Fracturability Index is a Mineralogical Index: A New Approach for Fracturing Decision

Abstract

Shale has ultra-low matrix permeability, and consequently requiring 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 challenging process to map the best zones to fracture and locate horizontal wells. A new Fracturability Index based on mineralogy has been developed to locate the best areas along horizontal wells to fracture. A good Mineralogical Index would prolong production plateau for shale plays.Current technology follow two schools, first one through equally spaced fracturing, and the more fractures the better production, second; guide through brittleness index, which distinguish brittle versus ductile zones along the well path, supporting the second school, we have a better correlation of Fracturability index, the new correlation indicates the most brittle parts of the reservoir (MI>0.6) versus the most ductile parts (MI <0.6), it became easier to map the producing shale with sweet or unattractive spots leading to the effective fracture locations. It is a new sweet spot identifiers, which guide the fracture design and fracture allocation along horizontal wellbore path, it may optimize well placement and hydraulic fracturing positioning in unconventional resources.A new Minerological Index is developed ranging from 0 to 1 which helps optimize the fracturing and shale development, in addition to guaranteeing fracture treatments are in the right place. This will facilitate connectivity with natural fracture network, priority of guiding fracture design start with High FI which corresponds to higher mineralogy index. MI value of 0.6 is a good starting point to map sweet spots. This may enhance far field Fracturing Complexity and help getting a branched fracture. Based on a sub category of quartz, type of treatment may be recommended.

A Review of Brittleness Index Correlations for Unconventional Tight and Ultra-Tight Reservoirs

“…Alzahabi et al [20] found a new MBI for the Wolfcamp Formation, with Late Pennsylvanian to Permian age. The porosity of this formation is relatively high (~10%) and the TOC ranges at about 2.3% [20]. This formation is highly heterogeneous in its mineralogy, TOC, and other reservoir properties.…”

“…The weight fractions reported from XRD measurements indicate average values of 60% silicates, 20% carbonates, and 20% clay [21]. This formation varies strongly in its calcite content, which ranges from 0% to 84% [20]. It is, overall, mostly shale-rich, except the upper part, which is rich in carbonate [20].…”

“…This formation varies strongly in its calcite content, which ranges from 0% to 84% [20]. It is, overall, mostly shale-rich, except the upper part, which is rich in carbonate [20]. Studies led to the following equation [20].…”

“…It is, overall, mostly shale-rich, except the upper part, which is rich in carbonate [20]. Studies led to the following equation [20].…”

“…These correlations take different minerals as brittle or non-brittle in account. As a brittle mineral, quartz [12], dolomite [8], calcite [6], feldspar, mica [19], and pyrite [20,22] were identified. However, brittle minerals have a different contribution in the prediction of BI, whereas quartz is more brittle, which is followed by dolomite and calcite [23].…”