This dissertation focuses on the design and the application of microchemical systems to understand multiphase flows in upstream hydrocarbon and natural gas productions. Offshore petroleum and natural gas catastrophes, such as the Deepwater Horizon spill of 2010, motivate the need to understand how to minimize the introduction of potentially invasive compounds while maximizing their efficacy during emergency remediation. The microfluidic stabilities of mineral oil-seawater multiphase flows in the presence of model dispersants were studied for We < 1. Introducing dispersants at varying dimensionless volumetric injection rates, ranging from 0.001 to 0.01, transitions from stable slug flow to the bubbly regime. Dimensionless mass ratios of three model dispersants to the mineral oil necessary to establish emulsions were estimated from 2.6x10^-3 to 7.7x10^-3. Residence time distributions of seawater single- and mineral oil-seawater multi-phase flows, laden with dispersants, were also investigated. Increasing the dimensionless dispersant injection rate from 0 to 0.01 was observed to increase convective dispersion, which was confirmed by estimations of the vessel dispersion number and the Bodenstein number. The deposition and dissolution of asphaltenes in porous media, an important problem in science and macromolecular engineering, was for the first time investigated in a transparent packed-bed microreactor (μPBR) with online analytics to generate high-throughput information. Residence time distributions of the μPBR before and after loading with ~29 μm quartz particles were measured using inline UV-Vis spectroscopy. Stable packings of quartz particles with porosity of ~40% and permeability of ~500 mD were obtained. Temperature (25.0-90.0 °C), n-heptane composition (50.0-80.0 vol%), and n-alkane (n-C_5 to n-C_9) were all observed to influence asphaltenes deposition in the porous media, and reduced dispersion was obtained in the damaged packed-bed by estimating disperision coefficients and the Bodenstein number. Deposition by mechanical entrapment dominated the mechanism in all scenarios, as discovered by the simplified Kozeny-Carman and Civan's permeability-porosity relationships. Role of water on the deposition mechanism was then investigated. Porosity loss and permeability impairment of the porous media for water mass fractions of <0.001 to 34.5 wt% were investigated. Interestingly, a switch in the mechanism of water (from 0.030 to 3.18 wt%) on the accumulation was discovered. Analyses of porosity-permeability relationships revealed competition between adsorption and desorption followed by pore-throat plugging via mechanical entrapment for all mass fractions of water studied. For the dissolution of asphaltenes in porous media, many factors, such as shut-in time, temperature, Reynolds number, and n-heptane compositions, were studied, and the dissolution of asphaltenes was investigated. The work described within this dissertation undergirds that microchemical systems are promising tools that impact dispersant science and asphaltenes science. Microchemical systems also potentially aid the design of reservoir treatments.