Abstract

The Triassic Yanchang formation is rich in tight oil resource at Ordos Basin. The oil sandstone and oil shale of Chang 7 member are widely spread in the basin and have huge potential in oil production. Due to low porosity and low permeability, producing oil from tight oil reservoir depends on hydraulic fracturing. A successful hydraulic fracture requires accurate estimations of horizontal stresses and rock elastic properties in design and operation.

Chang 7-2 is shale and sandstone interbed reservoir and Chang 7-3 is shale oil reservoir with lamination sedimentary structure. The rocks with lamination structure are very anisotropic, and it needs to be considered in computation of horizontal stresses and rock elastic properties.

In this paper, we present a case study to illustrate the advantages of anisotropic geomechanics model. Anisotropic horizontal stresses and rock elastic properties were calculated and used in hydraulic fracturing design. The perforation intervals were selected at depths with low stress magnitude based on stress profile. The perforations efficiency was analyzed, and perforation interval with low efficiency was removed. Major stimulation operation parameters, total volume, proppant volume and slurry rate, were optimized with anisotropic geomechanics model. Fracturing operation results showed that the total volume was decreased by 16.5%, proppant pumped increased by 11.4% and daily oil production increased by 73.7%. This case study demonstrated that anisotropic geomechanics model help to improve operation efficiency and increase oil production.

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