Effective porosity

About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.

Quantification of Rock Porosity Changes before and after Freezing

Abstract: Petroleum exploration and production from shale formations have gained great momentum throughout the world in the last decade. Producing hydrocarbons from shale is challenging because of the low porosity and permeability thus requiring fracturing completion, whose successes rely on the knowledge of rock properties and in-situ stress. It is imperative to investigate and understand the rock geomechanics in the shale formations. To the best of our knowledge, the freezing method is the most successful approach to prepare the shale core sample for lab test. Unfortunately, the preparation of shale core plugs includes the procedure of freezing that alters the rock properties. This paper quantifies the difference in rock porosity before and after the freezing based on data from numerous rock experiments. Porosities of different rocks had been measured before the rock samples were put into the freezer for freezing. After the rock porosities have been measured, the core samples were stored in the freezer. Then the porosities of core samples after freezing were measured. With above experiments, a porosity database was built and a non-linear regression method was used to derive correlations to quantify the changes in the porosity due to freezing. Our correlations is applicable for geoscientists and engineers to adjust the shale property to the values before freezing. With the correct porosity, more accurate original oil in place can be estimated and more reliable permeability from porosity-permeability correlation can be calculated. Eventually, the estimated ultimate recovery can be evaluated confidently. Results of this study can also be applied to other areas such as underground storage of liquid natural gas (LNG), underground energy storages, etc.

Determination of Shale Types using Well Logs

Abstract: Determination of shale type in shale formation has long been a difficult task Presence of shales in some of the Iranian reservoir formations are one of the most important subject Shale types have to be considered because existence of shale type reduces effective porosity and permeability of the reservoir to some extent Allogenic Shale is distributed in formations in three basic types Dispersed Laminar and structural Each of these shale types has different effect on porosity permeability and water saturation Dispersed shale type reduces effective porosity and permeability to a great extent but laminar and structural have less effect on petrophysical parameters In this investigation shale types Shale volume and effective porosity of shale formations have been determined from well logs based on cross plotting In other words a triangle Density Neutron cross plot is used to determine the above parameters The area of study chosen from central oil fields of Iran where some of the wells are used Tabnak Field Tabnak Well C selected for this study in Kangan Formation South Pars This study illustrates that distribution of shale types in Kangan Formation is mainly dispersed shale with few of laminar shale and the quality of effective porosity phi e decreases with increasing depth in the Kangan Formation

Methods based on density and neutron well-logging responses to distinguish characteristics of shaly sandstone reservoir rock. [Effective and total porosity]

Abstract: Resistivity well-logging devices respond to all of the electrically conductive matter found within their respective ranges of investigation To be consistent with this concept in shaly sand interpretation, the user must have some means to estimate the total rock porosity containing electrically conductive interstitial solutions and a means to estimate the contribution of each solution to the total conductivity It will be one f the purposes of this paper to show the user a method for ascertaining usable values of these important parameters for use in Archie's basic water saturation relationship A method for the evaluation of effective porosity from neutron and density well-logging responses has been developed by others, and is well documented in literature A method for the evaluation of total porosity, as defined herein, has not been described in literature In this paper, the neutron and density well-logging responses will be used to estimate the volumes of both effective and total porosities Before these volumes can be determined to any degree of reliability in heterogeneous shaly sands, the influences of constituents other than quartz and water must be recognized and nullified These constituents may be clay, cement or fragments of material other than quartz or clay, or more » hydrocarbon fluids which have densities different from that of interstitial water In the process of evaluating effective and total porosities, other distinguishing features about the reservoir rock may be recognized This additional information will help the user to understand the producibility of the reservoir rock of interest « less

Porosity Reduction in Cretaceous Sandstones of Alberta

Abstract: Low porosity in Cretaceous sandstones in Alberta is often the result of post-depositional changes. Misinterpretation of a secondary texture as primary will probably lead to erroneous evaluation of a sandstone as a potential reservoir. Silica cementation takes place as overgrowths on detrital quartz grains. Incomplete cementation produces easily recognized crystal faces and some remaining porosity, whereas complete cementation removes all effective porosity and leaves contacts sometimes mistaken for those caused by pressure solution. Carbonate cementation often follows partial silica cementation. It tends to be local or patchy, and reduction of porosity to less than five per cent may still leave the sandstone relatively friable. Secondary clay cement may be difficult to distinguish from detrital clay, though the former is more even in texture, composition, and color than the latter. Authigenic clay is common in the lower Mannville and basal Belly River where it may effectively fill all initial pore space. Porosity loss by pressure solution and compaction is general in chert-rich sandstones after burial of a few thousand feet. However, lack of silica cementation in such sandstones makes them better potential reservoirs at shallow depths than quartz sandstones.