Utilizing Sonic LWD Geomechanics 1D Modelling to Optimize Hydraulic Fracturing in High-Angle Deviated Wells of Offshore North-West Java Basin, Indonesia

Abstract In many studies, conventional oil or natural gas wells have an average life expectancy of 20 to 40 years, depending on their active production rate. The North-West Java Basin has been widely known in Indonesia to yield numerous fields, with active development wells producing since the 1970s. Currently, several of these fields have declined to 50-80 BOPD per well and are being evaluated on extending their economic life. To find new ways to extend well life and improve field economics, an operator has adopted innovative technologies via production enhancement of Hydraulic Stimulation or Hydraulic Fracturing (HF), specifically in the allocated low-quality reservoirs of their subject fields. HF is a well-stimulation method that generates fractures in rock formations through injection of hydraulically pressurized fluid. Optimum fracturing design is vital for an effective stimulation treatment, in terms of fracture length, aperture and height, fracture containment, proppant placement, and resulting fracture permeability. All properties are dependent on reservoir and geomechanical properties, derived from an understanding of near-wellbore phenomena. A geomechanical model consists of dynamic elastic properties (Young's modulus, Poisson's ratio, shear and bulk moduli) and rock strength properties (unconfined compressive strength, tensile strength, and friction angle) distributed in three dimensions within the reservoir. To determine elastic rock properties, changes in compressional and shear velocity through all layers of the reservoir rock are taken into consideration. Input data are commonly acquired through wireline or logging-while-drilling (LWD) acquisition, depending on operational constraints. This paper focuses on a geomechanics modelling case study using LWD acquisition in the Upper Cibulakan sandstone formation, where challenges arise from the laminated geology of intercalated sandstones with limestone streaks and the risk of a water zone below the targeted zone. Recorded data for modelling was taken from a 6.75-in. LWD tool configuration comprising gamma ray, resistivity, neutron porosity, density and sonic sensors, deployed in the 8.5-in. hole sections of two highly deviated wells in the same field. These wells had potential risks such as lost circulation and stuck pipe, hence LWD was deployed, while maintaining optimal drilling parameters. A geomechanical workflow was developed based on regional geology, quick-look petrophysics, and modified empirical equations to estimate data input into the geomechanical model covering the entire well intervals, even in areas with limited well log information. Geomechanical modelling aided the hydraulic stimulation design in both wells. A Mini Frac, a small preliminary simulation is used to calibrate the model and were found to be within the expected range prior final geomechanical modelling. Without geomechanical considerations, the HF design would have been less precise. Therefore, understanding the reservoir rock mechanics, their spatial heterogeneity, and stress profiles had a major impact on fracturing design optimization. Deploying sonic LWD as part of the drilling activity for geomechanics modelling has added efficiency in terms of cost and time.