Characterising Hydraulic Fracture Contribution in Shale Oil Wells Using High-Precision Temperature and Spectral Noise Logging

Abstract

Abstract Over the last decade, an industry-wide shift to shale plays has occurred due to advances in technology allowing for the economic recovery of previously unattractive reserves. The primary objective of well completions in shale reservoirs is to increase the effective surface area and thus maximise reservoir contact, as the fracture network area is the most important factor affecting production from such reservoirs. Understanding which hydraulic fractures actively contribute to production in shale reservoirs is essential for well performance evaluation and improving current completion design. This last point is, in turn, essential for expected high productivities to offset high drilling and completion costs of unconventional oil wells. Today, unconventional plays are economically developed through stimulation of horizontal wells by hydraulic fracturing. Conventional production logging (spinner, borehole fluid salinity, density and flowing temperature surveys) often fail to identify which stage produces the greatest effect on hydrocarbon production. The integration of High Precision Temperature (HPT) Logging and Spectral Noise Logging (SNL) data is the most effective method of Reservoir Flow Analysis due to the large radius of investigation of these tools. For this reason, HPT-SNL can be effectively used for post-hydrofracturing diagnostics. More specifically, it can assess individual fracture contributions to the overall well flow. Spectral Noise Logging can not only pick up flow in rocks behind multiple barriers of casing and cement but also tell whether such flow comes from fractures, the rock matrix, perforations or completion components. High Precision Temperature (HPT) logging detects minute variations in fluid temperature caused by heat exchange that depends on the thermodynamic properties (heat flux, thermal conductivities, etc.) of completion components, formation rocks and fluids. Both technologies have been successfully applied in the shale-oil wells of the Permian basin and clearly differentiated between contributing and inactive fractures. Such information is critical for improving hydraulic fracturing job designs for wells to be drilled in the Permian Basin.