In Situ Porosity from Cores: The Rock Mechanics Approach to Overburden Correction

Rune M. Holt, NTNU & SINTEF, Trondheim, Norway
Christian Lehr, Shell SEPTAR, Rijswijk, Netherlands
Cor J. Kenter, Shell SEPTAR, Rijswijk, Netherlands
Pier Spits, NAM, Assen, Netherlands

Abstract:
Improved reliability of porosity derived from core measurements leads to improved reliability of reserve estimates. This work presents a method to derive in situ porosity from core measurements by performing an appropriate in situ stress (so-called overburden) correction. The method is based on the fundamentals of poroelasticity, and builds on controlled laboratory and numerical simulations which show that the porosity correction can be obtained by loading isotropically to the in situ mean effective stress (effective stress = total stress - pore pressure). This is further justified by a set of tests on field sandstone cores, where different stress paths were employed.

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About the Society of Core Analysts

Objectives
The name of this organization is the Society of Core Analysts (SCA) and was founded in 1986. This organization is a Chapter-at-Large of The Society of Petrophysicists and Well Log Analysts (SPWLA) and is established with two objectives:

• To promote the aims, purposes, and membership of the SPWLA which is a non-profit scientific organization.
• To serve the interests of all persons who use or obtain reservoir evaluation information from rock and core samples.

As a guide for fulfilment of the first objective, this Chapter stands responsible to, and subject to, the rules and regulations of the SPWLA.

As a means toward the second objective this Chapter will sponsor technical speakers, projects, and presentation of papers dealing with formation evaluation. This Chapter will hold membership open to all core analysts, log analysts, geologists, geophysicists engineers, service company personnel and all others interested in the study of rocks and their interstitial fluids. This Chapter will also actively encourage membership and participation in the activities of the SPWLA.

Website: www.scaweb.org