Donald L. Katz

Threshold pressure phenomena in porous media

Threshold displacement pressures are needed to determine how much over-pressure can be used in storing natural gas. An experimental technique for determining threshold pressures by displacing water with gas from samples saturated with water is presented. Threshold pressures for 8 low permeability samples were measured. Threshold pressure data obtained in this work plus data on higher permeability samples reported in the literature are correlated with porosity, permeability, surface tension, and formation resistivity factor. Mercury injection pressures were also measured and correlated with air- water threshold pressures. A study of the effect of time on threshold pressures show that they are independent of time. An aerial photography of gas emerging from the top of a core shortly after its threshold pressure has been exceeded shows that the gas bubbles are uniformly distributed across the face of the core. Channeling will occur, however, when an increased gas phase permeability is reached. A porous medium can be resealed after its threshold pressure has been reached, provided it has not been desaturated below a fixed saturation. (18 refs.)

Overview of phase behavior in oil and gas production

A review is made of the growth in knowledge of phase behavior to permit the prediction of phase compositions in oil and gas reservoirs and for surface processing. Subjects treated include recovery of retrograde condensate, gas hydrates, surface tension, viscosity, and dense phases.

Review of Gas Hydrates with Implication for Ocean Sediments

This paper presents a general review of gas hydrate knowledge, the utilization of such knowledge in the natural gas industry, some contemplated uses of gas hydrates in sea water desalinization, and discusses the existence of natural gas hydrates under the permafrost of the Northern Hemisphere. The theory of how gases enter the water phase and cause premature crystallization of water into an ice-like hydrate structure is presented. With this background, hydrate formation in ocean sediments is considered.

Drainage of Water from Sand in Developing Aquifer Storage

The study investigated factors influencing the rate of vertical countercurrent gravity segregation of 2 phases in porous media. This process is important in developing aquifer storage of gas in that formation of the gas bubble requires that injected gas rise to displace water above it in the formation. Experimental work was performed using a closed vertical column packed with glass beads. Attempts were made to simulate experimental results by numerically solving the equation describing the process. This was only partially successful because complexity of the process necessitates use of dynamic capillary pressure and relative permeability data which are presently impractical to obtain. However, it was noted that the calculations consistently predicted quicker completion of the segregation process than the experimental results indicated. For this reason, it is felt that the type of calculation described can be used to give a reasonable lower bound on the length of time necessary for the segregation to occur.

Experimental determination of the enthalpy of mixing of N + CO2 under pressure

A once-through flow-calorimetric facility for measuring the enthalpy of mixing of binary gas mixtures at elevated pressures is described. The design of a new flow calorimetric incorporated in the facility is presented. Results for N 2 + CO 2 from mole fraction of nitrogen 0.22 to 0.73 are reported at the nominal conditions 40°C: 34.02 and 64.64 atm, and 31°C: 34.02 and 64.64 atm. The experimental results are interpreted and smoothed, and compared with predictions using the Benedict-Webb-Rubin equation of state. The probable accuracy of the results is discussed, along with a check on the assumption of adiabaticity in the calorimeter.

Predicting Yield of Revaporized Condensate in Gas Storage

The depletion program coupled with the Peng-Robinson equation of state has been enlarged and tested for the depletion of Michigan Reef condensate reservoirs during primary production. With the residue gas and retrograde condensate calculated to be in a reservoir, it was repressured with dry storage gas to above 4000 psig causing revaporization. Experience with the production depletion condensate yields during the first storage cycle shows only fair agreement with prediction because of operating problems during the initial withdrawal. Alternatives in conducting the storage operations are presented. Then, similar calculations are described to show the application of the method to repressurization of an oil reservoir being converted to storage. 13 refs.

Establishing the Effective Aquifer Pressure Controlling Water Drive for Gas Storage Cycles

In water drive gas storage reservoirs, water influx and efflux rates may be determined by the simplified pseudo steady-state method. It is necessary to determine the water movement rate per unit driving force and establish an appropriate distance in the aquifer from the gas reservoir at which the aquifer pressure is stable during the storage cycles. A method for this determination is demonstrated on an aquifer storage reservoir. The joining of the water movement with the p/z material balance permits a more accurate method of verifying gas inventory. This new procedure is presented to up-grade the verification of gas inventories as applied to an Illinois aquifer storage reservoir.

Temperature And Pressure Gradients In Gas Wells

A stepwise procedure has been developed for successsive calculation of pressure and temperature gradients in gas wells during production or injection. The method, based on a thermodynamic energy balance in the well bore and the usual equations for the flow of natural gas in vertical pipe, is shown to give reasonably accurate predictions when evaluated on the basis of actual field measurements. Assumptions of succession of steady states in the well bore and approximate independence from local unsteady heating or cooling of geothermal gradient appear to be justifiable for reasonably short flow times encountered in storage service. Considerations related to design of deep storage fields where use of down-hole chokes may permit elimination of heating and pressure regulation at the field gathering system are discussed in light of results obtained.

Direct determinations of the effect of pressure on the enthalpy of nitrogen

The isothermal throttling (Eucken) coefficient ϕ of nitrogen has been measured in a new apparatus. Measurements were made at 173.7, 273.5, and 367.2° K at pressures from 7 to 135 atm. The results are compared with other direct measurements, with Joule-Thomson data, and with pressure-volume-temperature data.

Underground Compressed-Air Storage for Electric Utility Load Leveling

This work discusses underground compressed-air storage reservoirs with respect to leveling the loads on electric utilities and compares them with natural-gas storage systems. Rapid injection and removal of air on a daily cycle is a major problem. Mined hard-rock caverns, solution-mined salt cavities, fixed-volume porous sand reservoirs, and aquifers are analyzed for possible use.