The results of experimental studies on the influence of drilling fluids on clay rocks which are unstable in the process of borehole drilling and other drilling agents on the sandy rocks for estimation of the changes in void space of collectors are presented. The experiments are executed with the core samples which are placed in drilling agents and stand there in definite time which give the opportunity to model the real processes of their influence on the rocks with high fracture or porosity. The preliminary estimation of the drilling agents influence on the rock void space is produced on the base of visual comparison of X-ray tomography imaginations of experimental samples before and after the agent influence. The quantitative estimation is carried out with application of the original methods of X-ray tomography data processing, with help of which the size distribution of fissures and pores is calculated, as well as the maps of volume fracture and porosity of samples are constructed. Under modeling the processes for clay covers two drilling fluids are used with different content of mineral salts. As to the influence of drilling agents on porosity space of sandy collector there are successively used drilling fluid, stimulation of afflux, and processing by acid composition. The getting data give the opportunity to produce the proved calculation of microcolmatant fractional composition for drilling fluids, to value its inhibiting properties, and to accept the reliable decisions on the use of acid compositions.
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