Characterisation of acid treatment for damaged zone in fractured granitic basement of Bach Ho field

Bach Ho is the largest reservoir in the continental shelf of Vietnam. This field consists of numerous oil pay zones, from Lower Miocene, Upper Oligocene, Lower Oligocene to Cenozoic fractured basement, which is known for a unique oil zone with nearly 2,000m in thickness. This oil zone features a large number of naturally flowing wells with production rate of approximately 1,000 tons per day, contributing to over 90% of total production. The oil pay zone in the fractured granitic basement is considered unconventional with extremely high degree of heterogeneity, anisotropy, and permeability. This requires more challenging production methods than those applied for conventional pay zones around the world. To achieve current optimal treatment methods, Vietsovpetro has been researching, selecting, and applying various acid treatment methods for damaged zones in this complicated basement. Nowadays, these treatment methods are successfully performed in most reservoirs in the continental shelf of Vietnam. The success of research and application of acid treatment for pay zones in Bach Ho fractured granitic basement has made significant scientific and technological contribution not only to Vietnam but also to the South East region and the world. This paper will present the acid treatment methods applied for Bach Ho fractured basement reservoir and their techniques to optimise the production.