Estimating Mechanical Properties of Shale From Empirical Correlations

TLDR

Borehole‑stability prediction and other subsurface evaluations require knowledge of shale mechanical properties, which are rarely available. This paper presents empirical correlations to predict shale mechanical properties. The correlations, derived from extensive North Sea shale core tests, use acoustic P‑wave velocity from wireline, MWD, or cuttings to estimate mechanical properties.

Abstract

Summary Borehole-stability prediction requires knowledge of the mechanical properties of the formations which is rarely available in shale sections. This paper presents empirical correlations to assist in predicting shale mechanical properties. The correlations are based on extensive laboratory testing of shale cores primarily from the North Sea. The acoustic P-wave velocity is a primary input parameter in several of the correlations; thus, various sources of the P-wave velocity such as sonic wireline, sonic measurement while drilling (MWD), and acoustic measurements on cuttings may be used to obtain somewhat continuous estimates of shale mechanical properties. Borehole-stability evaluations can be made at different stages in the drilling process (planning, while drilling, and post-analysis). Other applications of the correlations where shale mechanical properties are required are evaluation of overburden compaction during depletion and optimization of the drilling process (selection of bit type, bit parameters, etc.).