Patel, R; (2016) In Situ Studies of Clay Hydration for the Enhanced Exploration of Oil and Gas. Doctoral thesis , UCL (University College London).

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Abstract

A major problem in understanding the clay and shale hydration process in oil exploration is the ability to merge information on the microscopic and macroscopic swelling nature of the minerals. Added to this, is the introduction of elevated pressures and temperatures in forming a realistic picture of these processes. In this project, I present neutron diffraction experiments from 22 C and 50 bar to 140 C and 600 bar pressure in conjunction with isotopic substitution of hydrogen for deuterium, to determine full orientational structure of hydrophobic, clay swelling inhibitors tetramethylammonium chloride (TMA Cl) and intersolvent structure of hexamethylenediamine (HMDA) at 22 C and 1 bar. An increase in the intersolvent structure was observed within the inhibitor solution compared to bulk however followed bulk like trends with increasing p & T. Also investigated, for the first time at these elevated conditions, is the effect of TMA and HMDA inhibitors on the swelling response of vermiculites. Aside from an initial d-spacing increase of 3 %, no further interlayer expansion of the Li-vermiculites or TMA-vermiculites was observed with HMDA(aq) or D2O flooding respectively and increasing p & T. Conversely, macroscopic swelling measurements performed primarily on compacted Li and TMA-vermiculite samples, using a bespoke rig, have shown that there is fluid absorption and a height increase of up to 50% upon flooding with water, brine and HMDA(aq). Spin-echo small angle neutron scattering was employed to investigate the route of fluid into the compacted clay. Intuitively, it revealed that large pores ll before smaller (interlayer) pores highlighting that the locus of the swelling problem may shift to within the meso-macro pore spaces of the natural shale. Highlighting the speeds at which interlayer water diffuses, quasi-elastic neutron scattering performed on hydrated terephthalate (TA) exchanged layered double hydroxides showed that the terephthalate does not contribute to the translational diffusion of the system even at water content of 1:16.24 TA:water and up to temperatures of 320 K. A slightly elevated Dtrans = 6.0 x 10- 9m2s-1 for the interlayer water was measured at 320 K.

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