Universal apparatus module of radioactivity logging for the investigation of oil-and-gas reservoirs while drilling

Abstract

Logging-while-drilling (LWD) is the most advanced technology in geophysical well logging. It is widely used for determining the petrophysical and other parameters of oil-and-gas reservoirs in vertical, deviated, and horizontal boreholes. The LWD is particularly important for horizontal boreholes, obtained by directional drilling from vertical boreholes into predetermined hydrocarbon reservoirs. Horizontal boreholes allow multiplying the yield of hydrocarbons, increasing overall production, and using effectively both new vertical boreholes and exploited ones, as well as old boreholes. The opportunity of horizontal drilling to local (isolated) deposits, which are at a certain distance from vertical boreholes, is of also essential importance. All these factors are favourable for increased hydrocarbon production, which is of great significance for Ukraine. This paper concentrates on the apparatus developments aimed at creating a new module of radioactivity logging for LWD; the module is universal in the sense that it can be used in drill collars, which are employed while drilling all types of boreholes. The tool implements neutron-neutron logging, neutron-gamma logging, gamma-gamma logging, and gamma-ray logging. It allows a direct and combined determination of a broad set of petrophysical reservoir parameters. The advantages and disadvantages of the known nuclear logging modules for the LWD have been analyzed, and the features and merits of the proposed one are shown. During the laboratory and borehole operations with a pilot sample of the module, trends for its improvement were outlined. As an example of using the new module for LWD, the results of determining the petrophysical parameters of oil reservoirs of varying lithology in three horizontal boreholes are given. The process of LWD measurements demonstrated high technologicness and efficiency of the module. Comparison of the obtained parameters of the reservoirs with the data of independent measurements carried out in the open hole of the same boreholes using the PEX tool (Schlumberger) showed a qualitative consistency and a quantitative convergence of the results.