Rock mechanical characterization of the Upper Cretaceous carbonate mudrocks of Jordan

  • Regina Iakusheva

Student thesis: Master's Thesis

Abstract

Rock mechanical properties of subsurface strata, such as strength, hardness, brittleness, and elasticity, play an important role during reservoir development for wellbore stability, fracture prediction and generation, and the application of other engineering techniques. Specifically, for unconventional reservoir development characterization of the mechanical properties of organic-rich layered rocks is critical, including for the design of proper drilling, well completion, and production programs. This study evaluates rock mechanical properties of Jordanian Upper Cretaceous organic-rich carbonate mudrocks, which are comprised of carbonate mudstone, chalky marl and shale interlayers. They are characterized by high organic content, heterogeneous porosity (1.2%- 35%) and a nanodarcy permeability. The study mainly derives rock mechanical properties from core and laboratory investigations, with the aim to access the impact of compositional and sedimentary facies variation on rock mechanical properties. The rocks were examined for their lithology, mineralogy, and mechanical properties. Microscopic investigation allowed the definition of four different microfacies (organic-rich (OR) mudstone, OR wackestone, silica-rich packstone, OR packstone). X-Ray analysis shows that different microfacies types exhibit various mineralogical compositions, with carbonate, biogenic quartz, and apatite as the dominant components. All samples are rich in TOC content, ranging from 7.5 to 25.3% (average 16.6 wt.%). The data show that microfacies variation has a clear impact on the rock mechanical properties. Leeb Hardness (LH) is higher in silica-rich packstone and OR mudstone. Intrinsic specific energy (ISE) and wave velocities reach their maximum in OR mudstones. The average porosity values are much higher in OR wackestones (33.2%) and OR packstones (34.3%). The brittleness index (BI), which was calculated based on mineral composition, indicate that silica-rich packstones and OR mudstones are brittle, while the other two microfacies have properties of a ductile material. In addition, the good correlation between the ISE and BI suggests that ISE values are a useful proxy for brittleness. The present study improves the understanding of the relationships between stratigraphy, microfacies, TOC, and mechanical properties. These insights bear implications for improvement of exploitation of the JOS, understanding of rock mechanical properties of mature unconventional formations as well as provide the workflow for more efficient procedure to access the compressive strength
Date of AwardJul 2021
Original languageEnglish (US)
Awarding Institution
  • Physical Science and Engineering
SupervisorVolker Vahrenkamp (Supervisor)

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