«Geology, geophysics and development of oil and gas fields»

Sedimentological analysis as an instrument of substantiating the developed reservoir anisotropy of the Pokur formation

UDC: 550.8:553.98(470.56)
DOI: -

Authors:

¹ Tyumen Petroleum Research Center, Tyumen, Russia

Keywords: Cenomanian sediments, lithological and facies analysis, sedimentological analysis, tidal flat, facies, ichnofacies, heterogeneity, anisotropy

Annotation:

The object of the study is terrigenous Pokur Upper Cretaceous deposits of a large oil and gas field in the Pur-Taz oil and gas region of the West Siberian oil and gas basin. It was revealed that despite similar values of porosity and permeability, the sand reservoirs of the PK₁¹ and PK₁² layers differ, firstly, by the direction of anisotropy, and secondly, by the nature of the spatial distribution of sand bodies over the area of the deposit. This inequality is a fundamental factor when creating geological and hydrodynamic models that take into account the degree of the reservoir heterogeneity at the micro- and macro-levels.

The lithological-facial analysis resulted in determining facies confinement of the sand-siltstone reservoirs of the PK₁¹ and PK₁² layers to the tidal bars/channels (Tidal Bar/Cannel – TBC) and the Lower Shoreface zone (Lower Shoreface – LSF). The sedimentological analysis was based on the data obtained from 52 core wells (structural and textural specific features, presence of ichnophacies, granulometric composition, laboratory data) as well as geological and geophysical data on the drilled fund. It is shown how the hydrodynamic conditions of PK₁¹ and PK₁² layers sedimentation formed the corresponding textural specific features of the rock structure, which determined the anisotropic characteristics of reservoir filtration-capacitance properties. The influence of sediment-genesis on the patterns of spatial distribution of reservoirs has been established.

These conclusions about the differences of the void space isotropy caused by the sedimental genesis specifics are implemented in the model at the site of pilot development during hydrodynamic calculations, without additional adjustment of the model parameters in the process of its adaptation. This process is described in detail in the article [1].

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