Fracture Shadowing: Theory, Applications and Implications

Abstract The fluid pressure causing the extension of a hydraulic fracture also compresses the adjacent formation, mainly in the direction perpendicular to the fracture face. If there is a closed-in passive fracture within the compressed region, this causes an increase in its fluid pressure. The magnitude of pressure increase is a function of the distance between the two fractures (passive and active), the net extension pressure in the active fracture, and the overlap area. This pressure increase is defined as fracture shadowing and has been used for estimation of different fracture parameters, including orientation and length. This paper presents the mathematical background of fracture shadowing, including relationship between net extension pressure, distance between fractures, extent of each fracture, and volume of existing passive fracture system. Through actual field data, it shows that shadowing can be used as a very simple and cost effective tool for estimation of different fracture parameters. Shadowing in the same well is used to determine fracture growth pattern as well as a rough indicator of orientation. In offset wells, shadowing can provide estimation of fracture orientation, type, length, and in some cases conductivity. Paper demonstrates and recommends use of fracture shadowing as a simple and inexpensive additional diagnostic tool for determination of fracturing parameters.