Abstract:

Fracability is the capability of the shale that can be fractured effectively during hydraulic fracturing. Shale brittleness, nature fracture, quartz content, diagenesis are influencing factors of shale fracability as well as other factors. A mathematical model is established to quantitatively evaluate the shale fracability. First, standardize the parameters by range transform or assignment method, and then calculate each parameters weight in shale fracability via Analytic Hierarchy Process. Fracability index is equal to the weight between standardized value and weight coefficient. The model was applied to Well Yuye1 Longmaxi shale in the Southeast of Chongqing area and Barnett shale in Fort Worth Basin of US. Yuye1 fracability index is 0.4855 which is little higher than 0.4844 of Barnett shale and the fracability of Yuye1 shale is at the same level with Barnett shale. Shale fracability can be divided into three levels according to the reservoir parameters features. The shale with low fracability couldnt be stimulated effectively, which fracability index is 0.13200.2820. The shale with medium fracability could be fractured effectively, which fracability index is 0.28200.4567 and the shale with high fracability is the best choice to be fractured, which fracability index is 0.45670.7840. It is better to choose the shale to be fractured which fracability index is above 0.3607.

Key words: shale fracability, influence factors, evaluation methods, mathematical model；Well Yuye1；fracability comparison