Evaluation of void space types based on well logging suite case study of complexly-structured Cambrian carbonate reservoirs

Deposits of hydrocarbons composed of carbonate rocks are being increasingly involved in the development of the global resourse base. Carbonate rocks are characterized by complex geological and petrophysical properties, with the heterogeneous structure of the void space. In addition to intergranular pores, these deposits also exhibit secondary porosity such as fractures and caverns. These factors have a significant impact on the hydrodynamic characteristics of the reservoir. The modern expanded suites of well logging methods, along with standard methods, include electrical microimagers, borehole acoustic scanners, cross-dipole acoustic logging, waveform acoustic logging, nuclear magnetic resonance logging and other special methods. Such comprehensive logging suites enable almost complete determination of secondary changes in carbonate rocks. However, due to the high cost of special methods, they application is often limited. Moreover, in order to maintain the commonality of methods for assessing petrophysical properties, obtaining the maximum possible number of parameters, and the possibility of involving historical data in modeling, it is necessary to use a standard logging suites. This article analyzes the existing methods for determining pore space types of complex carbonate reservoirs. Based on total porosity, resistivity, and rock compressibility data, a four-component void space model was developed. The modeled parameters were compared with actual field data. The method was tested on a productive horizon stratigraphically assigned to the Bilir formation of the Lower Cambrian in Eastern Siberia.

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