Impact of Fluid Exposure History on Drill Cuttings Mechanical Properties Through Indentation Testing

Abstract Understanding the mechanical properties of rocks throughout the full length of a well is critical for optimizing drilling and production operations. Indentation testing offers a low-cost and time-effective method to obtain geomechanical properties from cuttings and enables access to data that were previously unattainable. Rock cuttings are a widely abundant resource of information, but encounter various fluid exposure histories before collection, which can alter their properties through hydro-chemo-mechanical interactions. This study investigates the influence of fluid exposure on the mechanical properties of cuttings using indentation testing. Four rock types with distinct mineralogies (Eagle Ford Shale, Mancos Shale, Indiana Limestone, and Crab Orchard Sandstone) were tested. Fluid exposure was simulated in two stages: a 24-hour soak in base fluids to represent formation fluids (oil-bearing or water-bearing), followed by a 1-hour soak in drilling fluids (water-based or oil-based mud). Four combinations of fluid exposure were tested accordingly for each rock type: oil-oil, oil-water, water-water, and water-oil. Indentation tests measured hardness and reduced modulus, with 16 indentations performed prior to fluid exposure and 8 each on soaked samples before and after polishing. Fluid history had little effect on Eagle Ford (±6 % modulus and hardness) and on the scatter-dominated Crab Orchard sandstone. Mancos shale stiffened when kept in oil (+26 % modulus, +35 % hardness) but weakened severely after an oil-to-water reversal (–42 % modulus, –48 % hardness), confirming the importance of wetting order. Indiana limestone behaved oppositely: any path ending in oil raised stiffness, whereas continuous water reduced modulus by 20 % and halved hardness, evidence of rapid carbonate dissolution. The results show that fluid sequence can shift indentation properties from negligible change to nearly fiftypercent loss. Recording oil–water contact history, protecting shale and limestone cuttings from prolonged water, and applying statistical treatment to coarse sandstones are practical steps to improve cuttings-based geomechanical profiles.