone reservoir in Iraq. The area of study is located in the Southern part of Iraq at Majnoon oil field, within the Mesopotamian basin. The thickness of the Zubair Formation is about 450 m in the studied area. It is divided into three lithofacies: The upper unit is composed mostly of shale layers, the middle unit is consisting of thick layers of sandstone rocks and the lower ones is consisting mainly of Shale with less sandstone layers. These units are characterized by three types of petrophysical features according to total porosity/effective porosity: High-moderate effective porosity rocks (type I), moderate effective porosity rocks (type II) and low-non pores rocks (type III). The upper unit of the Zubair Formation at Majnoon oil field is characterized by two horizons. The first is showing high resisitivity-high gamma ray which represent the upper part, while the lower part show low resisitivity-low gamma ray. There is a good reservoir horizon with high oil saturation (low water saturation) in this unit at the Majnoon oil field is appeared as a non-continuous horizon. The middle member is dominated by low resistivity-low gamma ray. The high percentage of water saturation in this unit caused the lack of clarity of the oil saturation, which appears in a narrow band. The lower member of Zubair Formation is distinguished by shale dominated rocks and poor sorted sandstone. This shows high resisitivity-high gamma ray. There are many sub horizons as bands within the lower horizon as high resistivity-low gamma ray. There is a good reservoir horizon with high oil saturation (low water saturation) in this unit.
2 citations
TL;DR: In this article , the authors evaluated the physical properties of shale reservoirs, which provides an important basis for shale reservoir evaluation and mining area selection, and a weight analysis was conducted using an analytic hierarchy process (AHP).
Abstract: The physical properties of shale reservoirs directly affect the form of shale gas and its preservation conditions, and an evaluation of these properties has great significance on the storage and exploitation of shale gas. In this study, the Longmaxi Formation shale in the Sichuan Basin was considered as the research object. The parameters of porosity, permeability, mineral composition, total organic carbon content, density, in-situ stress, brittleness index, and fluid saturation of the samples were obtained through a series of tests. The influence of each parameter on the porosity and permeability was analyzed, and a weight analysis was conducted using an analytic hierarchy process (AHP). The results show that: clay mineral content in the mineral composition has a positive correlation with porosity, and the content of brittle minerals can affect the fracture development density and improve the permeability of samples; the total organic carbon content has a positive correlation with porosity and permeability; increases in density and in-situ stress will significantly reduce the porosity and permeability of samples; the brittleness index has a negative correlation with porosity and a positive correlation with permeability; water saturation has a positive correlation with porosity, gas saturation has a negative correlation with porosity, and the movable oil saturation has an obvious logarithmic relationship with porosity and a negative correlation with permeability. Furthermore, the AHP was used to analyze the specific effects of various parameters on porosity and permeability, with the weight of total organic carbon content > mineral composition > brittleness index > density > in-situ stress > fluid saturation. In this study, we evaluated the physical properties of shale reservoirs, which provides an important basis for shale reservoir evaluation and mining area selection.
2 citations
TL;DR: In this paper, the authors used the well log responses of three wells from Upper Assam, India, for petrophysical estimation and rock physics analysis, and the results have been validated by testing these two rock physics templates in nearby wells with known lithology and fluid type.
Abstract: Estimation of petrophysical properties such as effective porosity, volume of shale, and water saturation using well log responses is a significant step for reservoir evaluation. Three wells from Upper Assam, India, have been considered for petrophysical estimation and rock physics analysis. The rock physics diagnostic modelling predicts the elastic properties of rocks by considering fluids and mineral mixture, pore texture, and mineral fractions. Friable sand and constant cement models have been used to predict the compressional sonic velocity (Vp), shear sonic velocity (Vs), and density logs and compared with the original logs in the Tipam Sandstone (TS) and Barail Arenaceous Sandstone (BAS) reservoirs of Upper Assam basin. The constant cement model is considered the best suitable in these reservoirs due to the excellent correlation between the modeled and measured logs. Various lithology and pore fluids can be identified by generating rock physics templates (RPT) using elastic parameters. RPT of Vp/Vs versus acoustic impedance (AI) has been generated in this study for the two reservoirs, TS and BAS, from the rock physics diagnostic study. The results have been validated by testing these two rock physics templates in nearby wells with known lithology and fluid type. The rock physics templates will help in identify hydrocarbon bearing sands, brine sands, and shale from well log data of formations with same depositional environment.
2 citations
Patent•
10 Nov 2003
TL;DR: In this paper, the results of well researches are used in determination of such parameters as open porosity determined by methods of neutron logging and gamma-ray logging; effective porosity by correlation relationships; dynamic porosity using method of nuclear magnetic logging; water saturation and initial oil saturation and also free and combined water saturation.
Abstract: FIELD: oil exploration geology; designed for revealing of nature of water saturation of producing formations, and evaluation of their oil saturation, and estimation of initial reserves of oil depositions. SUBSTANCE: method includes measurement of geophysical characteristics of section of drilled wells. Results of well researches are used in determination of such parameters as open porosity determined by methods of neutron logging and gamma-ray logging; effective porosity by correlation relationships; dynamic porosity by method of nuclear magnetic logging; water saturation and initial oil saturation by methods of neutron-gamma-ray, gamma logging and resistivity. Determined parameters are used for calculation of parameters of immovable part of oil saturation in form of difference of efficient and dynamic porosity related to open porosity, combined water saturation, movable part of oil saturation and free water saturation. For said calculations, respective relationships are offered. EFFECT: higher accuracy of determination of quantity and quality of oil initial reserves of producing formation due to determination of parameters characterizing fluid-saturation of formation pore space, particularly, movable and immovable parts of oil saturation and also free and combined water saturation. 1 tbl
2 citations
TL;DR: In this article, computer assisted log analyses were employed to evaluate the petrophysical parameters such as the shale volume, total porosity, effective porosity (EP), water saturation (Sw), and hydrocarbon saturation (Sh).
Abstract: Over the past years, the Anambra basin one of Nigeria’s inland basins has recorded significant level of hydrocarbon exploration activities. The basin has been confirmed by several authors from source rock analyses to have the potential for generating hydrocarbon. For the hydrocarbon to be exploited, it is imperative to have a thorough understanding of the reservoir. Computer-assisted log analyses were employed to effectively evaluate the petrophysical parameters such as the shale volume (Vsh), total porosity (TP), effective porosity (EP), water saturation (Sw), and hydrocarbon saturation (Sh). Cross-plots of the petrophysical parameters versus depth were illustrated. Five hydrocarbon bearing reservoirs were delineated in well 1, four in well 2. The reservoirs in well 3 do not contain hydrocarbon. The estimated reservoir porosity varies from 10% to 21% while their permeability values range from 20md to 1400md. The porosity and permeability values suggest that reservoirs are good enough to store and also permit free flow of fluid. The volume of shale (0.05% to 0.35%) analysis reveals that the reservoirs range from shaly sand to slightly shaly sand to clean sand reservoir . On the basis of petrophysics data, the reservoirs are interpreted a good quality reservoir rocks which has been confirmed with high effective porosity range between 20% and high hydrocarbon saturation exceeding 55% water saturation in well 1 and well 2. Water saturation 3 is nearly 100% although the reservoir properties are good.
2 citations