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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 80 (1996)

Issue: 5. (May)

First Page: 731

Last Page: 745

Title: Kinetic Modeling of Previous HitQuartzNext Hit Cementation and Porosity Loss in Deeply Buried Sandstone Reservoirs

Author(s): Olav Walderhaug (2)

Abstract:

A mathematically simple kinetic model simulates Previous HitquartzNext Hit cementation and the resulting porosity loss in quartzose sandstones as a function of temperature history. Dissolved silica is considered to be sourced from Previous HitquartzNext Hit dissolution at stylolites or individual Previous HitquartzNext Hit grain contacts containing clay or mica, and diffuses short distances to sites of precipitation on clean Previous HitquartzNext Hit surfaces. The modeled sandstone volume is located between stylolites, and no Previous HitquartzNext Hit dissolution or grain interpenetration takes place within this volume. After Previous HitquartzNext Hit cementation starts, compactional porosity loss is typically minor, and porosity loss within the modeled sandstone volume is therefore considered to be equal to the volume of precipitated Previous HitquartzNext Hit cement. The Previous HitquartzNext Hit cementation process is mod led as a precipitation rate-controlled reaction where Previous HitquartzNext Hit precipitation rate per unit time and surface area can be expressed by an empirically determined logarithmic function of temperature. When the sandstone's temperature history is known, precipitation rate per unit time and surface area can be expressed as a function of time, and the amount of Previous HitquartzNext Hit cement precipitated within a certain time interval can be calculated by multiplying the precipitation rate function with the surface area available for Previous HitquartzNext Hit precipitation and integrating with respect to time. Because Previous HitquartzNext Hit surface area will change as Previous HitquartzNext Hit cement precipitation proceeds, the calculations are performed for short time steps, and Previous HitquartzNext Hit surface area is adjusted after each time step. The total amount of Previous HitquartzNext Hit cement p ecipitated during a sandstone's burial history and the corresponding porosity loss are found by taking the sum of the increments of Previous HitquartzNext Hit cement precipitated during each time step.

The effect of variation in parameters such as grain size, detrital Previous HitquartzNext Hit content, abundance of clay or other grain coatings, prequartz cementation porosities, and temperature history is easily simulated with the presented algorithm. This flexibility is illustrated by presenting calculated histories of Previous HitquartzTop cementation and porosity loss for sandstones with a range of grain sizes, framework grain compositions, degree of clay coat development, prequartz cementation porosities, and temperature histories.

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