Interactions of crude oil and salt solutions with mineral surfaces

Understanding the fundamental interaction of liquids with mineral surfaces and their relation to larger scale mechanisms and phenomena in porous media is relevant to wide range of applications in oil recovery, soil remediation etc. Most previous imaged-based studies related to these applications were limited to two-dimensional space and rarely included multi-scale observations. Idealised systems, comprising monomineralic model porous media, simple liquids such as salt solutions and model oils have been successful in demonstrating predictable and reproducible trends. However, once the system is set closer to real environmental conditions, using realistically complex porous media with several minerals, and including variable aqueous conditions (e.g. salinity, ion valency or pH) and complex oils (e.g. crude oil), the results become too difficult to interpret. This thesis aims to unravel some of these complexities associated with the physics and chemistry of aqueous and hydrocarbon phases and mineralogy. The studies show the importance of interfacial interactions for industrial processes in porous media, which include carbonate and/or silicate minerals. In the first part of the thesis, sandstone cemented with dolomite and anhydrite was the porous medium for a case study of the effect of salinity on particle mobilization. Rock samples were imaged with micro-CT, and analysed digitally. This study was complimented by Atomic Force Microscopy (AFM) measurements of the adhesion forces between carbonate and quartz surfaces to better understand initial attraction between dolomite particles and quartz grain. The second part of the thesis was devoted to systems relevant to silicate minerals, in particular kaolinite and quartz, in contact with both salt solutions and crude oil. The focus was on the wettability alteration of such minerals, and its dependence on salinity, ion valency, pH and waterflooding. Wettability alteration was characterised by contact angle measurements and imaging of adsorbed/deposited crude oil polar compounds by scanning electron microscopy (SEM) and AFM. To study kaolinite wettability, a special procedure for kaolinite substrate preparation was developed, giving thin and smooth kaolinite coats, which remained stable in contact with liquids. The results showed that the wettability alteration of kaolinite by crude oil was generally similar to quartz, displaying a decrease in oil-wetness with increase in salinity and pH of the aqueous phase. The effect of subsequent waterflooding on wettability alteration was studied on glass and sandstone substrates. The preparation procedures developed showed that initial wettability alteration towards oil-wetness decreases, and its flooding-induced reversal towards water-wetness increases, with rising salinity and pH of the aqueous phase. Oil deposits after flooding were distributed as nano-blobs, with their substrate coverage and size similarly dependent on salinity and pH. It was found that the use of organic solvents to remove the bulk oil to inspect the deposits introduce preparation artefacts, which result in overestimation of deposit coverage. Analogous experiments on sandstone rock samples supported all findings for the glass model substrates. The final part of the thesis unified these new methodologies for wettability analysis with micro-CT analysis to study the pore-scale distribution of residual crude oil in plugs after waterflooding and relate this to the wettability state.--provided by Candidate

Factors within the event space which influences the customer experience : Case study: DuuniExpo and Contact Forum

There are several factors that can influence people’s experiences in events. These factors can many times be related to the state of mind of the participant. However, elements within the event environment plays a big role in influencing the emotions of attendees, and therefore, can affect their perceived experiences. This thesis objectives are to research what are the main elements within the space of job and recruitment fairs that can influence the experiences of the participants. There were events from two companies analyzed in this research. CF-opiskelijamessut Oy is the company that organizes Contact Forum, in Helsinki and Lahti University of Applied Sciences organizes DuuniExpo, which is held in Lahti. The theories used in this thesis cover basic of events and business events. In addition, it discusses the importance of the event design. Moreover, eventscape model is used as a base for the research, as it shows several elements that can help to build a suitable environment for an event, which will have an impact on guests satisfaction. The methods used for the research were based in the Service Design. Several tools were used in the different steps of the service design process in order to achieve better results. Service design tools used were customer profile, customer journey, service blueprint, shadowing, interviews and prototype. Furthermore, the outcome from the information gathered with the research and its analysis enabled the development of ideas. The ideas suggested are done for the certain type of events analyzed during the process. The recommendations the researchers suggests are related to the event space design and several elements that can be added in order to enhance the attendees’ experience

Nano-scale structure of crude oil deposits on water-wet substrates: Dependence on aqueous phase and organic solvents

