Measuring transport properties of rock samples under stress is essential to understanding and predicting the migration of fluids within the Earth's crust. Mudrocks play an essential role in petroleum systems as they are often the source rock and may act as a seal due to their low permeability. With increasing production from unconventional reservoirs where the mudrock is source, reservoir and seal, there is now even greater demand to understand the permeability and storativity of mudstones and tight sandstones. When hydraulic fracture treatment is used to enhance production, flow of hydrocarbons into the fractures will be ultimately controlled by the matrix permeability. Knowledge of the fluid transport properties of mudstones is currently hindered by a scarcity of published experimental data. In this thesis, a combination of permeability and ultrasonic velocity measurements allied with image analysis is used to distinguish the primary microstructural controls on effective stress dependent permeability. Permeabilities of cylindrical samples of Whitby Mudstone and Eagle Ford Shale have been measured using the oscillating pore pressure method at confining pressures ranging between 30-95 MPa and pore pressures ranging between 1-80 MPa. The results show that samples must be pressure cycled in order to obtain a reproducible behaviour, after which the relationship between permeability and effective stress can be described by an exponential law. The permeability of the Whitby Mudstone samples ranges between 7 ×10-21 m2 and 2 ×10-19 m2 (7 nd to 188 nd) and decreases by ~1 order of magnitude across the applied effective stress range. The permeability of the Eagle Ford Shale samples is slightly higher ranging between 2 ×10-18 m2 and 42 ×10-18 m2 (2 μd to 42 μd) and decreases by half an order of magnitude across the applied effective stress range. Permeability is shown to be more sensitive to changes in pore pressure than changes in confining pressure yielding values of alpha between 1.1-2.1 for Whitby Mudstone and 1.6-4.6 for Eagle Ford Shale. Gas slippage (Klinkenberg) effects are restricted to pore pressures below 10 MPa in the Whitby Mudstone and therefore do not affect the results presented. The permeability-effective stress relationship is thus empirically described using a modified effective stress law in terms of confining pressure, pore pressure and a Klinkenberg effect. Use of a simple reservoir model demonstrates that if pressure dependent permeability is not taken into account, substantial overestimation of gas flow rate and original gas in place will be made from well tests. Changes in ultrasonic velocity and pore volume were related to the observed loss of permeability with increasing effective stress, providing further insight into the nature of the permeability-controlling pore network. Combining the petrophysical data with pore conductivity modelling and microstructural analysis shows that at low effective stresses, permeability is controlled by a network of long, thin crack-like pores associated with grain boundaries. At high effective stresses, these cracks are closed and fluid is restricted to flowing through a less permeable network of higher aspect ratio, stiffer, nm-scale pores in the clay matrix. Applying the methods developed in the present work to different mudstones with a range of compositions and textures will help to refine understanding of the variability in fluid-conducting pore networks, thereby advancing the interpretation of data from well logs and well tests used for reservoir evaluation.

The classical Terzaghi Theory was extended by accounting for the variations of permeability during consolidation. With the aid of X-ray techniques, investigations on the significance of the variation of permeability, as well as the variations of void ratio and effective pressure, were conducted. Effects of the conventional consolidometer boundary on consolidation testing were studied. / Thesis / Master of Engineering (ME)

