Predicting the distribution of potential reservoir facies through sedimentological comparison of modern depositional analogs -A case of fluvial deltaic sandstone reservoirs in Eastern Venezuela-

摘要

The Guarico 13 field is located in the western Greater Oficina area, Eastern Venezuela basin. and consists of a large number of hydrocarbon accumulation in sandstones deposited in a coastal-plain environment. Trapping mechanisms for exploration opportunities in the study area combine structural faulting and stratigraphic pinch out. Individual reservoir thickness is normally 20ft or less and therefore it is hard to detect the reservoir distribution and the limits of hydrocarbon trapping area by using seismic data even if a seismic inversion process is carried out. Although the size of each individual reservoir is small. multiple reservoir sections were observed in each well and the sum of these reserves will be worth developing. It is very important to predict the potential reservoir facies to increase oil production and to discover additional new reservoirs in this kind of sandstones deposited in a fluvial-deltaic system. The high-resolution stratigraphy in the area was achieved by correlating all the lignite beds that occur between the major marine and lacustrine flooding surfaces. Then the core intersections. log character. borehole image logs and palynology were utilized to estimate the depositional environment of each hydrocarbon-bearing stratigraphic unit. After this environmental analysis. modern analogs and a geological model were applied to predict the reservoir facies and its extent. In this report. the authors demonstrate two case studies of estimating the reservoir distribution ; one uses a template model of a major bed-Ioad fluvial system with crevasse splay sands on interfluve area, and another employs a crosscutting tidal inlet and associated ebb'tidal delta system as an analog. This sort of approach that uses modern analogs as templates is worth applying to predict the potential distribution of reservoir sandstone if 3D seismic is not available or can not detect reservoir extent.