Determination of porosity in semi-consolidated and loose rocks

Abstract

Formulation of the problem. Due to the fact that the volume of drilling in the shallow horizons of the Mesozoic has recently been increased, the collectors are more often selected in the core with weakly cemented and loose sands and sandstones. Weak consolidation of rocks makes them difficult to study because of the impossibility of using standard, commonly used techniques. As a result, an interest in the methodological part of determining the collecting properties of such rocks became aggravated.

The aim of this work is to choose the most reasonable method of porosity determination of the semi-consolidated and friable rocks and its mastering to the operative complex of researches.

The basic content. The article considers the methods of determining the porosity used in engineering Geology and total porosity of the bulk rocks using the Remniov’s formula. The latter provides pre-compaction of samples under a pressure similar to the effective pressure on the sample and has a few options. The device for pre-consolidation and the method of its application have been developed. Ways to determine the values of effective pressure during compaction have been considered.

Conclusions. On the basis of the work final conclusions have been formulated according to the declared purpose of the work:

1. As long as it is technically possible, within the operational complex for determining porosity of semi-consolidated rocks it is better to use a standard saturation method.

2. In other cases on semi-consolidated and always on friable rocks it is needed to use the method of the direct measuring on a model, under effective pressure, calculation on a formula {3}, where rock pressure is calculation on the formula of Р=γh. Porosity should be calculated on a formula {2} with the use of quartz specific gravity.