Lessons learned and experiences gained in developing Waterflooding concept of Granite Basement Fractured Reservoir: 20 historical years case study

Cuong T.Q. Dang, Zhangxing Chen, Ngoc T.B. Nguyen, Wisup Bae, Thuoc H. Phung


Naturally fractured reservoirs (NFR) represent over 20% of the world’s oil and gas reserves. However, their characterization is complex and presents unique challenges in comparison with conventional reservoirs. It is immensely difficult to achieve the best results in the secondary recovery process for NFR.

This paper presents a successful development of waterflooding to overcome the complex geological characterization of the White Tiger field – the biggest fractured basement reservoir to date on the continental shelf of Vietnam. This reservoir has a complicated geological structure, very high heterogeneity, high temperature, and closure stress. The total oil initially in place (OIIP) of this field reached nearly four billion barrels from 2,000 m of oil bearing thickness and has been produced by more than 100 wells, ten of which have flowed at the rate of approximately one thousand barrels per day.

The geological study and fractured model have been carefully investigated in both micro and macro scales to improve its waterflooding performance. The authors have analyzed the advantages and disadvantages of injection systems in this basement reservoir during 20 historical years, and an artificial water buffer solution has been proposed to improve the waterflooding process. The authors have described the establishment and association of local artificial water buffer in the basement reservoir. An effective method to optimize the injected water volume has also been discussed. Promising results from the White Tiger field have proved that the average reservoir pressure and total oil recovery have significantly increased in comparison with previous injection schemes.

This paper presents useful guidelines to solve some typical problems of waterflooding in fractured basement reservoirs such as:

What can be applied in waterflooding for a fractured basement reservoir?
What is the optimal injected rate and injected volume for the fractured basement reservoir?
How to evaluate the probability of high water cut in production wells during the waterflooding process? How to predict the rise of an artificial water-oil contact?