«Oilfield engineering»

Substantiation of the degree of a formation drilling-in by perforation to increase the efficiency of deposits development with oil-water zones

UDC: 622.276.21.031:532.(1-04)-П
DOI: -

Authors:

¹ SamaraNIPIneft, Samara, Russia
² Kazan Scientific Center, Kazan, Russia

Keywords: oil displacement, perforation interval, coning, water-oil factor, forced fluid extraction, flushing rate, rescaling, aquifer

Annotation:

The authors of the article consider the influence of the degree of a formation drilling-in by perforation on the efficiency of oil deposits development, which are generally underlain by bottom water. A three type classification of such objects is proposed, depending on the direction of oil displacement by water (bottom-up or along the formations) and the completeness of the displacement coverage. Using two deposits (types 2 and 3) as an example, three-dimensional hydrodynamic models adapted to the development history were constructed. A computational experiment was performed with various perforation schemes – from drilling-in only the upper part of the formation up to complete perforation of the entire section, as well as scenarios with a dynamic change in the perforation interval during operation and with the organization of water-flooding. It is shown that for deposits of 1 and 2 types, limited opening is optimal – about half of the oil-saturated thickness of the formation from the roof.

It delays the bottom water breakthrough and allows achieving the maximum oil recovery factor with minimal water cut. On the contrary, for the deposits of type 3 (with local screens preventing vertical water inflow), the maximum oil recovery factor is achieved with complete opening of the oil zone, since the risk of coning is minimal. Perforation of only the upper third of the formation in all cases leads to oil shortage, and opening of the aquifer sharply worsens the indicators. For the first time, the high efficiency of timely shutdown of the lower watered perforation intervals and redistribution of perforation along the formation height to increase oil recovery has been quantitatively demonstrated. Additional flooding has a negative effect on 1 and 2 type deposits and slightly increases the oil recovery factor for type 3. The obtained results allow developing practical recommendations for selecting the perforation interval and tactics for changing it in deposits with bottom water, thereby increasing the efficiency of development and slowing down wells water- flooding.

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