Objective
Establishment of technical and economic design criteria and evaluation tools for oil and condensate recovery by nitrogen injection.
We performed a simulation study of condensate drop-out in a two-layer stratified reservoir, showing that condensate drop-out occurs at the displacement front and at the layer boundary. Drop-out increases with dispersion, where dispersion increases with heterogeneity. The amount of condensate drop-out depends on the transverse dispersion number, introduced by Lake. For values larger than 0.36 stratified systems become quasi one-dimensional due to Taylor dispersion, implying that for these combined systems conclusions as given earlier for one-dimensional systems are valid. (ref. 1-5)
a. DEPENDENCY ON OIL COMPOSITION : Phase behaviour calculations and experiments will be performed on synthetic oil-nitrogen systems.
b. APPLICATION OF SLIM TUBES : We shall systematically evaluate the pros and cons of nitrogen flooding experiments using our high pressure slim tube equipment. The proper design, execution and interpretation of slim tube experiments is complicated because of the numerous pittfalls and artifacts that may obscure the results.
c. MINIMUM MISCIBILITY PRESSURE : We shall evaluate the concept of the MMP for its applicability to nitrogen flooding. We shall develop theoretical (based on equations of state) and experimental (based on slim tube experiments) methods for the determination of the MMP.
d. SIMULATION : We shall analyse, test, extend and/or modify the available one-dimensional compositional simulators. For the validation of these simulators we shall use analytical models and slim tube experiments. Special attention will be paid to the effect of physical and numerical dispersion.
e. PHYSICAL PROPERTIES : We shall evaluate the existing prediction methods for physical properties of nitrogen/oil systems (e.g. viscosities, densities and interfacial tensions) by comparing their results with available experimental data and, if necessary, with specially designed experiments.
f. RELATIVE PERMEABILITY : We shall attempt to measure relative permeabilities under conditions of low interfacial tension.
g. LIQUID DROP OUT : A model will be formulated in which liquid drop out and the subsequent evaporation is taken into account.
The model will be tested against slim tube experiments using synthetic condensate gases.
h. NITROGEN GENERATION : We shall investigate, by means of a literature search, the relative advantages and disadvantages of membrane separation compared to cryogenic separation for application in oilfields onshore as well as offshore.
i. RESERVOIR HETEROGENEITY : We shall define reservoir geological prototypes for some commonlyencountered depositional environments. Using simplified mathematical models we shall simulate nitrogen flooding in the prototypes.
j. GRAVITY STABLE CONDITIONS : We shall make a conceptual reservoir engineering design of nitrogen flooding under gravity stable conditions using horizontal wells. Our design will be compared with a conventional design based on vertical wells.
k. TECHNICAL AND ECONOMICAL EVALUATION : At the conclusion of the project we shall carry out a technical and economic evaluation of nitrogen flooding for a realistic prototype reservoir preferably located in the North Sea.
Programme(s)
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DEM - Demonstration contractsCoordinator
2600 Delft
Netherlands