Low-permeability oil rim reservoirs can be developed using horizontal wells and multistage fractures. The challenge for operators is to find a hydraulic fracture design that improves production while minimising the risk of gas or water breakthrough from adjacent formations. Fluid breakthrough harms well economics and can lead to significant environmental impacts, for example, through the need for gas flaring.
Predicting and preventing water or gas breakthrough is one of the most important tasks faced by reservoir engineers. Operators will typically use pressure-transient analysis to assess fracture sweep efficiency, but this provides only average fracture parameters. A deeper understanding of downhole flow dynamics can provide an early warning of the locations where water or unwanted gas is reaching the well.
A horizontal well had been drilled into the oil rim of a low-permeability reservoir formation and hydraulically fractured in 12 stages. The gas/oil ratio for the well was high, indicating a potential issue with the fracture design that would need to be addressed before delivering or completing further wells in the field.