LWD AZIMUTHAL DENSITY LOGGING IN LIVERPOOL BAY, UK AS AN AID TO COMPLETION PLANNING VIA FAULT AND FRACTURE DETECTION

摘要

A logging while drilling (LWD) Azimuthal LithoDensity (ALD) imaging tool was run in horizontal dual lateral wells 110/15-L13 and 110/15-L13z with the aim of identifying fault and fracture intersections. The wells are located in the BHPBilliton operated Lennox Field, in the Liverpool Bay area of the East Irish Sea Basin, United Kingdom Continental Shelf (UKCS). Image quality is good and numerous geological features have been identified. Fractures have been classified as either high density or low density, relative to host formation. A total of 184 fractures have been identified in L13 while 121 fractures were identified in L13z. When corrected for borehole bias, 529 fractures are calculated to intersect L13 while 241 fractures are calculated to intersect L13z. Fracture orientations are consistent with the strike of regional scale faults. Fractures in L13 and L13z strike north-south, with minor north-northwest to south-southeast components.Significant drilling mud losses in the vicinity of fractures suggest that some fractures were open and therefore acted as fluid escape conduits. Drilling mud seepages within intervals that contain no apparent fractures may be related to fracture cuts that are below the resolution of the ALD sensor. It is also possible that some fractures became dilated after passage of the LWD tool assembly. Real time utilization of the LWD and ALD data enabled the operator to plan and locate External Casing Packers (ECPs) and the completion string quickly and accurately, thus removing conventional logging delays (and costs) while the drilling rig was on location.