Recently, global climate change and air quality have become increasingly important environmental concerns. Consequently, there has been a rise in collaborative international efforts to reduce the concentration of greenhouse gases and criteria pollutants. Greenhouse gases include carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), occurring naturally and as the result of human activity. In addition, criteria pollutants (1970 amendments to the Clean Air Act required EPA to set National Ambient Air Quality Standards for certain pollutants known to be hazardous to human health) include emissions of nitrogen oxide, sulfur dioxide, carbon monoxide, and total unburned hydrocarbons. International and national governments are implementing more regulations on air emissions.
Water separated from oil and gas during production contains dissolved solids, including salts. Produced water with sufficient salt concentrations can damage plants and soils, if improperly handled. Remediation of salt-affected sites can be performed for a number of reasons. The driving forces behind the need to assess and restore a site affected by a saltwater release can include landowner claims, lease agreements, federal, state, and local regulations, reduction in long-term liabilities, company policies, and/or protection of useable land and water resources Consulting the landowner and lease requirements is crucial before any remediation process starts. Landowners will often have opinions on various remediation options.
Valuations of oil and gas properties are needed for many of the same reasons appraisals are needed for homes, cars, jewelry, or any other assets. Lenders require some type of valuation when assets are used as collateral for a loan. Taxes are often assessed on the basis of property value. Property values have a bearing on rates for insurance policies and settlements after loss, damage, or foreclosure. Economic evaluations are seldom made simply for curiosity. In most cases, they are needed for some business reason. The primary method of evaluation discussed in this chapter is the deterministic cash flow method. Projected schedules of quantities of reserves from a deterministic reserves study projected in selected future time frames (usually calendar years) are displayed in the results, but computations are often made monthly. Schedules of future prices and costs are projected for the same time frames. Volumes are multiplied by prices, and costs are deducted to estimate future net revenue (FNR). Present worth calculations to factor in the time value of money are applied to the projected cash flow stream, and the results are reported. A table presenting a suite of present worth values over a range of discount rates is usually included. Individual projections are usually made by well or ownership entity. Each projection is classed in a reserves category (i.e., proved, probable, or possible) and more specific subclasses are common. The results are summarized at the reserves category level. This valuation procedure is based on the methods used to estimate reserves in the chapter on the estimation of oil and gas reserves in this section of the Handbook. Within the limits of the reserves category definitions, the parameters used in the estimation of reserves are generally average values. In the case of proved reserves, the results of the calculation are perceived to be best estimates.
Offshore drilling began in 1897, just 38 years after Col. Edwin Drake drilled the first well in 1859. H.L. Williams is credited with drilling a well off a wooden pier in the Santa Barbara Channel in California. He used the pier to support a land rig next to an existing field. By 1921, steel piers were being used in Rincon and Elwood (California) to support land-type drilling rigs. In 1932, a steel-pier island (60 90 ft with a 25-ft air gap) was built ½ mile offshore by a small oil company, Indian Petroleum Corp., to support another onshore-type rig. Although the wells were disappointing and the island was destroyed in 1940 by a storm, it was the forerunner of the steel-jacketed platforms of today. In 1938, a field was discovered offshore Texas.
Separation of gas and liquids is a key processing function for any production operation. Several approaches exist to accomplishing this separation subsea, as described on this page. Which is most appropriate to use depends on the fluids and conditions specific to the particular location. By separating the gas and liquid phases and pumping the liquid stream, this simplest of systems will capture most of the benefits of subsea processing. It will reduce backpressure to the wells and eliminate problems associated with multiphase flow.
The term "petrophysics" was coined by G.E. Archie and J.H.M.A. Thomeer in a quiet bistro in The Hague. By their definition, petrophysics is the study of the physical and chemical properties of rocks and their contained fluids. Petrophysics emphasizes those properties relating to the pore system and its fluid distribution and flow characteristics. The petrophysicist provides answers on products needed and used by team members, as well as physical and chemical insights needed by other teammates. It is easy to define these characteristics and to appreciate their part in the assessment of reserves.
An understanding of the geology of the reservoir is essential to its development, production, and management. This include both the external geology of the reservoir -- what created the hydrocarbon trap -- and the internal geology of the reservoir -- the nature of the rocks in which the hydrocarbons exist. This article focuses on what an engineer needs to know about the external and internal geology to understand the reservoir from which he or she is planning to produce hydrocarbons. The efficient extraction of oil and gas requires that the reservoir be visualized in 3D space. Engineers need a conceptual model of reservoirs. Conceptual models are an integral part of the decision-making process, whether that process involves selecting perforations or forecasting future production. For example, a core measurement has no dimensional information, wireline logs and continuous core measurements are 1D, and production data and pressure information are volumetric but with unconstrained spatial information. Geologic information, on the other hand, contains valuable spatial information that can be used to visualize the reservoir in 3D space.
Selection of appropriate completion equipment requires consideration of not just production operations, but other activities such as injection or treatment. Shutting-in the well also creates changes in temperature and pressure that need to be considered. This article discusses the temperature-depth profiles that occur under different modes of operation. While the primary application may be oil or gas production, any subsequent operations (such as acidizing or fracturing the well) and their associated pressure and temperature changes are extremely important to packer utilization success. Typical temperature vs. depth profiles are illustrated in Figs 1 through 4.
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.