ABSTRACT
Shale has ultralow matrix permeability and consequently requires the creation of hydraulic fracturing to maximize the contact area with the reservoir. The key to successful fracturing treatment in shale formation is the identification of the sweet spots. Productive shale consists of quartz, feldspar, or carbonate and clays, in addition to organic matter (kerogen). Thus, it is a challenging process to map the best zones to fracture and locate horizontal wells. A new mineralogical index (MI) has been developed to locate the best areas along horizontal wells to fracture. A good MI would prolong the production plateau for shale plays.
Current technology follows two schools of thought: the first considers equally spaced fracturing, with the more fractures, the better production; the second makes use of the brittleness index, which distinguishes brittle versus ductile zones along the well path. Supporting the second school, we have a better correlation of the MI; where the new correlation indicates the most brittle parts of the reservoir (MI > 0.6) versus the most ductile parts (MI < 0.6), it becomes easier to map the producing shale with sweet or unattractive spots, leading to effective fracture locations. This new sweet-spot identifier, which guides the fracture design and fracture allocation along the horizontal wellbore path, may optimize well placement and hydraulic fracturing positioning in unconventional resources.
A new MI is developed ranging from 0 to 1, which helps optimize fracturing and shale development, in addition to guaranteeing that fracture treatments are correctly placed. This approach will facilitate connectivity with the natural fracture network. Thus, a priority of guiding fracture design starts with high MI, which corresponds to higher mineralogy index. An MI value of 0.6 is a good starting point to map sweet spots. This correspondence may enhance far field fracturing complexity and help obtain a branched fracture. The type of treatment may be recommended according to the subcategory of quartz.
