The methods of improving the hydraulic fracturing technology for terrigenous and carbonate reservoirs of the fields of Udmurtneft named after V.I. Kudinov are considered, which make it possible to effectively stimulate wells taking into account complicated geological conditions. For terrigenous reservoirs, which include Devonian deposits, hydraulic fracturing makes it difficult to have nearby water-saturated layers from the interval of stimulation. The complexity of stimulation of carbonate reservoirs represented by medium carbon deposits, the main factors complicating hydraulic fracturing are a large floor of oil capacity (up to 150 m), high partition of productive layers, as well as a significant difference in the geological, physical and geomechanical properties of nearby layers, processing of which is impossible separately. The use of traditional hydraulic fracturing technologies for wells leads to breakthroughs in water-saturated formations or ineffective stimulation of the target reservoir, therefore there is a need to optimize the hydraulic fracturing technology. The article presents the technological solutions proposed for each factor complicating hydraulic fracturing. For terrigenous reservoirs (Visean Stage), acid injection before hydraulic fracturing, refusal of mini-hydraulic fracturing and a gradual increase in fluid viscosity during the main hydraulic fracturing process were recommended. When highly partitioned formations (Moscovian Stage) are stimulated with large perforation intervals, hydraulic fracturing is carried out with a proppant filling of the lower intervals during the injection process. This method of hydraulic fracturing is implemented according to the following scheme: at first the lower penetrated horizon is stimulated, and then the proppant agent is put to the bottomhole to the specified interval of perforation, after setting of the sand (proppant agent) in the wellbore the reservoir is stimulated through the upper intervals. In conditions of nearby water- or gas-saturated undesirable interlayers (Tournaisian Stage), it is effective to conduct hydraulic fracturing with a step-by-step, alternating with stops, and injection of acid stages with a gradual increase in the injection rate and subsequent fixing of the created crack with a proppant. In order to intensify production from simultaneously developed formations with different properties, it is recommended to conduct hydraulic fracturing according to an adaptive design, i.e., modified during the injection process.
The proposed methods will improve the efficiency of hydraulic fracturing, perform effective stimulation of wells in complicated geological conditions, as well as increase the pool of candidate wells for hydraulic fracturing.
References
1. Shekhodanov V.A., Provorov V.M., Fedorchuk Z.A., Sharonov L.V., Pogrebnyak M.M., Geologiya i neftenosnost' Udmurtskoy ASSR (Geology and oil-bearing capacity of the Udmurt ASSR), Izhevsk: Udmurtiya Publ., 1976, 128 p.
2. Topal A.Yu., Firsov V.V., Usmanov T.S. et al., Regional aspects of hydraulic fracturing in Udmurtneft OJSC (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2020, no. 4, pp. 45–48, DOI: 10.24887/0028-2448-2020-4-44-48
3. Topal A.Yu., Usmanov T.S., Zorin A.M. et al., Introduction of the acid and proppant hydrofracturing technology at Udmurtneft fields (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2018, no. 3, pp. 34–37, DOI: 10.24887/0028-2448-2018-3-34-37
4. Cleary M.P., Analysis of mechanisms and procedures for producing favourable shapes of hydraulic fractures, SPE-9260-MS, 1980.
5. Sharafeev R.R., Kondrat'ev S.A., Novokreshchennykh D.V. et al., Experience in propant hydraulic fracturing without a mini-frac stage (In Russ.) Neftepromyslovoe delo, 2021, no. 1, pp. 24–29, DOI: 10.33285/0207-2351-2021-1(625)-24-29