This thesis considers the effect of compression ratio on the performance of a direct injection diesel engine. One aspect of engine performance is considered in great detail, namely the combustion performance at increased clearance volume. This aspect was of particular interest because variable compression ratio (VCR) systems normally operate by varying the clearance volume. The investigation relied upon results obtained both from experimental and computer simulating models. The experimental tests were carried out using a single-cylinder direct-injection diesel engine, under simulated turbocharged conditions at a reduced compression ratio. A number of one-dimensional computer models were developed; these simulate the induction and compression strokes, and the fuel spray trajectories in the presence of air swirl. The major objectives of the investigation were: to assess the benefits of VCR in terms of improvements in output power and fuel economy; to assess the effects on combustion of increased clearance volume, and investigate methods for ameliorating resulting problems; develop computational models which could aid understanding of the combustion process under varying clearance volume conditions. It was concluded that at the reduced compression ratio of 12.9:1 (compared to the standard value of 17.4:1 for the naturally-aspirated engine), brake mean effective pressure (BMEP) could be increased by more than 50%, and the brake specific fuel consumption (BSFC) could be reduced by more than 20%. These improvements were achieved without the maximum cylinder pressure or engine temperatures exceeding the highest values for the standard engine. Combustion performance deteriorated markedly, but certain modifications to the injection system proved successful in ameliorating the problems. These included: increase in the number of injector nozzle holes from 3 to 4, increase in injection rate by about 28%, advancing injection timing by about 6°CA. In addition, operation with weaker air fuel ratio, in the range of 30 to 40:1 reduced smoke emissions and improved BSFC. Use of intercooling under VCR conditions provided only modest gains in performance. The NO emission was found to be insensitive to engine operating conditions (fixed compression ratio of 12.9:1), as long as the peak cylinder pressure was maintained constant. Engine test results were used in order to assess the accuracy of four published correlations for predicting ignition delay. The best prediction of ignition delay with these correlations deviated by up to 50% from the measured values. The computer simulation models provided useful insights into the fuel distribution within the engine cylinder. It also became possible to quantify the interaction between the swirling air and the fuel sprays, using two parameters: the crosswind and impingement velocities of the fuel spray when it impinges on the piston-bowl walls. Tentative trends were identified which showed that high crosswind velocity coincided with lower smoke emissions and lower BSFC.

Aleksandro Stulginskio Universitete, Transporto ir Jėgos Mašinų Inžinerijos Institute, atliktais tyrimais nustatyta, kad vieno cilindro tiesioginio įpurškimo dyzelinis variklis (,,Oruva“ F1L511) maitinamas pagerintu, 0,08; 0,12; 0,20vol% cetaninį skaičių (CS) didinančiu priedu, rapsų aliejumi (RA), gali efektyviai veikti ir išskirti mažesnę, kai kurių emisijos komponentų dalį. Dyzelinio variklio išvystytas didžiausias efektyvusis slėgis siekė 0,57MPa, varikliui veikiant 2000 min-1 sūkių dažniu. Variklio minimaliosios lyginamosios efektyviosios degalų sąnaudos sumažėjo nuo 272g/kWh iki 268g/kWh tai yra 1,5% panaudojus 0,12vol% cetaninį skaičių didinantį priedą rapsų aliejuje. Deginių dūmingumas sumažėjo 45% vidutinės (pe=0,4MPa) ir 40% didžiausios (pe=0,57MPa) apkrovos srityje atitinkamai panaudojus 0,12vol% ir 0,20vol% cetaninį skaičių didinantį priedą rapsų aliejuje. Bandymų metu didžiausias ƞe=0,364 variklio efektyvusis naudingumo koeficientas buvo pasiektas variklį maitinant 0,12vol% cetaninį skaičių didinančiu priedu apdorotu rapsų aliejumi ir jam išvysčius 5,3 kW efektyviąją galią. Tačiau mažesnės ir didesnės variklio išvystomos efektyviosios galios srityse aukštesnis variklio efektyvusis naudingumas buvo bazinio rapsų aliejaus naudojimo atveju. / Studies conducted at Aleksandas Stulginskis University (ASU) of Transport and Power Machinery Engineering Institute showed that a single-cylinder, air-cooled, direct-injection diesel engine (" Oruva " F1L511 ) can be with rapeseed oil treated with 0.08vol%, 0.12vol% and 0.20vol% the cetane number (CN) improving agent. Diesel engine developed the maximum effective pressure of 0.57MPa when running at 2000 rpm speed. Using of 0.12vol% of the cetane number improving agent (2-ethylheksyl-nitrate) to rapeseed oil the brake specific fuel consumption reduced in the range 272 g/kWh to 268 g/kWh, i.e. 1.5% when running at moderate (pe=0.38MPa) load and 2000 rpm speed. As a result of 0.12vol% the smoke opacity decreased by 45% at moderate (pe=0.4MPa) and 40% at maximum (pe=0.57MPa) load. During the tests, the highest ƞe=0.364 effective efficiency engine was when running on rapeseed oil treated with 0.12vol% cetane improving agent developed at the power output of 5.3 kW.