INVESTIGATION OF THE INJECTION WELL INDICATOR CURVE BEHAVIOR UNDER SPONTANEOUS HYDRAULIC FRACTURE PROPAGATION USING MATHEMATICAL MODELING
R.R. Kopeikin1,2, A.N. Baikin3,4, R.F. Abdullin4, S.A. Kalinin1,2, E.V. Shel’1,2, B.N. Starovoitova3,4
1Gazprom Neft, Saint Petersburg, Russia
2Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia
3Lavrentyev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences (LIH SB RAS), Novosibirsk, Russia
4Novosibirsk State University, Novosibirsk, Russia
Keywords: injection well, spontaneous hydraulic fracturing, prestressed state, indicator curve, fracture initiation pressure, hydraulic fracturing, waterflooding, poroelasticity, mathematical modeling
Abstract
A three-dimensional mathematical model for the propagation of a spontaneous hydraulic fracture in a poroelastic medium is presented, accounting for the prestressed state induced by a pre-existing propped fracture. The indicator curve behavior for an injection well experiencing spontaneous hydraulic fracturing is analyzed, and a physical interpretation of its characteristics is provided. A step-rate injection test is simulated, and the effects of the impermeable caprock thickness and the prestress due to the propped fracture on the indicator curve shape and fracture initiation pressure are evaluated. The slope of the indicator curve beyond the fracture initiation point is found to depend significantly on the fracture length and conductivity, as well as on poroelastic effects. In particular, increasing caprock thickness is revealed to raise the fracture initiation pressure due to additional stresses generated by elevated pore pressure-an effect that cannot be captured by two-dimensional models without further modifications. The simulation results demonstrate the sensitivity of the fracture initiation pressure to changes in reservoir pressure and confirm the need to account for three-dimensional poroelastic effects and prestress in the engineering design of waterflooding systems.
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