Figure 1.1 – Chemical nature of crude oils found worldwide (after Reservoir Fluid Database[68]). Figure 1.3 – Distribution of data used to prepare PVT correlations. Figure 1.6 – Variability defined by bubblepoint pressure correlations. Figure 1.7 – Effective molecular weight related to tank-oil gravity. This property is determined by rearranging the equations for calculating bubblepoint pressure as discussed in Secs. The physical property density is the ratio between mass and volume.

Champions have a crucial role in PetroWiki. SPE has established moderation for PetroWiki because we want to extend our reputation for technical excellence to PetroWiki, by ensuring that contributions are technically sound. Every page has a clear disclaimer about the need to apply sound engineering judgment to all information found in the wiki. SPE wants users to be confident the information they find in PetroWiki is credible and represents a reasonable technical approach they can evaluate for application to their specific situation. While we want PetroWiki to be a reliable resource, we also recognize that members from across the industry have experience that may be valuable.

Generally speaking, intellectual property is any product of the human intellect that the law protects from unauthorized use. Creators of intellectual property have exclusive ownership and rights to their intangible assets, which in the realm of the oil and gas industry usually applies to discoveries, inventions, words, phrases, and designs. Intellectual property is traditionally composed of four categories: patents, copyright, trademarks, and trade secrets. Trademarks are names, words, symbols, designs, or combinations of these, that are used to distinguish the goods or services of one company from those of another company. Copyrights protect creative works, like brochures or technical descriptions, from being copied without the creator's permission.

Interfacial or surface tension exists when two phases are present. These phases can be gas/oil, oil/water, or gas/water. Interfacial tension is the force that holds the surface of a particular phase together and is normally measured in dynes/cm. It is a function of pressure, temperature, and the composition of each phase. Two forms of correlations for calculating gas/oil surface tension have been developed.

Understanding the mechanisms and potential for wax precipitation are key factors in preventing production problems as a result of wax. Wax precipitation has a strong dependence on temperature and weak dependence on pressure. This page presents a general form of the thermodynamic relation used to define the K values for solid and liquid phases in equilibrium, and the effect of different simplifying assumptions and thermodynamic descriptions of the phases involved on the model results are examined. The thermodynamic basis of solid/liquid equilibrium of components in a melt or dissolved in a solution is well established and is described in many standard texts (e.g., Prausnitz et al.[1]). The basic principles continue to be applied to more complex systems as researchers attempt to develop more accurate models of solid wax precipitation. Lira-Galeana and Hammami[2] reviewed experimental techniques and thermodynamic models for studying wax precipitation in petroleum fluids. The predictive capability of the thermodynamic models is affected both by the form and assumptions of the models themselves and the characterization procedures used to quantify the number and properties of wax forming components present in a fluid. Thermodynamic models for predicting wax precipitation may be derived assuming single-component or multicomponent, single-phase or multiphase solid deposits.

Deposition of the high-molecular-weight components of petroleum fluids as solid precipitates in surface facilities, pipelines, downhole tubulars, and within the reservoir are well-recognized production problems. The deposits also can contain resins, crude oil, fines, scales, and water.[1] Asphaltenes and waxes are a general category of solids and, thus, cover a wide range of materials. Understanding the fundamental characteristics that define the nature of asphaltenes and waxes is valuable in reducing or avoiding the production impacts of their deposition. This page examines the general chemical classifications and types of asphaltenes and waxes, in addition to their solidification behaviors.

Natural petroleum gases contain varying amounts of different (primarily alkane) hydrocarbon compounds and one or more inorganic compounds, such as hydrogen sulfide, carbon dioxide, nitrogen (N2), and water. Characterizing, measuring, and correlating the physical properties of natural gases must take into account this variety of constituents. A dry-gas reservoir is defined as producing a single composition of gas that is constant in the reservoir, wellbore, and lease-separation equipment throughout the life of a field. Some liquids may be recovered by processing in a gas plant. A wet-gas reservoir is defined as producing a single gas composition to the producing well perforations throughout its life.

The electrical-distribution system furnishes electrical power and partial protection of the electrified oil field and consists of a primary system and a secondary system. It is important to the economics and longevity of the overall system that distribution be designed adequately before installation. To reduce power losses, electricity distributed to an oil field is brought to the field at higher voltages of between 4,000 and 15,000 V. This higher-voltage distribution system is called a primary system. Higher voltages allow the use of smaller conductors, but require more expensive transformers.

The two basic types of installations are the "fixed"-pump and the "free"-pump design. In the fixed installation, the downhole pump is attached to the end of a tubing string and run into the well. Free-pump installations are designed to allow the downhole pump to be circulated into and out of the well inside the power-fluid string, or it can also be installed and retrieved by wireline operations. Figure 1.2-Free and fixed hydraulic downhole pumping installations. Figure 1.3-Free pump (pump in-and-out operation).

The number of components present in a system determines the maximum number of phases that can coexist at fixed temperature and pressure. The phase rule of Gibbs states that the number of independent variables that must be specified to determine the intensive state of the system is given by ....................(8.1) For a single-component system, the maximum number of phases occurs when there are no constraints (Nc 0) and no degrees of freedom (F 0). Thus, the maximum number of possible phases is three. If only two phases are present in a pure component system, then either the temperature or the pressure can be chosen.