A study of well test analysis for the fractured basement of an oil field | |
| Author | Nguyen Hai Minh |
| Call Number | AIT Thesis no.GE-04-21 |
| Subject(s) | Oil fields--Vietnam Basements--Vietnam |
| Note | A thesis submitted in paitial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-04-21 |
| Abstract | Oil and gas fields in fractured basement represent only 5 percent of the total oil and gas reserve. The rest are found in clastic and carbonates rocks. The number of oil field in fractured basement is quite small, just about 35 all over the world. As a special case, most of the oil fields in Southern offshore of Vietnam produce from fractured granitic basement of several kilometers deep. Analysis of well test data in such a medium is very important to give such parameters as permeability, wellbore storage, skin and matrix-fracture exchanged flow parameter that are needed in reservoir simulation, operation and management with reference to a good oil and gas production and recovery. This study deals with procedures of curve matching for interpretation of a well test performed in a fractured basement, being considered as a double-porosity medium. All possible types of well tests for this type of reservoir were reviewed, among which the drawdown test was found as the most commonly used. Although the curve matching technique is not the only available technique of well test data it remains one of the most popular and useful tools for reservoir engineers. For curve matching, one first needs to be able to generate good sets of type curves based on the analytical and numerical solutions of the hydrocarbon flow in the fractured media. In this study, a Fortran code that Sabet (1991) has developed for generating type curves for the case of one-porosity medium was employed. The code was further improved to accommodate several types of double porosity medium as well as to be able to comparatively assess the interpretation error for different models in use. The modified Fortran code is named as Well_Frac, it is a robust and user-friendly program that can be run with any Fortran compiler available in the market. In this study, Digital Fortran by Microsoft was used. Once the type curves are generated and presented in dimensionless coordinates one can proceed to match them with the field curve obtained from a well test. The matching can be done manually or with the help of a computer software. In this study, a simple graphical matching procedure using Grapher software was employed. This procedure was proposed by Giao (2003) for a groundwater pumping test and could do very well for an oil well test as proved in this work. The Rang Dong (Break of the Day) oil field in Southern offshore of Vietnam was selected in this study. Two sets of well test data were analyzed based on the generated type curves by Well-Frac and the graphical matching procedure mentioned above. Three models of fractured basement were tried for the Rang Dong oil field, i.e., one-porosity, pseudo-steady state model of double porosity and transient model of double porosity. The interpretation error was estimated by Well_Frac and it was found that the pseudo-steady state model gave the best results. As the curve matching procedure proposed in this study is quite simple and easily used one can apply it for other oil fields in Southern offshore of Vietnam as a preliminary, quick and cheap analysis tool in parallel with complex analyses using the sophisticated commercial software. Improvements in Fortran code as well as other types of computer-assisted curve matching techniques are recommended to be further studied. |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-04-21 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Noppadol Phien-wej; Pham Huy Giao; |
| Examination Committee(s) | Bergado, Dennes Taganajan; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2005 |