FPWD Illuminates the Path for Brown Field Development in Bohai Bay

Abstract

Abstract In Bohai Bay of China, after several decades of field development, including water injection, these brown fields suffer from subsurface heterogeneous pressure profiles. This can result in complications with drilling optimization and reservoir management. This paper is aimed to demonstrate how FPWD (Formation Pressure While Drilling) can be used to identify and applied to address this predicament. The approach is run in tandem the advanced FPWD tool with the drilling BHA (Bottom Hole Assembly) to measure the reservoir pressure zone by zone to delineate the reservoir's energy profile. Using LWD (Logging While Drilling) measurements including density, porosity and resistivity, the depth of pretests can be picked along the reservoir sections. On each pretest, the FPWD tool will be set against the borehole, to measure drawdown and buildup to a pre-defined sequence before retracting off the wellbore. The final result is a measurement of the reservoir pressure on a defined depth. Consequently the profile of reservoir energy can be drawn. While this information can be used to dynamically adjust the mud weight, it will also provide the reservoir team a higher level of confidence in designing the production and injection program. 3 wells from 3 blocks Bohai bay effectively utilized FPWD for the purpose of drilling optimization and reservoir management. Within the 300 meters interval of a study well, significant fluctuations in pressure were observed, where the largest reservoir pressure measured was 261 psi above the original pressure, and the lowest was 1740 psi below with irregular changes between them. These direct pretest measurements surprised the drilling and the reservoir team as they had never expected that heterogeneity in the reservoir energy was so significant. Following the original mud weight, they would have most possibly faced a kick and severe mud loss. The reservoir team used these measurements to determine the water flooded zones to optimize the final perforation and completion program. This resulted in final production rates that were much better in comparison to its offset wells. On another well, the FPWD measurements are used to determine the connectivity across the fault. Based on the pressure comparison on the both sides of the fault, it could be confidently concluded that the fault was not sealing. In brown fields, variation in reservoir pressure can far beyond normal expectations. The predicted reservoir pressures from the simulation cannot reveal this variation. Only direct pressure measurements can expose mature reservoir pressure complexity to provide operators with the means to safely and effectively construct wells to develop brown fields.