Assessing injection-induced fracture geometry with well testing

Background. The paper describes a study of injection-induced fractures propagation with special well testing. It also concerns diagnostics of fracture opening and its trajectory.

There’s a lot of approaches to diagnosing injection-induced fractures, including IPR tests and pressure transient analysis: the presence of the fracture can be robustly determined. Although, the question of fracture geometry: if it opens mostly laterally or grows vertically connecting other reservoirs — is open. The lateral fracture growth may be good for oil displacement, e.g. in linear waterflood systems oriented along the regional stress. At the same time, there’s a risk of direct water breakthrough into producing wells, sometimes located miles from injectors [1].

Another substantial risk is fracture vertical propagation: connecting different reservoirs to injection can seriously and negatively affect the development [2, 3].

Fracture height can be successfully assessed with cased hole logging, but the success depends on the well trajectory. Even slight inclination creates a distance between a well and a fracture (mostly strictly vertical), growing further from the fracture initiation point. As a result, “behind-the-casing” sensors, such as noise and temperature, lose the informational capacity of seeing the fracture flow and injection into other reservoirs. That’s why diagnosing fracture vertical growth and its half-length is very important and relevant.

The goal of the study is to justify and test the well testing diagnostic routine to assess fracture geometry. The objectives are to:

• build a fracture propagation model;
• justify the well test program;
• test the program on the actual well;
• interpret the results and match them in the model.

Materials and methods. The diagnostic routine is based on a specially designed numerical-analytical model. The current state of the fracture (half-length, thickness and pressure profile) is being determined with a triple-linked calculation of fluid diffusion, fracture hydraulics and geomechanics.

Results. The result of the work is a field test, which successfully determined the fracture geometry and was matched in a model.

Conclusion. The paper justifies the special well-test based diagnostic routine and interpretation approach for assessing the injection-induced fracture geometry and the.

1. Davletbayev A., Baikov V., Bikbulatova G., Asmandiyarov R., Nazargalin E., Slabetskiy A., Sergeychev A., Nuriev R. Field Studies of Spontaneous Growth of Induced Fractures in Injection Wells. SPE-171232-MS, 2014.

2. Islamov A.I., Faskhutdinov R.R., Kolupaev D.Yu., Vereschagin S.A. On the mechanisms of the formation of zones with abnormally high rock pressure and methods for predicting them in undeveloped rock systems, Priobskoye field case study // Oil Industry. — 2018. — № 10. — p. 54–59.

3. Ipatov A.I., Kremenetskiy M.I., Gulyaev D.N., Krichevskiy V.M. Improving oil recovery of a field with high water cut and low recovery of initial recoverable reserves // Oil Industry. — 2022. — №11. — p. 98–102.

4. Krichevskiy V.M. Diffusion + geomechanical modeling of injection through induced fracture // Oil. Gas. Novation. — 2020. — №03. — p. 40–46.