Ultrasonic rate measurement of multiphase flow

On of the most important tools in production logging and well testing is the downhole flowmeter. Unfortunately, existing tools are inaccurate outside of an idealized single phase flow, regime. Spinner tools are inaccurate at extremely high or low, flow rates and when the flow rate is variable. Radioactive tracer tools have similar inaccuracies and are extremely sensitive to the flow regime. Both tools completely fail in the presence of multiphase flow, whether gas/ oil, gas/water or fluid/solid. Downhole flowmetering is important for locating producing zones and thief zones and monitoring production and injection rates. The effects of stimulation can also be determined. This goal of this project is the investigation of accurate downhole flowmetering techniques for all single phase flow regimes and multiphase flows. The measurement method investigated in this report is the use of ultrasound. There are two ways to use ultrasound for fluid velocity measurement. The first method, examined in Chapter 2, is the contrapropagation, or transit-time, method which compares travel times with and against fluid flow. Chapter 3 details the second method which measures the Doppler frequency shift of a reflected sound wave in the moving fluid. Both of these technologies need to be incorporated in order to build a true multiphase flowmeter. Chapter 4 describes the proposed downhole multiphase flowmeter. It has many advantages besides the ones previously mentioned and is in full in that chapter

Multivariate optimization of production systems: The time dimension

Traditional analysis of oil and gas production systems treats individual nodes one at a time. This only calculates a feasible solution which is not necessarily optimal. Multivariate optimization is able to determine the most profitable configuration, including all variables simultaneously. The optimization can also find the optimal recovery over a period of time, rather than just at a single instant as in traditional methods. This report describes the development of multivariate optimization for situations in which the decision variables may change as a function of time. For example, instead of estimating a tubing size which is optimal over the life of the project, this approach determines a series of optimal tubing sizes which may change from year to year. Examples show that under an optimal strategy, tubing size can be changed only infrequently while still increasing profitability of a project. The methods used in this work considered the special requirements of objectives which are not smooth functions of their decision variables. The physical problems considered included artificial lift production systems

Analysis of Injection-Backflow Tracer Tests in Fractured Geothermal Reservoirs

Tracer tests have been an important technique for determining the flow and reservoir characteristics in various rock matrix systems. While the interwell tracer tests are aimed at the characterization of the regions between the wells, single-well injection-backflow tracer tests may be useful tools of preliminary evaluation, before implementing long term interwell tracer tests. This work is concerned with the quantitative evaluation of the tracer return profiles obtained from single well injection-backflow tracer tests. First, two mathematical models of tracer transport through fractures, have been reviewed. These two models are based on two different principles: Taylor Dispersion along the fracture and simultaneous diffusion in and out of the adjacent matrix. Then the governing equations for the transport during the injection-backflow tests have been solved. Finally the results were applied to field data obtained from Raft River and East Mesa geothermal fields. In order to determine the values of the parameters of the models that define the transport mechanisms through fractures a non-linear optimization technique was employed. 26 refs., 10 figs

Geothermal research and development program

Progress is reported on the following projects: adsorption of water vapor on reservoir rocks, drawdown and buildup pressure analysis in multiwell reservoirs, adsorption parameters from experimental data, tritium tracer movement at the Geysers, adsorption modeling, and effects of earth tides on downhole pressures

Well Test Analysis Research

Well test analysis offers a rapid way to perform an initial assessment of geothermal systems. Well testing includes both pressure drawdown and buildup testing, and interference testing. Development of new well test analyses receives major emphasis in the Stanford Geothermal Program. During the year, quite a few studies were completed, and reports and papers presented on a variety of well test analysis methods. The paper summarizes some of the more important results

Doublet Tracer Testing in Klamath Falls, Oregon

A tracer test was carried out in a geothermal doublet system to study the injection behavior of a developed reservoir known to be fractured. The doublet produces about 320 gpm of 160 F water that is used for space heating and then injected; the wells are spaced 250 ft apart. Tracer breakthrough was observed in 2 hours and 45 minutes in the production well, indicating fracture flow. However, the tracer concentrations were low and indicated porous media flow; the tracers mixed with a reservoir volume much larger than a fracture

Geothermal reservoir engineering research at Stanford University. First annual report, October 1, 1980-September 30, 1981

The work on energy extraction experiments concerns the efficiency with which the in-place heat and fluids can be produced. The work on noncondensable gas reservoir engineering covers both the completed and continuing work in these two interrelated research areas: radon emanation from the rock matrix of geothermal reservoirs, and radon and ammonia variations with time and space over geothermal reservoirs. Cooperative research programs with Italy and Mexico are described. The bench-scale experiments and well test analysis section covers both experimental and theoretical studies. The small core model continues to be used for the study of temperature effects on absolute permeability. The unconsolidated sand study was completed at the beginning of this contract period. The Appendices describe some of the Stanford Geothermal program activities that results in interactions with the geothermal community. These occur in the form of SGP Technical Reports, presentations at technical meetings and publications in the open literature

Geothermal reservoir engineering research at Stanford University. Third annual report for the period October 1, 1982-September 30, 1983

Progress is reported in the following areas: heat extraction from hydrothermal reservoirs; radon reservoir engineering; well test analysis and bench scale experiments; field applications; workshop, seminars, and technical information; reinjection technology; and seismic monitoring of vapor/liquid interfaces. (MHR

Bench-Scale Experiments in the Stanford Geothermal Program

The emphasis of the smaller scale laboratory of the Stanford Geothermal Program is on improving the understanding of the physics of flow through porous materials in a geothermal environment. Three major investigations are in progress: (1) examination of the phenomenon of vapor pressure lowering in porous media, (2) determination of the temperature dependence of absolute and relative permeabilities of steam and water in sandstones under high confining pressures, and (3) observation of steady and unsteady, single- and two-phase flows of water or brine through permeable cores. In addition, development continues on the dielectric constant liquid content detector—a device which would prove extremely useful in these and subsequent experiments. 10 refs., 4 figs