Reservoir engineering

In gas reservoir engineering, the gas expansion factor, E, is commonly used. However, in oil reservoir engineering it is often more convenient to refer to the gas formation volume factor which is the reciprocal E, and is expressed in units of scf/stb (using field units). The reason for this will become apparent in Section 8. 

For the details of PVT analysis refer to Fundamentals of Reservoir Engineering, L.P. Dake, Elsevier, 1978. 

Below is a typical oil PVT table which is the result of PVT analysis, and which would be used by the reservoir engineer in calculation of reservoir fluid properties with pressure. The initial reservoir pressure is 6000 psia, and the bubble point pressure of the oil Is 980 psia. 

In Section 5.2.8 we shall look at pressure-depth relationships, and will see that the relationship is a linear function of the density of the fluid. Since water is the one fluid which is always associated with a petroleum reservoir, an understanding of what controls formation water density is required. Additionally, reservoir engineers need to know the fluid properties of the formation water to predict its expansion and movement, which can contribute significantly to the drive mechanism in a reservoir, especially if the volume of water surrounding the hydrocarbon accumulation is large. 

Reservoir engineers describe the relationship between the volume of fluids produced, the compressibility of the fluids and the reservoir pressure using material balance techniques. This approach treats the reservoir system like a tank, filled with oil, water, gas, and reservoir rock in the appropriate volumes, but without regard to the distribution of the fluids (i.e. the detailed movement of fluids inside the system). Material balance uses the PVT properties of the fluids described in Section 5.2.6, and accounts for the variations of fluid properties with pressure. The technique is firstly useful in predicting how reservoir pressure will respond to production. Secondly, material balance can be used to reduce uncertainty in volumetries by measuring reservoir pressure and cumulative production during the producing phase of the field life. An example of the simplest material balance equation for an oil reservoir above the bubble point will be shown In the next section. 

Analytical models using classical reservoir engineering techniques such as material balance, aquifer modelling and displacement calculations can be used in combination with field and laboratory data to estimate recovery factors for specific situations. These methods are most applicable when there is limited data, time and resources, and would be sufficient for most exploration and early appraisal decisions. However, when the development planning stage is reached, it is becoming common practice to build a reservoir simulation model, which allows more sensitivities to be considered in a shorter time frame. The typical sorts of questions addressed by reservoir simulations are listed in Section 8.5. 

Dake, Laurie (1994), The Praetice of Reservoir Engineering, 534p, Elsevier... 

Dake Laurie, (1978), Fundamentals of Reservoir Engineering,443p, Elsevier... 

Amyx, Bass Whiting, (1960), Petroleum Reservoir Engineering - Physical Properties, McGraw-Hill... 

Mark Cook is a Reservoir Engineer and Petroleum Economist. He has worked on international assignments mainly in Tanzania, Oman, the Netherlands and the UK. His main focus is in economic evaluation of field development projects, risk analysis, reservoir management and simulation. After 11 years with a multinational company he co-founded TRACS International of which he is Technical Director. 

N. E. V. Rodrigues, B. A. Robinson, and E. Counce, "Tracer Experiment Results During the Long-Term Flow Test of the Fenton Hill Reservoir", Proceedings of the Eighteenth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, Calif., 1994, in press. 

Not only is geology important in exploring for hydrocarbons, but also engineers must study the present composition and structure of the earth to successfully drill the borehole itself. Further, once hydrocarbons have been found and have proven to be economically recoverable, studies of the physical and chemical aspects of earth in such regions are important to the follow-on production and reservoir engineering. These studies help ensure that the accumulated hydrocarbons are recovered in an economic manner [24],... 

The fluid pressure in the rock at the bottom of a well is commonly defined as pore pressure (also called formation pressure, or reservoir pressure). Depending on the maturity of the sedimentary basin, the pore pressure will reflect geologic column overburden that may include a portion of the rock particle weight (i.e., immature basins), or a simple hydrostatic column of fluid (i.e., mature basins). The pore pressure and therefore its gradient can be obtained from well log data as wells are drilled. These pore pressure data are fundamental for the solution of engineering problems in drilling, well completions, production, and reservoir engineering. 

Chapter 5 — Reservoir Engineering Chapter 6 — Production Engineering Chapter 7 — Petroleum Economics... 

The specific petroleum engineering discipline chapters cover drilling and well completions, reservoir engineering, production, and economics and valuation. These chapters contain information, data, and example calculations related to practical situations that petroleum engineers often encounter. Also, these chapters reflect the growing role of natural gas in industrial operations by integrating natural gas topics and related subjects throughout both volumes. 

Fournier, R.O. (1981) Application of water geochemistry to geothermal exploration and reservoir engineering. In Ryback, L. and Muffler, L.J.P. (eds.). Geothermal Systems Principles and Case Histories. New York Wiley, pp. 109-143. 

History matching in reservoir engineering refers to the process of estimating hydrocarbon reservoir parameters (like porosity and permeability distributions) so that the reservoir simulator matches the observed field data in some optimal fashion. The intention is to use the history matched-model to forecast future behavior of the reservoir under different depletion plans and thus optimize production. 

By using automatic history matching, the reservoir engineer is not faced with the usual dilemma whether to reject a particular grid cell model because it is not a good approximation to the reservoir or to proceed with the parameter search because the best set of parameters has not been determined yet. 

Tan, T.B., "Parameter Estimation in Reservoir Engineering", Ph.D. Thesis, Dept, of Chemical Petroleum Engineering, University of Calgary, AB, Canada, 1991. 

Burk, J.H. "Comparison of Sodium Carbonace, Sodium Hydroxide, and Sodium Orthosilicate for EOR", SPE Reservoir Engineering, February 1987, 10-15. 

Yoshimura, A.S. Prud homme, R.K. "Viscosity Measurements in the Presence of Wall Slip in Capillary, Couette, and Parallel-Disk Geometries," SPE Reservoir Engineering, May 1988, 735-742. 

The Leverett J-function is used in reservoir engineering (22) to relate the permeability k, porosity < >, and wetting characteristics to water saturation S... 

Craig, F. F. The Reservoir Engineering Aspects of Waterflooding Monograph Series 3, Society of Petroleum Engineers Richardson, TX 1971. 

Dake L.P. Fundamentals of Reservoir Engineering Elsevier, 1978 chapter 5, 149. 

Timmerman E.H. Practical Reservoir Engineering PennWell Books, 1982 Vol. 1, 85. 

Sulfate scaling poses a special problem in oil fields of the North Sea (e.g., Todd and Yuan, 1990, 1992 Yuan et al., 1994), where formation fluids are notably rich in barium and strontium. The scale can reduce permeability in the formation, clog the wellbore and production tubing, and cause safety equipment (such as pressure release valves) to malfunction. To try to prevent scale from forming, reservoir engineers use chemical inhibitors such as phosphonate (a family of organic phosphorus compounds) in squeeze treatments, as described in the introduction to this chapter. 

It is seen that, actually by measuring y for such a system, the concentration of CH4 can be estimated. This fact has much relevance in oil reservoir engineering operations where CH4 is found in crude oil. 

Rojas, J., Menjos, A., Martin, J. C., Criaud, A. Fouillac, C. 1987. Development and exploitation of low enthalpy geothermal systems example of the Dogger in the Paris Basin, France. In Proceedings of the 12th Workshop on Geothermal Reservoir Engineering, Stanford University, 203 -212. 

Enedy, S., Enedy, K. Maney, J. 1991. Reservoir response to injection in the southeast Geysers. Proceedings of the 16th Workshop on Geothermal Reservoir Engineering, Stanford University, 75-82. 

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