Objective
The main objective of the project was to evaluate the possibility to enhance the recovery from oil reservoirs by addition of distillable oil to the injected steam during steamdrive recovery. This evaluation was effected in terms of a preliminary design of a field test for distillation enhanced steam drive recovery.
The idea to enhance distillation effects to improve oil recovery was first studied in tube experiments. It was verified experimentally that small amounts of distillable hydrocarbons added to the steam were indeed capable to enhance oil recoveries from 80% to 95%. We have experimentally verified that a distillable oil bank is indeed formed near the steam condensation front when liquid hydrocarbons are coinjected with the steam. Numerous experiments carried out on behalf of the present project allowed us to correlate the recovery with mixing effects which reduced the efficiency of the distillable oil bank. Dispersion is a possible mixing mechanism. Low oil saturations in the steamed out zone are in general attributed to distillation effects. Another effect, which reduces the residual oil saturations to extremely low values, is the film flow effect. Film flow in the steam zone was discovered in this project. Film flow also occurs in the absence of distillation. Film flow means that films of oil are formed between the steam and the water, which envelops the pore matrix. The result of film flow is that oil remains mobile at extremely low oil saturations.
We have quantified the film flow effect by measuring relative permeabilities in gravity drainage experiments.
Hardware requirements to implement distillation enhanced steam drive recovery in the field are simple. This is related to the fact that distillable oil can be injected as a liquid owing to its favourable phase behaviour. A schematic design of the surface equipment necessary for the addition of distillable hydrocarbons to the steam is given in the end report of Project TH/05038/82 "Distillation enhanced steamdrive recovery" by J. Bruining, D.W. van Batenburg and H. Ronde.
Extrapolation of the experimental data to a prototype field showed that only up to three barrels of oil can be recovered for each barrel of distillable oil coinjected. The extra recovery, however, will be less when film flow is effective.
On the other hand we have not, as yet, addressed the recovery improvement owing to the favourable mobility ratio, which results from the presence of the distillable oil bank. This aspect will be elaborated in our next project (TH 05064/85) "The beneficial effects of distillations during oil recovery by steam flooding "as part of a broader objective i.e. the economic competion of steamflooding and waterflooding of medium viscosity oil.
Small amounts of distillable oil added to the steam injected in a tube containing an oil sand are capable of enhancing the recovery efficiency, which may approach 100% in the steamed out region. Without this addition the comparable efficiency is 80%. We have studied this effect in detail to allow extrapolation to field conditions. The complexity of the process made it necessary to confine ourselves to the microscopic displacement process i.e. disregard sweep efficiency effects. This aspect will be addressed in a follow up contract "The beneficial effects of distillation during oil recovery by steamflooding."
In this project we have elaborated at length on the competition between film flow effects and the distillable oil bank to lower the "residual oil saturation" in the steam zone. Film flow effects, which were discovered in this project, tend to lower oil saturations in the steamed out zone in the absence of distillation effects.
Distillation effects have been attributed to the distillable oil bank, which is formed near the steam condensation front. This also leads to a lower (heavy) oil saturation in the steam swept zone.
In this project we have disregarded the sweep enhancement owing to a more favourable mobility ratio when a distillable oil bank is present.
The project consisted of the following phase :
i) Design and building of high pressure equipment.
ii) Continuation of experiments at atmospheric pressure.
iii) Experiments with transparent models.
iv) Experiments at high pressure.
v) Preliminary design of a field test.
Programme(s)
Topic(s)
Call for proposal
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DEM - Demonstration contractsCoordinator
2600 Delft
Netherlands