Optimizing Drilling Performance by Wellbore Stability and Pore-Pressure Evaluation in Deepwater Exploration

Geochemical analysis of rocks is fundamental to the understanding of geology and earth sciences. X-ray dispersive spectrometry and other automated techniques are increasingly being used to determined and quantify the abundances of the major, trace elements and other rock properties. This study utilized a combination of dispersive spectrometric techniques (MicroXRF) and impulse rebound hammer method to establish links between geochemical and mechanical properties of rocks through a non-destructive method. MicroXRF has high resolution and can detect trace elements within the parts per billion range. The micro-rebound hammer was used to generate a reduced Young's modulus (E*), which gives a measure of the rock strength with negligible impact on the rock itself. In order to explore, visualize and understand the dataset generated, principal component analysis (PCA) was applied to emphasize variation and bring out strong patterns in the dataset. The first two dimensions of PCA express 57.09% of the total dataset inertia; that means that 57.09% total variability in the data is explained by the planes/dimensions. The first dimension, which showed a strong positive correlation to clay forming minerals and rock strength, was tentatively identified as the clay gradient. The second dimension describes diagenetic alteration processes responsible for the enrichment of elements such as Ni, Mo etc. Further, a positive correlation was established between E* and four elements Cobalt (Co), Strontium (Sr), Titanium (Ti), and Zircon (Zr). Remarkably, Silicon (Si) had a negative correlation with all elements but positive correlation with porosity and permeability. We therefore identified Co, Ti, Sr, and Zr as proxy for the determination of rock strength specific for studied samples and proposed a workflow based on our sequences of analysis and interpretation. Furthermore, we identified four chemo-mechanical facies through hierarchical clustering of the product of the PCA. This presented methodology could be specifically useful for geomechanical characterization of rocks; a key requirement needed for in-situ stresses estimation, wellbore stability analysis, reservoir stimulation and compaction, pore pressure prediction, and more importantly for characterizing drill cuttings where size and time are limiting. Drilling operations require constantly evolving cost effective and time efficient techniques, the proposed workflow will serve these purposes i.e. rapid determination of elemental composition (microxrf) coupled with E*will give a reliable proxy for rock strength. The technique can be applied to, drill cuttings, slabs and whole core directly without prior sample preparation.

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Integrated Techniques for Continuous Rocks Elastic Properties Profile and Geomechanical Characterization

Hussain

Amao

Muqtadir

et al. 2019

Day 2 Tue, November 12, 2019

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The knowledge of rocks elastic properties (REP) is crucial to geomechanical modeling throughout an asset life cycle. Reliable geomechanical models requires calibration of well log REP with core measurements. However, sample availability, representativeness, time, and cost are problems associated with core measurements. In this paper, we integrated REP derived from two laboratory techniques performed on several core covering over 800 ft interval samples from Paleozoic tight sands and shale reservoirs to obtain a continuous REP profile for better- upscaling of reservoir model parameters. For lithology delineation, intact core samples were scanned utilizing MicroXRF. While, REP was measured using Autoscan and AutoLab systems. The Autoscan employs non- destructive technique to characterize the variability of REP. The AutoLab uses the standard triaxial testing method to provide REP at reservoir conditions. The results were tabulated and statistically treated to establish significant empirical relationships. REP derived from triaxial tests on selected samples include, the P and S wave velocities (Vp and Vs), static moduli (Young’s modulus (Es) and Poisson’s ratio (vs)), as well as dynamic moduli (Young’s modulus (Ed) and Poisson’s ratio (vd)). While the reduced Young’s modulus (E*) was obtained from non- destructive method. Lithofacies were established from elemental data. The E* reveals details of several geomechanical heterogeneity and anisotropy which are not possible with traditional triaxial method. There is a significant correlation between E* and Es, Ed, Vs, and Vp. A continuous REP profile was developed using E* with geochemical data. Based on the characterized profile, fracture height growth barriers identified were toughness/modulus and interface barriers. These can significantly affect hydraulic fracture vertical growth within the studied Paleozoic tight sands and shale reservoirs units. The approach, which uniquely considered scales of rock geochemical and mechanical properties and data analytics, demostrate the possibility of generating a continuous REP profile using laboratory aquired dataset. Thus, the difficulty associated with geomechanical characterization and model calibration of highly laminated unconventional reservoirs using actual laboratory data is resolved. This has a directly implication to both conventional and unconventional geomechanical modeling, where the determination of upscaled-reservoir model parameters matters.

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Optimizing Drilling Performance by Wellbore Stability and Pore-Pressure Evaluation in Deepwater Exploration

Cited by 4 publications

References 5 publications

Unconventional rocks elastic properties profile and geomechanical characterization

Unconventional rocks elastic properties profile and geomechanical characterization

Linking Geochemical and Mechanical Properties of Rock Samples Using New Non-Destructive Techniques

Integrated Techniques for Continuous Rocks Elastic Properties Profile and Geomechanical Characterization

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