Using Artificial Neural Network in Conjunction with Well Log Data to Assess the Permeability Distribution in Fractured Basement Reservoir, BP Oil Field, Vietnam Continental Shelf

Unlike sedimentary rocks, the permeability of fractured basement rock in BP oil field primary derives from dual pore structure and the geometric arrangement of the fracture and vuggy networks. Due to the complication of basement rock’s structure, the “conventional methods” used to assess and identify the permeability distribution of basement rocks are encountered difficulties and remain uncertainties. The permeability measurement from the core analysis is direct and trustful; however, it is not throughout representative for the fractured basement reservoir (FBR). Another reference is the average permeability encountered from production test, and it is strongly based on the effective thickness of the interval-a parameter is still difficult to be determined. In order to determine the permeability distribution, an Artificial Neural Network (ANN) system which 02 phases developed in conjunction with well log curves building the relationships between permeability and well log data. Therefore, the ANN is applied to reduce the uncertainty in identifying the permeability of BP FBR. In addition, each well log curve just expresses an aspect of the permeability; hence the permeability essence is fully described by the combination of multi well log curves. In the BP FBR there are four permeability profile types and the permeability values vary by both area and depth in the whole field with six specific areas. The variation trend decays from West to East and from top to bottom, significantly occurring at Central block and trivially occurring at North East block. According to the statistics, in BP FBR the permeability has a log-normal distribution pattern, the decreasing orders of average permeability in basement blocks are appropriately as: Central Block, North West Block, North Block, South Block, minima at North East Block. The study results by Permeability Profile Types allow to acquire more knowledge on FBR Structure, particularly in BP oil field.