Evaluation of drilling performance and penetration mechanisms using seismic while drilling and acoustic emission methods

Xiao, Yingjian (2017) Evaluation of drilling performance and penetration mechanisms using seismic while drilling and acoustic emission methods. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In oil and gas industry, drilling provides the path to exploit underground resources. Increasing rate of penetration (ROP) is one of the goal of drilling engineers to build this path. This dissertation focuses on study of a novel drilling technique, i.e. passive Vibration Assisted Rotary Drilling (pVARD) technique, and characterization of drilling mechanisms in comparison to the other two widely used drilling techniques, i.e. rotary drilling and rotary-percussion drilling (RPD). In terms of the fundamental differences between drill bit vibrations from three drilling techniques, seismic while drilling (SWD) and acoustic emission (AE) technologies are used to study drill bit sources and corresponding drilling mechanisms. First, geomechanics response of synthetic rock is studied using AE technique based on standard confined compressive strength (CCS) tests. This research aims to compare synthetic to natural rock in terms of deformation properties and provides support for the following drill-off test (DOT). Second, pVARD tool drillings are conducted in comparison to rotary drilling both in laboratory and field tests using AE and SWD techniques, respectively. In laboratory, AE signal energy and cutting size distribution are correlated to polycrystalline diamond compact (PDC) bit drilling performance. Results show that micro crack is generated from drag bit shearing action and the higher AE energy, coarser cuttings and higher ROP are obtained. In field test, surface wave energy and frequency bandwidth are correlated to drill bit vibration and drilling performance. Third, laboratory active vibration DOTs are conducted to study the penetration mechanisms from a diamond coring bit using AE technique. Spectral and energy analysis of the AE signals indicate that the higher ROP and larger cutting size are correlated with a higher AE energy and a lower AE frequency, indicating larger fractures are being created to generate the larger size of cuttings. Fourth, rotary-percussion drilling sources are studied by two field experiments on weak shales and hard arkose using SWD technique. Characterization of these sources consist of spectral analysis and mean power study, along with field measurements of the source radiation patterns. In addition, polarization analysis is conducted on P-waves recorded at surface geophones for understanding the particle motions.

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