Design Optimization of Hydraulic Fracturing for Oligocene Reservoir in Offshore Vietnam

Many fields in offshore Vietnam with high production have been operating for a long time; however their production has been declining in the past few years. The most challenging problem is dealing with the heterogeneous structures such as Oligocene reservoir with a porosity range from 12% - 16% and a permeability of 0.1mD - 2mD. Therefore, natural flow of oil from these reservoir into the wellbore is retarded. Need for increasing production, a good understanding of reservoir characteristics, and designing a hydraulic fracturing treatment in Oligocene reservoir to maximize oil recovery is necessary. The key factor for this success is optimum treatment design. This paper shows an integrated approach using technical and economic optimization of hydraulic fracturing design, as well as describing the recommended procedures coupled with fieldcase study and actual results. We optimize fracture treatment based on economic indicators not only Net Present Value (NPV), but also Discounted Return on Investment (DROI), and nodal analysis is used to help determine optimal fracture-length based on productivity potential. The hydraulic fracturing simulator M-Frac is used for accounting this design. Based on these concepts, the results of the optimum treatment design present that a fracture half-length between 90 and 200m is required to maximize NPV and the initial fracture design is scheduled for 150,000 lbs of intermediate strength proppant to create a fracture half-length of approximately 100m. The success of this study in estimating production capabilities is a valuable lesson for future application in Cuu Long basin, offshore Vietnam.