Effective porosity

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

New Approach for Geomodeling and Dynamic Calibration of Carbonate Reservoirs Using Porosity Determined System (PODS)

Abstract: More than 50% of oil and gas resources are located in carbonate reservoirs in the world. In reservoir management purposes, it is very essential to have a reliable simulation model in order to understand the production phenomena for these reservoirs. In this work we are introducing a new concept for geological modeling and dynamic simulation of carbonate reservoirs. The distribution of porosity is often the only mappable property in the subsurface with uncertain geometry (i.e a pod). Permeability can be predicted from porosity if the nature of the porosity is understood and by utilising the right rock type(s) for each pod. This workflow is based on understanding and simulation of the heterogeneity of reservoir caused by porosity variations with permeability predicted from a rock typing approach. We have developed the workflow during a modeling study of the Algerita Escarpment outcrop located in NewMexico to show how dynamic data might be incorporated to reduce the uncertainty in subsurface property prediction and ultimately improve oil recovery. The approach termed (Porosity Derived System) has wide application to other systems where the reservoir flow dynamics are controlled by, likely poorly constrained, clusters of porosity creating pods of permeability, whether depositionally, diagenetically or fracture-controlled.

Integrated source rock evaluation along the maturation gradient. Application to the Vaca Muerta Formation, Neuquén Basin of Argentina

Abstract: [Petroleum system modelling showing present‐day maturity (%Ro) of the Vaca Muerta Formation from from the Agrio Fold and Thrust Belt (west) to the NE Platform (east). The increase in TOC0 values from east to west is associated with thickening of the unit, which suggests the potential larger volumes of generated hydrocarbons for the same thermal gradient. The E–W thermal maturity trend is consistent with the decrease in HI and increase in TR values to the west, indicating that in conjunction with increased TOC0, organic pores represent the main control on total porosity in organic‐rich intervals of the unit. , Abstract The Vaca Muerta Formation (Tithonian–early Valanginian) is the main source rock in the Neuquen Basin and the most important unconventional shale resource in South America. In the present study, organic geochemistry, electron microscopy and basin and petroleum system modelling (BPSM) were combined to evaluate source rock properties and related processes along a transect from the early oil (east) to the dry gas (west) window. The unit is characterized by high present‐day (1%–8% average) and original (2%–16% average) total organic carbon contents, which increase towards the base of the unit and basinal (west) settings. Scanning electron microscopy shows that organic pores derived from the transformation of type II kerogen. Isolated bubble pores are typical of the oil window, whereas bubble and densely distributed spongy pores occur in the gas stage, indicating that the maturity gradient exerts strong control on organic porosity. Organic geochemistry, pressure and porosity data were incorporated into a 2D basin petroleum system model that includes the sequential restoration of tectonic events and calculation of compaction trends, kerogen transformation, hydrocarbon generation and estimation of pore pressure through geologic time. The W–E regional model extends from the Agrio Fold and Thrust Belts to the basin border and allows us to evaluate the relationship between thermal maturity and timing of hydrocarbon generation from highly deformed (west) to undeformed (east) regions. Modelling results show a clear decrease in maturity and organic matter (OM) transformation towards the eastern basin margin. Maximum hydrocarbon generation occurred in the inner sectors of the belt, at ca. 120 Ma; long before the first Andean compression phase, which started during the Late Cretaceous (ca. 70 Ma). Miocene compression (15–7 Ma) promoted tectonic uplift of the inner and outer sectors of the belt associated with a reduction in thermal stress and kerogen cracking, as well as massive loss of retained fluids and a decrease in pore pressure. The OM transformation impacted (a) the magnitude of effective porosity associated with organic porosity development, and (b) the magnitude and distribution of pore pressure within the unit controlled by hydrocarbon generation and compaction disequilibrium. BPSM shows a progressive increase in effective porosity from the top to the base and towards the west region related to the original organic carbon content and maturity increasing along the same trend. Overpressure intervals with high organic carbon contents are the most prone to develop organic pores. The latter represent favourable sites for the storage of hydrocarbons in the Vaca Muerta Formation.]

Effective porosities of basalt: A technical basis for values and probability distributions used in preliminary performance assessments

Abstract: The Basalt Waste Isolation Project in its role of evaluating the feasibility of siting a high-level nuclear waste repository in the deep basalts of the Columbia Plateau is gathering information on basalt parameters that define waste isolation capability. Effective porosity is an important parameter in fluid transport analysis on repository performance assessment. This report presents and discusses the technical basis for values and probability distributions of effective porosity for the candidate site in basalts of the Hanford Site in Washington State. The appropriateness of different types of probability distributions of values of effective porosity for the major basalt hydrogeologic units (i.e., flow tops and flow interiors) of candidate flows are considered with respect to their applicability in performance assessment models. 36 refs., 23 figs., 9 tabs.

Carbonate pore systems: porosity/permeability relationships and geologic analysis

Abstract: The porosity/permeability relationships of the common carbonate rock types have been studied, with emphasis on the variety of pore types in upward-shoaling grainstone sequences including: Smackover, Lansing, Salem, and San Andres Formations. A result of these studies is an improved conceptual understanding of permeability gained from the cross-plotting of porosity and permeability data from plugs and whole cores accompanied by textural and fabric analyses of rock samples, thin sections, serial sections, and pore casts. Once the depositional texture and fabric of the rock are defined in terms of porosity and permeability, the evaluation of fractures and secondary porosity can be addressed. The secondary porosity is observed to be as high as 14% of the rock volume in the Smackover example and 21% of an oolitic sample from the Lansing Formation. Pore casts and serial sections reveal that the grain-moldic porosity is poorly connected to the intragranular pore system and contributes little to the permeability of the rock. This insight allows quantitative estimates of this type of secondary porosity using standard porosity and permeability data. The geologic and quantitative analysis of the various pore types and porosity/permeability relationships also aided in the interpretation of the log data from the reservoirs studied.