: In this paper we present a novel method to estimate the magnitudes of the minor- and major horizontal effective in-situ rock stress. The method uses Acoustic Emission-controlled polyaxial re-loading of core in the laboratory. Contrary to other Acoustic Emission-based methods, our novel approach ensures that present-day stresses are measured, even if the core has been subjected in-situ to paleo-stresses that are higher than the present day stresses.
1 INTRODUCTION
Reviews of current in-situ stress estimation methods in hydrocarbon reservoir rocks show that especially the magnitudes of the horizontal stresses are often difficult to estimate reliably. A novel technique for stress estimation on core has been proposed and patented by Shell (Renter et al, 1998). The present paper outlines the idea behind the technique and presents the experimental work using outcrop sandstone, that forms the basis of the proposed Pestman-Kenter-van Munster (PKM) method. The technique is especially applicable to vertical wells and makes use of the observation that a core is taken through an extreme stress condition during drill-out. Just before the core sample enters the core barrel at the corebit in a vertical well, the vertical stress has been replaced by the (generally much lower) mud pressure, while the horizontal stresses are still acting on the core. This high stress differential between the horizontal effective stresses and the mud overbalance is likely to cause irreversible deformation of the rock.