Wettability alteration of glass substrates due to displacement of the surrounding salt solution by crude oil, and its reversal via salt solution flooding, were investigated as a function of salt concentration and solution pH, and the sample preparation procedure. The resulting wettability states were analyzed by microscopy of the substrate-bound oil residues and contact angle goniometry. Atomic force microscopy of the flooded state under its salt solution showed partial coverage of the substrate by adhering oil nano-blobs. Scanning electron microscopy provides a simpler means to acquire images of residues, but the need to rinse the bulk liquids and dry can introduce preparation artifacts. Three organic solvent rinsing procedures were examined, all showing that oil residue coverage decreases with increasing NaCl concentration and pH, and also decreases after flooding to follow these same trends. However, procedures in which bulk oil was rinsed from the flooded state using the solvents decalin and heptane created extraneous deposition; removal of the salt solution by methanol better preserved the oil residues. After flooding, even the salt solution allowing greatest adsorption/deposition of polar oil components, and strongest oil-substrate adhesion, had reduced coverage to only 20%. Analogous experiments on sandstone rock supported these findings. This suggests that local wettability of reservoirs can fluctuate in response to the oil and water slowly passing through pores during oil recovery by flooding

Wettability alteration of kaolinite exposed to crude oil in salt solutions

Adsorption and deposition of polar components of crude oils onto kaolinite in the presence of aqueous solutions of sodium and calcium chlorides is probed by spectroscopy, microscopy and drop contact angle. The fine kaolinite particles are thinly coated onto glass to remain immobile during the aging in salt solution and oil, and subsequent solvent rinsing. These thin coats facilitate quantification of the extent of deposition versus salt composition, while also allowing high-resolution microscopy of its spatial distribution. The asphaltene-based deposits take the form of nanoparticle aggregates decorating kaolinite faces and edges. At low salinity and low-neutral pH, water surrounding kaolinite is expelled by oil deposition and pore penetration to strongly alter wettability of the aggregate from hydrophilic to oleophilic, and trends are in qualitative agreement with expectations from DLVO theory. Higher ionic strength suppresses oil deposition, either by limiting it to kaolinite edges in the case of sodium chloride-rich solutions or protecting both faces and edges at high calcium chloride contents. Only the latter suffices for the kaolinite aggregate to substantially retain its hydrophilicity

Micro-CT and Wettability Analysis of Oil Recovery from Sand Packs and the Effect of Waterflood Salinity and Kaolinite

An image-based approach was developed by combining microtomography with electron microscopy and contact angle goniometry to determine the pore-scale distribution of crude oil in plugs after waterflooding and shed light on the molecularscale mechanisms responsible. The approach was applied to a model rock comprising a pack of quartz sand grains without or with a preapplied lining of kaolinite, imaged prior to and after capillary-driven oil recovery by flooding with a model brine of high or low salinity. The presence of kaolinite increased residual oil and reversed its brine dependence, with high-salinity flooding giving greatest recovery from the clean sand and least recovery from kaolinite-coated sand. These two extremes tended to exhibit the most connected residual oil clusters, while low salinity gave smaller blobs, to the detriment or advantage of oil recovery. Low-salinity flooding in secondary or tertiary recovery mode resulted in comparable oil residuals in kaolinite-coated sand. Surface analysis of the grains and model substrate analogs without or with this coating showed that recovery was correlated to the advancing contact angle. In particular, kaolinite was far more resistant than quartz to wettability alteration by this particular crude oil, resulting in a more water-wet state prone to oil trapping via bypassing and snap-off mechanisms

Adhesion of Oil to Kaolinite in Water

Uniform coats of kaolinite particles on a flat glass substrate were prepared to be sufficiently smooth and thin to allow reliable measurement of contact angles of captive crude oil drops in a range of salt solutions, without any particle removal. The contact angle hysteresis was used to infer the extent of oil adhesion via rupture of the intervening water film and anchoring of charged groups to kaolinite. For sodium chloride solutions, adhesion decreases monotonically with pH and/or salinity, with strong adhesion only manifested under acidic conditions with salinity at most 0.1 M. Calcium chloride solutions at pH around 6 switch from strong adhesion in the range 0.001-0.01 M to weak adhesion at higher concentrations. For all mixtures of sodium and calcium chlorides investigated, a total ionic strength above 0.1 M guarantees a weak adhesion of oil to kaolinite. Results are qualitatively consistent with theoretical expectations of electrostatic interactions, with H+ and Ca2+ being potential-determining ions for both interfaces

Changes in wettability state due to waterflooding

Some coreflood literature points to the initial wettability state undergoing change during waterflooding, usually towards water-wetness. The current study aimed to directly probe the adsorbed/deposited oil components on model silicate substrates prior t

Hydrodynamic modelling of the Onega River tidal estuary

Hydrodynamic conditions in a tidal estuary are very complex and depend on a wide range of factors. This was also demonstrated in the previous studies for the estuary of the Onega River, which were primarily based on the analysis of field measurements. In this paper, the results of numerical modelling performed using 1D and 2DH/3D «shallow water» approaches are presented, for summer and winter hydrological conditions in the Onega River estuary. The models were built and calibrated using extensive field data, which allowed assessing the opportunities to model the temporal and spatial variability of water levels, discharges, and velocities in a dynamic environment of a tidal estuary