Multistage proppant and acid fracturing stimulation technology have contributed to increased hydrocarbon production in carbonate reservoirs. This technology has been deployed primarily in the Middle East’s onshore oil and gas fields for certain horizontal wells completed using Open Hole Multistage System (OHMS) with limited application in offshore environment.
OHMS was assessed for a low permeability carbonate reservoir offshore to evaluate well deliverability for a gas field and demonstrate its added value. Performing multistage stimulation in offshore environment is challenging and requires extensive planning and resources. This example looks at a 5-stage OHMS with single injection ports in +3,000 ft. segmented open-hole section to ensure efficient stimulation fluid placement. A High Rate Matrix Acid (HRMA) stimulation that creates highly permeable wormholes by pumping below fracture gradient is considered. These wormholes are conductive paths that improve near wellbore deliverability and avoid connectivity to any water in lower reservoir zones. The design considerations, field implementation of OHMS and HRMA are discussed. The technology is capable of increasing production performance by 2 folds of increase (FOI) relative to similar unstimulated cases.
This paper outlines the selection, execution, and challenges in deploying this technology. It discusses pretreatment formation evaluation, data requirement, data acquisition strategy, and key considerations for effective well completion and stimulation design. As an outcome, the paper highlights results and increased opportunities by applying this technology in offshore gas developments. It demonstrates value addition from rock property testing test, 1D Mechanical Earth Modelling (MEM), logging while drilling (LWD) well placement operations, and integration of wireline data, coring, imaging, sonic, and other data that ensure success.