Results of Determining the Porosity Coefficient in Oil-Saturated Clay Rocks

The article studies the wells that opened clayey reservoirs of Paleogene age. When predicting the trajectory of a crack during hydraulic fracturing (HF), it is necessary to take into account the percentage of minerals in the rock, since cracks during hydraulic fracturing are formed at the contacts between mineral grains. This conclusion is indisputable, but obtaining complete information about the percentage of minerals in a rock is an expensive and not always feasible task. At the same time, the physical and mechanical characteristics of clayey rocks are no less significantly influenced by their porosity. Therefore, it is important to note that a reliable determination of the porosity coefficient from the exposed geological section will undoubtedly have a primary positive impact on the reliability of hydraulic fracturing modeling. Based on this, in wells that opened clayey reservoirs, the values of porosity coefficients determined by various methods were analyzed, including the direct one – analysis of core, cuttings and the indirect one – geophysical methods. During the work, a coincidence of the porosity coefficient in the core, cuttings and electrical logging was discovered. Based on the results of the study, it can be concluded that the porosity coefficient determined from acoustic logging (AL) significantly exceeds the values of the porosity coefficient determined from core, cuttings and induction logging. This is due both to the influence of clay content on the acoustic logging readings, and due to the low quality of AC materials induced by erosion of the wellbore. It should be noted that the calculations of porosity coefficients in the above-reference part – in the Batalpashinsky formation based on core and induction logging – coincide almost completely. However, in the sub-reference part of the formation the readings differ slightly. The porosity coefficient calculated is a maximum of 2% lower than the porosity coefficient determined from the core, which is quite acceptable.

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