Civil Engineering ETDs

Publication Date

9-3-2013

Abstract

Emergent interest in advanced hydrocarbon exploration and geological carbon dioxide (CO2) sequestration has brought about a requisite for improving existing oil well cementing materials and understanding the macro and microstructural characterization mechanisms of oil well cement (OWC). OWC slurries have stringent performance requirements, including low viscosity, rapid strength development, low permeability and enhanced degradation resistance. Preliminary research work showed that nanosilica is capable of reducing OWC porosity and therefore is was thought that nanosilica incorporation may have potential to improve the aforementioned performance requirements. In this research, Type G OWC paste specimens produced with water to binder (w/b) ratio of 0.45 and incorporating 0, 1 and 3% nanosilica by weight of cement are hydrated for 28 days under two conditions, ambient room condition (20 °C with 0.1 MPa pressure) and an elevated oil well simulated condition (80 °C with 10 MPa pressure). Macroscale mechanical characterization of the hardened cement pastes was investigated using axial compression, rapid chloride-ion penetration test (RCPT), and axial degradation/damage progression analysis and quantification after carbonic acid exposure testing. Degradation testing was performed by simulating conditions of geosequestration in a sandstone formation at a depth of roughly 1 km. These conditions were created by bubbling CO2 into a heated vessel containing 0.5 M NaCl (brine) to produce the carbonic acid. This newly produced composition was then pumped into the bottom of a heated reactor containing the freshly cured specimens creating the sandstone formation condition exposure. This process was sustained for 28 days with subsequent monitoring of constant temperature (50 °C) and pH (5). Slices of the cylindrical cement specimen were taken periodically, during and after 28 days of exposure, in order to quantify the OWC degradation progression. The compressive strength and modulus of elasticity of the specimens was examined prior, during and after exposure and damage metric was computed to quantify OWC degradation progress with time in a carbonated brine environment. The macroscale results showed that addition of 1% nanosilica can significantly limit OWC degradation in carbonated brine environments and enhance the accompanying performance requirements. Furthermore, microstructural characterization of the OWC specimens with and without nanosilica, before and after exposure, was performed using nanoindentation, the Brunauer-Emmett-Teller (BET) N2 theory and Barrett-Joyner-Halena (BJH) method, X-ray diffraction (XRD) analysis and 29Si magnetic spinning angle (MAS) using nuclear magnetic resonance (NMR). Microstructural characterization experiments were performed in order to adequately explain the results of the macroscale experiments and reinforce the stated hypothesis.

Keywords

Oil well cementing--Materials.

Sponsors

Department of Defense (DTRA), NSF, KFUPM

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Maji, Arup

Second Committee Member

Rahman, Muhammad Kalimur

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