Optimization of Orientation of Horizontal Wells and Direction of Fractures at Multistage Hydraulic Fracturing for Low-Permeability Reservoir: Tradeoff Between Initial Oil Production and Oil Recovery

Abstract

Abstract The technology of multistage fracturing of horizontal wells for the development of low-permeability reservoirs has gained wide acceptance. The performance of multistage fracturing treatments may vary significantly: one treatment may yield large initial oil production rates but rapid increase of water cut and low ultimate oil recovery, while the other treatment may result in low oil production rates but moderate water cut increase and higher oil recovery. The purpose of this study is to establish the technologies aimed at achieving the utmost production performance of low-permeability reservoirs; namely, maximum initial oil production rates and oil recoveries. This paper considers three patented technologies which have been designed based on the results of reservoir simulation modeling and actual multistage fracturing performance data in real wells. These technologies have comprised the following research results: the most efficient wellbore orientation and well spacing, optimal angles (30° to 60°) between maximum in-situ stress vector and horizontal wellbore direction as well as between multiple hydraulic fractures, displacement front and natural fractures; appropriate number of fracturing stages N (N=1+L/100, where L is horizontal length) and induced fracture spacing (10 to 100 m), well operation conditions depending on reservoir pressure reduction in the course of reservoir development (up to 3% a year) etc. Numerical reservoir simulation studies have shown incremental oil recoveries of 2–5% as compared to the existing technologies of multistage fracturing in horizontal wells. Actual field data from Well 2917G penetrating the Domanic deposits of the Bavlinskoye field suggest sufficiently high oil production rates and low water cut when hydraulic fractures propagate at 45- degree angle with respect to horizontal wellbore. In recent years, boosting production performance of low-permeability (up to 2 mD) oil reservoirs has become one of top-priority tasks in Russia owing to mineral extraction tax incentives. The proposed technologies enable enhanced oil production from such low-permeability oil-saturated reservoirs and increased production rates through improvement of sweep efficiency.