Hydraulic fracturing has been successfully utilized for several decades to develop tight gas and more recently unconventional plays resulting in improved well productivity and economics. This is achieved because of the increased reservoir surface area exposed to production and the rate acceleration resulting from it.
Khazzan field, located in central Oman, is a tight gas play developed on two main reservoirs: Miqrat and Barik. The Barik sandstone is further delineated by three zones, the Upper, the Middle and the Lower Barik. Upper and Lower Barik have a poorer reservoir quality characterized by lower average permeability, thinner sandstone layers and more frequent interbedded mudstones, resulting in frac treatments often terminated early. The Middle Barik sandstone does not present major execution difficulties, but several studies indicated that increased frac length and better frac conductivity are the two main components needed to improve frac and well performance.
To win these surface and subsurface challenges the industry has developed and implemented many methodologies with a variable range of success rate. One of these techniques, chosen for the trials described in this paper, is Channel Fracturing (CF).
CF utilizes proppant mixed with fibers in combination with surface pulse pumping methodology of alternating short burst of proppant slurry with clean fluid. CF aims to create proppant pillars to hold the fracture open and infinite conductive channels inside the formation, instead of the conventional continuous proppant pack. CF, with its pulses and better proppant transport from fibers, is also resulting in lower chances of screen out and lower injection pressures. Once the channels and pillar are created during the treatment injection, the fiber will dissolve during the shut in, while temperature rises, creating high conductive channels in between the pillars. The results of a high resolution and advanced simulator incorporating all the physic laws interacting during a fracture treatment was used to optimize the designs for Upper, Middle and Lower Barik formations will also be presented.
This paper describes the details of CF implementation in Khazzan field and how the technology successfully achieved the objectives of the trial. The proppant pulsing methodology enabled minimizing proppant entry largely due to narrow fracture width and near wellbore fracture complexity typical of Upper and Lower Barik. Higher volume of proppant placed created bigger frac geometry and improved well productivity. In Middle Barik, CF enabled to provide similar production with significantly better pumping parameters which would eventually develop in reducing the need of high-quality proppant and its quantity and potentially be a fundamental enabler for high frac density in multistage horizontal wells for specific field areas.
This work offers an example of the workflow utilized to plan and implement CF technology, and how this technology could potentially represent a critical component to enable high density frac in horizontal wells while minimizing screen out occurrences, and maximizing frac conductivity by shifting from a continuous high-quality proppant pack to a channel and pillar environment where proppant requirement could be derated without impacting overall frac conductivity. All these can reduce the economic impact of the contingencies and proppant requirements.
