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Since the most common use of matrix acidizing is the removal of formation damage, it is important to understand the nature of the damage that exists so that an appropriate treatment can be designed. Well testing and well test analysis generate a skin factor and well completion efficiency. This is insufficient alone for formation damage diagnosis. Well performance analysis has provided a beneficial tool to identify the location and thickness of damage at flow points in the near wellbore area. Models of flow into perforations and gravel-packed tunnels provide a way to relate the location and severity of damage to the completion procedure that preceded it.
Online pipeline-management systems provide real-time and look-ahead functionality for production networks. They are limited, however, by a dearth of data with which to inform their predictions. This represents a barrier to a true, high-fidelity digital twin. Greater integration with new sensor technologies is needed to bound model predictions and improve their reliability.
In most compositionally enhanced solvent displacements, some of the solvent will be trapped permanently in the reservoir and will not be produced. This happens when water is used to drive a solvent slug and the oil displaced by the solvent. Solvent is trapped by advancing water much like oil is left as a residual in a waterflood. Solvent also can be trapped by oil that crossflows into a previously solvent-swept zone. In water-alternating-gas (WAG) flooding, solvent trapping can affect saturation through the mechanism of relative permeability hysteresis.
This page provides a reservoir management case study for a sandstone field in which waterflooding and miscible gas injection techniques have been implemented. The field is a structural stratigraphic trap that has been divided into several vertical zones. Complex, systematic depositional and diagenetic changes resulted in a dual pore system that was further impacted by structural and hydrocarbon histories, resulting in a highly variable vertical and areal distribution of net pay, porosity, and water saturation. Porosity values range from 10 to 30% with an average of 22%. Average well-zone permeabilities ranged from 100 to 1800 md with a field average of 500 md.
Well-to-well tracer tests contribute significantly to the reservoir description, which is essential in determining the best choice of production strategy. Direct dynamic information from a reservoir may be obtained, in principle, from three sources: production history, pressure testing, and tracer testing. The value and importance of tracer tests are broadly recognized. Tracer testing has become a mature technology, and improved knowledge about tracer behavior in the reservoir, improved tracer analysis, and reduction of pitfalls have made tracer tests reliable. Many tracer compounds exist; however, the number of suitable compounds for well-to-well tracers is reduced considerably because of the harsh environment that exists in many reservoirs and the long testing period. Radioactive tracers with a half-life of less than one year are mentioned only briefly in this chapter because of their limited applicability in long-term tests. Tracers may be roughly classified as passive or active. In principle, a passive tracer blindly follows the fluid phase in which it is injected. Interpretation of tracer-production curves must account for this. The results from the application of active tracers may give information about fluid saturation and rock surface properties. This information is especially important when enhanced-oil-recovery techniques that use expensive fluids such as surfactants, micellar fluids, or polymers are considered. In the last 50 years, many tracer studies have been reported and even more have been carried out without being published in the open literature. Wagner pointed out six areas in which tracers could be used as a tool to improve the reservoir description. Many companies apply tracer on a routine basis. The reservoir engineer's problem generally is a lack of adequate information about fluid flow in the reservoir. The information obtained from tracer tests is unique, and tracer tests are a relatively cheap method to obtain this information. The information is an addendum to the general field production history and is used to reduce uncertainties in the reservoir model. Tracer tests provide tracer-response curves that may be evaluated further to obtain relevant additional information. Primarily, the information gained from tracer testing is obtained simply by observing breakthrough and interwell communication.
Tracers are used in well to well tests to gather data about the movement and saturation of fluids in the subsurface. Radioactive tracers can be used to gather data about water or gas. This article discusses some of the commonly used radioactive water tracers. In most field studies, the tracer is expected to behave exactly as the water it is going to trace. Very few compounds will behave as passive tracers in all situations, but near-passive tracers will, in many applications, work satisfactorily.
The calculation of reserves in an oil reservoir or the determination of its performance requires knowledge of the fluid's physical properties at elevated pressure and temperature. Of primary importance are those properties including bubblepoint pressure, solution gas/oil ratio (GOR), and formation volume factor (FVF). In addition, viscosity and surface tension must be determined for calculations involving the flow of oil through pipe or porous media. Ideally, these properties are determined from laboratory studies designed to duplicate the conditions of interest; however, experimental data are quite often unavailable because representative samples cannot be obtained or the producing horizon does not warrant the expense of an in-depth reservoir fluid study. In these cases, pressure-volume-temperature (PVT) properties must be determined by analogy or through the use of empirically derived correlations.
Crude oil characterization has long been an area of concern in refining; however, the need to identify the chemical nature of crude has gained importance in upstream operations. Traditionally, this has been done by simply stating the crude oil gravity, but more information is required to understand the oil well enough to estimate the volume in the reservoir and its recoverability. During the last 60 years, several correlations have been proposed for determining pressure-volume-temperature (PVT) properties. The most widely used correlations treat the oil and gas phases as a two-component system. Only the pressure, temperature, specific gravity, and relative amount of each component are used to characterize the oil's PVT properties. Crude oil systems from various oil-producing regions of the world were used in the development of the correlations.
Documentaries are used both to educate and tell stories that their makers believe should be heard. That applies to documentaries about the inner workings of various industries such as oil and gas. To many outside the petroleum industry, those inner workings are a black box: Money and engineering goes in, gasoline and petrochemical products come out. It is also full of stories, making it an industry ripe for documentarians. The following reviews consider a small handful of the documentaries covering the petroleum industry and what might be learned from them beyond their immediate message.
This page briefly describes some of the field applications of resin treatment for conformance improvement. Littlefield, Fader, and Surles reports on 26 production wells of the Kern River and San Ardo fields that were treated in 1990 and 1991 with furan resin jobs in which the treated production wells were suffering from water-encroachment problems. Most (24) of the wells were in the heavy oil Kern River field of the Lower San Joaquin Valley in California. When the furan resin treatments were applied, the Kern River field was undergoing steamflooding. Of the production wells treated, 79% showed significant reductions in water production after the treatments.