Shale Stability: Drilling Fluid Interaction and Shale Strength

Abstract

Abstract This paper presents main results of a shale stability study, related to the understanding of shale/fluid interaction mechanisms, and discusses shale strength correlation. The major shale/fluid interaction mechanisms: Capillary, osmosis, hydraulic, swelling and pressure diffusion, and recent experimental results are discussed. Factors affecting the shale strength are discussed, and a sonic compressional velocity-log based correlation for strength is proposed. Recommendations for modeling and improving shale stability are described, based on the current understanding of shale stability.