Вплив вторинних змін на колекторські властивості глибокозанурених порід-колекторів Внутрішньої зони Передкарпатського прогину

Abstract

The investigation of cavernous space secondary changes of deeply buried reservoirs of the Inner Zone of the Precarpathian foredeep has been carried out. As a result of studying and analysing core material, taken out from deep and ultradeep wells of the Inner Zone of the Carpathian foredeep, it has been determined that the formation of zones of postsedimental rocks unsolidation and, hence, the improvement of filtration and capacity properties of sandy aleurite reservoirs with abnormally high values of porosity and permeability, caused by wells position in the active tectonic area with wide development of disjunctive dislocations. Corresponding formation of secondary cavernous space is due to advanced front of carbon dioxide that enters the reservoir through fractured zones. It has been proved, that the main criteria of potential prediction of secondary porosity at great depths are the following: the presence in sections of individual zones with high porosity, permeability and uncosolidation of rock on the general background of natural deteriration of reservoir properties with the depth. The prediction and mapping of zones of postsedimental rock uncosolidation, as promising objects of oil and gas accumulations at great depths, should be conducted by the batching of all available geological and geophysical data involving mineral, petrographic, petrophysical and hydrochemical studies. In drilling it is necessary to prevent sharp decrease in back formation pressure in order to avoid the irreversible closure of cracks that leads to the short-term flowing of ultradeep wells (several tones a day), positioned in the depression.