Fracturing Stimulations Improve Oil Well Performance in Deep Tight Glutenite Reservoirs of the Shengli Oilfield

Abstract The glutenite oil reservoirs with target stratum between 3400 and 4000m TVD in Shengli oilfield in China are low core permeability within the range of 0.015-0.3mD, which needs to be stimulated to achieve commercial production. These reservoirs have thick pay intervals (gross pay thickness up to 80 meters in some wells), and the massive hydraulic fracturing (MHF) was widely applied with high-rate and large-scale proppant volume since 2007. However, post-fracture production responses showed the MHF weren't always effective in these reservoirs. This paper shows a new technique to stimulate these tight reservoirs with better economic results. It involves two steps including perforation optimization and MHF with proppant density varying. Due to the difference of reservoir properties in the vertical direction, it is required to perforate the pay section within a short interval to ensure that the fracture could penetrate the pay zone. Besides, MHF with low, medium and high density proppant improves the proppant placement in the vertical direction, owing to the difference of proppant falling velocity and the proppant convection among carrying fluid. This method will enhance fracture conductivity comparing with using the same density proppant. The novel technique has been successfully applied to four wells in Y104 Zones of the Shengli Oilfield. The five wells have better post-production than the other three wells with single density proppant. Net pressure matching and post-fracture pressure build-up testing were conducted to evaluate fracture geometry and conductivity. The results of post-fracture analysis and post-production evaluation demonstrate the benefits of this new fracture treatment. This paper presents a field case of a novel stimulation method in tight glutenite reservoir with large thickness. The proposed method solves one of the key fracturing technology difficulties in these reservoirs and improves stimulation performance, effectively promoting the economical development of such oil filed in China.