Pliocene Hyperpycnal flow and its sedimentary pattern in D block of Rakhine Basin in Bay of Bengal

Abstract Based on core, logging, lab test and seismic data, sedimentary characteristics and pattern of marine hyperpycnal flow, the distribution rules of hyperpycnal flow reservoir, prediction method of favorable hyperpycnal flow reservoir zones, hydrocarbon accumulation model in hyperpycnal flow reservoir in D block of Bay of Bengal were investigated, and the favorable exploration zone and well sites were predicted. Pliocene in D block has typical hyperpycnal flow sediment, which is a set of fine-medium sandstone held between thick layers of marine mudstone and features a series of reverse grading unit and normal grading unit pairs. The hyperpycnal flow sediment appears as heavily jagged box shape, bell shape and tongue shape facies on log curves with linear gradient, and corresponds to multiple phases of deep channels on the seismic section and high sinuous channel on stratal slices. The sedimentary bodies formed by a single phase hyperpycnal flow which include five types of microfacies, namely, supply channel (valley), channel complex, branch channel, levee and sheet sand. The hyperpycnal flow sediments appear in multiple branches, multiple generations and stages in space, forming high-quality reservoirs in strips on the plane and superposition vertically, with fairly good physical properties. The channel complex sandstone, with large thickness, coarse particle size and good physical properties, is the most favorable exploration facies. Based on the guidance of the sedimentary model, distribution of the channel complex microfacies was delineated in detail by seismic reflection structure analysis, spectrum waveform characteristic analysis, slice and attribute fusion, and combined with the structural feature analysis, the favorable drilling zone was sorted out, effectively guiding the exploration deployment of the block.