This report summarises the current state-of-the-art knowledge of the hydraulic fracturing process used by
the shale gas/oil industry using open peer-reviewed literature and from government commissioned
research reports. This report has been written to make statements on our knowledge of the following
questions:
• How do hydrofractures form?
• How far do hydrofractures extend during stimulation?
• What dictates where hydrofractures propagate?
• How do hydrofractures interact with the existing fracture network?
• Can the size and distribution of hydrofractures be controlled?
Gaps in our knowledge have been highlighted, with the largest of these resulting from differences between
North American and European shale rocks
