Analysis of depositional facies and palaeoenvironment of the lower miocene reservoir in the northern area, block 05-1(a), DH oil field, Nam Con Son basin

Sediment depositional environments are one of the important scientific basesin evaluation the reservoir potential of sedimentary rocks. This thesis focuses on studying the facies and environment of the terrigenous sediments of the Lower Miocene in the northern area of block 05-1(a), mine DH, Nam Con Son basin. The thesis has integrated the method of interpreting the geophysical data of the wells combined with the lithological analysis documents, the results of paleontological analysis to clarify some contexts of lower Miocene sedimentation of the study area. rescue. In which, it can be seen that at 3 wells DH-A, DH-B, DH-C, there are similarities in sedimentary environment as follows: From H170-H150, the sedimentary environment changes from the delta to the upstream delta and to the downstream delta. With an abundant supply of sedimentary material and mainly coarse-grained sand to siltstone, it is transported and deposited quickly in a high-energy environment and at a distance not too far from the source. From H150-H80 the sedimentary environment alternates in the cycle. Mainly alternating between the lower delta and Delta front along with the sedimentary origin formed mainly in the low-energy environment, petrography consists of debris sediments (sandstone, shale and coal). The sandstone is very fine to fine grained, moderately to fine graded, round in shape from periphery to rounded. They can therefore be transported long distances from the source. The sedimentary environment of the three wells has a strong connection with each other, possibly due to rapid subsidence and accretion with a huge amount of material forming sediments in the above environments and has a wide distribution through the data mentioned above. Sediments belonging to such environments are very favorable as well as valuable in terms of generating, storing and blocking oil and gas. Bay-pool lightning has high oil-producing potential. Pre-delta or estuarine sandstone has good storage capacity. Consolidated clay seams can also be retaining layers. Therefore, through the results of the study of the sedimentary environment, the lower Miocene layer of block 05-1(a) through the wells DH-A, DH-B, DH-C is very promising for petroleum.