TRANSPORT AND PHASE EQUILIBRIA PROPERITIES FOR STEAM FLOODING OF HEAVY OILS
Hydrocarbon/water and CO{sub 2} systems are frequently found in petroleum recovery processes, petroleum refining, and gasification of coals, lignites and tar sands. Techniques to estimate the phase volume and phase composition are indispensable to design and improve oil recovery processes such as steam, hot water, or CO{sub 2}/steam combinations of flooding techniques typically used for heavy oils. An interdisciplinary research program to quantify transport, PVT, and equilibrium properties of selected oil/CO{sub 2}/water mixtures at pressures up to 10,000 psia and at temperatures up to 500 F has been put in place. The objectives of this research include experimental determination and rigorous modeling and computation of phase equilibrium diagrams, and volumetric properties of hydrocarbon/CO{sub 2}/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils. Highlighting the importance of phase behavior, researchers ([1], and [2]) insist on obtaining truly representative reservoir fluids samples for experimental analysis. The prevailing sampling techniques used for compositional analysis of the fluids have potential for a large source of error. These techniques bring the sample to atmospheric conditions and collect the liquid and vapor portion of the samples for further analysis. We developed a new experimental technique to determine phase volumes, compositions and equilibrium K-values at reservoir conditions. The new methodology is able to measure phase volume and composition at reservoir like temperatures and pressures. We use a mercury free PVT system in conjunction with a Hewlett Packard gas chromatograph capable of measuring compositions on line at high pressures and temperatures. This is made possible by an essentially negligible disturbance of the temperature and pressure equilibrium during phase volume and composition measurements. In addition, not many samples are withdrawn for compositional analysis because a negligible volume (0.1 {micro}l to 0.5 {micro}l) is sent directly to the gas chromatograph through sampling valves. These amounts are less than 1 x 10{sup -5} % of total volume and do not affect the overall composition or equilibrium of the system. A new method to compute multi-component phase equilibrium diagrams based on an improved version of the Peng-Robinson equation has been developed [3]. This new version of the Peng-Robinson equation uses a new volume translation scheme and new mixing rules to improve the accuracy of the calculations. Calculations involving multicomponent mixtures of CO{sub 2}/water and hydrocarbons have been completed. A scheme to lump multi-component materials such as, oils into a small set of ''pseudo-components'' according to the technique outlined by Whitson [4] has been implemented. This final report presents the results of our experimental and predicted phase behavior diagrams and calculations for mixtures of CO{sub 2}/water and real oils at high pressures and temperatures.
- Research Organization:
- Prairie View A& M State University (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FG26-98FT40147
- OSTI ID:
- 836710
- Resource Relation:
- Other Information: PBD: 1 Sep 2002
- Country of Publication:
- United States
- Language:
- English
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