Characteristics of natural fractures in the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

Abstract

Borehole image log data from the JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate research well were analyzed for both natural and drilling-induced fractures. A total of 47 fractures were identified, of which 34 were interpreted to be natural in origin. Fractures are clustered into distinct populations and their development is depth and lithology dependent. Terzaghi-corrected natural fracture frequencies range from 1.0 to 12.8 fractures per metre. Approximately half of the observed natural fractures occur within or proximal to gas-hydrate-bearing zones. Heat distribution patterns observed during the thermal stimulation test of this well may be partially explained by the contribution of natural fractures that intersect the wellbore over the same depth range. Natural fractures are also believed to have affected microfracture stress tests and pressure transient test that show evidence of long linear flow periods. Natural fracturing in and adjacent to gas hydrate deposits in subpermafrost settings is significant and could have an important impact on the economic development of this energy resource.